Title of Invention

ELECTRONICS PACKAGING SYSTEM

Abstract

An electronics packaging system [1] comprising: a printer [3] to print solder to either land of a printed wiring board [2], wherein the printed wiring board [2] is held in a upright position; a placing unit [4] to place electronic parts on the lands of the printed wiring board [2], having the solder printed thereon by the printer [3]; and a reflow unit [5] to heat the printed wiring board [2] on which the electronic parts [10] have been placed by the placing unit [4] and solder the electronic parts [10] to the printed wiring board [2].

Full Text

FORM 2 THE PATENTS ACT 1970 [39 OF 1970] & THE PATENTS RULES, 2003 as amended by THE PATENTS [AMENDMENT] RULES, 2006 COMPLETE SPECIFICATION [See Section 10, Rule 13] "ELECTRONICS PACKAGING SYSTEM" SONY CORPORATION, a Japanese company of 7-35 Kitashinagawa 6-chome, Shinagawa-ku, Tokyo 141-0001, Japan, The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- The present invention relates to an electronic packaging system. Technical Field The present invention generally relates to an electronics packaging system for packaging electronic parts on a printed wiring board. Background Art Conventionally, cream solder is printed by a screen printing on the land of a printed wiring board on which electronic parts are to be mounted. As shown in FIG. 41, each of printers, generally indicated with a reference 300, used to print cream solder includes a transfer mechanism to bring a printed wiring board 301 while keeping it in horizontal position, a screen mechanism 303 provided opposite to the printed wiring board 301 being brought by the transfer mechanism 302, and a squeegee mechanism 304 to squeeze the cream solder from the screen mechanism 303 to the printed wiring board 301. First, the printed wiring board 301 is brought with one side thereof being directed opposite to the screen mechanism 303. When the printed wiring board 301 is brought to a predetermined position, the screen mechanism 303 is placed close to the printed wiring board 301, then the squeegee mechanism 304 is moved in the direction of arrow X in FIG. 41 to squeeze the cream solder to the printed wiring board 301. Thus the cream solder is printed on the printed wiring board 301. To print cream solder on the land on the other side of the printed wiring board 301, first the printed wiring board 301 is inverted for the other side thereof to be opposite to the screen mechanism 303. Next, the printer 300 used to print cream solder on the one side of the printed wiring board 301 is used to print cream solder on the land on the other side of the printed wiring board 301 in a similar manner. However, in case the printer 300 once used to print cream solder on the one side of the printed wiring board is used again to print cream solder on the land of the printed wiring board, the screen mechanism 303 is replaced with a screen mechanism 303 having formed thereon a pattern prepared for the other side of the printed wiring board 301 to print cream solder, by screen printing, to the land on the other side of the board 301. To print cream solder to either side of the printed wiring board 301 as in the above, a printer 300 has to be used for each side of the printed wiring board 301 in one pass, so that the electronics packaging system can hardly be designed more compact. Also, since cream solder has to be printed on each side of the printed wiring board 301 in one pass, the electronics packaging system can hardly package electronic parts with a further improved efficiency. An electronics packaging system generally indicated with a reference 400 in FIG. 42 is used to mount electronic parts on a printed wiring board 401 having cream solder printed thereon as in the above. As shown in FIG. 42, the packaging system 400 includes a printer 402 to print cream solder on the land of a printed wiring board 401 by the screen printing, a placing unit 404 to place an electronic part 403 on the printed wiring board 401 having cream solder printed on the land thereof, and a reflow unit 405 to heat the printed wiring board 401 having the electronic part 403 placed thereon to melt the solder and thus solder the electronic part 403. In the packaging system 400 for the electronic parts 403, the printed wiring boards 401 are brought one after another while being held horizontally or laid on the transfer mechanism. The printed wiring board 401 is brought through the printer 402, placing unit 404 and reflow unit 405 located in the upper portion of FIG. 42 and has the electronic parts 403 placed on the first side thereof, and then inverted. Then, the printed wiring board 401 is brought through other printer 402, placing unit 404 and reflow unit 405 located in the middle portion of FIG. 42 and thus has electronic parts 403 mounted on the second side thereof. As in the above, the electronics packaging system 400 needs the printer 402, placing unit 404 and reflow unit 405 to mount electronic parts 403 on the first side of the printed wiring board 401, and also the other printer 402, placing unit 404 and reflow unit 405 to mount electronic parts 403 on the second side of the printed wiring board 401. Further, the electronics packaging system 400 needs an inversion mechanism to invert the printed wiring board 401 having the electronic parts 403 soldered to the first side thereof. Thus, the electronics packaging system 400 can hardly be designed more compact and package the electronic parts 403 with a higher efficiency. Next, the electronic parts placed on the printed wiring board are soldered by a solder reflow unit. The solder reflow unit used to solder the electronic parts includes a transfer mechanism to bring a printed wiring board while keeping it in horizontal position, a reflow furnace to heat the printed wiring board and melt the cream solder printed on the land of the printed wiring board, and a heating mechanism to heat the inside of the reflow furnace. The heating mechanism is disposed to face each main side of a printed wiring board brought held in horizontal position in order to heat the printed wiring board from above and below. The printed wiring board first has electronic parts placed on one side thereof, and then brought into the reflow unit. The printed wiring board is heated in the reflow furnace of the reflow unit. The cream solder on the land is melted and then cooled, and thus the electronic parts are soldered. The printed wiring board having the electronic parts soldered to the one side thereof is inverted and has cream solder printed on the other side thereof, and then electronic parts are placed on the land. The printed wiring board is brought again into the reflow unit. The printed wiring board is heated in the reflow furnace of the reflow unit. The cream solder printed on the land on the other side is melted and cooled, an thus the electronic parts are soldered. As in the above, to solder electronic parts to either side of a printed wiring board, soldering has to be done twice in the reflow unit. Thus, the soldering process can hardly be shortened further. Also, to solder electronic parts to either side of a printed wiring board, a reflow unit has to be provided for each side of the printed wiring board. Thus, the electronics packaging system can hardly be designed more compact. In the conventional electronics packaging system, electronic parts are placed on a printed wiring board having been brought in horizontal position, namely, in laid position. More specifically, to mount electronic parts to either side of a printed wiring board, they are first placed on one side of the printed wiring board, then the printed wiring board is inverted, and electronic parts are placed on the other side of the printed wiring board. As in the above, the process of mounting electronic parts can hardly be shortened further. Also, a placing unit has to be provided for either side of a printed wiring board. Thus, the electronics packaging system can hardly be designed more compact. Disclosure of the Invention Accordingly, the present invention has a primary object to overcome the above-mentioned drawbacks of the prior art by providing an improved and novel electronics packaging system. The present invention has another object to provide a printer in which a printed wiring board on which electronic parts are to be mounted is brought while being held in generally upright position to make it possible to print solder to the land on either side of the printed wiring board at a the same time, and which thus enables a more compact design of the electronics packaging system and higher speed of cream solder printing. The present invention has a still another object to provide a novel electronics packaging system in which a printed wiring board on which electronic parts are to be mounted is brought while being held in generally upright position to make it possible to print solder to the land on either side of the printed wiring board at a the same time, and place and solder the electronic parts on the lands, and which thus enables a more compact design of the electronics packaging system and improved efficiency of electronics packaging. The present invention has a yet another object to provide a reflow unit in which a printed wiring board on which electronic parts are to be mounted is brought while being held in generally upright position to solder the electronic parts to either side of the printed wiring board at a the same time, and which thus enables a more compact design of the electronics packaging system and higher speed of soldering. The present invention has a still yet another object to provide an electronic part placing unit in which a printed wiring board on which electronic parts are to be mounted is brought while being held in generally upright position to place the electronic parts on either side of the printed wiring board at a the same time, and which thus enables a more compact design of the electronics packaging system and higher speed of electronic part placing. The above objects can be attained by providing an electronics packaging system including: a printer to print solder to either land of a printed wiring board; a placing unit to place electronic parts on the lands of the printed wiring board, having the solder printed thereon by the printer; and a reflow unit to heat the printed wiring board on which the electronic parts have been placed by the placing unit and solder the electronic parts to the printed wiring board. The printed wiring board is brought by a transfer mechanism, while being held in generally upright position, through the printer, placing unit and reflow unit in this order. That is, the printer, placing unit and reflow unit are provided to face either side of the printed wiring board brought while being held in generally upright position to print solder to either side of the printed wiring board at the same time, then place electronic parts on either side of the printed wiring board at the same time, and melt and cool the printed solder to solder the electronic parts placed on either side of the printed wiring board. In the above electronics packaging system, the printer includes a detecting mechanism which detects the position of the land of a printed wiring board going to have solder printed on the land thereof by the printer. The detecting mechanism provides land-position data to the placing unit which will place electronic parts on the printed wiring board on the basis of the land-position data. These objects and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the best mode for carrying out the present invention when taken in conjunction with the accompanying drawings. Brief Description of the Drawings FIG. 1 is a perspective view of the electronics packaging system according to the present invention. FIG. 2 is a perspective view of the printer included in the electronics packaging system according to the present invention. FIG. 3 is an exploded perspective view of the printer in FIG. 2. FIG. 4A is a perspective view of the printed wiring board transfer mechanism included in the printer, and FIG. 4B is a side elevation of the transfer mechanism. FIG. 5 is a perspective view of the carrying-arm moving mechanism. FIG. 6 is a perspective view of the printed wiring board posture detector. FIG. 7A is a perspective view of the printed wiring board inclination adjusting mechanism, and FIG. 7B is a side elevation of the adjusting mechanism. FIG. 8 is a side elevation of the screen mechanism and the squeegee mechanism provided in the screen mechanism. FIG. 9 is a perspective view of the squeegee mechanism. FIG. 10 is a side elevation of the squeegee mechanism in FIG. 9. FIG. 11 is a side elevation of the rolling promoting arm provided on the squeegee holder, showing the relation between the arm and cream solder. FIG. 12 is a side elevation of the squeegee mechanism, showing the operations of the squeegee mechanism. FIGS. 13A and 13B are side elevations of the screen and the holding plates included in the transfer mechanism, showing the relation between the deflection of the screen and the thickness of the holding plate. FIG. 14 is a side elevation of the printed wiring board, showing the states of the wiring board at different squeegee sliding speeds. FIG. 15 is a plan view of the drive mechanism to move the squeegee mechanism. FIG. 16 shows a flow of operations of the printer. FIG. 17 is a perspective view of the electrical-continuity testing unit, showing the testing by the testing unit. FIG. 18 is a block diagram of the placing unit. FIG. 19 is a side elevation of the placing units, showing the printed wiring board being over between the neighboring pairs of placing units. FIG. 20 is a plan view of the transfer mechanism included in the placing unit. FIG. 21 is a side elevation of the carrying block included in the transfer mechanism. FIGS. 22A to 22C are plan views of the transfer mechanism, showing the operations of the mechanism in the operating order. FIG. 23 is a side elevation of the placing mechanism. FIG. 24 is a plan view of the part holding mechanism, showing an electronic part held in the part feeder. FIG. 25 is a perspective view of the suction head. FIGS. 26A and 26B are plan views of the part holding mechanism, showing the operations of the latter. FIG. 27 is a plan view of the part holding mechanism in the second position. FIG. 28 is a perspective view of the part holding mechanism in the second position. FIG. 29 shows a flow of operations of the placing mechanism. FIG. 30 is a perspective view of the part feeding mechanism which feeds large electronic parts to the placing mechanism. FIG. 31 is a perspective view of the placing mechanism, showing the positioning by the placing mechanism. FIG. 32 is a perspective view of the placing mechanism, showing the entire construction of the latter. FIG. 33 is a perspective view of the adhesive applicator which applies adhesive to provisionally fix an electronic part to the printed wiring board. FIG. 34 is a perspective view of the part installer which screws an electronic part to the printed wiring board from either side of the latter. FIG. 35 is a perspective view of the reflow unit which solders an electronic part to the printed wiring board. FIG. 36 is a perspective view of the reflow furnace unit, showing the internal and 22, that is, in the direction of arrow A and opposite direction in FIG. 4A. The guide rail 16 is connected to drive units 23 and 24 formed from a cylinder mechanism etc. And which move the guide rail 16 in the direction of arrow A and opposite direction in FIG. 4A. The drive units 23 and 24 are driven synchronously with each other to move the guide rail 16 along the support members 21 and 22 in the direction of arrow A in FIG. 4A when forcing the printed wiring board 2 to the carrying guide rail 17. For insertion and removal of the printed wiring board 2, the drive units 23 and 24 are moved along the support members 21 and 22 in the direction opposite to the direction of arrow A in FIG. 4A. As shown in FIG. 5, the transfer mechanism 11 further includes a carrying-arm moving mechanism 26 to move the printed wiring board 2 caught and supported between the guide rails 16 and 17. The carrying-arm moving mechanism 26 includes a carrying arm 27 to bring the printed wiring board 2, a carrying pin 28 provided on the carrying arm 27 and which is to be engaged in an engagement hole 6b formed in the printed wiring board 2, and a drive mechanism 29 to move the carrying arm 27 in the direction of arrow B and opposite direction in FIG. 5 in which the printed wiring board is to be brought. The driving mechanism 29 includes a guide member 31 to guide the movement of the carrying arm 27, drive motors 32 and 33, and an endless driving belt 34 extended between and on the drive motors 32 and 33. Note that the engagement hole 6b is formed in a lower corner, of the printed wiring board 2, which is downstream with respect to the conveying direction. diameter marks disposed in line as will seen from FIG. 6. The camera 39 picks the position detection mark 7 when the printed wiring board 2 is supported between the guide rails 16 and 17. Next, when the printed wiring board 2 is brought in the direction of arrow D in FIG. 6, the camera 40 will pick up the position detection mark 8. Image data thus captured by the cameras 39 and 40 are supplied to a controller 15 which will detect, based on the image data, the inclination of the printed wiring board 2 supported between the guide rails 16 and 17. Note that the controller 15 generates, based on the image data supplied from the cameras 39 and 40, land-position data for use to correct the inclination of the printed wiring board 2, and controls, based on the land-position data, first to third motors 43 to 45 included in an adjusting mechanism 42 which will further be described below. Also note that the land-position data indicates the land position involving an inclination of the printed wiring board 2 carried by transfer mechanisms 121a to 121d. As shown in FIG. 7A, the transfer mechanism 11 includes the above-mentioned adjusting mechanism 42 to adjust the posture, that is, inclination, of the printed wiring board 2 being carried. The adjusting mechanism 42 includes the first motor 43 to adjust the position in the carrying direction of the printed wiring board 2 supported between the guide rails 16 and 17, namely, in the direction of arrow X in FIG. 7A, second motor 44 to adjust the height of the printed wiring board 2 on the side of the support member 21, namely, the height in the direction of arrow Y in FIG. 7A, and the third motor 45 to adjust the height of the printed wiring board 2 on the side of the Support member 22, namely, the height in the direction of arrow Y in FIG. 7A. As shown in FIG. 7A, the above support members 21 and 22 are fixed to a base plate 46 provided in parallel to the guide rails 16 and 17. The base plate 46 has adjusting members 47 and 48 provided on the side thereof opposite to the side where the support members 21 and 22 are provided. The adjusting members 47 and 48 are provided to adjust the height of the support members 21 and 22. Each of the adjusting members 47 and 48 has a rack 49 to adjust the height of the printed wiring board 2. The rack 49 extends in the direction of arrow Y in FIG. 7A. The base plate 46 to which the above support members 21 and 22 are fixed is fixed to the adjusting block 51. The adjusting block 51 consists of a flat plate 52 parallel to the carrying direction of the printed wiring board 2, and vertical plates 53 and 54 fixed to opposite ends of the flat plate 52. Thus the adjusting block 51 has a general shape of "C". The flat plate 52 has formed thereon a rack 55 to move the adjusting block 51 in the direction of arrow X in FIG. 7A. A gear 56 fixed to the drive shaft of the first motor 43 fixed to a stationary member is in mesh with the rack 55. The flat plate 52 has guide members 57 and 58 provided on the other side thereof. The guide members 57 and 58 are engaged on a rail 60 provided on a base 59 and extending in the direction of arrow X in FIG. 7A. When the first motor 43 runs, the adjusting block 51 is moved along the rail 60 in the direction of arrow X in FIG. 7A. As shown in FIG. 7B, each of the vertical plates 53 and 54 has fixed thereon a rail 61 which guides the base plate 46 moving in the direction of arrow Y in FIG. 7A. The rails 61 have engaged thereon the adjusting members 47 and 48, respectively, fixed to the base plate 46. Each of the adjusting members 47 and 48 has provided thereon the above-mentioned rack 49 on which there is engaged a gear 62 fixed to the drive shaft of each of the second and third motors 44 and 45 installed to the stationary members. Thus, the adjusting block 51 is moved along the rails 61 in the direction of arrow Y in FIG. 7A when the second and third motors 44 and 45 run. In the adjusting mechanism 42 constructed as in the above, the first to third motors 43,44 and 45 are independently controlled by the controller 15. For example, when it is detected by the detecting mechanism 38 that the printed wiring board 2 supported between the guide rails 16 and 17 is inclined downward on the side of the support member 22, the controller 15 will drive the third motor 45 to raise the base plate 46 on the side of the support member 22. When cream solder is to be printed, if it is detected by the detecting mechanism 38 that the printed wiring board 2 is found moved excessively in the direction of arrow D in FIG. 7A, namely, in the carrying direction, the controller 15 will drive the first motor 43 to move the base plate 46 in the direction opposite to the direction of arrow D in FIG. 7A. As shown in FIG. 8, each of the screen mechanisms 12 to print cream solder to the land on either side of the printed wiring board 2 supported in the transfer mechanism 11 includes a screen 64 having formed thereon a pattern corresponding to the land of the printed wiring board 2 on which the cream solder is to be printed, and a screen frame 65 to which the screen 64 is tensely attached. The screen mechanism 12 is disposed for the screen 64 thereof to face each side of the printed wiring board 2 supported in the transfer mechanism 11. The screen 64 is for example a metal screen of about 170 to 200 µm in thickness. The screen mechanism 12 disposed on either side of the printed wiring board 2 supported in the transfer mechanism 11 is moved towards the printed wiring board 2 only when cream solder is to be printed to the printed wiring board 2. For carrying the printed wiring board 2, the screen mechanism 12 is moved away from the printed wiring board 2 supported in the transfer mechanism 11. To move the screen mechanisms 12 in a direction towards or away from the printed wiring board 2 supported in the transfer mechanism 11, there are provided moving mechanisms 66 each including, as shown in FIG. 8, a guide member 67 and driving mechanism 68, provided to support the screen frames 65 and move the screen frame 65 towards and away from the printed wiring board 2 supported in the transfer mechanism 11 in the directions of arrow E and opposite direction in FIG. 8. Each of the driving mechanisms 68 includes a drive motor 69 and an endless driving belt 71 extended between and on the drive motor 69 and a drive motor 70. The screen frame 65 is fixed to the driving belt 71. When the drive motor 69 is put into operation, the driving belt 71 runs to move the screen frame 65 along the guide member 67 in the direction of the direction of arrow E and opposite direction in FIG. 8. As shown in FIG. 8, one of the screen frames 12 has a positioning pin 72 provided thereon, while the other screen frame 12 has a positioning concavity 73 rormea therein. When the screen frames 65 are moved close to each other, the positioning pin 72 is engaged into the positioning concavity 73 to position the screen frames 65. To squeeze cream solder supplied to the screen mechanisms 12 to the printed wiring board 2, there are provided the squeegee mechanisms 13 each disposed on the side of the screen mechanism 12 opposite to the side thereof facing the printed wiring board 2 as shown in FIG. 8. Each of the squeegee mechanisms 13 includes a first squeegee 75 adapted to be moved downward from the upper portion of the screen mechanism 12 to squeeze cream solder to the printed wiring board 2, and a second squeegee 76 adapted to be moved upward from the lower portion of the screen mechanism 12 to squeeze cream solder to the printed wiring board 12, as will be seen from FIG. 8. The squeegee mechanisms 13 will further be described below with reference to FIGS. 9 and 10. As shown, each of the squeegee mechanisms 13 includes the first and second squeegees 75 and 76 to squeeze cream solder supplied to the screen mechanism 12 to the printed wiring board 2, squeegee holders 77 and 78 to which the first and second squeegees 75 and 76 are fixed respectively, and cylinder mechanisms 79 and 80 to move the first and second squeegees 75 and 76 fixed to the squeegee holders 77 and 78, respectively, towards and away from the screen 64. The first and second squeegees 75 and 76 are made of an elastic material such as polyurethane resin. Also, the first and second squeegees 75 and 76 are fixed to the squeegee holders 77 and 78, respectively, for an acute angle to be defined between the screen 64 and moving directions of the first and second squeegees 75 and 76. Thus, the first and second squeegees 75 and 76 can positively squeeze cream solder from the screen 64 to the printed wiring board 2. Further, as shown in FIG. 9, the squeegee holder 77 (78) has a rolling promoting arm 81 provided near the first (second) squeegee 75 (76) to roll a cream solder 9 when the latter is going to be squeezed from the screen 64 to a position near the screen 64, for example, to a position of 5 mm from the screen 64. Note that when this rolling promoting arm 81 is not provided, the cream solder 9 will gravitationally flow down but the rolling prompting arm 81 will assure that the cream solder 9 is rolled in the direction of arrow and positively forced out by the first (second) squeegee 75 (76) to the side of the screen 64 opposite to the squeegee 75 as shown in FIG. 11. The cylinder mechanism 79 is provided on the squeegee holder 77 to which the first squeegee 75 is fixed as in the above, while the cylinder mechanism 80 is provided on the squeegee holder 78 to which the second squeegee 76 is fixed. The cylinder mechanism 79 provides a driving mechanism as in the above. As shown in FIG. 12, for example, when the squeegee mechanism 13 is moved down from above in FIG. 12, the cylinder mechanism 79 is activated to move the first squeegee 75 in the direction of arrow F in FIG. 12 towards the screen 64 to a position where the squeegee 75 is ready for squeezing the cream solder. At this time, the cylinder mechanism 80 is not in action but has been moved in the direction opposite to the direction of arrow F in FIG. 12 to a position where it is separate from the screen 64. When the squeegee mechanism 13 is moved upward from below in FIG. 12, the cylinder mechanism 80 is activated to move the second squeegee 76 in the direction of arrow F in FIG. 12 to a position where it is ready to squeeze the cream solder. At this time, the cylinder mechanism 79 is not in action but has been moved in the direction opposite to the direction of arrow F in FIG. 12 to a position where it is separate from the screen 64. Namely, the printed wiring board 2 supported in the transfer mechanism 11 will not be inclined during printing of the cream solder since each side of the printed wiring board 2 can be pressed at predetermined positions thereon by the first squeegee 75 and second squeegee 76 of each screen mechanism 12. As shown in FIG. 13B, when the screens 64 have been moved in the directions of arrow E in FIG. 8, respective, and the first squeegee 75 or second squeegee 76 has been moved in the direction of arrow F in FIG. 11 to squeeze the cream solder to the printed wiring boards 2, respectively, supported in the transfer mechanism 11, the screens 64 are deflected in the directions in which they are forced by the first squeegee 75 or second squeegee 76 and put into close contact with corresponding sides of the printed wiring board 2. At this time, if the holding plates 19 and 20 included in each of the guide rails 16 and 17 are too thick, the screens 64 will not be put in close contact with the printed wiring board 2 even when they are pressed by the first squeegee 75 or second squeegee 76, so that cream solder cannot be printed to a predetermined area on the printed wiring board 2. This is illustrated in FIG. 13A. For this reason, the holding plates 19 and 20 included in the transfer mechanism 11 may be designed to have a thickness of about 80 µm (conventionally, 170 to 200 p,m) for positive close contact between the deflected screens 64 and printed wiring board 2 as shown in FIG. 13B. If the first squeegee 75 or second squeegee 76 included in the screen mechanism 12 is slid at different speeds towards the screen 64 when the squeegee mechanism 13 constructed as in the above, a pressure will be applied to different positions on each side of the printed wiring board 2 and thus the printed wiring board 2 supported in the transfer mechanism 11 will be inclined, as shown in FIG. 14, so that cream solder cannot positively be printed on the printed wiring board 2. There is provided a driving mechanism 14 to slide the squeegee mechanism 13 towards the screen 64, and it includes, as shown in FIG. 15, a drive motor 84, driving force transmission 85 to transmit a driving force from the drive motor 84, and moving members 86 and 87 to move the squeegee mechanism 13 by means of the driving force transmission 85. The drive motor 84 has fixed to the drive shaft thereof a pinion 88 coupled to the driving force transmission 85. The drive motor 84 thus slides the squeegee mechanism 13 disposed in the screen mechanism 12 in relation to the screen 64. The moving member 86 has fixed thereto the squeegee holder 77 included in one of the squeegee mechanisms 13, while the moving member 87 has fixed thereto the squeegee holder 78 included in the other squeegee mechanism 13. The driving force transmission 85 having coupled thereto the pinion 88 fixed with the screens 64, respectively, in order to print cream solder to the corresponding lands of the printed wiring board 2. That is, when the drive motor 84 is put into action, the shaft 83 is rotated by means of the pinion 88 and intermediate gear 101 and also the worms 89 and 90 are rotated, as shown in FIG. 15. Then, the rollers 95 and 96 in mesh with the worms 89 and 90, respectively, are rotated while the driving force transmitting belts 91 and 92 are made to run in the same direction. As the rollers 97 and 98 on which the driving force transmitting belts 91 and 92 are wound, respectively, are rotated, the moving belts 93 and 94 wound on the rollers 97 and 98 are also made to run. Thus, the moving members 86 and 87 fixed to the moving belts 93 and 94, respectively, are moved in the direction of arrow G and opposite direction in FIG. 15. Thereby, the squeegee mechanisms 13 fixed to the moving members 86 and 87, respectively, are moved in the direction of arrow G and opposite direction in FIG. 15, that is, up and down in FIG. 8. At this time, the screens 64 are deflected in the directions in which they are forced by the first squeegee 75 or second squeegee 76, and put into close contact with the corresponding sides of the printed wiring board 2. Thus the cream solder is printed on the lands of the printed wiring board 2. At this time, since the holding plates 19 and 20 included in the transfer mechanism 11 are formed thinner than ever, so the deflected screens 64 will be positively put into close contact with the printed wiring board 2 as shown in FIG. 13A. Since the driving mechanism 14 transmits the driving force from the drive motor 84 to the shaft 83 having the worms 89 and 90 provided at the opposite ends thereof and thus to the driving force transmitting belts 91 and 92 wound on the worms 89 and 90 to rotate the moving belts 93 and 94 in the same direction at the same speed, so the squeegee mechanisms 13 included in the screen mechanisms 12, respectively, can be moved in the same direction at the same speed. Therefore, since the printed wiring board 2 supported in the transfer mechanism 11 is applied always at the same position thereof with the same pressure by the first squeegee 15 or second squeegee 76 included in the squeegee mechanism 13, so the driving mechanism 14 permits to positively print cream solder to the lands of the printed wiring board 2 while preventing the printed wiring board 2 from being inclined as shown in FIG. 14. When the cream solder printing is complete, the screen mechanisms 12 are moved away from the printed wiring board 2 in step S7. More specifically, when the drive motors 69 and 70 are put into action, the driving belt 71 runs as shown in FIG. 8, whereby the screen frames 65 are moved along the guide members 67, respectively, in the direction opposite to the direction of arrow E in FIG. 3. Thus, the printed wiring board 2 can be carried by the transfer mechanism 11 in the direction of arrow D in FIG. 3. In step S8, the drive units 23 and 24 are put into action to move the guide rail 16 along the support members 21 and 22 in the direction opposite to the direction of arrow A in FIG. 4A. Thereby, the transfer mechanism 11 is ready to carry the printed wiring board 2. In step S9, the printed wiring board 2 having the cream solder printed on the lands thereof is brought out. In the printer 3 constructed as in the above, since the printed wiring board 2 is supported in upright position in the transfer mechanism 11, so cream solder can be printed on the lands on both sides of the printed wiring board 2 at the same time, which leads to a shorter time for solder printing and more compact design of the electronics packaging system than in the conventional system in which cream solder is printed on each side of the printed wiring board. Also in the printer 3, since the holding plates 19 and 20 included in the transfer mechanism 11 are designed to have a thickness of about 80 \xm (conventionally, 170 to 200 [im) for positive close contact of the deflected screens 64 with the lands of the printed wiring board 2, so cream solder can positively be printed on the lands of the printed wiring board 2. Further, since in the driving mechanism 14, a driving force can be transmitted from the drive motor 84 to the driving shaft 83 with the worms 89 and 90 provided at the opposite ends thereof to allow, by means of the driving force transmitting belts 91 and 92, the moving belts 93 and 94 to run in the same direction at the same speed, so the squeegee mechanisms 13 disposed in the screen mechanisms 12 respectively can be moved in the same direction at the same speed. Also, since the printed wiring board 2 supported in the transfer mechanism 11 will be applied always at the same position on either side thereof with a pressure by the first squeegees 75 or second squeegees 76 in the squeegee mechanisms 13, so the driving mechanism 14 permits to prevent the printed wiring board 2 from being inclined as shown in FIG. 14 and cream solder can positively be printed on the lands of the printed wiring board 2. Note that besides the printing of cream solder, the printer 3 may be used to print solder resist in a predetermined pattern on the surface of a printed wiring board having a wiring pattern formed thereon. It should be reminded that the driving mechanism 14 can be used in an electrical-continuity testing unit 110 for testing the electrical continuity of a wiring pattern formed on the printed wiring board 2 as shown in FIG. 17. More specifically, the continuity testing unit 110 includes, in place of the aforementioned screen mechanism 12, a testing mechanism 113 having a support plate 111 and a plurality of testing pins 112 provided on the support plate 11 correspondingly to a wiring pattern formed on the printed wiring board 2 as shown in FIG. 17. The testing mechanism 113 is moved by the aforementioned driving mechanism 14 towards and away from the printed wiring board 2 supported in the transfer mechanism 11. When making an electrical-continuity test on the printed wiring board 2, the testing mechanism 113 is moved by the driving mechanism 14 towards the printed wiring board 2 supported by the transfer mechanism 11 and to a position off the carrying pin 28 which carries the printed wiring board 2. Since the printed wiring board 2 is applied with the same pressure from either side thereof when it is carried with the driving mechanism 14 for the electrical-continuity test thereof, so it can be prevented from being inclined during the test. Next, the placing unit 4 to place electronic parts onto the printed wiring board 2 having cream solder printed by the aforementioned printer 3 on the lands thereof will be described below with reference to FIGS. 18 to 32. As shown, the placing unit 4 includes transfer mechanisms 121a to 121d to carry the printed wiring board 2 while keeping it in generally upright position, and placing mechanisms 122a to 122h to place electronic parts 10 onto the printed wiring board 2. The placing mechanisms 122a, 122c, 122e and 122g and placing mechanisms 122b, 122d, 122f and 122h are disposed opposite to each other, respectively, across the transfer mechanism 121. The placing mechanisms 122a and 122b are controlled by a controller 123a, placing mechanisms 122c and 122d are by a controller 123b, placing mechanisms 122e and 122f are by a controller 123c, and the placing mechanisms 122g and 122h are by a controller 123d. The placing mechanisms 122a to 122d are provided to place electronic parts of standard sizes onto the printed wiring board 2, while the placing mechanisms 122e to 122h are provided to place electronic parts larger than the standard-size ones. Further, the placing unit 4 is controlled as a whole by a system controller 124. The system controller 124 has stored therein positions where electronic parts to be placed by the placing mechanisms 122a to 122h and supplies placing- post data to each of the controllers 123a to 123d. Also, the system controller 124 is supplied with land-position data on land positions on the printed wiring board 2, generated by the detecting mechanism 38 included in the transfer mechanism 11 of the printer 3, from the controller 15 of the printer 3. That is, the land-position data indicates land positions involving the inclination of the printed wiring board 2 carried by the transfer Thechanisms 121a to 121d. As will be described later, since the printed wiring board 2 is carried with the carrying pin 136 engaged in engagement holes 6a and 6b as in the conveyance by the conveying 11 of the printer 3 of the printed wiring board 2 with the carrying pin 28 engaged in the engagement hole 6b, so the placing unit 4 can use land-position data generated during conveyance of the printed wiring board 2 in the printer 3. The controllers 123a to 123d control the placing mechanisms 122a to 122h based on the placing-post data supplied from the system controller 124. The controller 123a to control the placing mechanisms 122a and 122b disposed most upstream of the transfer mechanism 121 is supplied with the land-position data from the system controller 124. The controller 123a supplies the land-position data to the placing mechanisms 122a and 122b for control of the latter. More particularly, the placing mechanisms 122a and 122b are controlled correspondingly to an inclination or the like of the printed wiring board 2 supported thereby. The controller 123a supplies the land-position data to the controller 123b as the printed wiring board 2 is being carried. Thereafter, the land-position data is transferred to the controller 123c and then to the controller 123d. Each of these controllers 123a to 123d controls the placing mechanisms 122a to 122h correspondingly to a posture of the printed wiring board 2 being carried on the basis of the land-position data. In the placing unit 4, when the printed wiring board 2 stays over between the neighboring pairs of placing itiechanisms 122a and 122b and neighboring placing mechanisms 122c and 122d, between the neighboring pairs of placing mechanisms 122c and 122d and neighboring placing mechanisms 122e and 122f, or between the neighboring pairs of placing inechanisms 122e and 122f and neighboring placing mechanisms 122g and 122h as shown in FIG. 19, both the neighboring pairs of placing mechanisms are used to place an electronic part in order to attain a higher efficiency of mounting. At this time, the downstream placing mechanisms are controlled by the controller which controls the upstream placing mechanisms. As shown in FIGS. 20 and 21, each of the transfer mechanisms 121a to 121 d of the placing unit 4 operative in the aforementioned system includes a pair of guide rails 131 and 132 which engage and support the opposite lateral edges of the generally rectangular printed wiring board 2. The lower guide rail 132 shown in the lower portion of FIG. 20 has carrying blocks 133 to carry the printed wiring board 2. As shown in FIG. 21, each of the carrying blocks 133 includes a support member 134 to support the printed wiring board 2 at one side of the latter, and a carrying member 135 which works with the support member 134 to hold the printed wiring board 2 between them. Between the support member 134 and carrying member 135, there is provided a rail member 138 forming a part of the guide rail 132. Also, the carrying member 135 is also provided with a carrying pin 136 which is to be engaged in the engagement holes 6a and 6b formed in the printed wiring board 2. The carrying pin 136 is moved by a cylinder mechanism 137 in the direction of arrow H and opposite direction in FIG. 21, namely, towards and away from the support member 134. When conveying the printed wiring board 2, the carrying member 135 is moved in the direction of arrow H in FIG. 21, namely, towards the support member 134, to engage the carrying pin 136 into the engagement holes 6a and 6b. The support member 134 is further provided with a driving mechanism 139 to move the support member 134 in the direction of arrow I in FIG. 20 in which the printed wiring board 2 is to be carried. Thus the printed wiring board 2 is carried by the support member 134 and carrying member 135 being moved along with the driving mechanism 139 in the direction of arrow I in FIG. 20. Note that the carrying blocks 133 are provided in two places, upstream (133a) and downstream (133b), on the guide rail 132. In the placing unit 4, the printed wiring board 2 is carried in relay by the transfer mechanisms 121a, 121b, 121c and 121d in this order. More specifically, when the printed wiring board 2 is set in between the guide rails 131 and 132 from the transfer mechanism 11 of the printer 3, first the carrying member 135 of the upstream carrying block 133a in the transfer mechanism 121a is moved in the direction of arrow H in FIG. 21, namely, towards the support member 134, and the carrying pin 136 is engaged into the engagement hole 6a located downstream in the carrying direction, as shown in FIG. 22A. Then, the carrying block 133 is driven by the driving mechanism 139 to carry, by towing, the printed wiring board 2 to a position where an electronic part is to be held, for placement, by the most upstream pair of placing mechanisms 122a and 122b. Here, an electronic part is placed in a predetermined position on the printed wiring board 2 by the pair of placing mechanisms 122a and 22b. Next, the upstream carrying block 133a carries, by towing, the printed wiring board 2 in the direction of arrow I in FIGS. 22A to 22C. As shown in FIG. 22B, the carrying member 135 of the upstream carrying block 133a is moved in the direction opposite to the direction of arrow H in FIG. 21, namely, away from the support member 134, and the carrying pin 136 is disengaged from the engagement hole 6a. Instead, the carrying member 135 of the downstream carrying block 133b on the guide rail 132 is moved in the direction of arrow H in FIG. 21, namely, towards the support member 134, and the carrying pin 136 is engaged into the engagement hole 6b. Note that at this time, the upstream carrying block 133a is moved upstream, namely, in the direction opposite to the direction of arrow H in FIGS. 22A to 22C to carry a next printed wiring board 2. Then, the downstream carrying block 133b on the guide rail 132 is driven by the driving mechanism 139 to carry, by pushing, the printed wiring board to a next placing post. This placing post is a position where the printed wiring board 2 stays over between the most upstream pair of placing mechanisms 122a and 122b and neighboring pair of placing mechanisms 122c and 122d as shown in FIG. 22C. In this position, electronic parts are placed in a predetermined position on the printed wiring board 2 by the downstream pair of placing mechanisms 122c and 122d and neighboring pair of placing mechanisms 122a and 122b. Thus, in the placing unit 5, electronic parts can be placed at the same time on the printed wiring board 2 by the four placing mechanisms 122a to 122d, where leads to an improved efficiency of electronic part mounting. At this time, the upstream placing mechanisms 122a and 122b are controlled by the controller 123b for the downstream placing mechanisms 122c and 122d. Thereafter, the downstream carrying block 133b carries, by pushing, the printed wiring board 2 in the direction of arrow I in FIGS. 22A to 22C. Then, the carrying member 135 of the downstream carrying block 133b is moved in the direction opposite to the direction of arrow H in FIG. 21, namely, away from the support member 134, and the carrying pin 136 is disengaged from the engagement hole 6b. Instead, the carrying member 135 of the upstream carrying block 133a on the guide rail 132 included in the next transfer mechanism 121b is moved in the direction of arrow H in FIG. 21, that is, towards the support member 134, to engage the carrying pin 136 into the engagement hole 6a. Then, the state shown in FIG. 22C is attained, and hereafter, the printed wiring board 2 is carried by the transfer mechanisms 121b to 121 d in this order. The placing mechanisms 122a to 122h disposed across the transfer mechanisms 121a to 121d are constructed as shown in FIG. 23. Note that since the placing mechanisms 122a to 122d are constructed similarly to each other, they will generically be referred to as "placing mechanism 122" hereunder. As shown in FIGS. 23 and 24, the placing mechanism 122 includes a part holding mechanism 142 to hold, by suction, an electronic part 10 supplied from a part feeder 141, a turning mechanism 143 to shuttle the part holding mechanism 142 between two positions, namely, a first position in which the electronic part 10 supplied from the part feeder 141 is held by suction and a second position where it is opposite to the printed wiring board 2 supported by the transfer mechanisms 121a to 121d, and a guide mechanism 144 to guide the up-down movement of the part holding mechanism 142 in the second position. The part feeder 141 is provided to supply electronic parts 10 of a standard size. As shown in FIGS. 24 and 25, the part holding mechanism 142 has a suction head 146 to hold, by suction, an electronic part 10. The suction head 146 is connected to a suction pump (not shown) and holds, by suction, the electronic parts 10 while transferring it from the part feeder 141 to the printed wiring board 2. Note that the part holding mechanism 142 is moved up and down by a lifting mechanism 160 in the direction of arrow J and opposite direction in FIG. 23, which will not be described any longer. Further, the part holding mechanism 142 has an adjusting mechanism 147 to adjust the held state of the electronic part 10 caught by the suction head 146 as shown in FIGS. 24, 26 and 27. The adjusting mechanism 147 includes a drive motor 149 fixed to a generally L-shaped fixture 148, a first pulley 150 fixed to the output shaft of the drive motor 149, a second pulley 152 fixed to a shaft 151 to which the suction head 146 is installed, en endless belt 153 to provide a ling between the first and second pulleys 150 and 152, and a shaft support 154 to support the shaft 151 rotatably. A detector 155 using a CCD (charge-coupled device) element is provided in a position where it will be opposite to the electronic part 10 when the suction head 146 stays in the second position where the electronic part 10 is opposite to the printed wiring board 2 supported by the transfer mechanisms 121a to 121d. When it is judged by the detector 155 that the electronic part 10 sucked and held by the suction head 146 is inclined, the drive motor 149 is put into action to rotate the shaft 151 for adjustment of the held state of the electronic part 10. The turning mechanism 143 shuttles the above-mentioned part holding mechanism 142 between the first position in which the electronic part 10 supplied from the part feeder 141 is held by suction and second position where it is opposite to the printed wiring board 2 supported by the transfer mechanisms 121a to 121d. The turning mechanism 143 includes, as shown in FIGS. 24, 27 and 28, a spindle 157 inserted through a pair of support pieces 156 which support the suction head 146 and a gear 158 fixed to the spindle 157 and between the support pieces 156, the spindle 157 and gear 158 being included in the part holding mechanism 142, and a rack 159 having a toothed portion formed along the up-down moving direction of the part holding mechanism 142 and fixed to the cabinet. When the part holding mechanism 142 is moved up by the lifting mechanism 160 in the direction of arrow J in FIG. 24, the gear 158 is engaged with the rack 159 and the part holding mechanism 142 is further moved up. The part holding mechanism 142 is turned about 90° about the spindle 157 as shown in FIGS. 27 and 28. Thus, the part holding mechanism 142 is shifted from the first position to the second position. In the second position, the held state of the electronic part 10 sucked and held by the suction hear 146 is detected by the detector 155. When it is judged by the detector 155 that the electronic part 10 sucked and held by the suction head 146 is inclined, the drive motor 149 is put into action to rotate the shaft 151, thereby adjusting the held state of the electronic part 10. As shown in FIG. 23, the guide mechanism 144 to guide the up-down movement of the part holding mechanism 142 in the second position includes first and second guide members 162 and 163. The first guide member 162 is disposed above the second guide member 163, and has a guide slot 164. The guide slot 164 consists of a first straight portion 164a to engage the gear 158 with the rack 159 of the above-mentioned turning mechanism 143, an inclined portion 164b formed contiguously to the first straight portion 164a and obliquely in the transfer mechanisms 121a to 121d of the first guide member 162, and a second straight portion 164c formed contiguously to the inclined portion 164b and in parallel to the first straight portion 164a on the side of the transfer mechanisms 121a to 121d. The second guide member 163 has a driving mechanism 166 to move the electronic part 10 towards the printed wiring board 2 for placement on the latter. The driving mechanism 166 is a cylinder mechanism to move the second guide member 163 in the up-down moving direction of the part holding mechanism 142, that is, in a direction generally perpendicular to the direction of arrow J and opposite direction in FIG. 23, and includes a shaft 167 and cylinder 168 fixed to the second guide member 163. When the part holding mechanism 142 has moved to the guide slot 165, the second guide member 163 moves in the direction of arrow K in FIG. 23 towards the printed wiring board 2 in relation to the first guide member 162. The second guide member 163 is thus moved by the driving mechanism 166 in the direction of arrow K in FIG. 23, and the suction head 146 places the electronic part 10 held thereby on the printed wiring board 2. The shaft 151 of the part holding mechanism 142 is engaged in the guide slots 164 and 165. As shown in FIGS. 26A and 26B, the part holding mechanism 142 has provided thereon an extension spring 169 to keep it in the second position by means of the turning mechanism 143. The extension spring 169 is engaged at one end thereof on the fixture 148 and at the other end on the suction head 146. The extension spring 169 pulls the suction head 146 towards the fixture 148 to hold the part holding mechanism 142 in the second position as shown in FIG. 26B. The placing mechanism 122 constructed as in the above works when the above-mentioned transfer mechanisms 121a to 121d are in the position where the electronic part 10 is placed onto the printed wiring board 2. A series of operations for placement of the electronic part 10 onto the printed wiring board 2 will be discussed herebelow with reference to FIG. 29. In step Sll, for holding the electronic part 10 supplied from the part feeder 141, the suction head 146 has been lowered by the lofting mechanism 160 as shown in FIG. 24 in the direction opposite to the direction of arrow J in FIG. 23 and the gear 158 is not engaged with the rack 159. That is, the suction head 146 . is forced to the first position, namely, to a position opposite to the part feeder 141, under the action of the extension spring 169 as shown in FIG. 26A. In this first position, the suction head 146 will suck and hold the electronic part 10 supplied from the part feeder 141. In step S12, the lifting mechanism 160 is put into operation, the part holding mechanism 142 is lifted in the direction of arrow J in FIG. 23 while the spindle 157 is being guided by the first straight portion 164a of the guide slot 164 in the first guide member 162, the gear 158 is engaged with the rack 159, and thus the part holding mechanism 142 is further lifted in the same direction. Thus, the part holding mechanism 142 is turned about 90° about the spindle 157. In this way, the part holding mechanism 142 is shifted from the first position to the second position as shown in FIG. 27. The suction head 146 is held in the second position, namely, in the position opposite to the detector 155, as shown in FIG. 26B under the action of the extension spring 169. In step S13, the detector 155 detects the held state of the electronic part 10 sucked and held by the suction head 146. When it is judged by the detector 155 that the electronic part 10 sucked and held by the suction head 146 is inclined, the drive motor 149 is put into action to rotate the shaft 151, thereby adjusting the held state of the electronic part 10. Thereafter in step S14, the lifting mechanism 160 is driven to lift up the part holding mechanism 142 in the direction of arrow J in FIG. 23 up to the height of the Second guide member 163. Namely, the spindle 157 is shifted from the first straight portion 164a to the second straight portion 164c via the inclined portion 164b and thus the suction head 146 is moved to near the transfer mechanisms 121a to 121d. As the suction head 146 is lifted by the lifting mechanism 160, the spindle 157 is moved to the guide slot 165 in the second guide member 163. In step S15, the lifting mechanism 160 is stopped at the height where the electronic part 10 is placed onto the printed wiring board 2 based on mounting-position data and land-position data. In step S16, the second guide member 163 is moved in the direction of arrow K in FIG. 23 towards the printed wiring board 2 in relation to the first guide member 162 as shown in FIG. 23. That is, the second guide member 163 is moved by the driving mechanism 166 in the direction of arrow K in FIG. 23 to allow the suction head 146 to place the electronic part 10 on the printed wiring board 2. As having previously been described, the placing mechanisms 122e to 122h are provided to place larger electronic parts than the standard-size electronic parts. For handling such a larger-size electronic part 10a, there is used a part feeding mechanism 171 different from the aforementioned part feeder 141. As shown in FIG. 30, the part feeding mechanism 171 includes a base plate 172 having provided thereon a tray 173 on which large electronic parts 10a are placed side by side and a positioning member 174 which provisionally position the electronic parts 10a before held by the aforementioned part holding mechanism 142. The part feeding mechanism 171 has provided thereon a transfer mechanism 175 which transfers an electronic part 10a from on the tray 173 to the positioning member 174. The positioning member 174 has formed therein a positioning concavity 176 having a shape corresponding to those of the electronic parts 10a placed on the tray 173. Since the electronic part 10a is pre-positioned in the positioning concavity 176 before being sucked by the suction head 146 of the part holding mechanism 142, so that the electronic part 10a can be accurately held, by suction, by the suction head 146. The transfer mechanism 175 to transfer the electronic part 10a from on the tray 173 to the positioning member 174 includes a guide rail 178 mounted on a support plate 177 fixed to the base plate 172 in parallel to the array of the tray 173 and positioning member 174, a transfer member 179 installed generally perpendicularly to, and movably along, the guide rail 178, and a holding mechanism 180 fixed to the transfer member 179 to hold the electronic part 10a on the tray 173. The transfer member 179 is engaged at one end thereof on the guide rail 178, and the transfer member 179 is moved by a driving mechanism (not shown) in the direction of arrow L and opposite direction in FIG. 30. The transfer member 179 has a moving mechanism 181 which moves the holding mechanism 180 in the direction of arrow M and opposite direction in FIG. 30, namely, perpendicularly to the guide rail 178. The moving mechanism 181 includes a drive motor 182, rollers 183 and 184 pivoted to opposite ends of the transfer member 179, and an endless belt 185 extended between and on the rollers 183 and 184. The roller 183 is connected to the output shaft of the drive motor 182. The holding mechanism 180 is connected to the endless belt 185. In the transfer mechanism 181, when the drive motor 182 is put into action, the endless belt 185 runs to move the holding mechanism 180 in the direction of arrow M and opposite direction in FIG. 30. The holding mechanism 180 to hold, by suction, the electronic part 10a includes a suction head 186 to suck and hold the electronic part 10a, and a lifting mechanism 187 to move up and down the suction head 186. The suction head 186 is connected to a suction pump (not shown). The lifting mechanism 187 includes a cylinder 188 and shaft 189. The shaft 189 has the suction head 186 fixed to one end thereof. For sucking and holding the electronic part 10a, the lifting mechanism 187 lowers the suction head 186. The part feeding mechanism 171 constructed as in the above operates as will be described below. First, the base plate 172 has disposed thereon the tray 173 on which the electronic parts 10a are placed. The transfer member 179 is moved along the guide rail 178 in the direction opposite to the direction of arrow L in FIG. 30. For catching the electronic part 10a, the moving mechanism 181 is put into action to move the holding mechanism 180 in the direction of arrow M in FIG. 30 to a predetermined position. Next, in the lifting mechanism 187, the suction head 186 sucks and holds the electronic part 10a, and then is moved up. Then, the transfer member 179 is moved by the driving mechanism (not shown) along the guide rail 178 in the direction of arrow L in FIG. 30. The moving mechanism 181 is put into action to move the holding ecnanism 180 in the direction of arrow M in FIG. 30 to above the positioning member 174. The suction head 186 is lowered by the lifting mechanism 187 to place the electronic part 10a into the positioning concavity 176 in the positioning member 174. Thereafter, the electronic part 10a is placed by the aforementioned placing mechanisms 122e to 122h onto the printed wiring board 2 supported by the transfer mechanism 121. Note that as shown in FIG. 31, in the placing mechanisms 122a to 122h provided across the transfer mechanisms 121a to 121d, a positioning plate 191 is included in each placing mechanism 122 and engaged in a positioning recess 194 formed in a base block 193 also provided in the placing unit 4. Thus, each placing mechanism 122 can be prevented from being displaced when an external force is applied, and so an electronic part can be placed positively. As shown in FIG. 32, each of the placing mechanisms 122a to 122h is fixed with a fixing member 196 to a mount plate 195 provided in parallel to the transfer mechanisms 121a to 121d. The fixing member 196 has a fixing recess 197 formed therein. Each of the placing mechanisms 122a to 122h can easily be installed to the mount plate 195 by engaging, in the fixing recess 197, a fixing plate 198 fixed to each of the placing mechanisms 122a to 122h. Next, the placing unit 4 constructed as having been described in the foregoing functions as will be described below. In the placing unit 4, the printed wiring board 2 is carried in relay by the transfer mechanisms 121a, 121b, 121c and 121d in this order. More specifically, when the printed wiring board 2 is brought by the transfer mechanism 11 of the printer 3 into between the guide rails 131 and 132, first the carrying block 133 is driven by the driving mechanism 139 to carry, by towing, the printed wiring board 2 to a placing post of the most upstream pair of placing mechanisms 122a and 122b as shown in FIG. 22A. Here, an electronic part is placed in a predetermined position on the printed wiring board 2 by the pair of placing mechanisms 122a and 22b. At this time, the suction head 146 stays in a position opposite to the part feeder 141 and where it will hold, by suction, the electronic part 10 supplied from the part feeder 141. Next, the part holding mechanism 142 is lifted up in the direction of arrow J in FIG. 23 with the spindle 157 thereof being guided along the first straight portion 164a of the guide slot 164 in the first guide member 162. Then, the rack 159 is engaged with the gear 158, and the part holding mechanism 142 is further lifted up in the same direction and thus turned about 90° about the spindle 157 as shown in FIGS. 27 and 28. Thereby, the part holding mechanism 142 is shifted from the first to second position as shown in FIG. 27. Now the detector 155 detects the held state of the electronic part 10 sucked and held by the suction head 146. When the result of detection from the detector 155 is that the electronic part 10 sucked and held by the suction head 146 is inclined, the drive motor 149 is put into action to rotate the shaft 151 for adjustment of the held state of the electronic part 10. Thereafter, the part holding mechanism 142 is further elevated in the direction of arrow J in FIG. 23 up to the position of the second guide member 163. Moreover, the suction head 146 is elevated by the lifting mechanism 160, the spindle 157 is moved to the guide slot 165 in the second member 163 and the part holding mechanism 142 is stopped at a higher where the electronic part 10 is placed onto the printed wiring board 2. As shown in FIG. 23, the second guide member 163 is moved in the direction of arrow K in FIG. 23 towards the printed wiring board 2 with respect to the first guide member 162. Then the second guide member 163 is moved by the driving mechanism 166 in the direction of arrow K in FIG. 23 to allow the suction head 146 to place the electronic part 10 onto the printed wiring board 2. Note that the pair of placing mechanisms 122a and 122b is controlled by the controller 123a, the pair of placing mechanisms 122c and 122d is controlled by the controller 123b, the pair of placing mechanisms 122e and 122f is controlled by the controller 123c, and the pair of placing mechanisms 122g and 122h is controlled by the controller 123d. When the placement of the electronic part 10 is complete, the upstream carrying block 133a will carry, by towing, the printed wiring board 2 in the direction of arrow I in FIG. 22. At this time, the carrying member 135 of the upstream carrying block 133a is moved away from the support member 134 and thus the carrying pin 136 is disengaged from the engagement hole 6a, as shown in FIG. 22B. Instead, the carrying member 135 of the downstream carrying block 133b on the guide rail 132 is moved towards the support member 134 and so the carrying pin 136 is engaged into the engagement hole 6b located upstream in the carrying direction. Next, the downstream carrying block 133 on the guide rail 132 carries, by pushing, the printed wiring board 2 to a next placing post. As shown in FIGS. 19 and 22C, in this the placing post, the printed wiring board 2 is over the most upstream placing mechanisms 122a and 112b and next placing mechanisms 122c and 122d. As having been described in the foregoing, the electronic part is placed in a predetermined on the printed wiring board 2 by the downstream placing mechanisms 122c and 122d and upstream placing mechanisms 122a and 122b. Note that when the printed wiring board 2 is in a position over the upstream pair of placing mechanisms 122a and 122b and next pair of placing mechanisms 122c and 122d, both these pairs of placing mechanisms are used to place electronic parts onto the printed wiring board 2 by both the pairs of placing mechanisms in order to attain an improved efficiency of electronics packaging. At this time, the downstream pair of placing mechanisms will be controlled by the controller which controls the upstream pair of placing mechanisms. In the above placing unit 4, since the printed wiring board 2 is supported in upright position by the transfer mechanisms 121a to 121 d, electronic parts 10 and 10a can be placed on respective sides of the printed wiring board 2 at the same time, which leads to a reduced time for electronics packaging and a smaller electronics packaging system than the conventional system in which electronic parts are mounted on each side of a printed wiring board in one pass. As shown in FIG. 18, in the placing unit 4, land-position data generated by the controller 15 in the printer 3 is supplied to the controller 123a in the placing mechanisms 122a and 122b via the system controller 124, and the data is supplied sequentially to the controllers 123b to 123d in this order to control the placing mechanisms 122a to 122h. Thus, it is not necessary to provide any land-position data detecting mechanism in the transfer mechanisms 121a to 121d, which contributes to a simplified construction of the electronics packaging system. When the printed wiring board 2 is in a position over the most upstream pair of placing mechanisms 122a dn 122b and next pair of placing mechanisms 122c and 122d, electronic parts 10 and 10a are placed in predetermined positions on the printed wiring board 2 by the upstream pair of placing mechanisms 122c and 122d and upstream pair of placing mechanisms 122a and 122b. Thus, it is possible to place electronic parts on the printed wiring board 2 at the same time by the four placing mechanisms 122a to 122d in the placing unit 4, which leads to an improved efficiency of electronics packaging. As shown in FIG. 33, the above placing mechanism 122 can be made as an adhesive applicator by forming a part of the suction head 146 as an adhesive application mechanism 199 to provisionally secure electronic parts 10 and 10a in a transfer process from the placement of the electronic parts 10 and 10a on the printed wiring board 2 up to transfer of the printed wiring board 2 to the reflow unit 5. In this case, the adhesive application is disposed between the printer 3 and placing unit 4. Especially, combination of the adhesive application mechanism 199 with the above placing unit 4 permits to place larger-size electronic parts on either side of a printed wiring board at the same time. As shown in FIG. 34, the suction head 146 may be constructed as a part fixing unit by forming a part of the suction head 146 as a screwing mechanism 200. Thereby, an electronic part can be screwed from either side of the printed wiring board (work), which also leads to an improved efficiency of electronics packaging. Next, there will be described with reference to the accompanying drawings the reflow unit 5 to solder, to the printed wiring board 2, the electronic parts 10 and 10a once placed on the printed wiring board 2 by the above-mentioned placing unit 4 as in the above. As shown in FIG. 35, the reflow unit 5 includes a transfer mechanism 211 to carry the printed wiring board 2 having cream solder printed on the lands thereof while being supported in generally upright position, a reflow furnace unit 212 to heat the printed wiring board 2 supported by the transfer mechanism 211 to melt the cream solder printed on the lands of the printed wiring board 2 by the printer 3, first and second heating mechanisms 213 and 214 provided opposite to respective sides of the printed wiring board 2 supported by the transfer mechanism 211, a third heating mechanism 215 provided inside the reflow furnace unit 212 to heat, from below, the printed wiring board 2 supported by the transfer mechanism 211, and a cooling block 216 to cool the melted cream solder on the lands of the printed wiring board 2. As shown in FIG. 36, the transfer mechanism 211 to carry the printed wiring board 2 has guide members 221 provided in the direction in which the printed wiring board 2 is brought. As shown in FIG. 36, each of the guide members 221 has formed therein guide recess 222 directed in the direction of arrow N in FIG. 36 in which the printed wiring board 2 is to be carried and in which the upper and lower edges of the printed wiring board 2 are engaged and supported, respectively. The transfer mechanism 211 has a carrying block 223 to carry the printed wiring board 2 as shown in FIG. 36. The carrying block 223 includes a carrying member 224 to carry the printed wiring board 2, a carrying pin 225 provided on the carrying member 224 for engagement in the engagement hole 6b formed in the printed wiring board 2. The carrying member 224 is connected to a cylinder mechanism 227 provided on a carrying-member guide member 226 which provides a guide for moving the carrying member 224 in the direction in which the printed wiring board 2 is to be brought. More particularly, the cylinder mechanism 227 has a shaft 228 fixed to the carrying member 224. The shaft 228 is engaged into, or disengaged from, the engagement hole 6b in the printed wiring board 2 by moving the carrying pin 225 in the direction of arrow O and opposite direction in FIG. 36. The carrying-member guide member 226 is moved by a driving mechanism 229 in the direction of arrow N in FIG. 36. The driving mechanism 228 includes a drive motor 230, and an endless belt 232 extended between and on a roller 231 fixed to the drive shaft of the drive motor 230 and a roller (not shown). The endless belt 232 has the carrying-member guide member 226 fixed thereto. Note that the carrying-member guide member 226 is guided on a rail member 234 on a guide member 233 provided in the direction in which the printed wiring board 2 is to be carried. The transfer mechanism 211 constructed as in the above functions as will be described below. Before the printed wiring board 2 having electronic parts 10 and 10a placed thereon by the aforementioned placing unit 4 is introduced into the transfer mechanism 211, the carrying member 224 has been moved in the direction opposite to the direction of arrow N in FIG. 36 and the carrying pin 225 has been moved by the cylinder mechanism 227 in the direction opposite to the direction O in FIG. 36. When the printed wiring board 2 is put into the transfer mechanism 211, it is engaged at the lateral edges thereof in the guide recesses 222 in the guide members 221. The carrying pin 225 is moved by the cylinder mechanism 227 in the direction of arrow O in FIG. 36 and engaged into the engagement hole 6b. Then, the driving mechanism 229 is put into action to allow the endless belt 232 to run, whereby the carrying member 224 is moved in the direction of arrow N in FIG. 36 while being guided along the rail 234 on the guide member 233, to thereby carry the printed wiring board 2 engaged and supported in the guide recess 222 in the same direction as the direction of arrow N. The printed wiring board 2 is carried by the transfer mechanism 211 through the reflow furnace unit 212 and cooling block 216. For removing the printed wiring board 2 from the transfer mechanism 211, the carrying pin 225 is moved by the cylinder mechanism 227 in the direction opposite to the direction of arrow O in FIG. 36, disengaged from the engagement hole 6b and thus can be removed from the transfer Mechanism 211. The reflow furnace unit 212 provided to cover the aforementioned transfer mechanism 211 consists of a pre-heating reflow furnace 212b and a heating reflow furnace 212b disposed contiguously to and downstream of the pre-heating reflow furnace 212a as shown in FIG. 35. The pre-heating reflow furnace 212a has formed in one side thereof an inlet opening 235a through which the printed wiring board 2 is introduced, and the heating reflow furnace 212b has formed in one side thereof an outlet opening 235b through which the printed wiring board 2 is brought out. Note that these openings 235a and 235b may be provided each with a curtain for preventing the temperature in the reflow furnaces 212a and 212b from being lower. As shown in FIGS. 36 and 37, each of the reflow furnaces 212a and 212b has the first to third heating mechanisms 213,214 and 215 provided therein. The first and second heating mechanisms 213 and 214 are disposed to face each main side of the printed wiring board 2 being carried while being supported in generally upright position by the transfer mechanism 211. Each of the first and second heating mechanisms 213 and 214 includes a three-phase heater of 200 V, 20 A. The third heating mechanism 215 is disposed in the lower portion inside the reflow furnaces 212a and 212b and under the transfer mechanism 211. The third heating mechanism 215 heats the reflow furnaces 212a and 212b from below. The third heating mechanism 215 includes a single-phase heater of 100 V, 15 A. Further, there are provided first to fourth heat storage plates 236, 237,238 and 239 to enclose the transfer mechanism 211 in the reflow furnaces 212a and 212b as shown in FIGS. 36 and 37. The first heat storage plate 236 is disposed between the first heating mechanism 213 and the printed wiring board 2 being carried by the transfer mechanism 211. The second heat storage plate 237 is disposed between the second heating mechanism 214 and the printed wiring board 2 being carried by the transfer mechanism 211. The third heat storage plate 238 is disposed above the third heating mechanism 215 under the reflow furnaces 212a and 212b. The fourth heat storage plate 239 is disposed opposite to the third heat storage plate 238 and near the ceiling of the reflow furnace unit 212. In the first to fourth heat storage plates 236 to 239, there are formed at regular intervals a plurality of through-holes 240a, 240b, 240c and 240d, respectively, to generate a convection of air heated by the first to third heating mechanisms 213, 214 and 215. Thus, since the first to fourth heat storage plates 236, 237, 238 and 239 are disposed in the reflow furnaces 212a and 212b to enclose the printed wiring board 2 supported by the transfer mechanism 211, the inside of the reflow furnaces 212a and 212b as a whole is evenly heated. For example, the pre-heating reflow furnace 212a provides a heating at 140°C while the heating reflow furnace 212b provides a heating at 220 to 240 °C. FIG. 38 shows the thermal characteristic found in the heating reflow furnace 212b. In FIG. 38, a dashed line 241 indicate the thermal characteristic in the upper portion of the reflow furnace 212b, a solid line 242 indicates the thermal characteristic in the middle of the reflow furnace 212b, and a broken line 243 indicates the thermal characteristic in the lower portion of the reflow furnace 212b. In case the first to third heating mechanisms 213,214 and 215 are disposed and the first to fourth heat storage plates 236 to 239 are disposed to enclose the transfer mechanism 211 as in the above, the temperature in the reflow furnace 212b can be nearly the same in all the upper, middle and lower portions of the reflow furnace 212b as will be seen from FIG. 38. For example, the temperature difference among these portions can be less than about 4°C. As shown in FIG. 35, an exhaust hood 244 is provided on the ceilings of the reflow furnaces 212a and 212b. The exhaust hood 244 is connected by connection tubes 245 to the pre-heating reflow furnace 212a, and by connection tubes 246 to the heating reflow furnace 212b. The exhaust hood 244 has an exhaust duct 247 as shown in FIG. 35. Air exhausted from inside the reflow furnaces 212a and 212b is accumulated once in the exhaust hood 244, and then exhausted from the exhaust duct 247, thereby permitting to prevent the temperature in the reflow furnaces 212a and 212b from being lower. As shown in FIG. 39, there is provided downstream of the heating reflow furnace 212b the cooling block 216 to cool the melted solder. In the cooling block 216, cooling fans 248 are disposed to face one side of the printed wiring board 2 supported in nearly upright position by the transfer mechanism 211, and cooling fans 249 are disposed to face the other side of the printed wiring board 2. The cooling fans 248 and 249 are disposed to face the main sides, respectively, of the printed wiring board 2 being carried while being support in generally upright position by the transfer mechanisms 121a to 121d, and so the melted solder on each main side of the printed wiring board 2 can be cooled and solidified with a high efficiency. The printer 3 constructed as in the above functions as will be described below with reference to FIG. 40. Before the printed wiring board 2 having the electronic parts 10 and 10a placed thereon by the placing unit 4 is introduced into the transfer mechanism 211, the carrying member 224 has been moved in the direction opposite to the direction of arrow N in FIG. 36 and the carrying pin 225 has been moved by the cylinder mechanism 227 in the direction opposite to the direction of arrow O in FIG. 36. In step S21, the printed wiring board 2 is introduced into the transfer mechanism 211. The printed wiring board 2 is engaged at the edge thereof engaged in the guide recess 222 in the guide member 221. The carrying pin 225 is moved by the cylinder mechanism 227 in the direction of arrow O in FIG. 36 and engaged into the engagement hole 6b in the printed wiring board 2. The driving mechanism 229 is put into action to cause the endless belt 232 to run. Thus the printed wiring board 2 is moved by the carrying member 224 in the direction of arrow N in FIG. 36 while being guided on the rail 234 on the guide member 233 into the pre-heating reflow furnace 212a. In step S22, the printed wiring board 2 having the electronic parts 10 and 10a placed thereon is left stopped inside the pre-heating reflow furnace 212a for a predetermined length of time and thus the cream solder printed on the lands of the printed wiring board 2 is semi-melted. When the cream solder is semi-melted, the printed wiring board 2 is carried by the carrying member 244 out of the pre-heating reflow furnace 212a in step S23 and carried into the heating reflow furnace 212b in step S24. Next in step S25, the printed wiring board 2 having the electronic parts 10 and 10a placed thereon with the cream solder being semi-melted is left stopped for a predetermined length of time in the heating reflow furnace 212b and thus the semi-melted cream solder is completely melted. Thereafter, in step S26, the printed wiring board 2 is brought out by the carrying member 244 from the heating reflow furnace 212b and then brought into the cooling block 216 in step S27. In this step S27, the melted cream solder is cooled and solidified in the cooling block 216, and thus the electronic parts 10 and 10a are soldered to the printed wiring board 2. Thereafter, the printed wiring board 2 is carried by the transfer mechanisms 211 to an outlet position where the carrying pin 225 is moved by the cylinder mechanism 227 in the direction opposite to the direction of arrow O in FIG. 36, disengaged from the engagement hole 6b and brought out by the transfer mechanism 211. In the above reflow unit 5, since the printed wiring board 2 is supported in upright position by the transfer mechanism 211, so the electronic parts 10 and 10a placed on either side of the printed wiring board 2 can be soldered to the latter at the same time. Therefore, the reflow unit 5 dedicates very much to a reduced time for mounting of the electronic parts 10 and 10a, and also to a smaller scale of the electronics packaging system than the conventional system in which electronic parts The printer 3 has the screen mechanisms 12 provided across the printed wiring board 2 supported by the transfer mechanism 11. The placing unit 4 has the placing mechanisms 122a to 122h provided across the printed wiring board 2 supported in the transfer mechanisms 121a to 121d. Further, the reflow unit 5 has the placing mechanisms 122a to 122h provided across the printed wiring board 2 supported by the transfer mechanisms 121a to 121d. Thus, in the electronics packaging system 1, the cream solder can be printed by the printer 3 on the land on either side of the printed wiring board at the same time, next the electronic parts 10 and 10a can be placed by the placing unit 4 on either side of the printed wiring board 2 at the same time, and then the electronic parts 10 and 10a placed on either side of the printed wiring board 2 can be soldered by the reflow unit 5 to the printed wiring board 2 at the same time. Therefore, the packaging system 1 can be designed to a size taking only a half of the space occupied by the conventional system in which cream solder is printed on each side of a printed wiring board and electronic parts are placed on, and soldered, to each side of the printed wiring boards in one pass, and can also dedicate to an improved efficiency of production. As shown in FIG. 18, in the placing unit 4, land-position data generated by the controller 15 of the printer 3 is supplied to the controller 123a for the placing mechanisms 122a and 122b via the system controller 124, and then the land-position data supplied to the controller 123a is sequentially supplied to the controllers 123b to 123d, to thereby control the placing mechanisms 122a to 122h. Thus, no mechanism To detect land positions may be provided for the placing mechanisms 121a to 121d, which will further dedicate to a simplification of the system. Industrial Applicability As having been described in the foregoing, the electronics packaging system according to the present invention carries a printed wiring board on which electronic parts are to be mounted while being held in generally upright position, which makes it possible to printed solder on the land on either side of the printed wiring board at the same time, place the electronic parts on the lands at the same time and solder the electronic parts to the printed wiring board at the same. Thus, the entire system can be desired more compact and electronic parts can be mounted with a higher efficiency. We claim: 1. An electronics packaging system [1] comprising: a printer [3] to print solder to either land of a printed wiring board [2], wherein the printed wiring board [2] is held in a upright position; a placing unit [4] to place electronic parts on the lands of the printed wiring board [2], having the solder printed thereon by the printer [3]; and a reflow unit [5] to heat the printed wiring board [2] on which the electronic parts [10] have been placed by the placing unit [4] and solder the electronic parts [10] to the printed wiring board [2]. 2. The electronics packaging system [1] as claimed in claim 1, comprising: a detecting mechanism [38] to generate land-position information before the solder is printed by the printer [3] on the lands of the printed wiring board [2]; and wherein, the electronic-part [10] is placed on the printed wiring board [2] on the basis of the land-position information. 3. An electronic-part placing unit [4] in an electronics packaging system [1] as claimed in claim 1, comprising: transfer mechanisms [11] to carry a printed wiring board [2] while keeping it in generally upright position; a part holding mechanism [142] to hold, by suction, an electronic part supplied from a part feeder [141]; a turning mechanism [143] to shuttle the part holding mechanism [142] between a first position in which the electronic part supplied from the part feeder [141] is held by suction and a second position where it is opposite to the printed wiring board [2] supported by the transfer mechanisms [11]; and a guide mechanism [144] including first and second guide members [162, 163] to guide the up-down movement of the part holding mechanism [142] in the second position. 4. The electronic-part placing unit [4] as claimed in claim 3, wherein: the turning mechanism [143] includes a rack disposed along the direction in which the part holding mechanism [142] is moved up and down, and a gear [158] provided integrally with the part holding mechanism [142] and engaged with the rack [159]; and the gear in mesh with the rack is rotated, as the part holding mechanism [142] is moved up and down, to shuttle the part holding mechanism [142] between the first and second positions. 5. The electronic-part placing unit [4] as claimed in claim 3, wherein: there is provided in a position opposite to the part holding mechanism [142] staying in the second position a detector to detect the held state of the electronic part [10] held by the part holding mechanism [142], the part holding mechanism [142] including an adjusting mechanism rotatable about a direction perpendicular to the up-down moving direction of the part holding mechanism [142] to adjust the held state of the electronic part [10]. 6. The electronic-part placing unit [4] as claimed in claim 3, wherein the electronic-part placing unit [4] is juxtaposed with the transfer mechanisms [11] and positioned by engagement with a positioning unit provided on a base plate [18]. 7. A printer in an electronics packaging system [1] as claimed in claim 1 comprising: a transfer mechanism [11] to carry a printed wiring board [2] while keeping it in generally upright position; a pair of screen mechanisms [12] each including a screen disposed opposite to the printed wiring board supported by the transfer mechanism [11] movably towards and away from the printed wiring board [2]; a squeegee mechanism [13] disposed correspondingly to each screen mechanism [12] to be slid by the screen and squeeze ink to the printed wiring board [2] as the screen is moved towards the printed wiring board [2]; and a driving mechanism [14] to move the screen mechanisms [12] so as to slide the squeegee mechanism [13]. 8. The printer [3] as claimed in claim 7, wherein the ink is cream solder. 9. The printer [3] as claimed in claim 7, wherein the driving mechanism [14] includes: a single drive motor [84]; a driving force transmission [85] to transmit the force from the drive motor [84]; and a moving member to move the squeegee mechanism [13] by means of the driving force transmission [85] when the drive motor [84] is in operation. 10. The printer [3] as claimed in claim 7, wherein: the transfer mechanism [211] include a pair of guide rails [16,17] to support the printed wiring board [2] at the edges being in parallel to the direction in which the printed wiring board [2] is to be carried; each of the guide rails [16,17] including a pair of engaging and support plates disposed opposite to each other to support, by engagement, the edges of the printed wiring board [2]; and each of the engagement and support plates has a thickness with which it is deflected into close contact with the printed wiring board [2] when the screen is pressed by the squeegee. 11. The printer [3] as claimed in claim 7, wherein there is provided near the end of the squeegee an auxiliary arm to roll the ink when the squeegee makes the screen slide. 12. The printer [3] as claimed in claim 7, further including a detector to detect a position detection mark provided on the printed wiring board [2] and thus detect the posture of the printed wiring board [2] supported on the guide rails [16,17]. 13. The printer [3] as claimed in claim 12, further including an adjusting mechanism to correct the posture of the printed wiring board [2] supported on the guide rails [16,17]. 14. A reflow unit in an electronics packaging system [1], as claimed in efafrn j! comprfsfngr a transfer mechanism [211] to carry a printed wiring board [2] having cream solder printed on lands thereof while keeping it in generally upright position; a reflow furnace [212] to heat the printed wiring board [2] supported by the transfer mechanism [211] and thus melt the cream solder printed on the lands; a first heating mechanism [213] provided in the reflow furnace [212] to face one main side of the printed wiring board [2] supported by the transfer mechanism [211]; a second heating mechanism [214] provided in the reflow furnace [212] to face the other main side of the printed wiring board [12] supported by the transfer mechanism [211]; and a third hearing mechanism [215] provided in the reflow furnace [212] to heat, for below, the printed wiring board [2] supported by the transfer mechanism [211]. 15. The reflow unit as claimed in claim 14, wherein the reflow furnace [212] has heat storage plates to enclose the printed wiring board [2] supported by the transfer mechanism [211], each of the heat storage plates having a plurality of holes formed therein. 16. The reflow unit as claimed in claim 15, wherein the reflow furnace has an exhaust hood [244] provided thereon to exhaust air from the reflow furnace through the exhaust hood [244]. Dated this 20/12/2001 (JAYANTA PAL) OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS]

Documents:

abstract1.jpg

in-pct-2001-01624-mum-cancelled pages(6-2-2007).pdf

in-pct-2001-01624-mum-claims(20-12-2001).pdf

in-pct-2001-01624-mum-claims(granted)-(5-11-2007).pdf

in-pct-2001-01624-mum-claims(granted)-(6-2-2007).doc

in-pct-2001-01624-mum-claims(granted)-(6-2-2007).pdf

in-pct-2001-01624-mum-correspondence(7-9-2007).pdf

in-pct-2001-01624-mum-correspondence(ipo)-(26-10-2006).pdf

in-pct-2001-01624-mum-correspondence(ipo)-(31-12-2007).pdf

in-pct-2001-01624-mum-declaration(20-12-2001).pdf

in-pct-2001-01624-mum-description(complete)-(20-12-2001).pdf

in-pct-2001-01624-mum-description(granted)-(5-11-2007).pdf

in-pct-2001-01624-mum-drawing(20-12-2001).pdf

in-pct-2001-01624-mum-drawing(6-2-2007).pdf

in-pct-2001-01624-mum-drawing(amended)-(6-2-2007).pdf

in-pct-2001-01624-mum-drawing(granted)-(5-11-2007).pdf

in-pct-2001-01624-mum-form 1(20-12-2001).pdf

in-pct-2001-01624-mum-form 1(6-2-2001).pdf

in-pct-2001-01624-mum-form 13(7-9-2007).pdf

in-pct-2001-01624-mum-form 18(27-4-2005).pdf

in-pct-2001-01624-mum-form 1a(6-2-2007).pdf

in-pct-2001-01624-mum-form 2(granted)-(5-11-2007).pdf

in-pct-2001-01624-mum-form 2(granted)-(6-2-2007).doc

in-pct-2001-01624-mum-form 2(granted)-(6-2-2007).pdf

in-pct-2001-01624-mum-form 2(title page)-(granted)-(5-11-2007).pdf

in-pct-2001-01624-mum-form 3(20-12-2001).pdf

in-pct-2001-01624-mum-form 3(6-2-2007).pdf

in-pct-2001-01624-mum-form 5(20-12-2001).pdf

in-pct-2001-01624-mum-form 5(6-2-2007).pdf

in-pct-2001-01624-mum-form-pct-isa-210(20-12-2001).pdf

in-pct-2001-01624-mum-petition under rule 138(7-2-2007).pdf

in-pct-2001-01624-mum-power of authority(10-12-2001).pdf

IN-PCT-2001-01624-MUM-POWER OF AUTHORITY(5-3-2002).pdf

in-pct-2001-01624-mum-power of authority(6-2-2007).pdf

in-pct-2001-01624-mum-specification(amended)-(6-2-2007).pdf