Title of Invention

A COOLING DEVICE FOR A HIGH-POWER SEMICONDUCTOR MODULE AND A METHOD FOR PRODUCING THE SAME

Abstract

A cooling device for a high-power semiconductor module, with the cooling device having a cooler lower part (1) and a cooler upper part (2), with the cooler lower part (1) being made of metal, with the cooler upper part (2) having a cooling plate (20) composed of a metal matrix composite, for at least one semiconductor component (4) to be placed on it, and the cooler upper part (2) comprising a metal border (21) surroUnding the cooling plate (20) on its periphery, the cooling plate (20) being infiltrated with the metal of metal border (21), forming a single piece upper part; wherein the cooler upper part (2) being connected to the cooler lower part (1) by an integral ma~erial connection between the metal border (21) and the cooler lower part (1). This results in a cooling device which can be produced easily and whose cost is low.

Full Text

FIELD OF THE INVENTION The invention relates to a cooling device for a high-power semiconductor module and a method for producing a cooling device for a high-power semiconductor module. The invention relates to the field of power electronics. DISCUSSION OF BACKGROUND High-power semiconductor modules, such as those that are known fi-om EP-A-0,597,144, have a number of semiconductor components (for example thyristors, IGBTs or diodes) which are combined in a common housing to form a logical functional unit. Such high-power semiconductor modules are nowadays operated in a voltage range up to 6.5 kV, and require appropriate cooling. To this end, the semiconductor components are soldered on a common cooling device, through which a cooling hquid generally flows. Heat sinks composed of aluminum are generally used as the cooling devices. However, aluminum has the disadvantage that its themial coefficient of expansion is not matched to the corresponding coefficients of the semiconductor components, in particular to their electrical insulation plates or to the semiconductor chips. In consequence, mechanical stresses occur which lead to fatigue in the solder layers between the semiconductor components and the cooling device, and thus to the electrical contacts becoming detached. DE-A-196,43,717 therefore proposes a cooling device whose thermal coefficient of expansion is matched to that of the semiconductor components. A cooling device is used for this purpose which is produced from a metal matrix composite, in particular from aluminum silicon-carbide (AlSiC) or copper silicon carbide (CuSiC). The production of such a metal ceramic composite material is described, for example, in James A. Comic, Advanced Pressure Infiltration Casting Technology Produces Near-absolute Net-Shape Metal Matrix Composite Components Cost Competitively, Materials Technology, Vol. 10, No. 34, March/April, 1995. This cooling device preferably has cooling elements in the form of studs or ribs, in order to increase the cooling area and thus to improve the heat transfer, so that it has a relatively complex geometry. In a first embodiment, the cooling device is cast integrally from the metal matrix composite. However, cooling devices such as this are relatively expensive, since, particularly if they have complex geometries, their production is expensive and, furthermore, they are composed of relatively expensive material, In another embodiment, only a cooling plate is composed of the metal matrix composite and the remainder is manufactured from a low-cost material, in particular from plastic, with the two parts being bonded together. A disadvantage of this embodiment is that the bonded joint is subject to age-dependent fatigue phenomena. A further cooling device is known from EP-A-0,661,917. This cooling device comprises a cooler lower part and a cooler upper part, with the cooler lower part being connected to the cooler upper part by an integral material connection. Both cooler parts are composed of a metal matrix composite (MMC), for example aluminum silicon-carbide. The integral material connection between the cooler parts is produced during the production process. For this purpose, ceramic preforms of the cooler parts are produced first of all, these are then placed one on top of the other, and metal is then infiltrated into both parts. The joint infiltration is intended to allow the metal to flow through the pores of both parts by capillary action, and thus to connect them together. Owing to the complexity of their production and owing to the choice of the material, these cooling devices are also relatively expensive. Since the quality of the connection depends on the capillary action, it is, furthermore, difficult to produce a sufficiently dense composite, depending on the shape of the cooler parts. SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a cooling device of the type mentioned initially, which can be produced at low cost and easily. This object is achieved by a cooling device as described herein, and by a method for producing a cooling device as described herein. Accordingly the present invention provides a cooling device for a high-power semiconductor module, with the cooling device having a cooler lower part and a cooler upper part, with the cooler lower part being made of metal, with the cooler upper part having a cooling plate composed of a metal matrix composite, for at least one semiconductor component to be placed on it, and the cooler upper part comprising a metal border surrounding the cooling plate on its periphery, the cooling plate being infiltrated with the metal of metal border, forming a single piece upper part; wherein the cooler upper part being cormected to the cooler lower part by an integral material connection between the metal border and the cooler lower part. Accordingly the invention also provides a method for producing a cooling device for a high-power semiconductor module, with a cooler lower part and a cooler upper part being formed, and the cooler upper part and the cooler lower part being connected to one another by an integral material connection, wherein in order to form the cooler upper part a cooling plate is produced from a metal matrix composite and a solid metal border is integrally formed on it, and in that the cooler upper part is connected to the cooler lower part by means of the metal border. The cooling device according to the invention comprises a cooler lower part and a cooler upper part, with the cooler upper part having a cooling plate composed of a metal matrix composite, preferably aluminum-silicon carbide, on which a metal border is integrally formed. The two cooler parts are in this case connected to one another via the metal border by an integral material connection. The cooling plate and the metal border can be manufactured in the same production step by using excess metal to form the metal border during metal infiltration of a ceramic preform in order to form the cooling plate. The metal border which is integrally formed on the cooling plate allows a strong and long-lasting connection to be produced in a simple way between the cooler upper part and the cooler lower part. The cooler lower part can be produced from low-cost materia! which is easy to form and process, in particular from aluminum. Suitable choice of the material for the cooler lower part allows stresses and faults in the connection to be avoided. The cooler lower part is preferably manufactured from the same material as the cooler upper part. Friction welding is preferred as the connection method, since this leads only to a local influence from heat in the cooling device. Such a cooling device combines the advantages of the already known cooling elements composed of metal matrix composite with the advantages of the already known aluminum cooler and can be produced simply and at low cost. The special border allows it to be connected to the cooler lower part in a simple manner, and faults can be avoided. Further advantageous embodiments are described herein. BRIEF DESCRIPTION OF THE DRAWINGS The subject matter of the invention will be explained in more detail in the following text with reference to a preferred exemplary embodiment which is illustrated in the attached drawings in which: FIG. 1 shows a cross section through a cooling device according to the invention; FIG. 2 shows a perspective illustration of the cooling device shown in FIG. 1 from above, and FIG. 3 shows a cross section through a mold for producing a cooling plate provided with a metal border. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show a cooling device according to the invention. This comprises a cooler lower part 1 in the form of a half-shell and a cooler upper part 2 which is essentially in the form of a plate. The cooler upper part 1 and lower part 2 enclose a cavity 3 through which a cooling medium can preferably flow, in particular water. The inlet and outlet openings 10, 11 required for this purpose are arranged in the cooler lower part I. The cooler lower part I is produced from a low-cost material which can be formed easily, in particular from a metal, for example from aluminum or copper. In the example illustrated here, the cooler lower part 1 has a rectangular outline, but other shapes are also possible. The cooler upper part 2 has a cooling plate 20 composed of a metal matrix composite, in particular of a silicon carbide composite. The cooling plate 20 is preferably composed of aluminum silicon-carbide (AlSiC). Other materials, such as copper silicon carbide (CuSiC) or copper carbide (CuC) may, however, also be used. An upper surface 20" of the cooling plate 20, facing away from the cooler lower part 1, is designed to be planar and is used to place semiconductor components 4 on it, for example IGBTs, thyristors or diodes. The semiconductor components 4 are preferably soldered directly on to the cooling plate 20. This presents no problems, particularly if the semiconductor components 4 have a lower face composed of aluminum nitrite (AIN), since this material has a similar thermal coefficient of expansion to that of aluminum silicon-carbide (AlSiC). Cooling elements 22 in the form of studs or cooling ribs, which are used to increase the heat transfer, are provided on the lower face of the cooling plate 20, facing the cooler lower part 1. The cooling plate 20 is completely surrounded by a metal edge 21 on its end surfaces 20". The metal border 21 is preferably composed of the same metal as that which has already been used for the metal matrix composite, in particular of aluminum (Al). The cooler lower part 1 is preferably also composed of the same metal. Typically thicknesses for the cooling plate 20 are 2-4 mm. The width b of the metal border is typically 5-20 mm. The metal border 21 and the cooling plate 20 are preferably of the same thickness. As shown in FIG. 2, the cooling plate 20 and the metal border 21 are shaped to be rectangular. However, other shapes are possible. The cooler upper part 2 lies on the cooler lower part 1 and is connected to it by an integral material connection. The connection, which is annotated by 5 in FIG. 1, is in this case produced via the metal border 21. In the exemplary embodiment illustrated here, the metal border 21 is designed to be planar and hes on a step 12 which runs round the periphery of the cooler lower part 1. However, other shapes are possible. The cooler upper part 2 can be manufactured in a simple way by producing the cooling plate 20 from a metal matrix composite and by the metal border 21 being integrally formed on it. The production of the metal border 21 and the production of the metal matrix composite can be carried out in the same process step. A preferred variant of the method will be described with reference to FIG. 3. A preform in the form of a porous ceramic plate 2" is placed in an excessively large mold 6 so that the end surfaces 20" of the ceramic plate 2" form an intermediate space 7, which runs around the periphery, with the walls 60 of the mold 6. As was normal in the prior art, the ceramic plate 2" is now infiltrated with metal 8. In the process, metal 8 is also cast into the intermediate space 7. The subsequent solidification of the metal results in the production firstly of the cooling plate 20, which is composed of a metal matrix composite, and, secondly, of the metal border 21. The shape of the metal border 21 can be selected by the choice of the mold 6. To produce the cooling device, the metal border 21 of the cooler upper part 2 now just has to be connected to the lower part I. Friction welding is suitable for this purpose, particularly if aluminum is used for the metal border 21 and the cooler lower part 1. The cooling device according to the invention and having an AlSiC plate and the cast-on aluminum border allows low-cost and simple production and ensures a tight connection which is resistant to aeeina. WE CLAIM : 1. A cooling device for a high-power semiconductor module, with the cooling device having a cooler lower part (1) and a cooler upper part (2), with the cooler lower part (1) being made of metal, with the cooler upper part (2) having a cooling plate (20) composed of a metal matrix composite, for at least one semiconductor component (4) to be placed on it, and the cooler upper part (2) comprising a metal border (21) surrounding the cooling plate (20) on its periphery, the cooling plate (20) being infiltrated with the metal of metal border (21), forming a single piece upper part; wherein the cooler upper part (2) being connected to the cooler lower part (1) by an integral material connection between the metal border (21) and the cooler lower part (])■ 2. The cooling device as claimed in claim 1, wherein said lower part (2) is made of the same metal as the solid metal border (21). 3. The cooling device as claimed in claim 1, wherein said soUd metal border (21) has a width in a range of from 5 to 20 mm. 4. The cooling device as claimed in claim 1, wherein said solid metal border (21) and the cooling plate (20) each have a thickness in a range of from 2 to 4 mm. 5. The cooling device as claimed in claim 1, wherein the cooling plate (20) is composed of copper silicon-carbide (CuSiC) or copper carbide (CuC) composite material. 6. The coohng device as claimed in claim 1, wherein the cooling plate (20) is composed of Aluminum-Silicon-carbide (AlSiC) and the solid metal border (21) is composed of Aluminum (Al). 7. A method for producing a cooling device for a high-power semiconductor module, with a cooler lower part (1) and a cooler upper part (2) being formed, and the cooler upper part (2) and the cooler lower part (1) being connected to one another by an integral material connection, wherein in order to form the cooler upper part (2) a cooling plate (20) is produced from a metal matrix composite and a solid metal border (21) is integrally formed on it, and in that the cooler upper part is connected to the cooler lower part (1) by means of the metal border (21). 8. The method as claimed in claim 7, wherein, in order to produce the cooler upper part (2), a porous ceramic plate (2") is placed in a mold (6), with end surfaces (20") of the ceramic plate (2") forming an intermediate space (7), which runs round the periphery of the ceramic plate (2"), with walls (60) of the mold (6), and in that metal (8) is cast onto the ceramic plate (2") and into the intermediate space (7), and the metal (8) is solidified. 9. The method as claimed in claim 8, wherein the metal (8) is introduced by means of pressure infiltration. 10. The method as claimed in claim 7, wherein the metal border (21) is connected to the cooler lower part (1) by means of friction welding. 11. A cooling device for a high-power semiconductor module, substantially as hereinabove described and illustrated with reference to the accompanying drawings. 12. A method for producing a cooling device for a high-power semiconductor module, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

129-mas-2001 abstract-duplicate.pdf

129-mas-2001 abstract.jpg

129-mas-2001 abstract.pdf

129-mas-2001 claims-duplicate.pdf

129-mas-2001 claims.pdf

129-mas-2001 correspondence-others.pdf

129-mas-2001 correspondence-po.pdf

129-mas-2001 description (complete)-duplicate.pdf

129-mas-2001 description (complete).pdf

129-mas-2001 drawings-duplicate.pdf

129-mas-2001 drawings.pdf

129-mas-2001 form-1.pdf

129-mas-2001 form-18.pdf

129-mas-2001 form-26.pdf

129-mas-2001 form-3.pdf

129-mas-2001 form-5.pdf

129-mas-2001 form-6.pdf

129-mas-2001 others.pdf

129-mas-2001 petition.pdf