Patent Publication Number: US-2022230943-A1

Title: Power module and manufacturing method therefor

Description:
TECHNICAL FIELD 
     This invention relates to a power module and a manufacturing method therefor. 
     BACKGROUND ART 
     Hitherto, there has been known a power module in which a resin portion is provided around a subassembly including a first substrate, a semiconductor substrate, and a second substrate superposed in the stated order, and in which the first substrate is joined to a heat sink via a joining material. The power module is manufactured by a manufacturing method for a power module including a transfer molding step and a heat sink joining step which is performed after the transfer molding step. In the transfer molding step, under a state in which the subassembly is arranged on an inner side of a molding die, a thermoplastic resin is injected into an inner side of the molding die. In the heat sink step, the first substrate is joined to the heat sink via the joining material (see, for example, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] JP 6328298 B 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, after each of the transfer molding step and the heat sink joining step, a curing step is required. As a result, there has been a problem in that a manufacturing time for the power module becomes longer. 
     This invention has been made to solve the above-mentioned problem, and has an object to provide a power module and a manufacturing method therefor which are capable of shortening the manufacturing time for the power module. 
     Solution to Problem 
     According to this invention, there is provided a power module, including: a subassembly including: a first electrode; a semiconductor device joined to the first electrode; and a second electrode joined to the semiconductor device; a heat sink to which the subassembly is joined via a joining material; and a resin portion molded integrally with the first electrode, the semiconductor device, a second-electrode inner portion being a portion of the second electrode joined to the semiconductor device, and the heat sink. 
     According to this invention, there is provided a manufacturing method for a power module, including: a subassembly arranging step of placing a subassembly including a first electrode, a semiconductor device joined to the first electrode, and a second electrode joined to the semiconductor device on a heat sink via a joining material; and a transfer molding step of injecting, after the subassembly arranging step, under a state in which the first electrode, the semiconductor device, and a second-electrode inner portion being a portion of the second electrode joined to the semiconductor device are arranged in a region surrounded by the heat sink and a molding die, a thermoplastic resin into the region, wherein, in the transfer molding step, the subassembly is joined to the heat sink via the joining material with use of the resin. 
     Advantageous Effects of Invention 
     According to the power module and the manufacturing method therefor of this invention, the manufacturing time for the power module can be shortened. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a circuit diagram for illustrating a main part of a power conversion apparatus including a power module according to a first embodiment of this invention. 
         FIG. 2  is a sectional view for illustrating a main part of the power module according to the first embodiment of this invention. 
         FIG. 3  is a sectional view for illustrating a subassembly of  FIG. 2 . 
         FIG. 4  is a flowchart for illustrating a procedure for manufacturing the power module of  FIG. 2 . 
         FIG. 5  is a sectional view for illustrating a state in which the subassembly, a joining material, and a heat sink of  FIG. 2  are arranged on an inner side of a molding die. 
         FIG. 6  is a sectional view for illustrating a state in which a water jacket is joined to the heat sink of  FIG. 2 . 
         FIG. 7  is a sectional view for illustrating a modification example of the power module of  FIG. 6 . 
         FIG. 8  is a plan view for illustrating a modification example of a frame of  FIG. 7 . 
         FIG. 9  is a sectional view for illustrating a main part of a power module manufactured by a manufacturing method for a power module according to a second embodiment of this invention. 
         FIG. 10  is a sectional view for illustrating a main part of a power module manufactured by a manufacturing method for a power module according to a third embodiment of this invention. 
         FIG. 11  is a sectional view for illustrating a state in which a subassembly, a joining material, and a heat sink of  FIG. 10  are arranged on an inner side of a molding die. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG. 1  is a circuit diagram for illustrating a main part of a power conversion apparatus including a power module according to a first embodiment of this invention. The power conversion apparatus includes a switching circuit for controlling electric power. Examples of the power conversion apparatus include a motor driving inverter to be mounted to an electric vehicle, a voltage reducing converter for converting a voltage from a high voltage to a low voltage, and a power charger to be connected to external power source equipment to charge an on-vehicle battery. 
       FIG. 1  shows a motor driving inverter. The motor driving inverter includes a U-phase switching circuit, a V-phase switching circuit, and a W-phase switching circuit. The U-phase switching circuit includes a U-phase upper arm  101  and a U-phase lower arm  102 . The V-phase switching circuit includes a V-phase upper arm  103  and a V-phase lower arm  104 . The W-phase switching circuit includes a W-phase upper arm  105  and a W-phase lower arm  106 . 
     The U-phase upper arm  101 , the U-phase lower arm  102 , the V-phase upper arm  103 , the V-phase lower arm  104 , the W-phase upper arm  105 , and the W-phase lower arm  106  are each formed of a semiconductor device. Examples of the semiconductor device include a metal-oxide-semiconductor field-effect transistor (MOS-FET), an insulated gate bipolar transistor (IGBT), and a diode. As a base material of the semiconductor device, there are used silicon, silicon nitride, and gallium nitride. 
     In order to achieve a larger capacity of the power conversion apparatus, a plurality of semiconductor devices are connected in parallel in the power conversion apparatus. Further, due to limitation on a manufacture yield of a base material of the semiconductor device, a plurality of semiconductor devices each having a small outer-shape size are used for the power conversion apparatus. 
       FIG. 2  is a sectional view for illustrating a main part of the power module according to the first embodiment of this invention. A power module  1  includes a subassembly  11 , a heat sink  12 , a joining material  13 , and a resin portion  14 . 
       FIG. 3  is a sectional view for illustrating the subassembly  11  of  FIG. 2 . The subassembly  11  includes a first electrode  111 , a semiconductor device  112 , a second electrode  113 , and a third electrode  114 . Further, the subassembly  11  includes a first joining material  115  and a second joining material  116 . 
     The semiconductor device  112  has a flat-plate shape. The semiconductor device  112  is joined to the first electrode  111  via the first joining material  115  under a state in which one surface of the semiconductor device  112  is opposed to the first electrode  111 . Examples of the first joining material  115  include solder. The semiconductor device  112  is joined to the first electrode  111  by die-bonding. 
     The semiconductor device  112  is joined to the second electrode  113  via the second joining material  116  under a state in which the other surface of the semiconductor device  112  is opposed to the second electrode  113 . Examples of the second joining material  116  include solder. The semiconductor device  112  and the second electrode  113  may be joined to each other by wire bonding. The third electrode  114  is joined to the first electrode  111  with use of solder. 
     As illustrated in  FIG. 2 , the resin portion  14  covers the first electrode  111 , the semiconductor device  112 , and a portion of the second electrode  113  joined to the semiconductor device  112 . The portion of the second electrode  113  joined to the semiconductor device  112  is a second-electrode inner portion  113 A. Thus, the second-electrode inner portion  113 A is covered by the resin portion  14 . A portion of the second electrode  113  arranged on an outer side of the resin portion  14  is a second-electrode outer portion  113 B. The second-electrode outer portion  113 B extends along the semiconductor device  112  from a side surface of the resin portion  14 . The second-electrode outer portion  113 B extends in a direction perpendicular to the side surface of the resin portion  14  from the side surface of the resin portion  14 . 
     The resin portion  14  covers one end portion of the third electrode  114 . The other end portion of the third electrode  114  is arranged on an outer side of the resin portion  14 . The other end portion of the third electrode  114  extends along the semiconductor device  112  from a side surface of the resin portion  14 . The other end portion of the third electrode  114  extends in a direction perpendicular to the side surface of the resin portion  14  from the side surface of the resin portion  14 . 
     The subassembly  11  is joined to the heat sink  12  via the joining material. The heat sink  12  includes a flat-plate portion  121  and a plurality of heat-radiation fins  122 . The flat-plate portion  121  has the subassembly  11  placed thereon via the joining material  13 . The plurality of heat-radiation fins  122  are provided to the flat-plate portion  121 . The flat-plate portion  121  has a first surface  123  and a second surface  124  facing a side opposite to the first surface  123 . The first surface  123  has the subassembly  11  placed thereon via the joining material  13 . The second surface  124  has the heat-radiation fins  122  provided thereon. 
     In this example, description is made of a configuration in which the subassembly  11  including one semiconductor device  112  is placed on one heat sink  12 . There may also be provided a configuration in which the subassembly  11  including a plurality of semiconductor devices  112  is placed on one heat sink  12 . Specifically, there may also be provided a configuration in which the subassembly  11  including two semiconductor devices  112  is placed on one heat sink  12  or a configuration in which the subassembly  11  including six semiconductor devices  112  is placed on one heat sink  12 . 
     The first electrode  111  is joined to the flat-plate portion  121  of the heat sink  12  via the joining material  13 . The joining material  13  has an insulating property. The joining material  13  is a resin composition obtained by impregnating a base material with a thermosetting resin, and is a resin composition semi-cured by drying. Examples of the base material of the joining material  13  include a fibrous reinforced material and a ceramic sintered body. Examples of the thermosetting resin impregnated into the base material of the joining material  13  include an epoxy resin. The joining material  13  has a film-like shape or a sheet-like shape. The term “semi-cured” corresponds to a state before the thermosetting resin is completely cured. In this example, description is made of a configuration in which an adhesive sheet is used as the joining material  13 . 
     The resin portion  14  is molded integrally with the first electrode  111 , the semiconductor device  112 , the second-electrode inner portion  113 A, and the heat sink  12 . Further, the resin portion  14  is molded integrally with the first surface  123  and a side surface of the heat sink  12 . The resin portion  14  covers a part of the heat sink  12 . 
     Next, a manufacturing method for the power module  1  is described.  FIG. 4  is a flowchart for illustrating a procedure for manufacturing the power module  1  of  FIG. 2 . First, in Step S 1 , a subassembly producing step is performed. In the subassembly producing step, the semiconductor device  112  is joined to the first electrode  111 , the second electrode  113  is joined to the semiconductor device  112 , and the third electrode  114  is joined to the first electrode  111 . In such a manner, the subassembly  11  is produced. 
     After that, in Step S 2 , a subassembly arranging step is performed.  FIG. 5  is a sectional view for illustrating a state in which the subassembly  11 , the joining material  13 , and the heat sink  12  of  FIG. 2  are arranged on an inner side of a molding die. In the subassembly arranging step, the heat sink  12  is arranged on a lower die  21  of a molding die  2 , and a first sealing member  22  is arranged between a peripheral edge portion of the second surface  124  of the flat-plate portion  121  of the heat sink  12  and the lower die  21  so as to prevent a resin from flowing to a periphery of the heat-radiation fins  122 . In such a manner, a part between the peripheral edge portion of the second surface  124  and the molding die  2  is sealed. Further, in the subassembly arranging step, the subassembly  11  is placed on the first surface  123  of the flat-plate portion  121  of the heat sink  12  via the joining material  13 . At this time, the first electrode  111  is superposed on the heat sink  12  via the joining material  13 . 
     Further, in the subassembly arranging step, a plurality of first pins  23  push the first electrode  111  toward the heat sink  12 . As a result, the first electrode  111  is positioned with respect to the heat sink  12 , and the first sealing member  22  ensures the air tightness between the heat sink  12  and the lower die  21 . 
     Further, in the subassembly arranging step, second pins  24  abut against at least two or more pin abutment portions formed on the joining material  13 . As a result, the joining material  13  is positioned with respect to the heat sink  12 . At this time, the two or more pin abutment portions provided on the joining material  13  are two or more side surfaces formed on the joining material  13 . The side surfaces of the joining material  13  which serve as the pin abutment portions may be, for example, side surfaces of the joining material  13  formed by chamfering corner portions of the joining material  13  having a quadrangular shape before being processed. The joining material  13  having a quadrangular shape before being processed corresponds to the joining material  13  having a quadrangular shape when the joining material  13  is viewed in a direction perpendicular to an upper surface of the joining material  13 . The two or more pin abutment portions of the joining material  13  may be two or more holes formed in the joining material  13 . 
     Further, in the subassembly arranging step, an upper die  25  is placed on the lower die  21 . At this time, a part of the second electrode  113  and a part of the third electrode  114  are arranged on an outer side of the molding die  2  through a gap defined between the lower die  21  and the upper die  25 . As a result, the first electrode  111 , the semiconductor device  112 , and the second-electrode inner portion  113 A are arranged in a region surrounded by the heat sink  12  and the molding die  2 . 
     After that, as illustrated in  FIG. 4 , in Step S 3 , a transfer molding step is performed. In the transfer molding step, the molding die  2  is heated until a temperature of the molding die  2  reaches a set temperature. Further, in the transfer molding step, the thermoplastic resin is pressurized until the thermoplastic resin reaches a set pressure. Under a state in which the temperature of the molding die  2  has reached the set temperature, and the thermoplastic resin has reached the set pressure, the thermoplastic resin passes through a gate  26  of the molding die  2  to be injected into an inner side of the molding die  2 . 
     In the transfer molding step, the pressure of the resin injected into the inner side of the molding die  2  causes the first electrode  111  to be pushed against the heat sink  12  via the joining material  13 . As a result, air bubbles included in the joining material  13  are removed from the joining material  13 . Further, in the transfer molding step, heat of the resin injected into the inner side of the molding die  2  causes the first electrode  111  and the heat sink  12  to be joined to each other via the joining material  13 . Removal of the air bubbles included in the joining material  13  improves a heat radiating property and an insulating property of the joining material  13 . The resin portion  14  is molded integrally with the first electrode  111 , the semiconductor device  112 , the second-electrode inner portion  113 A, and the heat sink  12  by the transfer molding step. 
     After that, in Step S 4 , a water jacket joining step is performed.  FIG. 6  is a sectional view for illustrating a state in which a water jacket is joined to the heat sink  12  of  FIG. 2 . In the water jacket joining step, a water jacket  15  is joined to the heat sink  12 . The water jacket  15  is included in the power module  1 . 
     A water passage through which a coolant to be used for forcible water cooling flows is formed around the heat-radiation fins  122  of the heat sink  12  by the water jacket joining step. Examples of a method of joining the heat sink  12  and the water jacket  15  to each other include welding and friction agitation joining. Further, a second sealing member  16  is arranged between the heat sink  12  and the water jacket  15 . In such a manner, a part between the heat sink  12  and the water jacket  15  is sealed. The second sealing member  16  is included in the power module  1 . Examples of the second sealing member  16  include an O-ring or a liquid packing. After the processes described above, the step for manufacturing the power module  1  is terminated. 
       FIG. 7  is a sectional view for illustrating a modification example of the power module  1  of  FIG. 6 . In  FIG. 6 , illustration is given of the configuration in which one water jacket  15  is joined to one heat sink  12 . However, as illustrated in  FIG. 7 , there may be provided a configuration in which one water jacket  15  is joined to two heat sinks  12 . In this case, the water jacket  15  includes a frame  151 , a tub portion, and a third sealing member  153 . The frame  151  has two through holes. The tub portion  152  is joined to the frame  151 . The third sealing member  153  is provided between the frame  151  and the tub portion  152 . The third sealing member  153  seals a part between the frame  151  and the tub portion  152 . In the water jacket joining step, under a state in which the two heat sinks  12  are inserted into the two through holes of the frame  151 , respectively, each of the two heat sinks  12  and the water jacket  15  are joined to each other. 
     The number of the heat sinks to be joined to one water jacket is not limited to two, and may be three or more.  FIG. 8  is a plan view for illustrating a modification example of the frame  151  of  FIG. 7 . When one water jacket  15  is to be joined to six heat sinks  12 , the frame  151  has six through holes  154 . 
     As described above, in the manufacturing method for the power module  1  according to the first embodiment of this invention, in the transfer molding step, the subassembly  11  is joined to the heat sink  12  via the joining material  13  with use of the resin injected into the inner side of the molding die  2 . In a related-art manufacturing method for a power module, the heat sink joining step of joining the subassembly  11  and the heat sink  12  to each other is a step separate from the transfer molding step. Thus, in the related-art manufacturing method for a power module, after each of the transfer molding step and the heat sink joining step, a curing step is required. As a result, a manufacturing time for the power module becomes longer. Meanwhile, in the manufacturing method for the power module  1  according to the first embodiment, the subassembly  11  and the heat sink  12  are joined to each other by the transfer molding step. In other words, the transfer molding step and the heat sink joining step are performed at the same time. Therefore, the curing step is performed once. As a result, the manufacturing time for the power module  1  can be shortened. Further, equipment for the heat sink joining step is not required. As a result, manufacturing equipment for the power module  1  can be simplified. Further, in the power module  1  according to the first embodiment of this invention, the resin portion  14  is formed integrally with the heat sink  12 . Accordingly, when the resin portion  14  is formed, the subassembly  11  is joined to the heat sink  12  via the joining material  13 . As a result, the manufacturing time for the power module  1  can be shortened. 
     Further, in the manufacturing method for the power module  1  according to the first embodiment of this invention, in the transfer molding step, the subassembly  11  is joined to the heat sink  12  via the joining material  13  with use of the resin injected into the inner side of the molding die  2 . In the related-art manufacturing method for a power module, the heat sink joining step is performed after the transfer molding step. Thus, in the related-art manufacturing method for a power module, pressure and heat applied to the subassembly  11  in the heat sink joining step may cause separation between the first electrode  111  and the semiconductor device  112  or between the second electrode  113  and the semiconductor device  112 . Thus, in the related-art manufacturing method for a power module, in the heat sink joining step, the pressure cannot be applied to the joining material  13  in such a manner that air bubbles included in the joining material  13  are removed from the joining material  13 . As a result, with the related-art manufacturing method for a power module, the heat radiating property and the insulating property of the joining material  13  are lowered. Meanwhile, with the manufacturing method for the power module  1  according to the first embodiment, the pressure can be applied to the joining material  13  with use of the pressure of the resin injected into the inner side of the molding die  2 . Thus, occurrence of the separation between the first electrode  111  and the semiconductor device  112  or between the second electrode  113  and the semiconductor device  112  can be prevented, and the heat radiating property and the insulating property of the joining material  13  can be improved. As a result, the reliability of the power module  1  can be improved. Further, in the power module  1  according to the first embodiment of this invention, the resin portion  14  is formed integrally with the heat sink  12 . Accordingly, when the resin portion  14  is formed, the subassembly  11  is joined to the heat sink  12  via the joining material  13 . Accordingly, the pressure is applied to the joining material  13  when the resin portion  14  is formed. Thus, occurrence of the separation between the first electrode  111  and the semiconductor device  112  and between the second electrode  113  and the semiconductor device  112  can be prevented, and the heat radiating property and the insulating property of the joining material  13  can be improved. As a result, the reliability of the power module  1  can be improved. 
     Further, in the manufacturing method for the power module  1  according to the first embodiment of this invention, in the transfer molding step, a part of the heat sink  12  is covered by the resin portion  14 . In the related-art manufacturing method for a power module, the heat sink  12  is not covered by the resin portion  14 . In other words, the heat sink  12  is not joined to the resin portion  14 . Thus, in the related-art manufacturing method for a power module, stress may act on the joining material  13  at the time of fluctuation in environmental temperature due to a difference in a linear expansion coefficient between the subassembly  11  and the heat sink  12  to cause separation between the joining material  13  and the subassembly  11  or between the joining material  13  and the heat sink  12 . As a result, in the related-art manufacturing method for a power module, the heat radiating property and the insulating property of the power module  1  are poor. Meanwhile, in the manufacturing method for the power module  1  according to the first embodiment, in the transfer molding step, a part of the heat sink  12  is covered by the resin portion  14 . Accordingly, the heat sink  12  is joined to the resin portion  14 . Thus, the stress which acts on the joining material  13  at the time of fluctuation in the environmental temperature is reduced. Accordingly, occurrence of the separation between the joining material  13  and the subassembly  11  or the heat sink  12  can be prevented. As a result, the heat radiating property and the insulating property of the power module  1  can be improved. Further, in the power module  1  according to the first embodiment of this invention, the resin portion  14  is formed integrally with the heat sink  12 . Thus, the stress which acts on the joining material  13  at the time of fluctuation in the environmental temperature is reduced. Accordingly, occurrence of the separation between the joining material  13  and the subassembly  11  or the heat sink  12  can be prevented. As a result, the heat radiating property and the insulating property of the power module  1  can be improved. 
     Further, in the manufacturing method for the power module  1  according to the first embodiment, in the transfer molding step, a part of the heat sink  12  is covered by the resin portion  14 . In the related-art manufacturing method for a power module, in the transfer molding step, the heat sink  12  is not covered by a resin. Thus, in the related-art manufacturing method for a power module, in order to increase the stiffness of the heat sink  12 , it is required to increase the thickness of the heat sink  12 . Meanwhile, in the manufacturing method for the power module  1  according to the first embodiment, in the transfer molding step, a part of the heat sink  12  is covered by the resin portion  14 . Accordingly, the stiffness of the heat sink  12  can be increased without increasing the thickness of the heat sink  12 . Further, in the power module  1  according to the first embodiment of this invention, the resin portion  14  is formed integrally with the heat sink  12 . The stiffness of the heat sink  12  can be increased without increasing the thickness of the heat sink  12 . 
     Second Embodiment 
       FIG. 9  is a sectional view for illustrating a main part of a power module manufactured by a manufacturing method for a power module according to a second embodiment of this invention. In  FIG. 9 , the water jacket  15  is not illustrated. The subassembly  11  further includes an insulation member  117  and a copper plate  118 . The insulation member  117  is made of, for example, ceramic. 
     The first electrode  111  is formed of, for example, a copper plate. The first electrode  111  and the insulation member  117  are joined to each other by brazing. The insulation member  117  and the copper plate  118  are joined to each other by brazing. 
     The copper plate  118  is joined to the first surface  123  of the flat-plate portion  121  of the heat sink  12  via the joining material  13 . The joining material  13  is made of a material having a high thermal conductivity. Further, the joining material  13  is made of a sintered material. Examples of the sintered material include Ag nanoparticles and Cu nanoparticles. The Ag nanoparticles and the Cu nanoparticles can be subjected to low-temperature sintering. 
     The joining material  13  is sintered with the pressure of the resin and the heat of the resin at the time of injection of the resin into the inner side of the molding die  2 . The sintering of the joining material  13  causes the copper plate  118  and the flat-plate portion  121  of the heat sink  12  to be joined to each other. Other configurations are the same as those of the first embodiment. 
     As described above, in the power module  1  and the manufacturing method therefor according to the second embodiment of this invention, the joining material  13  is made of a sintered material. Accordingly, as compared to the case in which the joining material  13  is formed of an adhesive sheet, the strength of joining between the subassembly  11  and the heat sink  12  can be improved. As a result, longer lifetime of the power module  1  can be achieved. 
     Third Embodiment 
       FIG. 10  is a sectional view for illustrating a main part of a power module manufactured by a manufacturing method for a power module according to a third embodiment of this invention. In  FIG. 10 , the water jacket  15  is not illustrated. The second-electrode outer portion  113 B of the second electrode  113  extends in a direction perpendicular to the flat-plate portion  121  of the heat sink  12  from the resin portion  14 . The third electrode  114  extends in a direction perpendicular to the flat-plate portion  121  of the heat sink  12  from the resin portion  14 . The resin portion  14  is molded integrally with the first surface  123  of the heat sink  12 . The resin portion  14  is not molded integrally with the side surface of the heat sink  12 . 
       FIG. 11  is a sectional view for illustrating a state in which the subassembly  11 , the joining material  13 , and the heat sink  12  of  FIG. 10  are arranged on the inner side of the molding die  2 . In the subassembly arranging step, one heat sink  12  is arranged on the lower die  21  of the molding die  2 , and a plurality of subassemblies  11  are placed on the first surface  123  of the flat-plate portion  121  of the heat sink  12  via the joining materials  13 . In  FIG. 11 , two subassemblies  11  are illustrated. However, in this example, six subassemblies  11  are placed on the first surface  123  of the flat-plate portion  121  of one heat sink  12  via the joining materials  13 . 
     Further, in the subassembly arranging step, a fourth sealing member  27  is arranged between the upper die  25  of the molding die  2  and the peripheral edge portion of the first surface  123  of the flat-plate portion  121  of the heat sink  12 . In such a manner, a part between the peripheral edge portion of the first surface  123  and the molding die  2  is sealed. The upper die  25  of the molding die  2  has six rooms corresponding to the six subassemblies  11 , respectively. The number of the subassemblies  11  is not limited to six, and it is only required that a plurality of subassemblies  11  be provided. Other configurations are the same as in the first embodiment or the second embodiment. 
     As described above, according to the manufacturing method for the power module  1  according to the third embodiment of this invention, in the transfer molding step, the plurality of subassemblies  11  are separately joined to the heat sink  12  via the joining materials  13 . The upper die  25  of the molding die  2  has a plurality of rooms corresponding to the plurality of subassemblies  11 , respectively. When the entirety of the plurality of subassemblies  11  is covered by one resin portion  14 , the amount of resin to be used at the time of forming the resin portion  14  becomes larger. Further, due to the difference in the linear expansion coefficient between the heat sink  12  and the resin portion  14 , significant warping of the resin portion  14  occurs. Meanwhile, in the manufacturing method for the power module  1  according to the third embodiment, the plurality of subassemblies  11  are covered by separate resin portions  14 , respectively. In other words, a plurality of separate resin portions  14  corresponding respectively to the plurality of subassemblies  11  are molded integrally with the heat sink  12 . Accordingly, the amount of resin to be used at the time of forming the resin portions  14  can be reduced. Further, the size of the resin portion  14  can be reduced, thereby being capable of preventing occurrence of warping of the resin portion  14 . Further, in the power module  1  according to the third embodiment of this invention, the plurality of subassemblies  11  are separately joined to the heat sink  12  via the joining materials  13 , and the plurality of separate resin portions  14  are molded integrally with the heat sink  12 . Accordingly, the amount of resin to be used at the time of forming the resin portions  14  can be reduced, and occurrence of warping of the resin portion  14  can be prevented. 
     REFERENCE SIGNS LIST 
       1  power module,  2  molding die,  11  subassembly,  12  heat sink,  13  joining material,  14  resin portion,  15  water jacket,  16  second sealing member,  21  lower die,  22  first sealing member,  23  first pin,  24  second pin,  25  upper die,  26  gate,  27  fourth sealing member,  101  U-phase upper arm,  102  U-phase lower arm,  103  V-phase upper arm,  104  V-phase lower arm,  105  W-phase upper arm,  106  W-phase lower arm,  111  first electrode,  112  semiconductor device,  113  second electrode,  113 A second-electrode inner portion,  113 B second-electrode outer portion,  114  third electrode,  115  first joining material,  116  second joining material,  117  insulating member,  118  copper plate,  121  flat-plate portion,  122  heat radiation fin,  123  first surface,  124  second surface,  151  frame,  152  tub portion,  153  third sealing member,  154  through hole.