Abstract:
A semiconductor module includes a first metal foil; an insulating sheet mounted on a top surface of the first metal foil; at least one second metal foil mounted on a top surface of the insulating sheet; at least one semiconductor device mounted on the second metal foil; and a resin case for surrounding the first metal foil, insulating sheet, second metal foil, and semiconductor device. A bottom end of a peripheral wall of the resin case is located above a bottom surface of the first metal foil. A resin is provided inside the resin case to fill the inside of the resin case. The bottom surface of the first metal foil and the resin form a flat bottom surface so that the flat bottom surface contacts an external mounting member.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     This invention relates to a semiconductor module and in particular relates to a semiconductor module mounted with a power semiconductor device. 
     In inverter devices, uninterruptible power supply devices, machining equipments, industrial robots, and other equipments, semiconductor modules, which are independent of the main unit of the equipment, are employed. 
     As the construction of such semiconductor modules, generally, a metal base plate of prescribed thickness is used as a foundation, and a package mounted with power semiconductor devices is provided on the metal base plate (see for example Japanese Unexamined Patent Publication No. 2003-289130). For example,  FIG. 7  is a schematic diagram of a semiconductor module employing a metal base plate as a foundation. 
     This semiconductor module  100  employs a metal base plate  101  with several millimeters in thickness as a foundation. Metal foil  103  is mounted onto the metal base plate  101  through a solder layer  102 . An insulating sheet  104  is mounted onto the metal foil  103 . And metal foils  105 ,  106  are mounted onto the insulating sheet  104 . Further, on the metal foils  105 ,  106  are mounted semiconductor devices  109 ,  110 , through solder layers  107 ,  108 . Here, the semiconductor devices  109 ,  110  are, for example, IGBTs (Insulated Gate Bipolar Transistors), FWDs (Free Wheeling Diodes), or other devices. And, onto the semiconductor devices  109 ,  110  are mounted heat spreaders  113 ,  114 , through solder layers  111 ,  112 . A resin case  115 , molded so as to surround the semiconductor devices  109 ,  110  and the like, is fixed onto the upper edge of the metal base plate  101 . 
     Although not shown, metal wires, lead frames, and similar are arranged on the periphery of the semiconductor devices  109  and  110 ; for example, electrodes of the semiconductor devices  109 ,  110  are electrically mounted to a circuit pattern formed on the insulating sheet  104 , or, electrical connections are formed between electrodes of the semiconductor devices  109 ,  110 . 
     Further, the interior of the resin case  115  is filled with a gel  116 , in order to prevent contact between metal wires and similar, and to protect the semiconductor devices  109 ,  110 , and similar from moisture, humidity, and dust. 
     A cooling member  130  is positioned below the semiconductor module  100 , bolts or similar are passed through holes  117  provided in the resin case  115  and metal base plate  101 , and the metal base plate  101  is brought into close contact with the cooling member  130  by tightening the bolts or similar. 
     There are cases in which the resin case  115  is damaged in the vicinity of the holes  117  by tightening the bolts or similar. In order to prevent such damage, reinforcing metal rings  118  are provided on the inside of the holes  117  in the resin case  115 . 
     However, such a semiconductor module  100  employs a thick metal base plate  101  as a foundation, so that the weight and size of the semiconductor module cannot be decreased. 
     Hence, there has been disclosed a small-size semiconductor module which does not use a metal base plate  101  as a foundation (see for example Komatsu, Saotome and Igawa, “Small-capacitance IGBT module”,  Fuji Jihou , Vol. 78, No. 4, 2005, pp. 260-263). 
       FIG. 8  is a schematic diagram of a semiconductor module which does not use a metal base plate. 
     This semiconductor module  200  is based on an insulating sheet  104 , metal foil  103  formed below the insulating sheet  104 , and metal foils  105 ,  106  formed above the insulating sheet  104 . Onto the metal foils  105 ,  106  are mounted semiconductor devices  109 ,  110 , through solder layers  107 ,  108 . In this type of semiconductor module  200 , a resin case  115 , molded so as to surround the semiconductor devices  109 ,  110 , is fixed onto the upper edge of the insulating sheet  104 . The interior of the resin case  115  is similarly filled with a gel  116  comprising a silicone material. 
     By means of such a semiconductor module  200 , a thick metal base plate needs not be used as a foundation, so that the semiconductor module can be made lighter and more compact, and costs can be reduced. 
     Further, in a semiconductor module  200  of this type where there is no metal base plate, a metal hook  119  for installation is separately provided on a side portion of the resin case  115 . A bolt or similar penetrates the metal hook  119 , and the semiconductor module  200  is fixed to the cooling member  130  by tightening the bolt or similar. 
     However, in the construction of a semiconductor module  200  shown in  FIG. 8 , a soft gel  116 , comprising a silicone material, is used as the sealing material in the resin case  115 . 
     When a bolt is used to firmly fasten the semiconductor module  200  sealed with such a gel  116  on the cooling member  130 , excessive amount of stress is applied to the insulating sheet  104  within the semiconductor module  200 , and in some cases the insulating sheet  104  is damaged. That is, because the gel  116  is soft, deformation (distortion) of the insulating sheet  104  cannot be avoided. As a result, the insulating sheet  104  is damaged. 
     In order to avoid such damage, the semiconductor module  200  must be fastened to the cooling member  130  in such a range that there is no damage to the insulating sheet  104 . Hence, in this structure of a semiconductor module  200 , the metal foil  103  cannot be firmly brought into close contact with the cooling member  130 . As a result, there has been a problem that an adequate cooling effect cannot be obtained. 
     Moreover, in the semiconductor module  200 , heat is dissipated each time the semiconductor devices  109 ,  110  are operated, and this heat also causes deformation of the insulating sheet  104 . Hence, as the semiconductor module  200  is used over a long period of time, deformation of the insulating sheet  104  repeatedly occurs. As a result, there has been a problem that the solder layers  107 ,  108  immediately below the semiconductor devices  109 ,  110  peel away. 
     Further, in such a semiconductor module  200 , the thickness of the insulating sheet  104  is increased in order to secure adequate mechanical strength (for example, approximately 0.6 mmt or greater). 
     However, in a semiconductor module  200  using such a thick insulating sheet  104 , there is a limit as to the thermal conductivity from the lower faces of the semiconductor devices  109 ,  110  to the cooling member  130 . For this reason, there has been a problem that high-power semiconductor devices could not be incorporated into such semiconductor modules  200 . 
     Also, this structure for a semiconductor module  200  necessitates the additional manufacturing step of separately installing a metal hook  119  for installation of the resin case  115 . 
     This invention has been made in light of the above problems, and has objectives to provide a semiconductor module which achieves reduced weight, smaller size, and lower cost for mounting with high-power semiconductor devices and has an adequate cooling effect. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     In order to achieve the objectives stated above, the invention provides a semiconductor module comprising an insulating sheet; a first metal foil mounted to a first main face of the insulating sheet; at least one second metal foil mounted to a second main face of the insulating sheet; at least one semiconductor device mounted onto the second metal foil; a resin case which surrounds the first metal foil, insulating sheet, second metal foil, and semiconductor device above the lower face of the first metal foil; and resin which is filled into the space between the inner surface of the resin case and the outer peripheral-edge face of the first metal foil and the outer faces of the insulating sheet, second metal foil, and semiconductor device. A flat face, which can be brought into close contact with an external mounting member, is formed by the lower face of the first metal foil and the resin exposed from the resin case. 
     Further, this invention provides a method for manufacturing a semiconductor module. The method includes the steps of: preparing a board having an insulating sheet, a first metal foil mounted to a first main face of the insulating sheet, and at least one second metal foil mounted to a second main face of the insulating sheet; mounting at least one semiconductor device on the second metal foil; placing a resin case which surrounds the first metal foil, insulating sheet, second metal foil, and semiconductor device above the lower face of the first metal foil, onto the board; pouring resin in paste form into the space between the inner face of the resin case and the outer peripheral-edge face of the first metal foil and the outer faces of the insulating sheet, second metal foil, and semiconductor device; and heat-curing the resin, wherein a flat face, which can be brought into close contact with an external mounting member, is formed by the lower face of the first metal foil and the resin exposed from the resin case. 
     According to the semiconductor module and method for manufacturing the semiconductor module, the first metal foil is mounted to the first main face of the insulating sheet, at least one second metal foil is mounted to the second main face of the insulating sheet, and at least one semiconductor device is mounted onto the second metal foil. And, the first metal foil, insulating sheet, second metal foil, and semiconductor device are surrounded by a resin case above the lower face of the first metal foil. The space between the inner face of the resin case and the outer peripheral-edge face of the first metal foil and the outer faces of the insulating sheet, second metal foil, and semiconductor device is filled with resin. And, a flat face is formed which can be brought into close contact with an external mounting member by the lower face of the first metal foil and the resin exposed from the resin case. 
     In a semiconductor module and a method for manufacturing a semiconductor module of this invention, a first metal foil is mounted to a first main face of an insulating sheet, at least one second metal foil is mounted to a second main face of the insulating sheet, and at least one semiconductor device is mounted onto the second metal foil. And, a resin case surrounds the first metal foil, insulating sheet, second metal foil, and semiconductor device above the lower face of the first metal foil, and resin is filled into the space between the inner face of the resin case and the outer peripheral-edge face of the first metal foil and the outer faces of the insulating sheet, second metal foil, and semiconductor device. Moreover, a flat face is formed which can be brought into close contact with an external mounting member by the lower face of the first metal foil and the resin exposed from the resin case. 
     By this means, a semiconductor module and a method for manufacturing a semiconductor module can be made such that the semiconductor module mounted with power semiconductor devices is light in weight, small in size, and low in cost, has an adequate cooling effect, and can be mounted with high-power semiconductor devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1(A) ,  1 (B),  1 (C) are schematic diagrams of principal portions, explaining the configuration of a semiconductor module; 
         FIG. 2  is a first diagram explaining a process in a semiconductor module manufacturing method; 
         FIG. 3  is a second diagram explaining a process in a semiconductor module manufacturing method; 
         FIG. 4  is a third diagram explaining a process in a semiconductor module manufacturing method; 
         FIG. 5  explains the structure of a board deformed into a convex shape; 
         FIG. 6  is a schematic diagram of a cross-section of principal portions, explaining a modified example of a semiconductor module; 
         FIG. 7  is a schematic diagram of a conventional semiconductor module employing a metal base plate as the foundation; and 
         FIG. 8  is a schematic diagram of a conventional semiconductor module not employing a metal base plate. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Below, the invention is explained in detail, referring to the drawings. 
     First, the configuration of a semiconductor module is explained. 
       FIGS. 1(A) ,  1 (B),  1 (C) are schematic diagrams of principal portions, explaining the configuration of a semiconductor module. Here, in  FIG. 1(A) , a schematic top view of principal portions of a semiconductor module  1  is shown, and in  FIG. 1(B) , a schematic diagram of a cross-section of principal portions of the semiconductor module  1  is shown. In  FIG. 1(C) , a schematic bottom view of principal portions of the semiconductor module  1  is shown. 
     Also, in  FIG. 1(B) , a cross-sectional view taken along a line  1 (B)- 1 (B) in  FIGS. 1(A) and 1(C)  is shown. In  FIGS. 1(A) ,  1 (B), a state is shown in which a cooling member  40  (cooling fins), which is the external mounting member, is mounted to the lower face of the semiconductor module  1 . In  FIG. 1(C) , however, the cooling member  40  is not shown in order to clearly display the lower face of the semiconductor module  1 . 
     In the semiconductor module  1  shown, a board is formed of a rectangular insulating sheet  10 , metal foil  11  formed by a DCB (Direct Copper Bonding) method on the lower face of the insulating sheet  10 , and at least one other metal foil  12  (in  FIG. 1 , two metal foils  12 ) formed by the same DCB method on the upper face of the insulating sheet  10 . At Semiconductor devices  14 ,  15  are mounted onto the metal foils  12  with a tin (Sn)-silver (Ag)-based lead-free solder layer  13  intervening. Here, the insulating sheet  10  is, for example, formed from an alumina (Al 2 O 3 ) sintered ceramic, and the metal foils  11 ,  12  are formed from metal whose main component is copper (Cu). The semiconductor devices  14 ,  15  are for example IGBT devices, FWD devices, power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), or other power semiconductor devices. 
     Further, heat spreaders  16 , whose main component is copper, are mounted, via a solder layer  17  of the same component, onto the surface electrodes (not shown) arranged on the upper faces of the semiconductor devices  14 ,  15 . 
     In the semiconductor module  1 , an insulating sheet with thickness approximately 0.35 mmt or less is used as the insulating sheet  10  in order to shorten the heat dissipation path from the lower faces of the semiconductor devices  14 ,  15  to the upper face of the cooling member  40 . Further, the thickness of the metal foils  11 ,  12  mounted to the main faces of the insulating sheet  10  is thicker than that of the metal foils  103 ,  105 ,  106  shown in  FIG. 7  and  FIG. 8 , for example, 0.5 to 0.6 mm. 
     In  FIGS. 1(A) ,  1 (B),  1 (C), particularly, although not shown, a plurality of semiconductor devices other than the semiconductor devices  14 ,  15  (for example, IGBT devices, FWD devices, power MOSFETs, and similar) is mounted on the insulating sheet  10 , and in addition to the metal foils  12 , a plurality of electrode terminals and similar is arranged on the insulating sheet  10 . On the periphery of the semiconductor devices  14 ,  15  are arranged metal wires, lead frames, and similar, to electrically connect, for example, the electrodes of the semiconductor devices  14 ,  15  and respective metal foils, or to connect the electrodes of the semiconductor devices  14 ,  15  to each other using metal wires. 
     Further, a molded resin case  20  is provided on the semiconductor module  1 , so as to surround the metal foil  11 , insulating sheet  10 , metal foils  12 , semiconductor devices  14 ,  15 , and heat spreader  16 , above the lower face  11   a  of the metal foil  11 . 
     Here, the material of the resin case  20  is, for example, PPS (polyphenylene sulfide). Further, fastening portions  20   a  for bolting are provided on a side portion of the resin case  20  so as to enable installation of the semiconductor module  1  on the cooling member  40 . The fastening portions  20   a  are integrally molded with the resin case  20 , and extend outward from side faces of the resin case  20 . 
     A highly rigid epoxy resin  30  is filled (sealed) into the space between the inner face of the resin case  20  and the outer peripheral-edge face of the metal foil  11  and the outer faces of the insulating sheet  10 , metal foils  12 , semiconductor devices  14 ,  15 , and heat spreader  16 . However, the lower face of the metal foil  11  is exposed from the epoxy resin  30 . 
     This epoxy resin  30  is poured into a resin-inflow opening  20   b  provided in the center of the upper face of the resin case  20 , to seal the semiconductor devices  14 ,  15 , insulating sheet  10 , and similar (details are explained below). Further, the epoxy resin  30  is filled so as to enter into the interior of the fastening portions  20   a . Holes  21 , through which bolts or other screw portions are to be passed, are formed penetrating the fastening portions  20   a  and the epoxy resin  30  inside the fastening portions  20   a.    
     The epoxy resin  30  is filled up to the same height as the lower face  11   a  of the metal foil  11 . And, a broad flat face  22  is formed by an outer face  30   a  formed by epoxy resin  30  exposed from the resin case  20  and the lower face  11   a  of the metal foil  11 . That is, the flat face  22 , in which the outer face  30   a  of epoxy resin  30  is combined with the lower face  11   a  of the metal foil  11 , becomes the bottom face of the semiconductor module  1 . By providing this flat face  22 , the semiconductor module  1  can be brought into firm and close contact with the cooling member  40  at the bottom face. The above-described epoxy resin  30  comprises an inorganic filler, which is not shown. 
     Further, in the semiconductor module  1 , the thermal expansion coefficient of the epoxy resin  30  is adjusted so as to match, as much as possible, the thermal expansion coefficients of the metal foils  11 ,  12 . For example, if the thermal expansion coefficient of the metal foils  11 ,  12 , formed from copper is approximately 16.5 ppm/K, then the thermal expansion coefficient of the epoxy resin  30  filled into the resin case  20  is approximately 15 ppm/K. By this means, when, for example, the semiconductor module  1  is operating, even if expansion and contraction of the metal foils  11 ,  12  occur, there is no occurrence of local stresses on the insulating sheet  10  or on the semiconductor devices  14 ,  15  because the thermal expansion coefficients are matched. 
     Also, whereas the thermal conductivity of the silicone gel used in the past as a sealing material is approximately 0.3 W/mK, the thermal conductivity of the epoxy resin  30  filled into the resin case  20  is adjusted to approximately 1 W/mK. Hence, heat generated by the semiconductor devices  14 ,  15  in the semiconductor module  1  is dissipated on the side of the cooling member  40 , and is also dissipated on the side of the epoxy resin  30 . As a result, heat generated by the semiconductor devices  14 ,  15  is dispersed above the semiconductor module  1  and in lateral directions, and so the semiconductor module  1  has a greater cooling effect. 
     The semiconductor module  1  is mounted to the cooling member  40  by passing bolts or similar through the holes  21  and fixing to the cooling member  40 . 
     In order to further promote the cooling effect, a thermal compound (not shown) or similar may be applied between the bottom face of the semiconductor module  1  and the upper face of the cooling member  40 . 
     By means of this construction of the semiconductor module  1 , the outer faces of the insulating sheet  10 , metal foils  11 ,  12 , and semiconductor devices  14 ,  15  are backed by highly rigid epoxy resin  30 . 
     Specifically, a highly rigid epoxy resin  30  is filled into the space between the inner face of the resin case  20  and the outer peripheral-edge face of the metal foil  11  and the outer faces of the insulating sheet  10 , metal foils  12 , and semiconductor devices  14 ,  15 . And, a broad flat face  22  is formed by means of an outer face  30   a  formed of epoxy resin  30  exposed from the resin case  20  and the lower face  11   a  of the metal foil  11 . Further, this flat face  22  is brought into contact with the upper face of the cooling member  40 . 
     A fastening portion  20   a , integrally formed with the resin case  20 , extends from a side face of the resin case  20 , and the interiors of the fastening portions  20   a  are also filled with highly rigid epoxy resin  30 . 
     By means of this construction of the semiconductor module  1 , by passing bolts or similar through the holes  21  provided in a side portion of the resin case  20 , the entirety of the semiconductor module  1  can be firmly fastened by the bolt or similar to the cooling member  40 . And, by means of this firm fastening, the flat face  22  and the upper face of the cooling member  40  can be brought into firm and close contact. As a result, a greater cooling effect can be secured for the semiconductor module  1 . 
     Because a broad flat face  22  is formed on the semiconductor module  1 , even when the entirety of the semiconductor module  1  is firmly fastened to the cooling member  40  by means of a bolt or similar, the contact pressure is uniformly distributed over the flat face  22 . As a result, even when the entirety of the semiconductor module  1  is firmly fastened to the cooling member  40  by means of a bolt or similar, there is no occurrence of local stresses in the insulating sheet  10 , deformation of the insulating sheet  10  is suppressed, and damage to the insulating sheet  10  is prevented. 
     Also, even when heat generated during operation of the semiconductor devices  14 ,  15  would cause deformation of the insulating sheet  10 , deformation of the insulating sheet  10  during operation of the semiconductor devices  14 ,  15  is suppressed, and damage to the insulating sheet  10  is prevented because stresses occurring within the insulating sheet  10  are distributed within the epoxy resin  30  as described above. 
     Further, peeling and similar of the solder layer  13  immediately below the semiconductor devices  14 ,  15  can also be prevented because deformation of the insulating sheet  10  is suppressed. 
     The interiors of the fastening portions  20   a  are filled with the highly rigid epoxy resin  30 , and the strength thereof is reinforced. Hence, even when bolts or similar are directly passed through the holes  21  and firmly tightened, damage to the fastening portions  20   a  does not occur. For this reason, there is no need to provide a metal ring  118  on the inside of the holes  21  for reinforcement, as shown in  FIG. 7 . 
     In the semiconductor module  1 , a thick metal base plate  101  is not used as in the case of the semiconductor module  200  shown in  FIG. 7 . As a result, the semiconductor module can be made lighter and more compact, and costs can be reduced. 
     In the semiconductor module  1 , an insulating sheet  10 , which is thinner than in the semiconductor module  200  shown in  FIG. 8 , is used, and still thinner metal foils  11 ,  12  are used. Hence, a greater cooling effect is obtained in the case of the semiconductor module  1  than the semiconductor module  200 . As a result, the semiconductor devices  14 ,  15  in the semiconductor module  1  can operate with greater stability. 
     Further, because the cooling effect of the semiconductor module  1  is enhanced, it is possible to mount a semiconductor more powerful, compared to the semiconductor module  200 . 
     Specifically, comparing the structure of PIMs (Power Integrated Modules) configured in the circuitry of inverters, converters and brakes, and structures (6-in-1 structures) where six pairs of IGBTs and FWDs connected in parallel in inverter circuits are combined in one package, the structure of a semiconductor module  200  enables mounting of semiconductor devices with a current rating at 1200 V of up to 15 A in the case of a PIM structure, and a current rating at 1200 V of up to 35 A in the case of a 6-in-1 structure. Whereas, when employing the structure of the semiconductor module  1 , semiconductor devices can be mounted with a current rating at 1200 V of up to 35 A in the case of a PIM structure, and with a current rating at 1200 V of up to 50 A in the case of a 6-in-1 structure. 
     Further, in the semiconductor module  1 , holes  21  with high rigidity are provided in a side portion of the resin case  20 , so that there is no need to separately provide a metal hook  119  for protection, as in the semiconductor module  200  shown in  FIG. 8 . As a result, semiconductor module manufacturing processes can be shortened, and costs can be reduced. 
     Next, a method for manufacturing the semiconductor module  1  is explained. In the following drawings, members which are the same as in  FIGS. 1(A) ,  1 (B),  1 (C) are assigned with the same symbols, and detailed explanations thereof are omitted. 
       FIG. 2  is used to explain one process in the method for manufacturing a semiconductor module. 
     First, as shown in  FIG. 2 , a board  50  is prepared in such a way that at least one metal foil  12  is mounted by the DCB method onto an insulating sheet  10 . Then, the semiconductor devices  14 ,  15  are mounted onto the metal foil  12  through a solder layer (not shown). Here, the material of the metal foil  12  includes copper, for example, as the main component, and is for example 0.5 to 0.6 mm thick. Then, a heat spreader  16  is mounted onto each of the main electrodes of the semiconductor devices  14 ,  15  through a solder layer (not shown). The heat spreaders  16  are electrically connected to the metal foils  12  by metal wires  18 . 
     Patterned metal foil (copper of thickness 0.5 to 0.6 mm) is mounted to the lower face of the insulating sheet  10  in the board  50  by the DCB method, but this metal foil is not shown in the figure. 
     In  FIG. 2 , a lid portion  20   c  forming the upper lid of the resin case  20  is shown. A plurality of lead frames  23  for external connection terminals is arranged in advance so as to penetrate the main face of the lid portion  20   c  substantially in the direction perpendicular thereto. 
     After performing positioning of the lid portion  20   c  relative to the board  50 , the lid portion  20   c  is moved in the direction of the arrow, to place the lid portion  20   c  onto the board  50  from above the board  50 . 
       FIG. 3  explains one process in the method for manufacturing the semiconductor module. 
     As shown in  FIG. 3 , as a result of placing the lid portion  20   c  on the board  50 , the plurality of lead frames  23  and the plurality of metal foils  12  on the board  50  are in contact. The portions to be in contact are soldered, so that the lead frames  23  are electrically connected to the respective metal foils  12 . By mounting the lead frames  23  onto the respective metal foils  12 , the lid portion  20   c  is fixed onto the board  50 . 
     Next, as shown in  FIG. 3 , the outer frame portion  20   d  which forms a large portion of the resin case  20  is positioned above the board  50  and lid portion  20   c . As stated above, this outer frame portion  20   d  has fastening portions  20   a  on the sides which are integrally formed. 
     Then, the outer frame portion  20   d  is moved in the direction of the arrow toward the board  50 , and the outer frame portion  20   d  is mated with the board  50  and lid portion  20   c  from above. 
       FIG. 4  explains one process in the method for manufacturing the semiconductor module. 
     In  FIG. 4 , a state where the outer frame portion  20   d  is mated with the board  50  and lid portion  20   c  is shown. In this state, on the side above the lower face of the metal foil, not shown, mounted to the lower face of the insulating sheet  10 , the metal foil, insulating sheet  10 , metal foils  12 , semiconductor devices  14 ,  15 , and heat spreaders  16  are surrounded by the resin case  20  (lid portion  20   c , outer frame portion  20   d ). 
     Then, the mated member  51  is sandwiched between a lower jig  60  and upper jig  61  for molding, as shown in  FIG. 4 , and a heat-curing type epoxy resin  31  is poured into a resin-inflow opening  20   b  provided in the center of the lid portion  20   c . At this stage, the epoxy resin  31  is in paste form. 
     When the epoxy resin  31  is poured into the resin-inflow opening  20   b , the epoxy resin  31  flows into the space between the inner face of the resin case  20  and the outer peripheral-edge face of the metal foil  11  and the outer faces of the insulating sheet  10 , metal foils  12 , and semiconductor devices  14 ,  15 , as well as the heat spreaders  16 . In addition, the epoxy resin  31  is filled in the fastening portions  20   a . The inner face  60   a  of the lower jig  60 , which is in contact with the lower portion of the mated member  51 , forms a broad flat face wider than the mated member  51 . 
     Then, after completely pouring the epoxy resin  31  in paste form into the resin case  20 , the mated member  51  is heated for a prescribed time at the curing temperature of the epoxy resin  31 . 
     By means of this heat treatment, the epoxy resin  31  which has been poured into the resin case  20  is cured, and the highly rigid epoxy resin  30  shown in  FIG. 1  seals the space between the inner face of the resin case  20  and some of the outer faces of the semiconductor devices  14 ,  15 , insulating sheet  10 , metal foils  11 ,  12 , and heat spreaders  16 . 
     Further, because the inner face of the lower jig  60  in contact with the mated member  51  is a flat face, a broad and flat bottom face is formed by the main face of the metal foil  11  and epoxy resin  31  exposed from the resin case  20 . 
     During pouring the epoxy resin  31 , circular column-shape protruding portions  61   a  provided on the upper jig  61  are inserted into holes formed in advance in the fastening portions  20   a , and the tips of the protruding portions  61   a  are brought into contact with the lower jig  60 . By this means, epoxy resin  31  does not flow into the portions where the protruding portions  61   a  are positioned, and after the epoxy resin  31  is cured, the holes  21  shown in  FIG. 1  are formed. 
     Through these manufacturing processes, the semiconductor module  1  shown in  FIGS. 1(A) ,  1 (B),  1 (C) is completed. 
     The metal foil  11  may be structured so as to have a lower-side convex shape in the bottom face. 
     For example, as shown in  FIG. 4 , at the uppermost contact face  20   e  of the resin case  20  making contact with the upper jig  61 , the interior of the resin case  20  is filled with epoxy resin  31  while adjusting the force pressing on the contact face  20   e  by the upper jig  61 . That is, the force with which the upper jig  61  presses against the contact face  20   e  is adjusted, and while causing distortion of the entirety of the mated member  51 , the interior is filled with epoxy resin  31 , and heat treatment is performed to cure the epoxy resin  31 . 
     The state of a board  50  manufactured using this method is shown in  FIG. 5 . 
       FIG. 5  is used to explain the construction of a board distorted into a convex shape. In this figure, only the board  50  formed from the metal foils  11 ,  12  and insulating sheet  10  is shown, and other members such as the semiconductor devices  14 ,  15  are omitted. 
     As explained above, while forcibly distorting the entirety of the mated member  51 , epoxy resin  31  is injected and cured to form convex-shape metal foil  11  on the lower side. The degree of warping is such that the outer edges of the metal foil  11  are distorted upwardly by 0 to 100 μm from the horizontal plane tangent at the center portion of the metal foil  11 . 
     Immediately after placing the semiconductor module  1 , provided with this convex-shape metal foil  11 , on the cooling member  40 , only the vicinity of the center portion of the metal foil  11  and the cooling member  40  are in contact. However, the metal foil  11  is made from metal so that it has an elasticity. Hence, by passing bolts or similar through the holes  21  positioned on side portions of the semiconductor module  1 , and fastening the semiconductor module  1  to the cooling member  40  at the side portions, the contact plane between the metal foil  11  and the cooling member  40  is broadened gradually outwardly from the center portion, and ultimately the entire face of the metal foil  11  is brought into firm and close contact with the cooling member  40 . 
     If the lower face of the metal foil  11  were deformed into a concave shape, the center portion of the metal foil  11  would not be in contact with the cooling member  40  even after fastening with bolts or similar. 
     By bonding such a convex-shape metal foil  11  to the semiconductor module  1 , the metal foil  11  and cooling member  40  can be brought into firm and close contact, and the cooling effect of the semiconductor module  1  can be further promoted. 
     Finally, an example of deformation of the structure of the semiconductor module  1  is explained. 
       FIG. 6  is a schematic cross-sectional diagram of principal portions, explaining an example of deformation of a semiconductor module. 
     In the semiconductor module  2  shown in  FIG. 6 , at least one protruding portion  20   f  is provided on the inner face of the resin case  20 , in order that the resin case  20  and epoxy resin  30  may be in firm and close contact by an “anchor effect”. These protruding portions  20   f  are integrally formed with the resin case  20 . 
     By this means, even when there is some difference in the thermal expansion coefficients of the resin case  20  and epoxy resin  30 , the resin case  20  and epoxy resin  30  remain reliably in close contact due to the anchor effect of the protruding portions  20   f . For example, even when the resin case  20  and epoxy resin  30  are heated due to operation of the semiconductor devices  14 ,  15 , and there is a difference in the expansion and contraction of the resin case  20  and epoxy resin  30 , due to this anchor effect, no slippage occurs at the interface between the resin case  20  and the epoxy resin  30 . Further, no peeling occurs at the interface between the resin case  20  and the epoxy resin  30 . 
     In the above, examples are explained in which the semiconductor modules  1 ,  2  are provided with heat spreaders  16 . However, the invention is not limited to such a configuration, and heat spreaders do not have to be provided. 
     The disclosure of Japanese Patent Application No. 2007-132572, filed on May 18, 2007, is incorporated in the application. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.