Semiconductor module, method for manufacturing semiconductor module, and power conversion device

Abstract

A semiconductor module (10) according to the present disclosure is characterized by comprising: a semiconductor device (1); an external case (14) that stores the semiconductor device (1) therein and maintains the pressure of a gas or a liquid filled therein; a heat sink (12) on which the external case (14) is placed; and a fastener (13a) that co-fastens the semiconductor device (1) and the external case (14) to the heat sink (12).

Description

Semiconductor module, semiconductor module manufacturing method, and power conversion device

[0001] The present disclosure relates to a semiconductor module incorporating a semiconductor device, a method for manufacturing a semiconductor module, and a power conversion device.

[0002] A conventional semiconductor module in which a semiconductor device is housed in a housing is disclosed, for example, in Patent Document 1. Specifically, the structure of the semiconductor module is disclosed in which the semiconductor device is fixed onto a heat sink with screws, and the heat sink and the housing are joined together to hermetically seal the semiconductor device.

[0003] Japanese Patent Application Laid-Open No. 2019-75415

[0004] When a semiconductor device is used in a high-altitude environment, such as on an aircraft, the surrounding air pressure is low. In a low-pressure environment, the discharge electric field is lower than that at atmospheric pressure, making discharge more likely to occur. Therefore, when a high voltage is applied to the terminals of the semiconductor device, discharge may occur between the high-voltage terminal and the low-voltage terminal, or between the high-voltage terminal and the heat sink.

[0005] Furthermore, in the structure of the semiconductor module disclosed in Patent Document 1, the fixing of the semiconductor device onto the heat sink and the joining of the heat sink to the housing must be carried out separately, which increases the number of manufacturing steps.

[0006] In view of the above circumstances, an object of the present invention is to provide a semiconductor module that can be easily manufactured and that suppresses discharge at terminals in a low-pressure environment.

[0007] The semiconductor module according to the present disclosure is characterized by comprising a semiconductor device, an external case that houses the semiconductor device and maintains the pressure of the gas or liquid filled inside, a heat sink on which the external case is placed, and a fastener that fastens the semiconductor device and the external case together to the heat sink.

[0008] According to the configuration of the present disclosure, a semiconductor module that suppresses discharge at terminals can be easily manufactured.

[0009] 13 is an enlarged view of a portion A in FIG. 13. FIG. 13 is an enlarged view of a modified example of the bonding surface 25 of portion A in FIG. 13. FIG. 13 is a sectional view of a semiconductor module according to a first embodiment. FIG. 13 is a sectional view of a semiconductor module according to a seventh embodiment. FIG. 13 is a sectional view of a semiconductor module according to an eighth embodiment. FIG. 13 is a sectional view of a semiconductor module according to a modified example of the eighth embodiment. FIG. 13 is a block diagram showing a configuration of a power conversion system to which a power conversion device according to a ninth embodiment is applied.

[0010] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts will be denoted by the same reference numerals, and redundant explanations will not be repeated. Note that the embodiments described below are merely examples, and the scope of the present disclosure is not limited to the embodiments described below.

[0011] Semiconductor devices are designed to maintain insulation in atmospheric pressure environments. However, if insulation measures are not implemented in the structure of the semiconductor device, high voltage discharges may occur in low-pressure environments, which may cause malfunctions. For example, insulation measures are implemented by designing the clearance distance and creepage distance between terminals. However, changing the structure of the semiconductor device and implementing insulation measures depending on the application of the semiconductor module in which the semiconductor device is used (e.g., whether it is for a high-altitude environment or a normal-pressure environment) requires individually optimizing the design based on the performance, type, size, etc. of the semiconductor device, which is cumbersome. As an alternative to this hassle, the inventors of the present application have devised a semiconductor module that can maintain the operating environment of the semiconductor device at atmospheric pressure even in low-pressure environments by sealing the semiconductor device in a housing.

[0012] First Embodiment <Configuration of Semiconductor Module> A semiconductor module according to a first embodiment will be described below.

[0013] FIG. 1 is a cross-sectional view of a semiconductor module according to a first embodiment. In a semiconductor module 10, a semiconductor device 1 is housed within an external case 14. The interior of the external case 14 forms a sealed space S, which is maintained at an internal pressure adjusted to approximately atmospheric pressure. The internal pressure of the sealed space S does not need to be strictly maintained; as described below, the pressure may be reduced to a level that suppresses discharge. Because the internal space of the external case 14 is maintained at approximately atmospheric pressure, even if the external space of the external case 14 is in a low-pressure environment, discharge from the high-voltage terminal 8a of the semiconductor device 1 when a high voltage is applied is suppressed compared to the external space environment. To maintain the internal pressure of the external case 14, it is sufficient that the external case 14 has a gap-free structure. If the external case 14 is composed of multiple components, it is preferable to sandwich a sealing member such as a packing between the components.

[0014] As shown in FIG. 1 , the external case 14 is composed of a bottom 14a, walls 14b, and a lid 14c. The bottom 14a of the external case is preferably a heat sink such as a metal plate or a highly thermally conductive resin. Meanwhile, the walls 14b and lid 14c of the external case are preferably made of an insulating material such as epoxy resin or polyphenylene sulfide (PPS) resin. The bottom 14a of the external case is joined to the walls 14b of the external case to form an integrated unit. A packing 15 is interposed between the lid 14c of the external case and the walls 14b, and the two are fastened together with screws 13b as fasteners. Note that the external case 14 only needs to enclose the semiconductor device 1, and unlike the present embodiment, it may be a one-piece case without the lid 14c.

[0015] The external case 14 is placed on the heat sink 12 and is fastened together with the semiconductor device 1 to the heat sink 12 by screws 13a, which serve as fasteners. The screws 13a pass through through holes 11a and 11b provided in the external case 14 and the semiconductor device 1 and are fastened to screw holes 19 on the heat sink 12 (see FIG. 7; for convenience, the through holes 11a and 11b and the screw holes 19 are not shown in FIG. 1). With this configuration, a sealed space S is formed inside the external case 14, and an internal pressure approximately equal to atmospheric pressure is maintained (here, the gas filled in the sealed space S is air). The semiconductor device 1 is sealed by the fastening together and the internal pressure of the external case 14.

[0016] To prevent gas leakage from gaps between the screw 13a and the through holes 11a, 11b, which are fastened together, a rubber sealant or the like may be sandwiched between the head of the screw 13a and the semiconductor device 1, between the heat sink 5 of the semiconductor device and the bottom 14a of the external case, and between the wall 14b of the external case and the heat sink 12. Heat dissipation grease may also be sandwiched between the bottom 14a of the external case and the heat sink 12. Note that instead of the screw 13a, bolts, fasteners, or the like may also be used as fasteners.

[0017] A weakened portion may be provided in either or both of the wall 14b and the lid 14c of the outer case. The weakened portion can be provided by designing or processing a thin portion or a notch in any part of the wall 14b or the lid 14c of the outer case. This has the effect of releasing the pressure by preferentially destroying the weakened portion when an increase in internal pressure occurs due to a sudden rise in temperature, such as when the semiconductor device 1 is short-circuited and an excessively large current flows.

[0018] 1, for the sake of convenience, the internal structure of the semiconductor device 1 is omitted. A normal semiconductor device 1 that maintains insulation in an atmospheric pressure environment may be used, and there is no need to take any special insulation measures based on the structure of the semiconductor device 1 that is intended for use in a low-pressure environment.

[0019] The type of the semiconductor device 1 is not particularly limited, and may be, for example, an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), a bipolar transistor, or a package of an integrated circuit thereof.

[0020] The semiconductor device 1 has a heat sink 5 on its bottom surface. Heat generated during operation of the semiconductor device 1 is diffused and dissipated in the order of the heat sink 5, the bottom 14a of the external case, and the heat sink 12. From the viewpoint of heat dissipation, it is preferable to use a heat sink as the material for the bottom 14a of the external case. Note that the semiconductor device 1 does not necessarily have to have a heat sink 5 on its bottom surface.

[0021] The semiconductor device 1 has a high-voltage terminal 8a and a low-voltage terminal 8b (hereinafter, referred to as terminals 8 when the two are not distinguished from each other). The high-voltage terminal 8a is a terminal to which a high voltage is applied, and the low-voltage terminal 8b is a terminal to which a voltage lower than that of the high-voltage terminal 8a is applied. Insulated conductors 16 are connected to each terminal, and the insulated conductors 16 pass through the outer case 14 and are drawn out to the outside. The insulated conductors 16 are configured such that the conductors 17 are insulated and coated with insulating material 18 at the portions that pass through the outer case 14. The number of terminals 8 is not particularly limited, and it is sufficient that the semiconductor device 1 has terminals 8.

[0022] 2 is a cross-sectional view of a case where a plurality of semiconductor devices 1 are arranged in parallel in this embodiment. As shown in Fig. 2, a plurality of semiconductor devices 1 may be arranged in parallel and sealed inside an outer case 14. In this case, the high-voltage terminals 8a of each semiconductor device 1 are connected in parallel to one of the conductors 17, and the low-voltage terminals 8b are also connected in parallel to the other of the conductors 17.

[0023] Fig. 3 is a cross-sectional view showing the internal structure of the semiconductor device 1. The internal structure of the semiconductor device 1 shown in Fig. 3 is one example, and the internal structure of the semiconductor device 1 is not particularly limited as long as it has the module structure of the semiconductor module 10 described in Fig. 1 .

[0024] As shown in FIG. 3 , semiconductor device 1 has a heat sink 5 on its bottom surface, an insulating layer 4 bonded to the top surface of heat sink 5, and two metal layers 3a and 3b bonded to the top surface of insulating layer 4. A semiconductor chip 2 is mounted on the top surface of one metal layer 3a, and is connected to the other metal layer 3b via a wire 9. The internal structure of semiconductor device 1 is covered by a semiconductor case 6, and the interior is sealed with an insulating sealant 7. A high-voltage terminal 8a is connected to metal layer 3a, and a low-voltage terminal 8b is connected to metal layer 3b, both of which extend to the outside of semiconductor case 6. During operation of semiconductor device 1, heat is generated from semiconductor chip 2 and dissipated by passing through metal layer 3, insulating layer 4, and heat sink 5 in that order. Semiconductor device 1 also has a through-hole 11b through which a screw 13a is inserted and fastened to heat sink 12 together with external case 14 (for convenience, the reference numerals for screw 13a, heat sink 12, and external case 14 are not shown in FIG. 3 ).

[0025] <Method of Manufacturing Semiconductor Module> A method of manufacturing a semiconductor module according to this embodiment will now be described. Fig. 4 is a flowchart showing steps in the method of manufacturing a semiconductor module. Figs. 5 to 9 are diagrams showing the respective steps in the flowchart of Fig. 4. Below, the steps shown in the flowchart of Fig. 4 will be described with reference to Figs. 5 to 9, which show each step.

[0026] First, as shown in Fig. 5, an outer case 14 is prepared before the lid 14c is attached. The outer case 14 before the lid 14c is attached is composed of a bottom 14a and a wall 14b of the outer case. Two insulated conductors 16 are passed through the wall 14b of the outer case (step S1).

[0027] 6, the outer case 14 prepared in step S1 before the lid 14c is attached is placed on the top surface of the heat sink 12. When placing the outer case 14, the screw holes 19 of the heat sink 12 are aligned with the through holes 11a in the bottom 14a of the outer case (step S2).

[0028] 7, the semiconductor device 1 is placed from above onto the bottom 14a of the external case so that the through-holes 11a in the bottom 14a of the external case, the through-holes 11b in the semiconductor device 1, and the screw holes 19 on the heat sink 12 are aligned. At this time, the insulated conductors 16 are bent so as not to interfere with the installation of the semiconductor device 1 (step S3).

[0029] Thereafter, as shown in FIG. 8, the screws 13a are passed through the through holes 11a of the semiconductor device 1 and the through holes 11b of the outer case 14 and are fastened together by being fastened into the screw holes 19 of the heat sink 12 (step S4).

[0030] Furthermore, as shown in FIG. 9, the insulated conductor wires 16 are connected to the high-voltage terminal 8a and the low-voltage terminal 8b of the semiconductor device 1 (step S5).

[0031] Finally, the lid 14c is placed on the top surface of the wall 14b of the outer case via the packing 15 and fastened with the screws 13b (step S6). The interior of the outer case 14 is sealed by the wall 14b and the lid 14c, so that the gas pressure inside the outer case 14 is maintained even if the outside air pressure drops after this step. In this way, the semiconductor module according to this embodiment shown in FIG. 1 is manufactured.

[0032] <Effects of the embodiment> In the semiconductor module according to the present embodiment, the semiconductor device 1 is housed inside the outer case 14 and sealed at the internal pressure, maintaining a constant internal pressure and suppressing terminal discharge in a low-pressure environment. Therefore, it is possible to use a general-purpose semiconductor device without preparing a separate semiconductor device specifically designed for a low-pressure environment. Furthermore, because the semiconductor device 1 and the outer case 14 are fastened together to the heat sink 12 with the screws 13a, fewer manufacturing steps are required compared to when each component is fastened separately. Therefore, the semiconductor module according to the present embodiment can be easily manufactured and can suppress terminal discharge in a low-pressure environment.

[0033] Embodiment 2. <Configuration of Semiconductor Module> A semiconductor module according to embodiment 2 will now be described. In this embodiment, a valve 21 capable of injecting gas is provided in the lid 14c of the outer case, and the air inside the outer case 14 is replaced with dry nitrogen.

[0034] Fig. 10 is a cross-sectional view of a semiconductor module according to embodiment 2. As shown in Fig. 10, the semiconductor module according to this embodiment has two pipes 20, each having a valve 21, attached to a lid 14c of an outer case. The interior of the outer case 14 is filled with dry nitrogen.

[0035] The air inside the outer case 14 can be replaced with dry nitrogen, for example, by the following method. First, both of the two valves 21 are opened, dry nitrogen is allowed to flow through one of the pipes 20, and the air is released through the other pipe 20. After the air has been sufficiently replaced, the valve 21 is closed. Note that the replacement method is not limited to this method, and any method can be used as long as it is possible to fill the interior with dry nitrogen. For example, the air inside can be first evacuated, and then dry nitrogen can be allowed to flow into the sealed space, which has now become a near-vacuum state.

[0036] The gas to be filled may be a gas other than dry nitrogen. The pressure of the filled gas may be atmospheric pressure or higher, and the higher the pressure, the higher the insulation performance. Furthermore, the pipe 20 having the valve 21 may be provided at a location other than the lid 14c of the outer case. For example, it may be provided in the wall portion 14b of the outer case. Furthermore, a hole may be provided in the outer case 14 and the valve 21 may be attached directly to the outer case 14.

[0037] <Effects of the embodiment> In this embodiment, in addition to the same effects as those of the first embodiment, the inside of the outer case 14 can be replaced with any gas in any amount using the valve 21, making it easy to adjust the internal air pressure of the outer case 14.

[0038] Third Embodiment <Configuration of Semiconductor Module> A semiconductor module according to a third embodiment will now be described. In this embodiment, the interior of the outer case is filled with insulating liquid.

[0039] FIG. 11 is a cross-sectional view of a semiconductor module according to a third embodiment. As shown in FIG. 11 , in the semiconductor module according to this embodiment, the interior of the outer case 14 is filled with an insulating liquid 22. Because the outer case 14 is sealed, the pressure of the insulating liquid 22 inside the outer case 14 is maintained. Examples of the insulating liquid 22 include insulating oil and fluorine-based liquid. The insulating liquid 22 does not have to fill the entire interior of the outer case 14, and a gas may also be filled together with the insulating liquid 22. Note that the insulating liquid 22 of this embodiment may be applied to the first and second embodiments. In this case, the interior of the outer case 14 is filled with both the insulating liquid 22 and a gas.

[0040] <Method for manufacturing semiconductor module> The semiconductor module of this embodiment can be manufactured by filling the inside of the outer case 14 with insulating liquid 22 before the step of fastening the lid 14c to the upper surface of the wall portion 14b of the outer case (step S6) in the above-described method for manufacturing the semiconductor module of embodiment 1.

[0041] <Effects of the embodiment> In addition to the same effects as in the first embodiment, the present embodiment further improves the creepage dielectric strength voltage of the semiconductor device 1 because the insulating liquid 22 filled has higher insulating performance than air. This makes it possible to shorten the creepage distance and clearance distance around the periphery of the semiconductor device 1, enabling a more compact package design. Furthermore, by filling the periphery of the semiconductor device 1 with the insulating liquid 22, the cooling performance for heat dissipation from the terminals 8 and semiconductor case 6 of the semiconductor device is also improved, thereby improving the overall heat dissipation performance.

[0042] Fourth Embodiment <Configuration of Semiconductor Module> A semiconductor module according to a fourth embodiment will now be described. In this embodiment, instead of using insulated conductor wire 16 as in the first embodiment, insulatingly coated bus bars (23 a, 23 b) are used for connection to terminals 8 of a semiconductor device.

[0043] 12 is a cross-sectional view of a semiconductor module according to embodiment 4. As shown in Fig. 12, the semiconductor module according to this embodiment uses bus bar 23a as a conductive member that penetrates wall portion 14b of the outer case, and connects terminal 8 to bus bar 23a via another bus bar 23b inside outer case 14. Bus bar 23a and bus bar 23b are, for example, copper plates, and preferably have a sufficient thickness.

[0044] The bus bar 23a is covered with an insulating coating 24. The insulating coating 24 is an insulating material with high heat dissipation properties, such as an inorganic filler-filled resin, so that heat generated from the terminal 8 is conducted through the bus bar (23a, 23b) and dissipated to the outside air from the insulating coating 24.

[0045] The reason for separating the bus bars 23a and 23b is that, for convenience of manufacturing, the semiconductor device 1 is placed inside the outer case 14. First, the semiconductor device 1 is placed inside the outer case 14 with the bus bar 23b removed, and then the bus bar 23b is connected to the bus bar 23a and the semiconductor device 1. The bus bars 23a and 23b of this embodiment may be applied to the first to third embodiments.

[0046] <Effects of the embodiment> In the present embodiment, in addition to the same effects as in the first embodiment, the use of bus bars (23a, 23b) that are thicker than the insulated conductor wires 16 can improve heat dissipation from the terminals 8 of the semiconductor device. Since the terminals 8 become hot due to heat generated by the semiconductor chip 2 inside the semiconductor device 1, the present embodiment is advantageous in terms of heat dissipation.

[0047] Fifth Embodiment <Configuration of Semiconductor Module> A semiconductor module according to a fifth embodiment will now be described. In this embodiment, the outer case 14 has a structure that reinforces the joint between the wall portion 14b and the bottom portion 14a.

[0048] Fig. 13 is a cross-sectional view of a semiconductor module according to embodiment 5. As shown in Fig. 13, in the semiconductor module according to this embodiment, the joining surface 25 between the wall portion 14b and the bottom portion 14a of the outer case 14 is stepped. That is, the wall portion 14b and the bottom portion 14a of the outer case 14 are engaged with each other, and the shape of the engaging portion is stepped. Fig. 14 is an enlarged view of portion A in Fig. 13.

[0049] Fig. 15 is an enlarged view of a modified example of the joint surface 25 of part A in Fig. 13. The shape of the engaging portion between the wall portion 14b and the bottom portion 14a of the outer case that forms the joint surface 25 is not limited to the stepped shape shown in Fig. 14, but may also be tapered as shown in Fig. 15.

[0050] In this embodiment, the joining surface 25 between the wall 14b and bottom 14a of the external case only needs to have a portion where the wall 14b protrudes toward the bottom 14a. In this case, the joining area between the wall 14b and bottom 14a of the external case is larger than when the joining surface 25 is flat and perpendicular to the heat sink 12 on which the external case 14 is placed (see FIG. 1 , the reference numeral for the joining surface 25 is not shown). In this embodiment, the joining surface 25 only needs to satisfy these conditions, and the shape of the engagement portion between the wall 14b and bottom 14a of the external case that forms the joining surface 25 is not limited to the stepped or tapered shape shown in FIGS. 14 and 15 , and may have other shapes. Note that the joining portion of this embodiment may also be applied to Embodiments 1 to 4.

[0051] The wall 14b and bottom 14a of the outer case are made of different materials, and their sides are joined together with adhesive or the like. If the contact area between the two is small, the strength of the joint decreases. If the interior of the outer case 14 is sealed in a low-pressure environment, the difference in pressure between the inside and outside creates a force that causes the outer case 14 to expand. Therefore, if the joint strength between the wall 14b and bottom 14a of the outer case is weak, the joint may break.

[0052] <Effects of the embodiment> In addition to the effects of the first embodiment, the present embodiment has the following advantages: when a pressure difference between the inside and outside of the external case 14 in a low-pressure environment generates a force that causes the external case 14 to expand, the side of the bottom 14a of the external case catches on the side of the wall 14b, thereby preventing the bond at the bonding surface 25 from breaking. Furthermore, the bonding surface 25 is pressed from the inside of the external case 14 by the mold clamping force due to co-clamping and the pressure difference between the inside and outside of the external case 14, thereby further sealing the inside of the external case 14. Note that when the bonding portion of the present embodiment is applied to the third embodiment, the inside of the external case 14 is also further sealed by the pressure of the insulating liquid 22.

[0053] Sixth Embodiment <Configuration of Semiconductor Module> A semiconductor module according to a sixth embodiment will now be described. In this embodiment, a socket 26 is provided on the lid 14c of the outer case, thereby assisting in connecting the terminals 8 of the semiconductor device and the insulated conductor wires 16.

[0054] 16 is a cross-sectional view of a semiconductor module according to a sixth embodiment. As shown in FIG. 16, in the semiconductor module according to this embodiment, a socket 26 is provided on the lid 14c of the outer case 14 on the inner side thereof. An insulated conductor 16 is attached to the socket 26, passes through the socket 26, and penetrates the lid 14c of the outer case. A terminal 8 of the semiconductor device is fitted in the socket 26 and is electrically connected to the insulated conductor 16. The socket 26 of this embodiment may also be applied to the first to fifth embodiments.

[0055] <Operations and Effects of the Embodiment> In the present embodiment, the attachment position of the socket 26 relative to the lid 14c of the external case is adjusted so that the socket 26 fits into the terminal 8 of the semiconductor device when the lid 14c of the external case is fastened to the external case 14. That is, during the process of fastening the lid 14c of the external case to the external case 14, the insulated conductors 16 and the terminal 8 of the semiconductor module are simultaneously connected inside the socket 26. Therefore, in addition to the same effects as in the first embodiment, the present embodiment has the additional effect of facilitating wiring of the semiconductor device 1.

[0056] Seventh Embodiment <Configuration of Semiconductor Module> A semiconductor module according to a seventh embodiment will now be described. In this embodiment, a connection electrode 27 and a spring 28 are provided between a terminal 8 of the semiconductor device and an insulated conductor 16, and the pressing force of the spring 28 assists in connecting the terminal 8 of the semiconductor device and the insulated conductor 16 via the connection electrode 27.

[0057] 17 is a cross-sectional view of a semiconductor module according to embodiment 7. As shown in Fig. 17, the semiconductor module according to this embodiment has connection electrodes 27 connected to insulated conductors 16 provided on lid 14c of the external case directly above terminals 8 of the semiconductor device, and springs 28 sandwiched between connection electrodes 27 and lid 14c of the external case. Note that connection electrodes 27 and springs 28 of this embodiment may also be applied to embodiments 1 to 5.

[0058] <Effects of the embodiment> In the present embodiment, when the lid 14c of the outer case is fastened to the outer case 14, the connection electrodes 27 come into contact with the terminals 8 of the semiconductor device, and by pressing and fixing the lid 14c of the outer case, the springs 28 are compressed, and the connection electrodes 27 come into contact with the terminals 8 while exerting a pressing force against them. Therefore, in addition to the same effects as in the first embodiment, the present embodiment has the additional effect of facilitating the connection of the terminals 8 of the semiconductor device 1 with the insulated conductors 16.

[0059] Eighth Embodiment <Configuration of Semiconductor Module> A semiconductor module according to an eighth embodiment will now be described. In this embodiment, a heat dissipation member 29 is provided between the semiconductor device 1 and the lid 14c of the outer case.

[0060] 18 is a cross-sectional view of a semiconductor module according to the eighth embodiment. As shown in FIG. 18, the semiconductor module according to the present embodiment has a heat dissipation member 29 provided between the semiconductor device 1 and the lid 14c of the outer case. The heat dissipation member 29 can be made of any of resin, ceramic, and metal, but a material with high thermal conductivity is preferable. When using metal for the heat dissipation member 29, it is necessary to provide a sufficient insulating distance from the terminals 8 or to insert an insulator therebetween.

[0061] To improve heat dissipation performance, it is preferable to sandwich heat dissipation grease between the upper surface of the semiconductor device 1 and the heat dissipation member 29, and between the heat dissipation member 29 and the lid 14c of the outer case.

[0062] The heat dissipation member 29 may be integrated with the lid 14c of the external case. Fig. 19 is a cross-sectional view of a semiconductor module according to a modification of the eighth embodiment. As shown in Fig. 19, when the lid 14c of the external case is the heat dissipation member 29, the shape of the lid 14c of the external case may be such that it comes into contact with the upper surface of the semiconductor device 1. The heat dissipation member 29 of this embodiment may be applied to the first to fifth embodiments.

[0063] <Effects of the embodiment> In the present embodiment, heat generated by the semiconductor device 1 can be dissipated not only toward the heat sink 12 but also toward the lid 14c of the external case via the heat dissipation member 29. Therefore, in addition to the same effects as in the first embodiment, the present embodiment has the additional effect of improving heat dissipation.

[0064] Ninth Embodiment In this embodiment, the semiconductor modules according to the above-described first to eighth embodiments are applied to a power conversion device. Although the present invention is not limited to a specific power conversion device, the following will describe a case in which the present invention is applied to a three-phase inverter as the ninth embodiment.

[0065] FIG. 20 is a block diagram showing the configuration of a power conversion system to which the power conversion device according to this embodiment is applied.

[0066] The power conversion system shown in Fig. 20 is composed of a power supply 300, a power conversion device 400, and a load 500. The power supply 300 is a DC power supply and supplies DC power to the power conversion device 400. The power supply 300 can be composed of various components, such as a DC system, a solar cell, or a storage battery, or it may be composed of a rectifier circuit connected to an AC system or an AC / DC converter. The power supply 300 may also be composed of a DC / DC converter that converts DC power output from a DC system into a predetermined power.

[0067] The power conversion device 400 is a three-phase inverter connected between the power source 300 and the load 500, and converts DC power supplied from the power source 300 into AC power and supplies the AC power to the load 500. As shown in Fig. 20 , the power conversion device 400 includes a main conversion circuit 401 that converts DC power into AC power and outputs it, and a control circuit 403 that outputs a control signal to the main conversion circuit 401 to control the main conversion circuit 401.

[0068] The load 500 is a three-phase electric motor driven by AC power supplied from the power conversion device 400. The load 500 is not limited to a specific application, but is an electric motor mounted on various electrical devices, and is used as an electric motor for, for example, a hybrid vehicle, an electric vehicle, a railroad car, an elevator, or an air conditioning device.

[0069] The power conversion device 400 will be described in detail below. The main conversion circuit 401 includes switching elements and freewheel diodes (not shown). The switching elements convert DC power supplied from the power source 300 into AC power, which is supplied to the load 500. The main conversion circuit 401 can have a variety of specific circuit configurations. The main conversion circuit 401 according to this embodiment is a two-level, three-phase full-bridge circuit, which can be configured with six switching elements and six freewheel diodes connected in anti-parallel to each switching element. Each switching element and freewheel diode of the main conversion circuit 401 is configured using a semiconductor module 402 corresponding to any one of the first to eighth embodiments described above. Two of the six switching elements are connected in series to form upper and lower arms, which constitute each phase (U phase, V phase, and W phase) of the full-bridge circuit. The output terminals of each upper and lower arm, i.e., the three output terminals of the main conversion circuit 401, are connected to the load 500.

[0070] The main conversion circuit 401 also includes a drive circuit (not shown) that drives each switching element, but the drive circuit may be built into the semiconductor module 402, or may be provided separately from the semiconductor module 402. The drive circuit generates drive signals that drive the switching elements of the main conversion circuit 401 and supplies them to the control electrodes of the switching elements of the main conversion circuit 401. Specifically, in accordance with control signals from a control circuit 403 (described later), the drive circuit outputs to the control electrodes of each switching element a drive signal that turns the switching element on and a drive signal that turns the switching element off. To maintain a switching element in the on state, the drive signal is a voltage signal (on signal) that is equal to or greater than the threshold voltage of the switching element, and to maintain a switching element in the off state, the drive signal is a voltage signal (off signal) that is equal to or less than the threshold voltage of the switching element.

[0071] The control circuit 403 controls the switching elements of the main conversion circuit 401 so that the desired power is supplied to the load 500. Specifically, it calculates the time (on time) that each switching element of the main conversion circuit 401 should be in the on state based on the power to be supplied to the load 500. For example, the main conversion circuit 401 can be controlled by PWM control, which modulates the on time of the switching elements according to the voltage to be output. The control circuit 403 then outputs a control command (control signal) to a drive circuit included in the main conversion circuit 401 so that an on signal is output to a switching element that should be in the on state at each time point, and an off signal is output to a switching element that should be in the off state at each time point. In accordance with this control signal, the drive circuit outputs an on signal or an off signal as a drive signal to the control electrode of each switching element.

[0072] In the power conversion device according to this embodiment, a semiconductor module according to any one of embodiments 1 to 8 is applied as the switching element and freewheel diode of the main conversion circuit 401, thereby realizing a highly reliable power conversion device.

[0073] In this embodiment, an example in which the present invention is applied to a two-level three-phase inverter has been described, but the present invention is not limited to this and can be applied to various power conversion devices. In this embodiment, a two-level power conversion device is described, but a three-level or multi-level power conversion device may also be used. In addition, when power is supplied to a single-phase load, the present invention may also be applied to a single-phase inverter. Furthermore, when power is supplied to a DC load, etc., the present invention can also be applied to a DC / DC converter or an AC / DC converter.

[0074] Furthermore, the power conversion device to which the present invention is applied is not limited to cases in which the above-mentioned load is an electric motor, but can also be used, for example, as a power supply device for an electric discharge machine, a laser processing machine, an induction heating cooker, or a contactless power supply system, and can also be used as a power conditioner for a solar power generation system, a power storage system, etc.

[0075] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Unless there is a contradiction, at least two of the embodiments disclosed herein may be combined. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0076] The above embodiments can be combined as appropriate.

[0077] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0078] REFERENCE SIGNS LIST 1 semiconductor device, 2 semiconductor chip, 3a, 3b metal layer, 4 insulating layer, 5 heat sink, 6 semiconductor case, 7 insulating sealing material, 8 terminal, 8a high voltage terminal, 8b low voltage terminal, 9 wire, 10 semiconductor module, 11a, 11b through hole, 12 heat sink, 13a, 13b screw (fastener), 14 outer case, 14a bottom, 14b wall, 14c lid, 15 packing, 16 insulated conductor, 17 conductor, 18 insulating member, 19 screw hole, 20 piping, 21 valve, 22 insulating liquid, 23a, 23b bus bar, 24 insulating coating, 25 joint surface, 26 socket, 27 connection electrode, 28 spring, 29 heat dissipation member, 300 power supply, 400 power conversion device, 401 main conversion circuit, 402 Semiconductor module, 403 control circuit, 500 load, S enclosed space

Claims

1. A semiconductor module comprising: a semiconductor device; an external case that houses the semiconductor device and maintains the pressure of gas or liquid filled inside; a heat sink on which the external case is placed; and a fastener that fastens the semiconductor device and the external case together to the heat sink.

2. The semiconductor module according to claim 1, wherein the outer case has a lid, walls, and a bottom, and the lid is joined to the upper surface of the walls of the outer case, sealing the interior of the outer case.

3. The semiconductor module according to claim 2, wherein the bottom of the outer case is a heat sink.

4. The semiconductor module according to claim 2, wherein a weakened portion is provided in either or both of the wall portion and the lid of the outer case.

5. The semiconductor module according to any one of claims 1 to 4, wherein the outer case is provided with a valve through which gas can be injected.

6. A semiconductor module according to any one of claims 1 to 5, wherein the interior of the outer case is filled with an insulating liquid.

7. A semiconductor module according to any one of claims 1 to 6, wherein a plurality of said semiconductor devices are housed in parallel inside said outer case.

8. A semiconductor module according to any one of claims 1 to 7, wherein the semiconductor device has terminals, the terminals are connected to insulatingly covered or insulatingly coated conductive members, and the conductive members pass through the outer case.

9. The semiconductor module according to claim 8, wherein the conductive member is a bus bar.

10. The semiconductor module according to claim 2, wherein the bottom and wall of the outer case are engaged and joined, and the wall has a portion that protrudes toward the bottom at the joining surface between the bottom and wall.

11. The semiconductor module according to claim 10, wherein the engaging portion where the bottom and the wall engage is stepped or tapered.

12. A semiconductor module according to claim 10 or 11, characterized in that the outer case seals the joint between the wall and the bottom by the pressure of the gas or liquid or by the clamping together.

13. The semiconductor module according to any one of claims 1 to 12, wherein the lid of the outer case is provided with sockets into which the terminals of the semiconductor device fit.

14. A semiconductor module according to any one of claims 1 to 13, characterized in that the lid of the outer case is provided with an electrode equipped with a spring capable of contacting the terminal of the semiconductor device.

15. The semiconductor module according to any one of claims 1 to 14, wherein a heat dissipation member is sandwiched between the lid of the outer case and the semiconductor device.

16. The semiconductor module according to any one of claims 1 to 15, wherein the lid of the outer case contacts the top surface of the semiconductor device.

17. A power conversion device comprising a semiconductor module according to any one of claims 1 to 16, a main conversion circuit that converts input power and outputs it, and a control circuit that outputs a control signal to the main conversion circuit to control the main conversion circuit.

18. A method for manufacturing a semiconductor module, comprising the steps of: placing an external case having walls and a bottom on a heat sink; placing a semiconductor device inside the external case; fastening the semiconductor device and the external case together to the heat sink; connecting an insulating coated conductive member that has been passed through the external case to the terminal of the semiconductor device; and joining a lid to the external case to seal the semiconductor device inside the external case so that the pressure of the gas or liquid inside the external case is maintained when the outside air pressure drops.

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