Title of Invention	"ELECTRONIC CONTROL APPARATUS"
Abstract	To obtain an electronic control apparatus enabling a reduction in size as well as increases in output and in lifetime, the electronic control apparatus includes: a housing (3) made of an insulating resin, having opening portions on both ends; a heat sink (5) attached to one of the ends of the housing (3), the heat sink (5) having a surface on a housing (3) side, on which a semiconductor switching element (2) is mounted; and a circuit board (4) provided to be opposed to the heat sink (5), in which a plurality of low-current components including a microcomputer (41) for controlling driving of the semiconductor switching element (2) are mounted on one surface of the circuit board (4), whereas a plurality of high-current components including a capacitor for absorbing a ripple of a current flowing through the semiconductor switching element (2) are mounted on another surface of the circuit board (4).

Title of Invention

"ELECTRONIC CONTROL APPARATUS"

Abstract

To obtain an electronic control apparatus enabling a reduction in size as well as increases in output and in lifetime, the electronic control apparatus includes: a housing (3) made of an insulating resin, having opening portions on both ends; a heat sink (5) attached to one of the ends of the housing (3), the heat sink (5) having a surface on a housing (3) side, on which a semiconductor switching element (2) is mounted; and a circuit board (4) provided to be opposed to the heat sink (5), in which a plurality of low-current components including a microcomputer (41) for controlling driving of the semiconductor switching element (2) are mounted on one surface of the circuit board (4), whereas a plurality of high-current components including a capacitor for absorbing a ripple of a current flowing through the semiconductor switching element (2) are mounted on another surface of the circuit board (4).

Full Text	ELECTRONIC CONTROL APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic control apparatus used for, for example, an electric power steering device for assisting in biasing a steering device of a vehicle with a rotary force of an electric motor. 2. Description of the Related Art Conventionally, there is known an electronic control apparatus, which includes a field effect transistor (FET) as a semiconductor switching element, which being a power device to be mounted on a metal substrate, and has a structure in which a connection member fixed onto the metal substrate, for electrically connecting the metal substrate and components provided outside the metal substrate to each other. For example, an electronic control apparatus described in JP 3644835 B includes a power substrate, a housing, a control substrate, a connection member, a heat sink, and a case. On the power substrate, a bridge circuit including the semiconductor switching elements for switching a current of an electric motor is mounted. The housing includes a conductive plate or the like which is insert molding into an insulating resin and a high-current component mounted thereon. A low-current component such as a microcomputer is mounted on the control substrate. The connection member electrically connects the power substrate, and the housing and the control substrate to each other. The heat sink is brought into close contact with the power substrate. The case is formed by press molding of a metal plate to cover the power substrate, the housing, and the control substrate, and is attached to the heat sink. In the electronic control apparatus described in JP 3644835 B, the power substrate on which the semiconductor switching elements are mounted, the housing on which the high-current components are mounted, and the control substrate on which the low-current components are mounted are required. Therefore, there is a problem that the size, complexity, and cost of the apparatus are increased by the increased number of components. SUMJVIARY OF THE INVENTION The present invention is devised to solve the problem described above, and has an object of providing an electronic control apparatus enabling a reduction in size, in complexity, and in cost as well as increases in output and in lifetime. According to an aspect of the present invention, there is provided an electronic control apparatus including: a housing made of an insulating resin, having opening portions on both ends; a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and a circuit board provided to be opposed to the heat sink, in which a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a capacitor for absorbing a ripple of a current flowing through the power device are mounted on another surface of the circuit board. According to another aspect of the present invention, there is provided an electronic control apparatus including: a housing made of an insulating resin, having opening portions on both ends; a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and a circuit board provided to be opposed to the heat sink, in which a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a shunt resistor for detecting a current flowing through the power device are mounted on another surface of the circuit board. According to the electronic control apparatus of the present invention, the power device is mounted on the heat sink. At the same time, the low-current components are mounted on one of the surfaces of the circuit board, whereas the high-current components are mounted on the other surface of the circuit board. Therefore, in addition to a reduction in size, in complexity, and in cost, increases in output and in lifetime can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. 1 is an exploded perspective view illustrating an electronic control apparatus according to a first embodiment of the present invention; FIG. 2 is an exploded perspective view of the electronic control apparatus illustrated in FIG. 1, which is viewed from a direction vertically opposite to a direction from which the exploded perspective view of FIG. 1 is viewed; FIG. 3 is a side view of the electronic control apparatus illustrated in FIG. 1 when viewed from a vehicle connector side; FIG. 4 is a side view of the electronic control apparatus illustrated in FIG. 1 when viewed from a motor connector side; FIG. 5 is a perspective view of a housing of the electronic control apparatus illustrated in FIG. 1 when viewed from a direction of attachment of a heat sink; FIG. 6 is an enlarged view of a principal part of FIG. 5; FIG. 7 is a block diagram of the electronic control apparatus illustrated in FIG. 1 FIG. 8 is a side sectional view of the electronic control apparatus illustrated in FIG. 1: FIG. 9 is a perspective view illustrating the fixation between conductive plates and connector terminals of the electronic control apparatus illustrated in FIG. 1; FIG. 10 is another perspective view illustrating the fixation between conductive plates and connector terminals of the electronic control apparatus illustrated in FIG. 1; FIG. 11 is a side sectional view of the electronic control apparatus illustrated in FIG. 1, which is parallel to the side cross-section of FIG. 8; FIG. 12 is a further perspective view illustrating the fixation between conductive plates and connector terminals of the electronic control apparatus illustrated in FIG. 1; FIG. 13 is a perspective view illustrating the fixation between a holding member and a spring member of the electronic control apparatus illustrated in FIG. 1; FIG. 14 is a side sectional view of the electronic control apparatus illustrated in FIG. 1, which is parallel to the side cross-section of FIG. 8; FIG. 15 is a sectional view of the electronic control apparatus illustrated in FIG. 1, which is cut along a direction perpendicular to the side cross-section of FIG 8; FIG. 16 is another side sectional view of the electronic control apparatus illustrated in FIG. 1, which is parallel to the side cross-section of FIG. 8; FIG. 17 is a front view illustrating a circuit board of the electronic control apparatus illustrated in FIG. 1; FIG. 18 is an exploded perspective view illustrating a positional relation between the heat sink and the housing of the electronic control apparatus illustrated in FIG. 1; FIG. 19 is a perspective view illustrating the positional relation between the heat sink and the housing of the electronic control apparatus illustrated in FIG. 1; FIG. 20 is a perspective view of the principal part of the electronic control apparatus illustrated in FIG. 1; FIG. 21 is a side sectional view illustrating the electronic control apparatus according to a second embodiment of the present invention; and FIG. 22 is a perspective view illustrating a modification of the electronic control apparatuses according to the first and second embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, an electronic control apparatus according to each embodiment of the present invention is described based on the accompanying drawings. In each of the drawings, the same or eqgivalent components or parts are denoted by the same reference numerals for description. In the first embodiment, an electronic control apparatus 1 is described as an example. The electronic control apparatus 1 is used for an electric power steering device for assisting in biasing a steering device for a vehicle with a rotary force of an electric motor. FIG. 1 is an exploded perspective view illustrating the electronic control apparatus 1 according to a first embodiment of the present invention; FIG. 2 is an exploded perspective view of the electronic control apparatus 1 illustrated in FIG. 1, which is viewed from a direction vertically opposite to a direction from which the exploded perspective view of FIG. 1 is viewed; FIG. 3 is a side view illustrating a side of the electronic control apparatus 1 illustrated in FIG. 1 where a vehicle connector 8 is provided; FIG. 4 is a side view illustrating a side of the electronic control apparatus 1 illustrated in FIG. 1 where a motor connector 9 and a sensor connector 10 are provided; FIG. 5 is a perspective view of a housing 3 of the electronic control apparatus 1 illustrated in FIG. 1 when viewed from a direction of attachment of a heat sink 5; FIG. 6 is an enlarged view of a principal part of FIG. 5; FIG. 7 is a block diagram of the electronic control apparatus 1 illustrated in FIG. 1; and FIG. 8 is a sectional view of the electronic control apparatus 1 illustrated in FIG. 1. The electronic control apparatus 1 includes the housing 3, the heat sink 5, semiconductor switching elements 2, a circuit board 4, and a cover 7. The housing 3 is made of an insulating resin, and has opening portions formed on both ends. The heat sink 5 is made of aluminum, and is attached onto one of the ends of the housing 3 by using a screw 20. On a surface of the heat sink 5, an insulating coating is formed. Each of the semiconductor switching elements 2 corresponds to a power device. The semiconductor switching elements 2 are mounted on the heat sink 5, and are pressed toward the heat sink 5 by a plate spring 21. The circuit board 4 is provided to be opposed to the heat sink 5. In cooperation with the heat sink 5, the cover 7 accommodates the semiconductor switching elements 2 and the circuit board 4 therein. On a surface of the circuit board 4 on the cover 7 side, a plurality of low-current components, through which a low current for signals flows, are mounted by soldering. The low-current components respectively correspond to, as illustrated in FIG. 1, a microcomputer 41, a power supply 10 42, and a driver 10 43. The microcomputer 41 calculates an assist torque based on a steering torque of a handle and a velocity of a vehicle, and provides feedback of a motor current to generate a driving signal corresponding to the assist torque. The power supply 10 42 drives the electronic control apparatus 1. The driver 10 43 controls an operation of each of the semiconductor switching elements 2. On a surface of the circuit board 4 on the heat sink 5 side, a plurality of high-current components, through which a high current for driving a motor flows, are mounted by soldering. The high-current components correspond to, as illustrated in FIG. 2, a coil 44, capacitors 45, a relay 46, and a shunt resistor 47. The coil 44 prevents electromagnetic noise, which is generated at the time of a switching operation of each of the semiconductor switching elements 2, from leaking to the outside. Each of the capacitors 45 absorbs a ripple of a current flowing through each of the semiconductor switching elements 2. The relay 46 turns ON and OFF a motor current supplied from a battery 24 through an intermediation of the semiconductor switching elements 2 of a bridge circuit to an electric motor 22. The shunt resistor 47 detects the current flowing through the semiconductor switching elements 2. A current circuit of the circuit board 4 includes a high-current circuit and a low-current circuit. The high-current circuit, which is constituted by a wiring pattern, is electrically connected to the bridge circuit constituted by the semiconductor switching elements 2, the coil 44, the capacitors 45, the relay 46, and the shunt resistor 47. Through the high-current circuit, the high current for driving the motor flows. The low-current circuit, which is constituted by a wiring pattern, is electrically connected to the microcomputer 41, the power supply IC 42, and the driver 10 43. Through the low-current circuit, the low current for signals flows. The electronic control apparatus 1 also includes the vehicle connector 8, the motor connector 9, and the sensor connector 10. The vehicle connector 8 is provided on one lateral surface of the housing 3, and is electrically connected to a wiring of the vehicle. The motor connector 9 is provided on the other lateral surface of the housing 3, and is electrically connected to the electric motor 22. The sensor connector 10 neighbors the motor connector 9, and is electrically connected to a torque sensor 23. As illustrated in FIG. 3, the vehicle connector 8 includes a power connector terminal 11 and a signal connector terminal 12. The power connector terminal 11, which is electrically connected to the battery 24 of the vehicle, is made of copper or copper alloy at a thickness of 0.8 mm. The signal connector terminal 12 is made of phosphor bronze at a thickness of 0.64 mm. From/to the signal connector terminal 12, a signal is input/output through an intermediation of the wiring of the vehicle. Moreover, as illustrated in FIG. 4, the motor connector 9 includes a motor connector terminal 13, whereas the sensor connector 10 includes a sensor connector terminal 14. The motor connector terminal 13 is made of copper alloy or phosphor bronze having a high electrical conductivity at a thickness of 0.8 mm. The sensor connector terminal 14 is made of phosphor bronze at a thickness of 0.64 mm. Further, as illustrated in FIG. 5, the electronic control apparatus 1 includes power conductive plates 6a, output conductive plates 6b, signal conductive plates 6c, and conductive plates 6d. A base portion of each of the power conductive plates 6a, the output conductive plates 6b, and the signal conductive plates 6c is integrally formed with the housing 3 by insert molding. The power conductive plates 6a, the output conductive plates 6b, and the signal conductive plates 6c electrically connect the circuit board 4 and the semiconductor switching elements 2 to each other. A base portion of each of the conductive plates 6d is integrally formed with the housing 3 by the insert molding. The conductive plates 6d electrically connect the circuit board 4 and the power connector terminal 11 to each other. The electronic control apparatus 1 also includes conductive plates 6e and a holding member 6f. The conductive plates 6e electrically connect the circuit board 4, and the signal connector terminal 12 and the sensor connector terminal 14 to each other. The holding member 6f has a role in connecting a ground of the circuit board 4 to the heat sink 5. The components such as the power connector terminal 11, the signal connector terminal 12, the motor connector terminal 13, and the sensor connector terminal 14 are formed by the insert molding simultaneously with the insert molding of the power conductive plates 6a, the output conductive plates 6b, the signal conductive plates 6c, the conductive plates 6d and 6e and the holding member 6f for the formation of the housing 3. The vehicle connector 8, the motor connector 9, and the sensor connector 10 are integrally formed with the housing 3. Moreover, on the lateral surface of the housing 3 on the opening portion side opposite to the opening portion to which the heat sink 5 is attached, attachment leg portions 3L for attaching the electronic control apparatus 1 to the vehicle corresponding to an attachment target body. Terminals of each of the pair of lf»mpnt«; P nrnwiHprl in parallel are arranged, from the right in FIG. 6, in the order of: a power supply terminal VS, a gate terminal GT1 of a high-side MOSFET 2H, a bridge output terminal OUT, a gate terminal GT2 of a low-side MOSFET 2L, and a ground terminal GND. The power supply terminal VS, the bridge output terminal OUT, and the ground terminal GND are high-current terminals through which a high current of up to about 50A flows to operate the electric motor 22, whereas the gate terminals GT1 and GT2 are low-current terminals through which a low current for signals, up to about 3A, flows. The high-current terminals and the low-current terminals are arranged alternately. Each of the terminals OUT of the semiconductor switching elements 2 arranged in parallel is bent in the same crank-like shape with a standing portion and a lying portion in the middle, and extends in the same direction, as illustrated in FIG 8. The other terminals VS, GT1, GT2, and GND are also bent and extend in the same manner. Each of the terminals VS, GT1, GT2, OUT, GT2, and GND of the semiconductor switching elements 2 is formed at a width of 0.8 mm, a thickness of 0.5 mm and intervals of 1.7 mm between the terminals. As illustrated in FIG. 7, in each of the semiconductor switching elements 2, the high-side MOSFET 2H and the low-side MOSFET 2L are integrated to form a half-bridge. In each of the semiconductor switching elements 2, the half-bridge is housed within a single package. In addition, a pair of the semiconductor switching elements 2 constitute a bridge circuit for switching a current of the electric motor 22. Moreover, as illustrated in FIGS. 5 and 6, a positioning portion 3d for positioning a main body of each of the semiconductor switching elements 2 and the housing 3 is formed within the housing 3. The positioning portion 3d has a tapered portion at its distal end. The positioning portion 3d is guided by the tapered portion to be inserted into a hole 2a formed in the heat spreader of each of the semiconductor switching elements 2, thereby performing the positioning. The positioning portion 3d also performs the positioning for the direction in which each of the terminals VS, GT1, OUT, GT2, and GND extends. Moreover, a pair of positioning portions 3e for positioning each of the terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2 and the conductive plates 6a, 6b, and 6c are formed in a similar manner within the housing 3. The positioning portions 3e perform positioning for a direction perpendicular to the extending direction of each of the terminals VS, GT1, OUT, GT2, and GND. The positioning portions 3e are formed on both outer sides of the terminals VS and GND of each of the semiconductor switching elements 2. Each of the positioning portions 3e has a tapered portion at its distal end. The outer side of each of the terminals VS and GND of each of the semiconductor switching elements 2 is guided by the tapered portion to position each of the terminals VS, GT1, OUT, GT2, and GND and the conductive plates 6a, 6b, and 6c. As illustrated in FIG. 6, the conductive plates 6a, 6b, and 6c are arranged to overlap the terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2 to extend in the same direction as the direction in which the terminals VS, GT1, OUT GT2, and GND extend. The terminals VS, GT1, OUT GT2, and GND and the conductive plates 6a, 6b, and 6c are arranged on the surface of the housing 3, which is opposite to the heat sink 5. After the positioning and the fixation of the semiconductor switching elements 2 with the positioning portions 3d and 3e, the terminals VS, GT1, OUT, GT2, and GND and the semiconductor plates 6a, 6b, and 6c are welded to each other by, for example, laser welding. The laser welding is performed by radiating a laser LB from the direction of attachment of the heat sink 5 toward the surfaces of the terminals VS, GT1, OUT, GT2, and GND prior to the attachment of the heat sink 5. As illustrated in FIG. 6, proximal end portions of the power conductive plates 6a are respectively connected to a distal end portion of the power supply terminal VS and a distal end portion of the grand terminal GND of each of the semiconductor switching elements 2. A proximal end portion of the output conductive plate 6b is connected to a distal end portion of the bridge output terminal OUT. Proximal end portions of the signal conductive plates 6c are respectively connected to distal end portions of the gate terminals GT1 and GT2. FIG. 9 is a perspective view of the conductive plates 6a, 6b, and 6c and the peripheral components connected thereto. Press-fit terminals 6ap, a press-fit terminal 6bp, and press-fit terminals 6cp are respectively formed on the conductive plates 6a, 6b, and 6c. A wiring pattern made of a copper foil is formed on the circuit board 4, whereas a plurality of through holes 4a to be electrically connected to the wiring pattern are formed through the circuit board 4. An inner surface of each of the through holes 4a is plated with copper. The press-fit terminals 6ap, 6bp, and 6cp are press-fitted into the through holes 4a of the circuit board 4, respectively. As a result, the terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2 are electrically connected to the wiring pattern of the circuit board 4. The power conductive plates 6a and the output conductive plates 6b are formed of rolled copper or copper alloy. A high current flows through the conductive plates 6a and 6b when the conductive plates 6a and 6b and the terminals VS, OUT, and GND of the semiconductor switching elements 2 are welded to each other. Therefore, it is necessary to ensure a sufficiently large volume for each of the conductive plates 6a and 6b. In terms of formation of the press-fit terminals and the press working, however, it is difficult to increase the thickness of each of the conductive plates 6a and 6b. Therefore, in this embodiment, the thickness of each of the power conductive plates 6a and the output conductive plates 6b is set to 0.8 mm, which is the same value as that of the width of each of the terminals VS, OUT, and GND of the semiconductor switching elements 2. Thus, a width of each of the conductive plates 6a and 6b is formed larger than the thickness. In this manner, the conductive plates 6a and 6b are welded to the terminals VS, OUT, and GND of the semiconductor switching elements 2. Note that, a low current flows through the conductive plates 6c used for signals, and hence it is unnecessary to take a reduction in electric resistance into consideration. However, those conductive plates 6c are made of the same material as that of the power conductive plates 6a and the output conductive plate 6b through which the high current flows. As illustrated in FIGS. 8 and 9, the bridge output terminals OUT of the semiconductor switching elements 2 are respectively connected to the output conductive plates 6b. Moreover, an end potion 13a of the motor connector terminal 13 is connected to an end of the proximal end portion of the output conductive plate 6b, which is on the side opposite to the bridge output terminal OUT. As in the case where the output conductive plate 6b is connected to the bridge output terminal OUT of each of the semiconductor switching elements 2, the end portion 13a of the motor connector terminal 13 is provided on the surface of the end portion of the output conductive plate 6b, which is opposed to the heat sink 5, and is welded thereto by radiating the laser beam LB from the direction of attachment of the heat sink 5 toward the surface of the motor connector terminal 13. The motor current from the bridge output terminal OUT of each of the semiconductor switching elements 2 is adapted to directly flow into the electric motor 22 through the motor connector terminal 13 without passing through the circuit board 4. In the middle portion of the output conductive plate 6b, the press-fit terminal 6bp extending toward the circuit board 4 is formed. Through the press-fit terminal 6bp, a signal for monitoring a voltage of the motor connector terminal 13 is output to the circuit board 4. FIG. 10 is a perspective view illustrating the power source conductive plates 6d and the peripheral components connected thereto. As illustrated in FIGS. 8 and 10, an end portion 11a of the power connector terminal 11 is connected to each of the power conductive plates 6d. As in the case where the output conductive plate 6b is connected to the end portion 13a of the motor connector terminal 13, the power connector terminal 11 is provided on a surface of the end portion of the power conductive plate 6d, which is opposed to the heat sink 5, and Is welded thereto by radiating the laser beam LB from the direction of attachment of the heat sink 5 toward the surface of the end portion 11a of the power connector terminal 11. In the middle of each of the power source conductive plates 6d, the press-fit terminals 6dp extending toward the circuit board 4 are formed. The press-fit terminals 6dp are press-fitted into the through holes 4a of the circuit board 4 to be electrically connected to the wiring pattern of the circuit board 4. Then, the current from the battery 24 is supplied to the circuit board 4 through the power connector terminal 11, the power source conductive plate 6d, and the press-fit terminals 6dp. FIG. 11 is a sectional view parallel to FIG. 8, which is cut along the vehicle connector 8 and the sensor connector 10. FIG. 12 is a perspective view illustrating the conductive plates 6e and the peripheral components connected thereto. As illustrated in FIGS. 11 and 12, the conductive plates 6e are caused to overlap end portions 12a of the signal connector terminal 12 and end portions 14a of the sensor connector terminal 14, respectively. The contact surfaces between the conductive plates 6e and the end portions 12a and 14a are formed in the vicinity of the heat sink 5 to be parallel to the heat sink 5. At this time, the end portions 12a of the signal connector terminal 12 and the end portions 14a of the sensor connector terminal 14 are provided on the heat sink 5 side, and are welded thereto by radiating the laser LB from the direction of attachment of the heat sink 5 toward the surfaces of the end portions 12a of the signal connector terminal 12 and the end portions 14a of the sensor connector terminal 14. Moreover, a press-fit terminal 6ep is formed on an end portion of each of the conductive plates 6e, which is on the side opposite to the welded portion. The press-fit terminals 6ep are press-fitted into through holes 4b of the circuit board 4 to electrically connect the signal connector terminal 12 and the sensor connector terminal 14, which are connected to the conductive plates 6e, to the wiring pattern of the circuit board 4. FIG. 13 is a perspective view of the holding member 6f and the peripheral components connected to the holding member 6f. FIG. 14 is a sectional view parallel to FIG 8, which is cut along the center of the holding member 6f. The holding member 6f has a function of connecting the ground of the circuit board 4 to the heat sink 5. However, an insulating coating 52 is formed on the surface of the heat sink 5, and hence the holding member 6f cannot be brought into direct contact with the heat sink 5. Therefore, the circuit board 4 and the heat sink 5 are electrically connected to each other through an intermediation of the screw 20 and the plate spring 21. The plate spring 21 illustrated in FIG. 13 is formed of a conductive material such as a stainless steel plate for springs or phosphor bronze for springs. A slit 21s is provided on one end of the plate spring 21. The holding member 6f is press-fitted into the slit 21s to be secured. As a result, the holding member 6f and the plate spring 21 are electrically connected to each other. As illustrated in FIG. 14, the plate spring 21, to which the holding member 6f is fixed, is located between the housing 3 and a head of the screw 20, and is screwed together with the housing 3 to the heat sink 5 so as to be secured thereto. A screw hole provided through the heat sink 5 is not subjected to insulation processing, and hence the holding member 6f and the heat sink 5 are electrically connected to each other. A press-fit terminal 6fp is formed at the distal end of the holding member 6f, and is press-fitted into the through hole 4a of the circuit board 4. With the structure described above, the wiring pattern of the circuit board 4 and the heat sink 5 are electrically connected to each other through an intermediation of the press-fit terminal 6fp, the holding member 6f, the plate spring 21, and the screw 20. As illustrated in FIGS. 8 and 11, in this embodiment, the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep are located on the cover 7 side, whereas the laser-welded portions are located on the heat sink 5 side. With this structure, a distance between the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep and the laser-welded portions becomes long. Therefore, heat and reflected light, which are generated at the time of laser welding, and a shielding gas used at the time of laser welding, less affect the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep. Moreover, an insulating resin 3a and the circuit board 4 are interposed between the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep and the laser-welded portions, and hence the reflected light generated at the time of laser welding hardly reaches the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep. Moreover, the terminals VS, GT1, OUT, GT2, GND, 11, 12, 13, and 14 are welded to the conductive plates 6a, 6b, 6c, 6d, and 6e at the welded portions on lines which are apart from and parallel to center lines respectively passing through each of the centers of the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep (for example, dot lines illustrated in FIG. 11). As described above, the welded portions are located apart from the respective centers of the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep. In this manner, a load applied when the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep are press-fitted into the circuit board 4 can be prevented from directly acting on the welded portions. As a result, the distortion or peel-off of the welded portions can be prevented from occurring. The press-fit terminal portions 6ap, 6bp, 6cp, 6dp, 6ep, and 6fp are respectively press-fitted into the through holes 4a to mechanically hold the circuit board 4. Moreover, the respective base portions of the conductive plates 6a to 6f are formed by insert molding with the insulating resin 3a of the housing 3, and hence the insulating resin 3a is interposed between the heat sink 5 and the base portions of the conductive plates 6a to 6f when the press-fit terminals 6ap, 6bp, 6cp, 6dp, 6ep and 6fp are press-fitted into the circuit board 4, as illustrated in FIGS. 8, 11, and 14. Therefore, the press-fitting force can be received by the heat sink 5. However, depending on fabrication precision, a slight gap is generated between the insulating resin 3a and the heat sink 5. In the press-fitting, a relative height accuracy between the press-fit terminal portions 6ap, 6bp, 6cp, 6dp, 6ep, and 6fp and the circuit board 4 is important. However, the generation of the slight gap between the insulating resin 3a and the heat sink 5 degrades the relative height accuracy. Therefore, an adhesive (not shown) is applied to the gap so as to eliminate the effects of the gaps. In this embodiment, two press-fit terminals 6ap are formed on each of the power conductive plates 6a, one press-fit terminal 6bp is formed on each of the output conductive plates 6b, and one press-fit terminal 6cp is formed on each of the signal conductive plates 6c. Therefore, in total, seven press-fit terminals 6ap, 6bp, and 6cp are provided to each of the semiconductor switching elements 2. Moreover, the press-fit terminals 6ap, 6bp, and 6cp of the adjacent conductive plates 6a, 6b, and 6c are arranged in a zig-zag pattern. In this manner, a distance between the press-fit terminals 6ap, 6bp, and 6cp is increased to prevent the occurrence of a short-circuit between the terminals 6a, 6b, and 6c. Two press-fit terminals 6dp are formed on each of the conductive plates 6d for the single power connector terminal 12. Six press-fit terminals to be connected to the signal connector terminal 12 and five press-fit terminals so as to be connected to the sensor connector terminal 14 are formed on the conducive plates 6e. In total, eleven press-fit terminals 6ep are formed on the conductive plates 6e. Moreover, one press-fit terminal 6fp is formed on the holding member 6f. A diameter of each of the through holes 4a of the circuit board 4, into which the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6fp are pressed, is formed to be 1.45 mm. A diameter of each of the through holes 4b, into which the press-fit terminals 6ep are pressed, is formed to be 1 mm. In the electronic control apparatus 1 having the structure described above, when the microcomputer 41 generates the driving signal, the current flows through the circuit to cause each component to generate heat. At this time, the amount of heat generated by the coil 44, the capacitors 45, the relay 46, and the shunt resistor 47, which are electrically connected to the high-current circuit, is larger than that generated by the microcomputer 41, the power supply IC 42, and the driver IC 43, which are electrically connected to the low-current circuit. If these components are arranged within the same space, the microcomputer 41, the power supply IC 42, and the driver IC 43, which generate a small amount of heat, are affected by the heat generated from the coil 44, the capacitor 45, the relay 46, and the shunt resistor 47, which generate a large amount of heat. As a result, a temperature of each of the microcomputer 41, the power supply IC 42, and the driver IC 43 is increased. In this embodiment, the coil 44, the capacitors 45, the relay 46, and the shunt resistor 47, which correspond to the high-current components, are mounted on the surface of the circuit board 4, which is opposite to the surface on which the microcomputer 41, the power supply IC 42, and the driver IC 43 are mounted. In addition, the coil 44, the capacitors 45, and the relay 46 are provided on the circuit board 4 to be opposed to the surface of the heat sink 5, on which the semiconductor switching elements 2 are mounted. The positional relation of the current components provide on the circuit board 4 in this embodiment is illustrated in FIGS. 15 and 16. FIG. 15 illustrates another cross-section parallel to the cross-section of FIG. 8, and FIG. 16 illustrates a cross-section cut perpendicular to the cross-section of FIG. 15. As illustrated in FIG. 15, the coil 44, the capacitors 45, and the relay 46 are provided in a space surrounded by the respective inner wall surfaces of the circuit board 4, the heat sinl Moreover, as illustrated in FIG. 16, the shunt resistor 47 and the semiconductor switching elements 2 mounted on the heat sink 5 are also arranged within the same space. The surface of the circuit board 4, on which microcomputer 41, the power supply IC 42, and the driver IC 43 corresponding to the low-current components are mounted, is arranged so as to be opposed to the cover 7. Specifically, the microcomputer 41, the power supply IC 42, and the driver IC 43 are arranged in a space surrounded by the respective inner wall surfaces of the circuit board 4 and the cover 7. In this arrangement, the inner space of the electronic control apparatus 1, which is formed by the housing 3, the heat sink 5, and the cover 7, Is divided by the circuit board 4 into two spaces, that is, a space A accommodating the high-current components and a space B accommodating the low-current components. In the space A, the high-current components through which the high current flows, that is, the high-current components which generate a large amount of heat are accommodated. Therefore, a temperature in the space A becomes high. On the other hand, the low-current components which generate a small amount of heat are accommodated in the space B. In addition, the circuit board 4 plays a role as a heat insulator to insulate the heat from the space A. Therefore, a temperature in the space B becomes low. A small-sized high-performance integrated circuit is incorporated into each of the microcomputer 41, the power supply IC 42, and the driver IC 43. Therefore, the microcomputer 41, the power supply IC 42, and the driver IC 43 are more sensitive to heat as compared with the other current components. Therefore, the arrangement of the above-mentioned heat-sensitive components in the space B at a low temperature prevents the temperature from being increased by heat reception. A component having the lowest temperature among all the components constituting the electronic control apparatus 1 is the housing 3 which is a non-heat generating body and is made of an insulating resin having a low thermal conductivity. A thermal boundary, layer develops in the vicinity of the inner wall surfaces of the housing 3, and hence a low-temperature space having a temperature lower than that of the other part is formed in the vicinity of the inner wall surfaces of the housing 3. Moreover, it is apparent that the heat is more likely to be released to outside air because a distance between the vicinity of the inner wall surfaces and the outside air is smaller than that between the other part and the outside air. Specifically, when the current components to be mounted on the circuit board 4 are arranged in a peripheral portion of the circuit board 4, the current components are located in the vicinity of the inner wall surfaces of the housing 3. Therefore, heat release is accelerated so that an increase in temperature can be prevented. In particular, if the current components are arranged at the corners of the circuit boards 4, each of the current components is arranged in proximity to two of the inner wall surfaces of the housing 3. Therefore, the heat can be more effectively released. As a result, the electronic control apparatus 1 can be reduced in size and increased in output as well as in lifetime. FIG. 17 is a front view of the circuit board 4 in this embodiment. As can be seen from FIG. 17, the capacitors 45 are arranged at the corner of the circuit board 4, and hence the capacitors 45 are located in the vicinity of the corner formed by the inner walls of the housing 3 at the time of assembly. Moreover, the shunt resistor 47 is also arranged in the peripheral portion of the circuit board 4, and is located in the vicinity of the inner wall of the housing 3 at the time of assembly. Note that the components to be arranged in the peripheral portion of the circuit board 4 are not limited to the capacitors 45 and the shunt resistor 47. For example, the coil 44, the relay 46, the microcomputer 41, the power supply IC 42, and the driver IC 43 may be arranged in the peripheral portion of the circuit board 4 without any problem. Moreover, a plurality of the high-current components and the low-current components may be arranged in the peripheral portion of the circuit board 4 without any problem. Moreover, as illustrated in FIGS. 16 and 17, a connection point between each of the capacitors 45 and the wiring formed on the circuit board 4 and a connection point between the shunt resistor 47 and the wiring formed on the circuit board 4 are in proximity to each other. Therefore, the capacitors 45 and the shunt resistor 47 are arranged in proximity to each other on the circuit board 4, If a distance between the connection point between each of the capacitors 45 and the wiring and the connection point between the shunt resistor 47 and the wiring becomes long, an inductance of the system becomes greater, resulting in larger noise. Therefore, the capacitors 45 and the shunt resistor 47 are arranged to make a distance between the respective connection points be 3 mm or less. Moreover, the heat sink 5 includes a heat sink main body 51 and an anodized aluminum coating 52 corresponding to an insulating coating formed on a surface of the heat sink main body 51. The heat sink 5 is formed in the following manner. An elongated extruded profile is formed by extruding aluminum or aluminum alloy from a die. A heat sink material is fabricated by forming the anodized aluminum coating 52 in advance on an entire surface of the extruded profile. The heat sink material is cut into a desired length by a cutter, and then holes and the like are formed in the cut material using mechanical processing, thereby forming the heat sink 5. According to the fabrication method, it is unnecessary to form the anodized aluminum coating 52 for individual heat sink. Therefore, the fabrication steps are simplified to reduce the fabrication cost. The anodizing process is a surface treatment method for anodizing aluminum or aluminum alloy to form an insulating oxide coating on the surface. The metallic oxide coating generally has a high emissivity of about 0.8 to 0.9. Specifically, the heat release due to natural cooling and the heat release due to emission occur on the surface of the heat sink 5 which has been subjected to the anodizing process, and hence high heat release performance can be obtained. The heat sink 5 is fabricated by cutting a material on which the anodized aluminum coating 52 is already formed, and hence each end surface 5a is not subjected to the anodizing process. The metal generally has an emissivity of about 0.1 to 0.2, and hence sufficient heat release performance cannot be obtained even if each of the end surfaces 5a of the heat sink 5 is externally exposed. Therefore, each of the end surfaces 5a of the heat sink 5 is arranged to be opposed to an inner wall surface 3c of the opening portion of the housing 3 made of the insulating resin in proximity thereto. FIGS. 18 and 19 are perspective views, each illustrating a positional relation between the inner wall surface 3c of the housing 3 and each of the end surfaces 5a of the heat sink 5 in this embodiment. The insulating resin has a sufficiently high thermal emissivity in comparison with the metal. Moreover, a surface area of the housing 3 is sufficiently larger than that of the end surfaces 5a of the heat sink 5. Therefore, each of the end surfaces 5a of the heat sink 5 and the inner wall surface 3c of the housing 3 are brought into surface contact with each other. As a result, a large amount of heat from the heat sink 5 passes through the end surfaces 5a to smoothly flow into the housing 3 having a large heat releasing area and a high thermal emissivity to be externally released through the housing 3. Therefore, higher heat release performance can be obtained as compared with the case where the end surfaces 5a of the heat sink 5 are directly externally exposed. Note that, one lateral surface 5b of the heat sink 5, on which the anodized aluminum coating 52 is formed, is adapted to be externally exposed, as illustrated in FIG. 19. The the heat sink 5 includes the heat sink main body 51 made of aluminum or aluminum alloy having a high thermal conductivity, and hence a thermal resistance of the heat sink 5 Itself can be regarded as substantially zero. Moreover, the anodized aluminum coating 52 is formed of aluminum oxide (AL2O3) and has an extremely small thickness of about 10 ixm, and hence a thermal resistance of the anodized aluminum coating 52 can be regarded as substantially zero. The anodized aluminum coating 52 is formed on the surfaces except for on the end surfaces 5a of the heat sink 5. Specifically, the anodized aluminum coating 52 is formed even on the surface of the heat sink 5, on which the semiconductor switching elements 2 are mouthed, and the surface of the heat sink 5, which is opposed to the terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2. The anodized aluminum coating 52 has not only a role as an oxide coating for improving the emissivity but also a role as an insulating coating. Although the high current flows through the semiconductor switching elements 2, a short-circuit between the semiconductor switching elements 2 and the heat sink 5 can be prevented because the anodized aluminum coating 52 is formed on the surfaces of the heat sink 5. Moreover, even if an insulation failure due to a crack of the anodized aluminum coating 52 or the like occurs in the vicinity of the semiconductor switching elements 2, the surfaces of the heat sink 5 are insulated by the anodized aluminum coating 52 and the housing 3. Therefore, the heat sink 5 is not short-circuited with the semiconductor switching elements 2 from the exterior of the electronic control apparatus 1. As a result, the electronic control apparatus 1 with an improved insulating performance can be obtained. Although the heat sink 5 is fabricated by using an extruded profile in this embodiment, the heat sink 5 may be fabricated by using a hot- or cold-rolled plate material. Moreover, although the anodized aluminum coating 52 is used as the insulating coating, an insulating resin for pre-coating the heat sink 5 may be used as the insulating coating. Further, the surface of the heat sink 5 made of aluminum or aluminum alloy may be painted with a paint. For placing the semiconductor switching elements 2 on the heat sink 5, the semiconductor switching elements 2 are fixed through a thermally conductive adhesive (not shown) interposed between each heat spreader portion of each of the semiconductor switching elements 2 and the anodized aluminum coating 52 of the heat sink 5. Small concavity and convexity are present at the boundary between the heat sink 5 and each heat spreader, and hence a slight gap is generated even when each heat spreader portion Is brought into close contact with the heat sink 5. Therefore, an actual contact area is smaller than an apparent contact area. If the contact area becomes smaller, the thermal resistance in a heat transfer path for transferring the heat generated from the semiconductor switching elements 2 to the heat sink 5 becomes larger. Therefore, the heat release from the semiconductor switching elements 2 Is hindered. Therefore, the thermally conductive adhesive is filled in the gap. As a result, the thermal resistance between the semiconductor switching elements 2 and the heat sink 5 can be reduced to improve the heat release performance. Moreover, the semiconductor switching elements 2 and the heat sink 5 are fixed through the thermally conductive adhesive. As a result, for example, when an external force is applied to the electronic control apparatus 1 or vibrations occur in the electronic control apparatus 1, a stress applied to the welded portions of the semiconductor switching elements 2 is reduced. Moreover, the plate spring 21 has not only a role in connecting the ground of the circuit board 4 and the heat sink 5 to each other but also a role in securing the semiconductor switching elements 2 to the housing 3. FIG. 20 is a perspective view of a principal part, illustrating the plate spring 21 and the components in the periphery thereof. As illustrated in FIGS. 14, 16, and 20, a locking portion 21b of the plate spring 21 is locked to the holding portion 3b of the housing 3, and is also secured to the heat sink 5 by the screw 20 through an intermediation of the housing 3. At this time, pressure portions 21a of the plate spring 21 are pressed against resin package surfaces of the semiconductor switching elements 2. As a result, the thermally conductive adhesive is uniformly spread at a small thickness by the pressure of the plate spring 21. Thus, a variation in thermal resistance between the anodized aluminum coating 52 of the heat sink 5 and the semiconductor switching elements 2 can be reduced. Further, the semiconductor switching elements 2 are secured by the pressure of the plate spring 21 in addition to by an adhesive force of the thermally conductive adhesive, and hence the peel-off of the anodized aluminum coating 52, which is caused by a difference in thermal expansion between the heat sink 5 and the semiconductor switching elements 2, and the peel-off of the anodized aluminum coating 52, which is caused by the external force or the vibrations, can be prevented. Moreover, each of the semiconductor switching elements 2 includes the heat spreader portion which is electrically connected to the bridge output terminal OUT. At the same time, the semiconductor switching elements 2 are electrically insulated from the heat sink 5 by the anodized aluminum coating 52 and the highly thermally conductive adhesive. The cover 7 is formed of the same insulating resin as that used for the housing 3, and is welded to the opening portion of the housing 3 by an ultrasonic welder. The welding between the cover 7 and the housing 3 may be vibration welding using a vibration welder. The vibration welding is performed as follows. The cover 7 is caused to make reciprocating motions along a plane direction of the joint surface between the cover 7 and the housing 3. The resins of the cover 7 and the housing 3 are melted by frictional heat to bond the cover 7 and the housing 3 to each other. The vibration welding is used when the joint surface between the cover 7 and the housing 3 is large. Moreover, in place of the ultrasonic welding, laser welding using a laser welder may be used. The laser welding is used when the cover 7 is made of a material having a high laser transmittance and the housing 3 is made of a material having a high laser absorption rate. When the laser beam is radiated from the cover 7 side, the laser beam is transmitted through the cover 7 to be absorbed at the joint surface between the cover 7 and the housing 3 to generate heat. The generated heat is also transferred to the cover 7 side. As a result, the heat is also generated from the cover 7 to melt the cover 7 and the housing 3 at their joint surface to weld the cover 7 and the housing 3 to each other. The laser welding cannot be used in the case of resin molding with large warp or sink mark because it becomes difficult to focus the laser beam on the joint surface. In the case of resin molding with small warp or sink mark, however, the laser welding is advantageous in that there is no transfer of vibrations to the internal components because the welding itself generates neither burr nor vibration. As described above, according to the electronic control apparatus 1 of the first embodiment, the semiconductor switching elements 2 are mounted on the heat sink 5. Therefore, the heat release properties of the semiconductor switching elements 2 are improved. At the same time, a power substrate, which was conventionally required to mount the semiconductor switching elements 2 thereon, is no longer required. Therefore, a total height can be reduced to reduce the size of the electronic control apparatus 1. Moreover, the plurality of low-current components including the microcomputer 41 for controlling the driving of the semiconductor switching elements 2 are mounted on one of the surfaces of the circuit board 4, whereas the plurality of high-current components including the capacitors 45 are mounted on the other surface of the circuit board 4. Thus, both the high-current components and the low-current components are mounted on the single circuit board, and hence the total height can be further reduced to reduce the size of the electronic control apparatus 1. Moreover, the high-current components which generate a large amount of heat and the low-current components which generate a small amount of heat are separated from each other through an intermediation of the circuit board 4. The low-current components with a low thermal resistance are prevented from being affected by the heat from the high-current components. As a result, the lifetime of the electronic control apparatus 1 can be increased. Further, the low-current components are mounted on the surface of the circuit board 4, which is opposite to the surface opposed to the semiconductor switching elements 2, and hence the low-current components are also prevented from being affected by the heat from the semiconductor switching elements 2 through which the high current flows. As a result, the lifetime of the electronic control apparatus 1 can be further increased. Moreover, the capacitors 45 and the shunt resistor 47 are provided in the peripheral portion of the circuit board 4, and hence the heat release properties of the capacitors 45 and the shunt resistor 47 are improved. Moreover, the shunt resistor 47 and the capacitors 45 are mounted in proximity to each other on the circuit board 4, and hence the distance between the connection point of the shunt resistance 47 to the wiring and the connection point of each of the capacitors 45 to the wiring can be reduced. As a result, the inductance of the system can be reduced to prevent noise from occurring. Moreover, the anodized aluminum coating 52 is formed on the surface of the heat sink 5, on which the semiconductor switching elements 2 are mounted, and the surface on a back side thereof, the thermal emissivity of the heat sink 5 can be increased to improve the thermal emission properties of the heat sink 5. Moreover, each of the exposed end surfaces 5a of the heat sink 5, which does not have the anodized aluminum coating 52 thereon, is in surface contact with the inner wall surface 3c of the housing 3. Therefore, a large amount of heat from the heat sink 5 passes through the end surfaces 5a to smoothly flow into the housing 3 having the large heat release area and the high thermal emissivity. Then, the heat is externally released through the housing 3. Therefore, the heat release properties of the heat sink 5 are improved. Moreover, the heat sink 5 includes the heat sink main body 51 made of aluminum or aluminum alloy having the high thermal conductivity and the anodized aluminum coating 52 having the thermal resistance of substantially zero, which is formed on the surface of the heat sink main body 51. Therefore, the heat release properties of the heat sink 5 are high. Moreover, the semiconductor switching elements 2 are fixed onto the surface of the anodized aluminum coating 52 by using the thermally conductive adhesive, and hence the thermal resistance between the semiconductor switching elements 2 and the heat sink 5 is reduced. As a result, the heat release properties of the semiconductor switching elements 2 are improved. Moreover, when the external force is applied to the semiconductor switching elements 2, the stress on the welded portions of the semiconductor switching elements 2 is reduced. As a result, the connectability of the semiconductor switching elements 2 to the heat sink 5 is improved. Moreover, the semiconductor switching elements 2 are pressed against the heat sink 5 by the plate spring 21. Therefore, the semiconductor switching elements 2 and the heat sink 5 are firmly connected to each other. As a result, the peel-off of the semiconductor switching elements 2 due to a difference in thermal expansion between the semiconductor switching elements 2 and the heat sink 5 and due to the external force or the vibrations can be prevented from occurring. Moreover, the plate spring 21 is locked to the housing 3, and is also secured to the heat sink 5 by the screw 20 through an intermediation of the housing 3. Therefore, it can be ensured that the plate spring 21 presses the semiconductor switching elements 2 against the heat sink 5. Second Embodiment FIG. 21 is a sectional view illustrating a principal part of the electronic control apparatus 1 according to a second embodiment of the present invention. The electronic control apparatus 1 illustrated in FIG. 21 differs from the structure illustrated in FIG. 15 in that: each of the capacitors 45 corresponding to the high-current components is in contact with the heat sink 5 through an intermediation of an inclusion 45a; and the microcomputer 41, the power supply IC 42, and the driver IC 43 are in contact with the cover 7 respectively through an intermediation of inclusions 41a, 42a, and 43a. The remaining structure is the same as that of the first embodiment. In the electronic control apparatus 1 of the first embodiment illustrated in FIG. 15, the current components are in contact with the circuit board 4 only in a portion where the wiring pattern is provided. The surfaces of the other current components are exposed to air inside a casing formed by the housing 3, the heat sink 5, and the cover 7. Therefore, the most part of the heat generated from the current components is released to the air inside the housing 3. A thermal conductivity of air is 0.03 W/mK at a normal temperature, and is smaller than that of a solid. Moreover, the casing is sealed, and an air convection generated inside the casing is a natural convection generated by a difference in density of air, which is generated by a difference in temperature. A flow rate of the natural convection is generally 0.1 m/s or less, and therefore, heat releasing effects are extremely small. Specifically, if the air is present around the current components, the thermal resistance is increased to remarkably degrade the heat release performance. Thus, the capacitors 45 are brought into contact with the heat sink 5 through an intermediation of the inclusions 45a, whereas the microcomputer 41, the power supply IC 42, and the driver IC are brought into contact with the cover 7 respectively through an intermediation of the inclusions 41a, 42a, and 43a. As a result, the heat generated from each of the current components can be directly externally released by heat transfer without using the air convection with low heat release performance. However, the current components are fixed to the circuit board 4 by a solder. 25 and hence it is difficult to ensure sufficiently high height accuracy of the current components. If the height is small, sufficient contact effects cannot be obtained. On the other hand, if the height is too large, an excessive force is applied at the time of assembly to adversely break the current components. Moreover, even if the current components are brought into contact with the heat sink 5 or the cover 7, the actual contact area becomes smaller than the apparent contact area because a large number of extremely small concavity and convexity are present on the surfaces of the current components. When the contact area becomes small, the thermal resistance becomes large. As a result, it becomes difficult to obtain sufficiently high heat transfer performance. To cope with this problem, as illustrated in FIG. 21, for bringing the current components into contact with the heat sink 5 or the cover 7, a means is effective for interposing a gel-like material or an elastic material between the target components to bring the components into contact with each other. As the inclusion satisfying the conditions, for example, a thermally conductive grease, a thermally conductive adhesive, a heat-transfer sheet, or a heat-radiating rubber can be given. The above-mentioned materials can be deformed by the application of a pressure. Therefore, when the inclusion is applied or attached to a target position, the inclusion sandwiched between the current component and the heat sink 5 or the cover 7 is pressurized to be deformed at the time of assembly. As a result, the gap is filled to allow the components to come into contact with each other. Moreover, the inclusions 41a, 42a, 43a, and 45a of this embodiment are made of any of the thermally conductive grease, the thermally conductive adhesive, the heat transfer sheet, and the heat-radiating rubber. Therefore, with the improvement of the heat release performance, a speed of increase of the temperature of the current components can be lowered. The electronic control apparatus 1 is operated upon detection of the steering torque of the handle, and hence an unsteady operation in which a current value is instantaneously switched is repeated. Specifically, it is also supposed that the high current instantaneously flows. In such a case, it is considered that a temperature of a small-sized current component having a small thermal capacity suddenly increases to cause a malfunction. To cope with this problem, the current components are in contact with the heat sink 5 or the cover 7 through an intermediation of the inclusions 41a, 42a, 43a, and 45a. As a result, an apparent thermal capacity of each of the current components increases, and hence the speed of increase of the temperature of the current components can be lowered. In terms of a handle operation within the same period of time, the thermal capacity is increased with the presence of the inclusions 41a, 42a, 43a, and 45a. As a result, the speed of increase of the temperature of the current components is lowered, and hence a temperature increase value can be reduced. Moreover, in the electronic control apparatus 1 of the first embodiment, which is illustrated in FIG. 15, the current components are in contact with the circuit board 4 only in the portion where the wiring pattern is provided. Therefore, it is only the wiring pattern that supports the current components. Therefore, the current components are required to be supported by the extremely small portion in this structure, and hence there is a possibility that the stress due to the external force or the vibrations or a thermal stress due to thermal expansion occurs to damage or peel off the current components. On the other hand, in the second embodiment, the inclusions 41a, 42a, 43a, and 45a have the characteristics of the gel-like or elastic member. Therefore, an area for supporting the current components is increased. As a result, the effects of the stress caused by the external force or the vibrations or the thermal stress due to the thermal expansion can be reduced. Moreover, the effects of absorbing the vibrations and suppressing the thermal expansion owing to the spring effects of the inclusions 41 a, 42a, 43a, and 45a are also produced. Note that, although the capacitors 45 are in contact with the heat sink 5 through the inclusions 45a in the second embodiment, the capacitors 45 may be in contact with the housing 3 instead. Moreover, as in the case of the capacitors 45, the relay 46 corresponding to the high-current component may also be in contact with the heat sink 5 or the housing 3 through an intermediation of an inclusion. As described above, according to the electronic control apparatus 1 of the second embodiment, the cover 7 is attached to the end of the housing 3. in this manner, the housing 3, the heat sink 5, and the cover 7 constitute the casing. The high-current components and the low-current components provided in the casing are contact with the inner wall surfaces of the casing through an intermediation of the inclusions 41a, 42a, 43a, and 45a having a thermal conductivity, and hence the heat generated from each of the current components can be directly externally released by the heat transfer without using the air convection having the low heat release performance. Moreover, each of the inclusions 41a, 42a, 43a, and 45a is the gel-like or elastic material, and hence a variation in gap between the casing, and the high-current components and the low-current components is absorbed by the deformation at the time of assembly. Therefore, an excessive force is prevented from being applied to the casing, the high-current components, and the low-current components. Note that, although the externally exposed surface of the heat sink 5 is a plane in the first and second embodiments as illustrated in FIG. 19, radiating fins 5c may be provided on the externally exposed surface of the heat sink 5 as illustrated in FIG. 22 to improve the heat release properties of the heat sink 5. Note that, although each of the terminals VS, GT1, OUT, GT2, and GND and the connector terminals 11,12, 13, and 14 of the semiconductor switching elements 2 and the conductive plates 6a, 6b, 6c, 6d, and 6e are bonded to each other by the laser welding, the bonding may be performed by other welding methods such as resistance welding and TIG welding. Alternatively, the bonding may be performed by a method other than welding, such as ultrasonic bonding. Moreover, the half-bridge formed by integrating the high-side MOSFET 2H and the low-side MOSFET 2L is housed in one package to form the semiconductor switching element 2, and the two semiconductor switching elements 2 form a pair to constitute the bridge circuit for switching the current of the electric motor 22. However, the high-side MOSFET 2H and the low-side MOSFET 2L may be separately configured to allow four semiconductor switching elements 2 to constitute the bridge circuit. Alternatively, the bridge circuit may be constituted by six semiconductor switching elements 2 to control the driving of a three-phase brushless motor. Note that, although the semiconductor switching element 2 is used as the power device, other power devices such as a diode and a thyristor may be used. The example in which the present invention is applied to the electric power steering device for the automobile has been described in the above-mentioned embodiments. However, the present invention is also applicable to an electronic control apparatus dealing with the high current (for example, 25A or higher), which includes the power device, such as the electronic control apparatus for an anti-lock brake system (ABS) and the electronic control apparatus for air-conditioning, to obtain the same effects. Note that, the size, shape, and number of each of the components described above are mere examples. It is apparent that the size, shape, and number of each of the components are not limited thereto. WHAT IS CLAIMED IS: 1. An electronic control apparatus comprising: a housing made of an insulating resin, having opening portions on both ends; a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and a circuit board provided to be opposed to the heat sink, wherein a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a capacitor for absorbing a ripple of a current flowing through the power device are mounted on another surface of the circuit board. 2. An electronic control apparatus comprising: a housing made of an insulating resin, having opening portions on both ends; a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and a circuit board provided to be opposed to the heat sink, wherein a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a shunt resistor for detecting a current flowing through the power device are mounted on another surface of the circuit board. 3. An electronic control apparatus according to Claim 1 or 2, wherein the plurality of low-current components are mounted on the surface of the circuit board on a side opposite to the surface opposed to the power device. 4. An electronic control apparatus according to any one of Claims 1 to 3, wherein a coil for preventing electromagnetic noise, which is generated at time of driving of the power device, from leaking to an outside is mounted on the another surface of the circuit board. 5. An electronic control apparatus according to any one of Claims 1 to 4, wherein a relay for turning ON/OFF the current flowing through the power device is mounted on the another surface of the circuit board. 6. An electronic control apparatus according to any one of Claims 1 to 5, wherein at least one current component of the plurality of low-current components and the plurality of high-current components is provided in a peripheral portion of the circuit board. 7. An electronic control apparatus according to Claim 1, wherein a shunt resistor for detecting the current flowing through the power device is mounted on the another surface of the circuit board to be in proximity to the capacitor. 8. An electronic control apparatus according to any one of Claims 1 to 7, wherein a coating for increasing a thermal emissivity is formed on at least one of a surface of the heat sink, on which the power device is provided, and a surface on a back side thereof. 9. An electronic control apparatus according to Claim 8, wherein the heat sink has an exposed end surface without the coating, the exposed end surface being in surface contact with an inner wall surface of the housing. 10. An electronic control apparatus according to Claim 8 or 9, wherein the coating comprises an anodized aluminum coating. 11. An electronic control apparatus according to any one of Claims 1 to 10, wherein a radiating fin is formed on the surface of the heat sink, on a side opposite to the surface on which the power device is mounted. 12. An electronic control apparatus according to any one of Claims 1 to 11, wherein the heat sink comprises a heat sink main body made of any one of aluminum and aluminum alloy. 13. An electronic control apparatus according to any one of Claims 8 to 11, wherein the power device is fixed on a surface of the coating through an intermediation of a thermally conductive adhesive. 14. An electronic control apparatus according to any one of Claims 1 to 13, wherein the power device is pressed against the heat sink by a plate spring. 15. An electronic control apparatus according to Claim 14, wherein the plate spring is locked to the housing and is secured to the heat sink by a screw through an intermediation of the housing. 16. An electronic control apparatus according to any one of Claims 1 to 15, wherein a cover is attached to another of the ends of the housing to allow the housing, the heat sink, and the cover to constitute a casing, and wherein at lease one current component of the plurality of high-current components and the plurality of low-current components in the casing is in contact with an inner wall surface of the casing through an intermediation of an inclusion having a thermal conductivity. 17. An electronic control apparatus according to Claim 16, wherein the inclusion comprises any one of a gel-like material and an elastic material. 18. An electronic control apparatus according to any one of Claims 1 to 17, wherein the power device comprises a semiconductor switching element. 19. An electronic control apparatus according to any one of Claims 1 to 18, comprising an electric power steering device.

Full Text

ELECTRONIC CONTROL APPARATUS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic control apparatus used for, for example, an electric power steering device for assisting in biasing a steering device of a vehicle with a rotary force of an electric motor.
2. Description of the Related Art
Conventionally, there is known an electronic control apparatus, which includes a field effect transistor (FET) as a semiconductor switching element, which being a power device to be mounted on a metal substrate, and has a structure in which a connection member fixed onto the metal substrate, for electrically connecting the metal substrate and components provided outside the metal substrate to each other.
For example, an electronic control apparatus described in JP 3644835 B includes a power substrate, a housing, a control substrate, a connection member, a heat sink, and a case. On the power substrate, a bridge circuit including the semiconductor switching elements for switching a current of an electric motor is mounted. The housing includes a conductive plate or the like which is insert molding into an insulating resin and a high-current component mounted thereon. A low-current component such as a microcomputer is mounted on the control substrate. The connection member electrically connects the power substrate, and the housing and the control substrate to each other. The heat sink is brought into close contact with the power substrate. The case is formed by press molding of a metal plate to cover the power substrate, the housing, and the control substrate, and is attached to the heat sink.
In the electronic control apparatus described in JP 3644835 B, the power substrate on which the semiconductor switching elements are mounted, the housing on which the high-current components are mounted, and the control substrate on which the low-current components are mounted are required. Therefore, there is a problem that the size, complexity, and cost of the apparatus are increased by the increased number of components.

SUMJVIARY OF THE INVENTION
The present invention is devised to solve the problem described above, and has an object of providing an electronic control apparatus enabling a reduction in size, in complexity, and in cost as well as increases in output and in lifetime.
According to an aspect of the present invention, there is provided an electronic control apparatus including: a housing made of an insulating resin, having opening portions on both ends; a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and a circuit board provided to be opposed to the heat sink, in which a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a capacitor for absorbing a ripple of a current flowing through the power device are mounted on another surface of the circuit board.
According to another aspect of the present invention, there is provided an electronic control apparatus including: a housing made of an insulating resin, having opening portions on both ends; a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and a circuit board provided to be opposed to the heat sink, in which a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a shunt resistor for detecting a current flowing through the power device are mounted on another surface of the circuit board.
According to the electronic control apparatus of the present invention, the power device is mounted on the heat sink. At the same time, the low-current components are mounted on one of the surfaces of the circuit board, whereas the high-current components are mounted on the other surface of the circuit board. Therefore, in addition to a reduction in size, in complexity, and in cost, increases in output and in lifetime can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is an exploded perspective view illustrating an electronic control apparatus according to a first embodiment of the present invention;
FIG. 2 is an exploded perspective view of the electronic control apparatus illustrated in FIG. 1, which is viewed from a direction vertically opposite to a direction from which the exploded perspective view of FIG. 1 is viewed;
FIG. 3 is a side view of the electronic control apparatus illustrated in FIG. 1 when viewed from a vehicle connector side;
FIG. 4 is a side view of the electronic control apparatus illustrated in FIG. 1 when viewed from a motor connector side;
FIG. 5 is a perspective view of a housing of the electronic control apparatus illustrated in FIG. 1 when viewed from a direction of attachment of a heat sink;
FIG. 6 is an enlarged view of a principal part of FIG. 5;
FIG. 7 is a block diagram of the electronic control apparatus illustrated in FIG.
1
FIG. 8 is a side sectional view of the electronic control apparatus illustrated in
FIG. 1:
FIG. 9 is a perspective view illustrating the fixation between conductive plates and connector terminals of the electronic control apparatus illustrated in FIG. 1;
FIG. 10 is another perspective view illustrating the fixation between conductive plates and connector terminals of the electronic control apparatus illustrated in FIG. 1;
FIG. 11 is a side sectional view of the electronic control apparatus illustrated in FIG. 1, which is parallel to the side cross-section of FIG. 8;
FIG. 12 is a further perspective view illustrating the fixation between conductive plates and connector terminals of the electronic control apparatus illustrated in FIG. 1;
FIG. 13 is a perspective view illustrating the fixation between a holding member and a spring member of the electronic control apparatus illustrated in FIG. 1;
FIG. 14 is a side sectional view of the electronic control apparatus illustrated in FIG. 1, which is parallel to the side cross-section of FIG. 8;

FIG. 15 is a sectional view of the electronic control apparatus illustrated in FIG. 1, which is cut along a direction perpendicular to the side cross-section of FIG 8;
FIG. 16 is another side sectional view of the electronic control apparatus illustrated in FIG. 1, which is parallel to the side cross-section of FIG. 8;
FIG. 17 is a front view illustrating a circuit board of the electronic control apparatus illustrated in FIG. 1;
FIG. 18 is an exploded perspective view illustrating a positional relation between the heat sink and the housing of the electronic control apparatus illustrated in FIG. 1;
FIG. 19 is a perspective view illustrating the positional relation between the heat sink and the housing of the electronic control apparatus illustrated in FIG. 1;
FIG. 20 is a perspective view of the principal part of the electronic control apparatus illustrated in FIG. 1;
FIG. 21 is a side sectional view illustrating the electronic control apparatus according to a second embodiment of the present invention; and
FIG. 22 is a perspective view illustrating a modification of the electronic control apparatuses according to the first and second embodiments of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
Hereinafter, an electronic control apparatus according to each embodiment of the present invention is described based on the accompanying drawings. In each of the drawings, the same or eqgivalent components or parts are denoted by the same reference numerals for description.
In the first embodiment, an electronic control apparatus 1 is described as an example. The electronic control apparatus 1 is used for an electric power steering device for assisting in biasing a steering device for a vehicle with a rotary force of an electric motor.
FIG. 1 is an exploded perspective view illustrating the electronic control apparatus 1 according to a first embodiment of the present invention; FIG. 2 is an exploded perspective view of the electronic control apparatus 1 illustrated in FIG. 1,

which is viewed from a direction vertically opposite to a direction from which the exploded perspective view of FIG. 1 is viewed; FIG. 3 is a side view illustrating a side of the electronic control apparatus 1 illustrated in FIG. 1 where a vehicle connector 8 is provided; FIG. 4 is a side view illustrating a side of the electronic control apparatus 1 illustrated in FIG. 1 where a motor connector 9 and a sensor connector 10 are provided; FIG. 5 is a perspective view of a housing 3 of the electronic control apparatus 1 illustrated in FIG. 1 when viewed from a direction of attachment of a heat sink 5; FIG. 6 is an enlarged view of a principal part of FIG. 5; FIG. 7 is a block diagram of the electronic control apparatus 1 illustrated in FIG. 1; and FIG. 8 is a sectional view of the electronic control apparatus 1 illustrated in FIG. 1.
The electronic control apparatus 1 includes the housing 3, the heat sink 5, semiconductor switching elements 2, a circuit board 4, and a cover 7. The housing 3 is made of an insulating resin, and has opening portions formed on both ends. The heat sink 5 is made of aluminum, and is attached onto one of the ends of the housing 3 by using a screw 20. On a surface of the heat sink 5, an insulating coating is formed. Each of the semiconductor switching elements 2 corresponds to a power device. The semiconductor switching elements 2 are mounted on the heat sink 5, and are pressed toward the heat sink 5 by a plate spring 21. The circuit board 4 is provided to be opposed to the heat sink 5. In cooperation with the heat sink 5, the cover 7 accommodates the semiconductor switching elements 2 and the circuit board 4 therein.
On a surface of the circuit board 4 on the cover 7 side, a plurality of low-current components, through which a low current for signals flows, are mounted by soldering. The low-current components respectively correspond to, as illustrated in FIG. 1, a microcomputer 41, a power supply 10 42, and a driver 10 43. The microcomputer 41 calculates an assist torque based on a steering torque of a handle and a velocity of a vehicle, and provides feedback of a motor current to generate a driving signal corresponding to the assist torque. The power supply 10 42 drives the electronic control apparatus 1. The driver 10 43 controls an operation of each of the semiconductor switching elements 2.
On a surface of the circuit board 4 on the heat sink 5 side, a plurality of high-current components, through which a high current for driving a motor flows, are

mounted by soldering. The high-current components correspond to, as illustrated in FIG. 2, a coil 44, capacitors 45, a relay 46, and a shunt resistor 47. The coil 44 prevents electromagnetic noise, which is generated at the time of a switching operation of each of the semiconductor switching elements 2, from leaking to the outside. Each of the capacitors 45 absorbs a ripple of a current flowing through each of the semiconductor switching elements 2. The relay 46 turns ON and OFF a motor current supplied from a battery 24 through an intermediation of the semiconductor switching elements 2 of a bridge circuit to an electric motor 22. The shunt resistor 47 detects the current flowing through the semiconductor switching elements 2.
A current circuit of the circuit board 4 includes a high-current circuit and a low-current circuit. The high-current circuit, which is constituted by a wiring pattern, is electrically connected to the bridge circuit constituted by the semiconductor switching elements 2, the coil 44, the capacitors 45, the relay 46, and the shunt resistor 47. Through the high-current circuit, the high current for driving the motor flows. The low-current circuit, which is constituted by a wiring pattern, is electrically connected to the microcomputer 41, the power supply IC 42, and the driver 10 43. Through the low-current circuit, the low current for signals flows.
The electronic control apparatus 1 also includes the vehicle connector 8, the motor connector 9, and the sensor connector 10. The vehicle connector 8 is provided on one lateral surface of the housing 3, and is electrically connected to a wiring of the vehicle. The motor connector 9 is provided on the other lateral surface of the housing 3, and is electrically connected to the electric motor 22. The sensor connector 10 neighbors the motor connector 9, and is electrically connected to a torque sensor 23.
As illustrated in FIG. 3, the vehicle connector 8 includes a power connector terminal 11 and a signal connector terminal 12. The power connector terminal 11, which is electrically connected to the battery 24 of the vehicle, is made of copper or copper alloy at a thickness of 0.8 mm. The signal connector terminal 12 is made of phosphor bronze at a thickness of 0.64 mm. From/to the signal connector terminal 12, a signal is input/output through an intermediation of the wiring of the vehicle.
Moreover, as illustrated in FIG. 4, the motor connector 9 includes a motor

connector terminal 13, whereas the sensor connector 10 includes a sensor connector terminal 14. The motor connector terminal 13 is made of copper alloy or phosphor bronze having a high electrical conductivity at a thickness of 0.8 mm. The sensor connector terminal 14 is made of phosphor bronze at a thickness of 0.64 mm.
Further, as illustrated in FIG. 5, the electronic control apparatus 1 includes power conductive plates 6a, output conductive plates 6b, signal conductive plates 6c, and conductive plates 6d.
A base portion of each of the power conductive plates 6a, the output conductive plates 6b, and the signal conductive plates 6c is integrally formed with the housing 3 by insert molding. The power conductive plates 6a, the output conductive plates 6b, and the signal conductive plates 6c electrically connect the circuit board 4 and the semiconductor switching elements 2 to each other. A base portion of each of the conductive plates 6d is integrally formed with the housing 3 by the insert molding. The conductive plates 6d electrically connect the circuit board 4 and the power connector terminal 11 to each other.
The electronic control apparatus 1 also includes conductive plates 6e and a holding member 6f. The conductive plates 6e electrically connect the circuit board 4, and the signal connector terminal 12 and the sensor connector terminal 14 to each other. The holding member 6f has a role in connecting a ground of the circuit board 4 to the heat sink 5.
The components such as the power connector terminal 11, the signal connector terminal 12, the motor connector terminal 13, and the sensor connector terminal 14 are formed by the insert molding simultaneously with the insert molding of the power conductive plates 6a, the output conductive plates 6b, the signal conductive plates 6c, the conductive plates 6d and 6e and the holding member 6f for the formation of the housing 3. The vehicle connector 8, the motor connector 9, and the sensor connector 10 are integrally formed with the housing 3.
Moreover, on the lateral surface of the housing 3 on the opening portion side opposite to the opening portion to which the heat sink 5 is attached, attachment leg portions 3L for attaching the electronic control apparatus 1 to the vehicle corresponding to an attachment target body.
Terminals of each of the pair of lf»mpnt«; P nrnwiHprl

in parallel are arranged, from the right in FIG. 6, in the order of: a power supply terminal VS, a gate terminal GT1 of a high-side MOSFET 2H, a bridge output terminal OUT, a gate terminal GT2 of a low-side MOSFET 2L, and a ground terminal GND. The power supply terminal VS, the bridge output terminal OUT, and the ground terminal GND are high-current terminals through which a high current of up to about 50A flows to operate the electric motor 22, whereas the gate terminals GT1 and GT2 are low-current terminals through which a low current for signals, up to about 3A, flows. The high-current terminals and the low-current terminals are arranged alternately.
Each of the terminals OUT of the semiconductor switching elements 2 arranged in parallel is bent in the same crank-like shape with a standing portion and a lying portion in the middle, and extends in the same direction, as illustrated in FIG 8. The other terminals VS, GT1, GT2, and GND are also bent and extend in the same manner.
Each of the terminals VS, GT1, GT2, OUT, GT2, and GND of the semiconductor switching elements 2 is formed at a width of 0.8 mm, a thickness of 0.5 mm and intervals of 1.7 mm between the terminals.
As illustrated in FIG. 7, in each of the semiconductor switching elements 2, the high-side MOSFET 2H and the low-side MOSFET 2L are integrated to form a half-bridge. In each of the semiconductor switching elements 2, the half-bridge is housed within a single package. In addition, a pair of the semiconductor switching elements 2 constitute a bridge circuit for switching a current of the electric motor 22.
Moreover, as illustrated in FIGS. 5 and 6, a positioning portion 3d for positioning a main body of each of the semiconductor switching elements 2 and the housing 3 is formed within the housing 3.
The positioning portion 3d has a tapered portion at its distal end. The positioning portion 3d is guided by the tapered portion to be inserted into a hole 2a formed in the heat spreader of each of the semiconductor switching elements 2, thereby performing the positioning. The positioning portion 3d also performs the positioning for the direction in which each of the terminals VS, GT1, OUT, GT2, and GND extends.
Moreover, a pair of positioning portions 3e for positioning each of the

terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2 and the conductive plates 6a, 6b, and 6c are formed in a similar manner within the housing 3. The positioning portions 3e perform positioning for a direction perpendicular to the extending direction of each of the terminals VS, GT1, OUT, GT2, and GND. The positioning portions 3e are formed on both outer sides of the terminals VS and GND of each of the semiconductor switching elements 2. Each of the positioning portions 3e has a tapered portion at its distal end. The outer side of each of the terminals VS and GND of each of the semiconductor switching elements 2 is guided by the tapered portion to position each of the terminals VS, GT1, OUT, GT2, and GND and the conductive plates 6a, 6b, and 6c.
As illustrated in FIG. 6, the conductive plates 6a, 6b, and 6c are arranged to overlap the terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2 to extend in the same direction as the direction in which the terminals VS, GT1, OUT GT2, and GND extend. The terminals VS, GT1, OUT GT2, and GND and the conductive plates 6a, 6b, and 6c are arranged on the surface of the housing 3, which is opposite to the heat sink 5.
After the positioning and the fixation of the semiconductor switching elements 2 with the positioning portions 3d and 3e, the terminals VS, GT1, OUT, GT2, and GND and the semiconductor plates 6a, 6b, and 6c are welded to each other by, for example, laser welding.
The laser welding is performed by radiating a laser LB from the direction of attachment of the heat sink 5 toward the surfaces of the terminals VS, GT1, OUT, GT2, and GND prior to the attachment of the heat sink 5.
As illustrated in FIG. 6, proximal end portions of the power conductive plates 6a are respectively connected to a distal end portion of the power supply terminal VS and a distal end portion of the grand terminal GND of each of the semiconductor switching elements 2. A proximal end portion of the output conductive plate 6b is connected to a distal end portion of the bridge output terminal OUT. Proximal end portions of the signal conductive plates 6c are respectively connected to distal end portions of the gate terminals GT1 and GT2.
FIG. 9 is a perspective view of the conductive plates 6a, 6b, and 6c and the peripheral components connected thereto.

Press-fit terminals 6ap, a press-fit terminal 6bp, and press-fit terminals 6cp are respectively formed on the conductive plates 6a, 6b, and 6c. A wiring pattern made of a copper foil is formed on the circuit board 4, whereas a plurality of through holes 4a to be electrically connected to the wiring pattern are formed through the circuit board 4. An inner surface of each of the through holes 4a is plated with copper. The press-fit terminals 6ap, 6bp, and 6cp are press-fitted into the through holes 4a of the circuit board 4, respectively. As a result, the terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2 are electrically connected to the wiring pattern of the circuit board 4.
The power conductive plates 6a and the output conductive plates 6b are formed of rolled copper or copper alloy. A high current flows through the conductive plates 6a and 6b when the conductive plates 6a and 6b and the terminals VS, OUT, and GND of the semiconductor switching elements 2 are welded to each other. Therefore, it is necessary to ensure a sufficiently large volume for each of the conductive plates 6a and 6b.
In terms of formation of the press-fit terminals and the press working, however, it is difficult to increase the thickness of each of the conductive plates 6a and 6b. Therefore, in this embodiment, the thickness of each of the power conductive plates 6a and the output conductive plates 6b is set to 0.8 mm, which is the same value as that of the width of each of the terminals VS, OUT, and GND of the semiconductor switching elements 2. Thus, a width of each of the conductive plates 6a and 6b is formed larger than the thickness. In this manner, the conductive plates 6a and 6b are welded to the terminals VS, OUT, and GND of the semiconductor switching elements 2.
Note that, a low current flows through the conductive plates 6c used for signals, and hence it is unnecessary to take a reduction in electric resistance into consideration. However, those conductive plates 6c are made of the same material as that of the power conductive plates 6a and the output conductive plate 6b through which the high current flows.
As illustrated in FIGS. 8 and 9, the bridge output terminals OUT of the semiconductor switching elements 2 are respectively connected to the output conductive plates 6b.

Moreover, an end potion 13a of the motor connector terminal 13 is connected to an end of the proximal end portion of the output conductive plate 6b, which is on the side opposite to the bridge output terminal OUT. As in the case where the output conductive plate 6b is connected to the bridge output terminal OUT of each of the semiconductor switching elements 2, the end portion 13a of the motor connector terminal 13 is provided on the surface of the end portion of the output conductive plate 6b, which is opposed to the heat sink 5, and is welded thereto by radiating the laser beam LB from the direction of attachment of the heat sink 5 toward the surface of the motor connector terminal 13.
The motor current from the bridge output terminal OUT of each of the semiconductor switching elements 2 is adapted to directly flow into the electric motor 22 through the motor connector terminal 13 without passing through the circuit board 4.
In the middle portion of the output conductive plate 6b, the press-fit terminal 6bp extending toward the circuit board 4 is formed. Through the press-fit terminal 6bp, a signal for monitoring a voltage of the motor connector terminal 13 is output to the circuit board 4.
FIG. 10 is a perspective view illustrating the power source conductive plates 6d and the peripheral components connected thereto.
As illustrated in FIGS. 8 and 10, an end portion 11a of the power connector terminal 11 is connected to each of the power conductive plates 6d. As in the case where the output conductive plate 6b is connected to the end portion 13a of the motor connector terminal 13, the power connector terminal 11 is provided on a surface of the end portion of the power conductive plate 6d, which is opposed to the heat sink 5, and Is welded thereto by radiating the laser beam LB from the direction of attachment of the heat sink 5 toward the surface of the end portion 11a of the power connector terminal 11.
In the middle of each of the power source conductive plates 6d, the press-fit terminals 6dp extending toward the circuit board 4 are formed. The press-fit terminals 6dp are press-fitted into the through holes 4a of the circuit board 4 to be electrically connected to the wiring pattern of the circuit board 4. Then, the current from the battery 24 is supplied to the circuit board 4 through the power connector

terminal 11, the power source conductive plate 6d, and the press-fit terminals 6dp.
FIG. 11 is a sectional view parallel to FIG. 8, which is cut along the vehicle connector 8 and the sensor connector 10. FIG. 12 is a perspective view illustrating the conductive plates 6e and the peripheral components connected thereto.
As illustrated in FIGS. 11 and 12, the conductive plates 6e are caused to overlap end portions 12a of the signal connector terminal 12 and end portions 14a of the sensor connector terminal 14, respectively. The contact surfaces between the conductive plates 6e and the end portions 12a and 14a are formed in the vicinity of the heat sink 5 to be parallel to the heat sink 5.
At this time, the end portions 12a of the signal connector terminal 12 and the end portions 14a of the sensor connector terminal 14 are provided on the heat sink 5 side, and are welded thereto by radiating the laser LB from the direction of attachment of the heat sink 5 toward the surfaces of the end portions 12a of the signal connector terminal 12 and the end portions 14a of the sensor connector terminal 14.
Moreover, a press-fit terminal 6ep is formed on an end portion of each of the conductive plates 6e, which is on the side opposite to the welded portion. The press-fit terminals 6ep are press-fitted into through holes 4b of the circuit board 4 to electrically connect the signal connector terminal 12 and the sensor connector terminal 14, which are connected to the conductive plates 6e, to the wiring pattern of the circuit board 4.
FIG. 13 is a perspective view of the holding member 6f and the peripheral components connected to the holding member 6f. FIG. 14 is a sectional view parallel to FIG 8, which is cut along the center of the holding member 6f.
The holding member 6f has a function of connecting the ground of the circuit board 4 to the heat sink 5. However, an insulating coating 52 is formed on the surface of the heat sink 5, and hence the holding member 6f cannot be brought into direct contact with the heat sink 5. Therefore, the circuit board 4 and the heat sink 5 are electrically connected to each other through an intermediation of the screw 20 and the plate spring 21.
The plate spring 21 illustrated in FIG. 13 is formed of a conductive material such as a stainless steel plate for springs or phosphor bronze for springs. A slit 21s

is provided on one end of the plate spring 21. The holding member 6f is press-fitted into the slit 21s to be secured. As a result, the holding member 6f and the plate spring 21 are electrically connected to each other. As illustrated in FIG. 14, the plate spring 21, to which the holding member 6f is fixed, is located between the housing 3 and a head of the screw 20, and is screwed together with the housing 3 to the heat sink 5 so as to be secured thereto.
A screw hole provided through the heat sink 5 is not subjected to insulation processing, and hence the holding member 6f and the heat sink 5 are electrically connected to each other.
A press-fit terminal 6fp is formed at the distal end of the holding member 6f, and is press-fitted into the through hole 4a of the circuit board 4.
With the structure described above, the wiring pattern of the circuit board 4 and the heat sink 5 are electrically connected to each other through an intermediation of the press-fit terminal 6fp, the holding member 6f, the plate spring 21, and the screw 20.
As illustrated in FIGS. 8 and 11, in this embodiment, the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep are located on the cover 7 side, whereas the laser-welded portions are located on the heat sink 5 side.
With this structure, a distance between the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep and the laser-welded portions becomes long. Therefore, heat and reflected light, which are generated at the time of laser welding, and a shielding gas used at the time of laser welding, less affect the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep.
Moreover, an insulating resin 3a and the circuit board 4 are interposed between the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep and the laser-welded portions, and hence the reflected light generated at the time of laser welding hardly reaches the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep.
Moreover, the terminals VS, GT1, OUT, GT2, GND, 11, 12, 13, and 14 are welded to the conductive plates 6a, 6b, 6c, 6d, and 6e at the welded portions on lines which are apart from and parallel to center lines respectively passing through each of the centers of the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep (for example, dot lines illustrated in FIG. 11). As described above, the welded portions are located

apart from the respective centers of the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep. In this manner, a load applied when the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6ep are press-fitted into the circuit board 4 can be prevented from directly acting on the welded portions. As a result, the distortion or peel-off of the welded portions can be prevented from occurring.
The press-fit terminal portions 6ap, 6bp, 6cp, 6dp, 6ep, and 6fp are respectively press-fitted into the through holes 4a to mechanically hold the circuit board 4.
Moreover, the respective base portions of the conductive plates 6a to 6f are formed by insert molding with the insulating resin 3a of the housing 3, and hence the insulating resin 3a is interposed between the heat sink 5 and the base portions of the conductive plates 6a to 6f when the press-fit terminals 6ap, 6bp, 6cp, 6dp, 6ep and 6fp are press-fitted into the circuit board 4, as illustrated in FIGS. 8, 11, and 14. Therefore, the press-fitting force can be received by the heat sink 5. However, depending on fabrication precision, a slight gap is generated between the insulating resin 3a and the heat sink 5.
In the press-fitting, a relative height accuracy between the press-fit terminal portions 6ap, 6bp, 6cp, 6dp, 6ep, and 6fp and the circuit board 4 is important. However, the generation of the slight gap between the insulating resin 3a and the heat sink 5 degrades the relative height accuracy. Therefore, an adhesive (not shown) is applied to the gap so as to eliminate the effects of the gaps.
In this embodiment, two press-fit terminals 6ap are formed on each of the power conductive plates 6a, one press-fit terminal 6bp is formed on each of the output conductive plates 6b, and one press-fit terminal 6cp is formed on each of the signal conductive plates 6c. Therefore, in total, seven press-fit terminals 6ap, 6bp, and 6cp are provided to each of the semiconductor switching elements 2.
Moreover, the press-fit terminals 6ap, 6bp, and 6cp of the adjacent conductive plates 6a, 6b, and 6c are arranged in a zig-zag pattern. In this manner, a distance between the press-fit terminals 6ap, 6bp, and 6cp is increased to prevent the occurrence of a short-circuit between the terminals 6a, 6b, and 6c.
Two press-fit terminals 6dp are formed on each of the conductive plates 6d for the single power connector terminal 12. Six press-fit terminals to be connected

to the signal connector terminal 12 and five press-fit terminals so as to be connected to the sensor connector terminal 14 are formed on the conducive plates 6e. In total, eleven press-fit terminals 6ep are formed on the conductive plates 6e.
Moreover, one press-fit terminal 6fp is formed on the holding member 6f. A diameter of each of the through holes 4a of the circuit board 4, into which the press-fit terminals 6ap, 6bp, 6cp, 6dp, and 6fp are pressed, is formed to be 1.45 mm. A diameter of each of the through holes 4b, into which the press-fit terminals 6ep are pressed, is formed to be 1 mm.
In the electronic control apparatus 1 having the structure described above, when the microcomputer 41 generates the driving signal, the current flows through the circuit to cause each component to generate heat. At this time, the amount of heat generated by the coil 44, the capacitors 45, the relay 46, and the shunt resistor 47, which are electrically connected to the high-current circuit, is larger than that generated by the microcomputer 41, the power supply IC 42, and the driver IC 43, which are electrically connected to the low-current circuit. If these components are arranged within the same space, the microcomputer 41, the power supply IC 42, and the driver IC 43, which generate a small amount of heat, are affected by the heat generated from the coil 44, the capacitor 45, the relay 46, and the shunt resistor 47, which generate a large amount of heat. As a result, a temperature of each of the microcomputer 41, the power supply IC 42, and the driver IC 43 is increased.
In this embodiment, the coil 44, the capacitors 45, the relay 46, and the shunt resistor 47, which correspond to the high-current components, are mounted on the surface of the circuit board 4, which is opposite to the surface on which the microcomputer 41, the power supply IC 42, and the driver IC 43 are mounted. In addition, the coil 44, the capacitors 45, and the relay 46 are provided on the circuit board 4 to be opposed to the surface of the heat sink 5, on which the semiconductor switching elements 2 are mounted.
The positional relation of the current components provide on the circuit board 4 in this embodiment is illustrated in FIGS. 15 and 16. FIG. 15 illustrates another cross-section parallel to the cross-section of FIG. 8, and FIG. 16 illustrates a cross-section cut perpendicular to the cross-section of FIG. 15.
As illustrated in FIG. 15, the coil 44, the capacitors 45, and the relay 46 are

provided in a space surrounded by the respective inner wall surfaces of the circuit board 4, the heat sinl Moreover, as illustrated in FIG. 16, the shunt resistor 47 and the semiconductor switching elements 2 mounted on the heat sink 5 are also arranged within the same space.
The surface of the circuit board 4, on which microcomputer 41, the power supply IC 42, and the driver IC 43 corresponding to the low-current components are mounted, is arranged so as to be opposed to the cover 7. Specifically, the microcomputer 41, the power supply IC 42, and the driver IC 43 are arranged in a space surrounded by the respective inner wall surfaces of the circuit board 4 and the cover 7.
In this arrangement, the inner space of the electronic control apparatus 1, which is formed by the housing 3, the heat sink 5, and the cover 7, Is divided by the circuit board 4 into two spaces, that is, a space A accommodating the high-current components and a space B accommodating the low-current components.
In the space A, the high-current components through which the high current flows, that is, the high-current components which generate a large amount of heat are accommodated. Therefore, a temperature in the space A becomes high. On the other hand, the low-current components which generate a small amount of heat are accommodated in the space B. In addition, the circuit board 4 plays a role as a heat insulator to insulate the heat from the space A. Therefore, a temperature in the space B becomes low.
A small-sized high-performance integrated circuit is incorporated into each of the microcomputer 41, the power supply IC 42, and the driver IC 43. Therefore, the microcomputer 41, the power supply IC 42, and the driver IC 43 are more sensitive to heat as compared with the other current components.
Therefore, the arrangement of the above-mentioned heat-sensitive components in the space B at a low temperature prevents the temperature from being increased by heat reception.
A component having the lowest temperature among all the components constituting the electronic control apparatus 1 is the housing 3 which is a non-heat generating body and is made of an insulating resin having a low thermal conductivity.

A thermal boundary, layer develops in the vicinity of the inner wall surfaces of the housing 3, and hence a low-temperature space having a temperature lower than that of the other part is formed in the vicinity of the inner wall surfaces of the housing
3. Moreover, it is apparent that the heat is more likely to be released to outside air
because a distance between the vicinity of the inner wall surfaces and the outside air
is smaller than that between the other part and the outside air.
Specifically, when the current components to be mounted on the circuit board 4 are arranged in a peripheral portion of the circuit board 4, the current components are located in the vicinity of the inner wall surfaces of the housing 3. Therefore, heat release is accelerated so that an increase in temperature can be prevented. In particular, if the current components are arranged at the corners of the circuit boards
4, each of the current components is arranged in proximity to two of the inner wall
surfaces of the housing 3. Therefore, the heat can be more effectively released.
As a result, the electronic control apparatus 1 can be reduced in size and increased
in output as well as in lifetime.
FIG. 17 is a front view of the circuit board 4 in this embodiment.
As can be seen from FIG. 17, the capacitors 45 are arranged at the corner of the circuit board 4, and hence the capacitors 45 are located in the vicinity of the corner formed by the inner walls of the housing 3 at the time of assembly.
Moreover, the shunt resistor 47 is also arranged in the peripheral portion of the circuit board 4, and is located in the vicinity of the inner wall of the housing 3 at the time of assembly.
Note that the components to be arranged in the peripheral portion of the circuit board 4 are not limited to the capacitors 45 and the shunt resistor 47. For example, the coil 44, the relay 46, the microcomputer 41, the power supply IC 42, and the driver IC 43 may be arranged in the peripheral portion of the circuit board 4 without any problem.
Moreover, a plurality of the high-current components and the low-current components may be arranged in the peripheral portion of the circuit board 4 without any problem.
Moreover, as illustrated in FIGS. 16 and 17, a connection point between each of the capacitors 45 and the wiring formed on the circuit board 4 and a connection

point between the shunt resistor 47 and the wiring formed on the circuit board 4 are in proximity to each other. Therefore, the capacitors 45 and the shunt resistor 47 are arranged in proximity to each other on the circuit board 4,
If a distance between the connection point between each of the capacitors 45 and the wiring and the connection point between the shunt resistor 47 and the wiring becomes long, an inductance of the system becomes greater, resulting in larger noise. Therefore, the capacitors 45 and the shunt resistor 47 are arranged to make a distance between the respective connection points be 3 mm or less.
Moreover, the heat sink 5 includes a heat sink main body 51 and an anodized aluminum coating 52 corresponding to an insulating coating formed on a surface of the heat sink main body 51.
The heat sink 5 is formed in the following manner. An elongated extruded profile is formed by extruding aluminum or aluminum alloy from a die. A heat sink material is fabricated by forming the anodized aluminum coating 52 in advance on an entire surface of the extruded profile. The heat sink material is cut into a desired length by a cutter, and then holes and the like are formed in the cut material using mechanical processing, thereby forming the heat sink 5.
According to the fabrication method, it is unnecessary to form the anodized aluminum coating 52 for individual heat sink. Therefore, the fabrication steps are simplified to reduce the fabrication cost.
The anodizing process is a surface treatment method for anodizing aluminum or aluminum alloy to form an insulating oxide coating on the surface.
The metallic oxide coating generally has a high emissivity of about 0.8 to 0.9.
Specifically, the heat release due to natural cooling and the heat release due to emission occur on the surface of the heat sink 5 which has been subjected to the anodizing process, and hence high heat release performance can be obtained.
The heat sink 5 is fabricated by cutting a material on which the anodized aluminum coating 52 is already formed, and hence each end surface 5a is not subjected to the anodizing process. The metal generally has an emissivity of about 0.1 to 0.2, and hence sufficient heat release performance cannot be obtained even if each of the end surfaces 5a of the heat sink 5 is externally exposed.
Therefore, each of the end surfaces 5a of the heat sink 5 is arranged to be

opposed to an inner wall surface 3c of the opening portion of the housing 3 made of the insulating resin in proximity thereto.
FIGS. 18 and 19 are perspective views, each illustrating a positional relation between the inner wall surface 3c of the housing 3 and each of the end surfaces 5a of the heat sink 5 in this embodiment.
The insulating resin has a sufficiently high thermal emissivity in comparison with the metal. Moreover, a surface area of the housing 3 is sufficiently larger than that of the end surfaces 5a of the heat sink 5.
Therefore, each of the end surfaces 5a of the heat sink 5 and the inner wall surface 3c of the housing 3 are brought into surface contact with each other. As a result, a large amount of heat from the heat sink 5 passes through the end surfaces 5a to smoothly flow into the housing 3 having a large heat releasing area and a high thermal emissivity to be externally released through the housing 3. Therefore, higher heat release performance can be obtained as compared with the case where the end surfaces 5a of the heat sink 5 are directly externally exposed.
Note that, one lateral surface 5b of the heat sink 5, on which the anodized aluminum coating 52 is formed, is adapted to be externally exposed, as illustrated in FIG. 19.
The the heat sink 5 includes the heat sink main body 51 made of aluminum or aluminum alloy having a high thermal conductivity, and hence a thermal resistance of the heat sink 5 Itself can be regarded as substantially zero.
Moreover, the anodized aluminum coating 52 is formed of aluminum oxide (AL2O3) and has an extremely small thickness of about 10 ixm, and hence a thermal resistance of the anodized aluminum coating 52 can be regarded as substantially zero.
The anodized aluminum coating 52 is formed on the surfaces except for on the end surfaces 5a of the heat sink 5.
Specifically, the anodized aluminum coating 52 is formed even on the surface of the heat sink 5, on which the semiconductor switching elements 2 are mouthed, and the surface of the heat sink 5, which is opposed to the terminals VS, GT1, OUT, GT2, and GND of the semiconductor switching elements 2. The anodized aluminum coating 52 has not only a role as an oxide coating for improving the emissivity but

also a role as an insulating coating.
Although the high current flows through the semiconductor switching elements 2, a short-circuit between the semiconductor switching elements 2 and the heat sink 5 can be prevented because the anodized aluminum coating 52 is formed on the surfaces of the heat sink 5.
Moreover, even if an insulation failure due to a crack of the anodized aluminum coating 52 or the like occurs in the vicinity of the semiconductor switching elements 2, the surfaces of the heat sink 5 are insulated by the anodized aluminum coating 52 and the housing 3. Therefore, the heat sink 5 is not short-circuited with the semiconductor switching elements 2 from the exterior of the electronic control apparatus 1. As a result, the electronic control apparatus 1 with an improved insulating performance can be obtained.
Although the heat sink 5 is fabricated by using an extruded profile in this embodiment, the heat sink 5 may be fabricated by using a hot- or cold-rolled plate material.
Moreover, although the anodized aluminum coating 52 is used as the insulating coating, an insulating resin for pre-coating the heat sink 5 may be used as the insulating coating.
Further, the surface of the heat sink 5 made of aluminum or aluminum alloy may be painted with a paint.
For placing the semiconductor switching elements 2 on the heat sink 5, the semiconductor switching elements 2 are fixed through a thermally conductive adhesive (not shown) interposed between each heat spreader portion of each of the semiconductor switching elements 2 and the anodized aluminum coating 52 of the heat sink 5. Small concavity and convexity are present at the boundary between the heat sink 5 and each heat spreader, and hence a slight gap is generated even when each heat spreader portion Is brought into close contact with the heat sink 5. Therefore, an actual contact area is smaller than an apparent contact area.
If the contact area becomes smaller, the thermal resistance in a heat transfer path for transferring the heat generated from the semiconductor switching elements 2 to the heat sink 5 becomes larger. Therefore, the heat release from the semiconductor switching elements 2 Is hindered.

Therefore, the thermally conductive adhesive is filled in the gap. As a result, the thermal resistance between the semiconductor switching elements 2 and the heat sink 5 can be reduced to improve the heat release performance.
Moreover, the semiconductor switching elements 2 and the heat sink 5 are fixed through the thermally conductive adhesive. As a result, for example, when an external force is applied to the electronic control apparatus 1 or vibrations occur in the electronic control apparatus 1, a stress applied to the welded portions of the semiconductor switching elements 2 is reduced.
Moreover, the plate spring 21 has not only a role in connecting the ground of the circuit board 4 and the heat sink 5 to each other but also a role in securing the semiconductor switching elements 2 to the housing 3.
FIG. 20 is a perspective view of a principal part, illustrating the plate spring 21 and the components in the periphery thereof.
As illustrated in FIGS. 14, 16, and 20, a locking portion 21b of the plate spring 21 is locked to the holding portion 3b of the housing 3, and is also secured to the heat sink 5 by the screw 20 through an intermediation of the housing 3.
At this time, pressure portions 21a of the plate spring 21 are pressed against resin package surfaces of the semiconductor switching elements 2. As a result, the thermally conductive adhesive is uniformly spread at a small thickness by the pressure of the plate spring 21. Thus, a variation in thermal resistance between the anodized aluminum coating 52 of the heat sink 5 and the semiconductor switching elements 2 can be reduced.
Further, the semiconductor switching elements 2 are secured by the pressure of the plate spring 21 in addition to by an adhesive force of the thermally conductive adhesive, and hence the peel-off of the anodized aluminum coating 52, which is caused by a difference in thermal expansion between the heat sink 5 and the semiconductor switching elements 2, and the peel-off of the anodized aluminum coating 52, which is caused by the external force or the vibrations, can be prevented.
Moreover, each of the semiconductor switching elements 2 includes the heat spreader portion which is electrically connected to the bridge output terminal OUT. At the same time, the semiconductor switching elements 2 are electrically insulated from the heat sink 5 by the anodized aluminum coating 52 and the highly thermally

conductive adhesive.
The cover 7 is formed of the same insulating resin as that used for the housing 3, and is welded to the opening portion of the housing 3 by an ultrasonic welder.
The welding between the cover 7 and the housing 3 may be vibration welding using a vibration welder.
The vibration welding is performed as follows. The cover 7 is caused to make reciprocating motions along a plane direction of the joint surface between the cover 7 and the housing 3. The resins of the cover 7 and the housing 3 are melted by frictional heat to bond the cover 7 and the housing 3 to each other.
The vibration welding is used when the joint surface between the cover 7 and the housing 3 is large.
Moreover, in place of the ultrasonic welding, laser welding using a laser welder may be used.
The laser welding is used when the cover 7 is made of a material having a high laser transmittance and the housing 3 is made of a material having a high laser absorption rate.
When the laser beam is radiated from the cover 7 side, the laser beam is transmitted through the cover 7 to be absorbed at the joint surface between the cover 7 and the housing 3 to generate heat. The generated heat is also transferred to the cover 7 side. As a result, the heat is also generated from the cover 7 to melt the cover 7 and the housing 3 at their joint surface to weld the cover 7 and the housing 3 to each other.
The laser welding cannot be used in the case of resin molding with large warp or sink mark because it becomes difficult to focus the laser beam on the joint surface. In the case of resin molding with small warp or sink mark, however, the laser welding is advantageous in that there is no transfer of vibrations to the internal components because the welding itself generates neither burr nor vibration.
As described above, according to the electronic control apparatus 1 of the first embodiment, the semiconductor switching elements 2 are mounted on the heat sink 5. Therefore, the heat release properties of the semiconductor switching elements 2 are improved. At the same time, a power substrate, which was

conventionally required to mount the semiconductor switching elements 2 thereon, is no longer required. Therefore, a total height can be reduced to reduce the size of the electronic control apparatus 1.
Moreover, the plurality of low-current components including the microcomputer 41 for controlling the driving of the semiconductor switching elements 2 are mounted on one of the surfaces of the circuit board 4, whereas the plurality of high-current components including the capacitors 45 are mounted on the other surface of the circuit board 4. Thus, both the high-current components and the low-current components are mounted on the single circuit board, and hence the total height can be further reduced to reduce the size of the electronic control apparatus 1.
Moreover, the high-current components which generate a large amount of heat and the low-current components which generate a small amount of heat are separated from each other through an intermediation of the circuit board 4. The low-current components with a low thermal resistance are prevented from being affected by the heat from the high-current components. As a result, the lifetime of the electronic control apparatus 1 can be increased.
Further, the low-current components are mounted on the surface of the circuit board 4, which is opposite to the surface opposed to the semiconductor switching elements 2, and hence the low-current components are also prevented from being affected by the heat from the semiconductor switching elements 2 through which the high current flows. As a result, the lifetime of the electronic control apparatus 1 can be further increased.
Moreover, the capacitors 45 and the shunt resistor 47 are provided in the peripheral portion of the circuit board 4, and hence the heat release properties of the capacitors 45 and the shunt resistor 47 are improved.
Moreover, the shunt resistor 47 and the capacitors 45 are mounted in proximity to each other on the circuit board 4, and hence the distance between the connection point of the shunt resistance 47 to the wiring and the connection point of each of the capacitors 45 to the wiring can be reduced. As a result, the inductance of the system can be reduced to prevent noise from occurring.
Moreover, the anodized aluminum coating 52 is formed on the surface of the heat sink 5, on which the semiconductor switching elements 2 are mounted, and the

surface on a back side thereof, the thermal emissivity of the heat sink 5 can be increased to improve the thermal emission properties of the heat sink 5.
Moreover, each of the exposed end surfaces 5a of the heat sink 5, which does not have the anodized aluminum coating 52 thereon, is in surface contact with the inner wall surface 3c of the housing 3. Therefore, a large amount of heat from the heat sink 5 passes through the end surfaces 5a to smoothly flow into the housing 3 having the large heat release area and the high thermal emissivity. Then, the heat is externally released through the housing 3. Therefore, the heat release properties of the heat sink 5 are improved.
Moreover, the heat sink 5 includes the heat sink main body 51 made of aluminum or aluminum alloy having the high thermal conductivity and the anodized aluminum coating 52 having the thermal resistance of substantially zero, which is formed on the surface of the heat sink main body 51. Therefore, the heat release properties of the heat sink 5 are high.
Moreover, the semiconductor switching elements 2 are fixed onto the surface of the anodized aluminum coating 52 by using the thermally conductive adhesive, and hence the thermal resistance between the semiconductor switching elements 2 and the heat sink 5 is reduced. As a result, the heat release properties of the semiconductor switching elements 2 are improved.
Moreover, when the external force is applied to the semiconductor switching elements 2, the stress on the welded portions of the semiconductor switching elements 2 is reduced. As a result, the connectability of the semiconductor switching elements 2 to the heat sink 5 is improved.
Moreover, the semiconductor switching elements 2 are pressed against the heat sink 5 by the plate spring 21. Therefore, the semiconductor switching elements 2 and the heat sink 5 are firmly connected to each other. As a result, the peel-off of the semiconductor switching elements 2 due to a difference in thermal expansion between the semiconductor switching elements 2 and the heat sink 5 and due to the external force or the vibrations can be prevented from occurring.
Moreover, the plate spring 21 is locked to the housing 3, and is also secured to the heat sink 5 by the screw 20 through an intermediation of the housing 3. Therefore, it can be ensured that the plate spring 21 presses the semiconductor

switching elements 2 against the heat sink 5.
Second Embodiment
FIG. 21 is a sectional view illustrating a principal part of the electronic control apparatus 1 according to a second embodiment of the present invention.
The electronic control apparatus 1 illustrated in FIG. 21 differs from the structure illustrated in FIG. 15 in that: each of the capacitors 45 corresponding to the high-current components is in contact with the heat sink 5 through an intermediation of an inclusion 45a; and the microcomputer 41, the power supply IC 42, and the driver IC 43 are in contact with the cover 7 respectively through an intermediation of inclusions 41a, 42a, and 43a.
The remaining structure is the same as that of the first embodiment.
In the electronic control apparatus 1 of the first embodiment illustrated in FIG. 15, the current components are in contact with the circuit board 4 only in a portion where the wiring pattern is provided. The surfaces of the other current components are exposed to air inside a casing formed by the housing 3, the heat sink 5, and the cover 7.
Therefore, the most part of the heat generated from the current components is released to the air inside the housing 3. A thermal conductivity of air is 0.03 W/mK at a normal temperature, and is smaller than that of a solid.
Moreover, the casing is sealed, and an air convection generated inside the casing is a natural convection generated by a difference in density of air, which is generated by a difference in temperature. A flow rate of the natural convection is generally 0.1 m/s or less, and therefore, heat releasing effects are extremely small.
Specifically, if the air is present around the current components, the thermal resistance is increased to remarkably degrade the heat release performance.
Thus, the capacitors 45 are brought into contact with the heat sink 5 through an intermediation of the inclusions 45a, whereas the microcomputer 41, the power supply IC 42, and the driver IC are brought into contact with the cover 7 respectively through an intermediation of the inclusions 41a, 42a, and 43a. As a result, the heat generated from each of the current components can be directly externally released by heat transfer without using the air convection with low heat release performance.
However, the current components are fixed to the circuit board 4 by a solder.
25

and hence it is difficult to ensure sufficiently high height accuracy of the current components. If the height is small, sufficient contact effects cannot be obtained. On the other hand, if the height is too large, an excessive force is applied at the time of assembly to adversely break the current components.
Moreover, even if the current components are brought into contact with the heat sink 5 or the cover 7, the actual contact area becomes smaller than the apparent contact area because a large number of extremely small concavity and convexity are present on the surfaces of the current components. When the contact area becomes small, the thermal resistance becomes large. As a result, it becomes difficult to obtain sufficiently high heat transfer performance.
To cope with this problem, as illustrated in FIG. 21, for bringing the current components into contact with the heat sink 5 or the cover 7, a means is effective for interposing a gel-like material or an elastic material between the target components to bring the components into contact with each other. As the inclusion satisfying the conditions, for example, a thermally conductive grease, a thermally conductive adhesive, a heat-transfer sheet, or a heat-radiating rubber can be given.
The above-mentioned materials can be deformed by the application of a pressure. Therefore, when the inclusion is applied or attached to a target position, the inclusion sandwiched between the current component and the heat sink 5 or the cover 7 is pressurized to be deformed at the time of assembly. As a result, the gap is filled to allow the components to come into contact with each other.
Moreover, the inclusions 41a, 42a, 43a, and 45a of this embodiment are made of any of the thermally conductive grease, the thermally conductive adhesive, the heat transfer sheet, and the heat-radiating rubber. Therefore, with the improvement of the heat release performance, a speed of increase of the temperature of the current components can be lowered.
The electronic control apparatus 1 is operated upon detection of the steering torque of the handle, and hence an unsteady operation in which a current value is instantaneously switched is repeated.
Specifically, it is also supposed that the high current instantaneously flows. In such a case, it is considered that a temperature of a small-sized current component having a small thermal capacity suddenly increases to cause a

malfunction.
To cope with this problem, the current components are in contact with the heat sink 5 or the cover 7 through an intermediation of the inclusions 41a, 42a, 43a, and 45a. As a result, an apparent thermal capacity of each of the current components increases, and hence the speed of increase of the temperature of the current components can be lowered.
In terms of a handle operation within the same period of time, the thermal capacity is increased with the presence of the inclusions 41a, 42a, 43a, and 45a. As a result, the speed of increase of the temperature of the current components is lowered, and hence a temperature increase value can be reduced.
Moreover, in the electronic control apparatus 1 of the first embodiment, which is illustrated in FIG. 15, the current components are in contact with the circuit board 4 only in the portion where the wiring pattern is provided. Therefore, it is only the wiring pattern that supports the current components. Therefore, the current components are required to be supported by the extremely small portion in this structure, and hence there is a possibility that the stress due to the external force or the vibrations or a thermal stress due to thermal expansion occurs to damage or peel off the current components.
On the other hand, in the second embodiment, the inclusions 41a, 42a, 43a, and 45a have the characteristics of the gel-like or elastic member. Therefore, an area for supporting the current components is increased. As a result, the effects of the stress caused by the external force or the vibrations or the thermal stress due to the thermal expansion can be reduced.
Moreover, the effects of absorbing the vibrations and suppressing the thermal expansion owing to the spring effects of the inclusions 41 a, 42a, 43a, and 45a are also produced.
Note that, although the capacitors 45 are in contact with the heat sink 5 through the inclusions 45a in the second embodiment, the capacitors 45 may be in contact with the housing 3 instead.
Moreover, as in the case of the capacitors 45, the relay 46 corresponding to the high-current component may also be in contact with the heat sink 5 or the housing 3 through an intermediation of an inclusion.

As described above, according to the electronic control apparatus 1 of the second embodiment, the cover 7 is attached to the end of the housing 3. in this manner, the housing 3, the heat sink 5, and the cover 7 constitute the casing. The high-current components and the low-current components provided in the casing are contact with the inner wall surfaces of the casing through an intermediation of the inclusions 41a, 42a, 43a, and 45a having a thermal conductivity, and hence the heat generated from each of the current components can be directly externally released by the heat transfer without using the air convection having the low heat release performance.
Moreover, each of the inclusions 41a, 42a, 43a, and 45a is the gel-like or elastic material, and hence a variation in gap between the casing, and the high-current components and the low-current components is absorbed by the deformation at the time of assembly. Therefore, an excessive force is prevented from being applied to the casing, the high-current components, and the low-current components.
Note that, although the externally exposed surface of the heat sink 5 is a plane in the first and second embodiments as illustrated in FIG. 19, radiating fins 5c may be provided on the externally exposed surface of the heat sink 5 as illustrated in FIG. 22 to improve the heat release properties of the heat sink 5.
Note that, although each of the terminals VS, GT1, OUT, GT2, and GND and the connector terminals 11,12, 13, and 14 of the semiconductor switching elements 2 and the conductive plates 6a, 6b, 6c, 6d, and 6e are bonded to each other by the laser welding, the bonding may be performed by other welding methods such as resistance welding and TIG welding.
Alternatively, the bonding may be performed by a method other than welding, such as ultrasonic bonding.
Moreover, the half-bridge formed by integrating the high-side MOSFET 2H and the low-side MOSFET 2L is housed in one package to form the semiconductor switching element 2, and the two semiconductor switching elements 2 form a pair to constitute the bridge circuit for switching the current of the electric motor 22. However, the high-side MOSFET 2H and the low-side MOSFET 2L may be separately configured to allow four semiconductor switching elements 2 to constitute

the bridge circuit.
Alternatively, the bridge circuit may be constituted by six semiconductor switching elements 2 to control the driving of a three-phase brushless motor.
Note that, although the semiconductor switching element 2 is used as the power device, other power devices such as a diode and a thyristor may be used.
The example in which the present invention is applied to the electric power steering device for the automobile has been described in the above-mentioned embodiments. However, the present invention is also applicable to an electronic control apparatus dealing with the high current (for example, 25A or higher), which includes the power device, such as the electronic control apparatus for an anti-lock brake system (ABS) and the electronic control apparatus for air-conditioning, to obtain the same effects.
Note that, the size, shape, and number of each of the components described above are mere examples. It is apparent that the size, shape, and number of each of the components are not limited thereto.

WHAT IS CLAIMED IS:
1. An electronic control apparatus comprising:
a housing made of an insulating resin, having opening portions on both ends;
a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and
a circuit board provided to be opposed to the heat sink,
wherein a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a capacitor for absorbing a ripple of a current flowing through the power device are mounted on another surface of the circuit board.
2. An electronic control apparatus comprising:
a housing made of an insulating resin, having opening portions on both ends;
a heat sink attached to one of the ends of the housing, the heat sink having a surface on a housing side, on which a power device is mounted; and
a circuit board provided to be opposed to the heat sink,
wherein a plurality of low-current components including a microcomputer for controlling driving of the power device are mounted on one surface of the circuit board, whereas a plurality of high-current components including a shunt resistor for detecting a current flowing through the power device are mounted on another surface of the circuit board.
3. An electronic control apparatus according to Claim 1 or 2, wherein the plurality of low-current components are mounted on the surface of the circuit board on a side opposite to the surface opposed to the power device.
4. An electronic control apparatus according to any one of Claims 1 to 3, wherein a coil for preventing electromagnetic noise, which is generated at time of driving of the power device, from leaking to an outside is mounted on the another surface of the circuit board.

5. An electronic control apparatus according to any one of Claims 1 to 4, wherein a relay for turning ON/OFF the current flowing through the power device is mounted on the another surface of the circuit board.
6. An electronic control apparatus according to any one of Claims 1 to 5, wherein at least one current component of the plurality of low-current components and the plurality of high-current components is provided in a peripheral portion of the circuit board.
7. An electronic control apparatus according to Claim 1, wherein a shunt resistor for detecting the current flowing through the power device is mounted on the another surface of the circuit board to be in proximity to the capacitor.
8. An electronic control apparatus according to any one of Claims 1 to 7, wherein a coating for increasing a thermal emissivity is formed on at least one of a surface of the heat sink, on which the power device is provided, and a surface on a back side thereof.
9. An electronic control apparatus according to Claim 8, wherein the heat sink has an exposed end surface without the coating, the exposed end surface being in surface contact with an inner wall surface of the housing.

10. An electronic control apparatus according to Claim 8 or 9, wherein the coating comprises an anodized aluminum coating.
11. An electronic control apparatus according to any one of Claims 1 to 10, wherein a radiating fin is formed on the surface of the heat sink, on a side opposite to the surface on which the power device is mounted.
12. An electronic control apparatus according to any one of Claims 1 to 11, wherein the heat sink comprises a heat sink main body made of any one of aluminum and aluminum alloy.

13. An electronic control apparatus according to any one of Claims 8 to 11,
wherein the power device is fixed on a surface of the coating through an
intermediation of a thermally conductive adhesive.
14. An electronic control apparatus according to any one of Claims 1 to 13,
wherein the power device is pressed against the heat sink by a plate spring.
15. An electronic control apparatus according to Claim 14, wherein the plate
spring is locked to the housing and is secured to the heat sink by a screw through an
intermediation of the housing.
16. An electronic control apparatus according to any one of Claims 1 to 15,
wherein a cover is attached to another of the ends of the housing to allow the
housing, the heat sink, and the cover to constitute a casing, and
wherein at lease one current component of the plurality of high-current components and the plurality of low-current components in the casing is in contact with an inner wall surface of the casing through an intermediation of an inclusion having a thermal conductivity.
17. An electronic control apparatus according to Claim 16, wherein the
inclusion comprises any one of a gel-like material and an elastic material.
18. An electronic control apparatus according to any one of Claims 1 to 17,
wherein the power device comprises a semiconductor switching element.
19. An electronic control apparatus according to any one of Claims 1 to 18,
comprising an electric power steering device.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=DYdI+IFlSBkhBgKu+MMVWQ==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

272125

Indian Patent Application Number

2100/CHE/2009

PG Journal Number

13/2016

Publication Date

25-Mar-2016

Grant Date

18-Mar-2016

Date of Filing

31-Aug-2009

Name of Patentee

MITSUBISHI ELECTRIC CORPORATION

Applicant Address

7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310

Inventors:

#	Inventor's Name	Inventor's Address
1	ITO, SHINICHI	C/O MITSUBISHI ELECTRIC CORPORATION, 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310
2	TOMINAGA,TSUTOMU	C/O MITSUBISHI ELECTRIC CORPORATION, 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310
3	KIFUKU, TAKAYUKI	C/O MITSUBISHI ELECTRIC CORPORATION, 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310
4	AKIYAMA, SHUZO	C/O MITSUBISHI ELECTRIC CORPORATION, 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 102-0073
5	TANIGAWA, MASAAKI	C/O MITSUBISHI ELECTRIC ENGINEERING COMPANY, LIMITED, 1-13-5, KUDANKITA, CHIYODA-KU, TOKYO 102-0073

PCT International Classification Number

B62D 5/04

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2009-138343	2009-06-09	Japan