Power module and power conversion device

Abstract

The purpose of the present invention is to provide a power module that can inhibit the warping of a heat dissipation member caused by thermal stress. This power module comprises semiconductor elements (21, 22), a ceramic substrate (10) having a mounting surface on which the semiconductor elements (21, 22) are mounted, and a fin base (70) that is joined to a surface of the ceramic substrate (10) on the side opposite from the mounting surface, wherein a joining region of the ceramic substrate (10) with the fin base (70) corresponds to a portion where the semiconductor elements (21, 22) are mounted, and the area of the joining region of the ceramic substrate (10) with the fin base (70) is smaller than the area of the portion where the semiconductor elements (21, 22) are mounted.

Description

Technical Field

[0001] The present disclosure relates to a power module and a power conversion device.

Background Art

[0002] Power modules are mounted on all products such as industrial equipment, household appliances, and information terminals, and high productivity is required for power modules. For power modules mounted on electric vehicles, high heat dissipation is required, and high flatness is required to ensure fastening to the water-cooling jacket. Also, since the operating temperature is high and the efficiency is excellent, it is also required to be a package form that can be adopted for SiC semiconductors, which are likely to become mainstream in the future.

[0003] With the increasing environmental problems, power modules are becoming more and more popular in all scenarios of electric energy generation, power transmission, and regeneration. In power modules, a ceramic substrate having high insulation and heat dissipation is used as an insulating substrate in order to handle large currents and high voltages. However, materials such as aluminum nitride and silicon nitride, which are ceramic base materials, have a significantly smaller linear expansion coefficient compared to copper and aluminum used for heat dissipation members and the like. Therefore, when these members are joined, a large thermal stress is generated at the joint, and there is a problem that warping occurs in the heat dissipation member and cracks are likely to occur during temperature cycling.

[0004] For example, Patent Document 1 proposes a structure of a power module in which a semiconductor element is mounted on a ceramic substrate, a circuit is formed by wire bonding, and pin terminals are used as external terminals.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the technology described in Patent Document 1, a surface conductor layer serving as a circuit pattern is provided on the upper surface of the ceramic substrate to mount semiconductor elements and pin terminals, but a back surface conductor layer is provided on almost the entire lower surface of the ceramic substrate.

[0007] In the case of an in-vehicle power module such as an electric vehicle, the element size exceeds 10 mm square, and in the case of a 6-in-1 module, the number of elements is 12, and the size of the ceramic substrate becomes as large as 60 mm to 70 mm square.

[0008] When a large ceramic substrate is joined to a heat dissipation member made of copper or aluminum, since the difference in the linear expansion coefficients between the ceramic substrate and the heat dissipation member is large, excessive warping occurs in the heat dissipation member. When water cooling (liquid cooling) is performed using the heat dissipation member, it is usually necessary to fix it to a water cooling jacket which is a rigid body made of metal. Although warping to a certain extent is suppressed by fastening such as screwing, it is necessary to further suppress the warping in order to evenly apply the deformation pressure to the O-ring for obtaining watertightness.

[0009] Therefore, an object of the present disclosure is to provide a technology capable of suppressing warping of a heat dissipation member caused by thermal stress in a power module.

Means for Solving the Problems

[0010] The power module according to the present disclosure a plurality of includes a semiconductor element, a plurality of an insulating substrate having a surface conductor layer on which the semiconductor element is mounted and a back surface conductor layer on the side opposite to the surface conductor layer, a plurality of and a heat dissipation member joined to the back surface conductor layer. 、 a plurality of A joining region of the insulating substrate with the heat dissipation member a plurality of is a region corresponding to a portion where the semiconductor element is mounted, and the area of the surface conductor layer is larger than the area of the back surface conductor layer. wherein the plurality of semiconductor elements are six sets of transistors and diodes, and two or three sets of the six sets of the transistors and the diodes are mounted on each of the insulating substrates .

Advantages of the Invention

[0011] According to the present disclosure, by reducing the area of the bonding region between the heat dissipation member and the insulating substrate, warping of the heat dissipation member caused by thermal stress can be suppressed.

[0012] The objectives, features, aspects, and advantages of this disclosure will become clearer from the following detailed description and the accompanying drawings.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

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Figure 8

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Figure 10

Figure 11

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Figure 15

Mode for Carrying Out the Invention

[0014] <Embodiment 1> <Configuration of the Power Module> Embodiment 1 will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a power module 202 according to Embodiment 1. FIG. 2 is a top view showing the state of the power module 202 according to Embodiment 1 with the encapsulating resin 82 removed.

[0015] As shown in FIGS. 1 and 2, the power module 202 is a 6-in-1 module, and includes six sets of semiconductor elements 21, 22, two ceramic substrates 10A, 10B, a case 5, a plurality of external electrodes 61, a plurality of signal electrodes 63, an encapsulating resin 82, and a fin base 70. Here, when the two ceramic substrates 10A and 10B are not distinguished, they are simply referred to as the ceramic substrate 10. Here, the ceramic substrate 10 corresponds to an insulating substrate, and the fin base 70 corresponds to a heat radiating member. Also, the number of the semiconductor elements 21, 22 and the ceramic substrate 10 is not limited to six sets and two, respectively.

[0016] The case 5 is made of PPS (Polyphenylenesulfide) resin and is formed in a rectangular frame shape in a top view. The size of the case 5 is 100 mm in width, 80 mm in depth, and 6 mm in thickness. The external electrodes 61 and the signal electrodes 63 are integrally formed with the case 5 by insert molding.

[0017] The fin base 70 is made of an aluminum alloy and includes a base portion 70a and a plurality of pin portions 70b protruding downward from the base portion 70a. The base portion 70a is formed in a rectangular shape when viewed from above. The size of the base portion 70a is 100 mm in width, 80 mm in depth, and 3 mm in thickness. The size of each pin portion 70b is 1.5 mm in diameter and 5 mm in length.

[0018] The peripheral portion on the upper surface of the base portion 70a is fixed by the case 5 and the adhesive 81. The region excluding the peripheral portion on the upper surface of the base portion 70a is nickel-plated and joined to the ceramic substrate 10 by the solder 30. The solder 30 is composed of 96.5% tin, 3% silver, and 0.5% copper, and the melting point of the solder 30 is 217°C.

[0019] Each of the two ceramic substrates 10 includes a base material 11, a front surface conductor layer 12, and a back surface conductor layer 13. The base material 11 is made of aluminum nitride, and the thickness of the base material 11 is 0.64 mm. The front surface conductor layer 12 is made of copper and is provided on the upper surface of the base material 11. The front surface conductor layer 12 forms a mounting surface on which the semiconductor elements 21 and 22 in the ceramic substrate 10 are mounted. The back surface conductor layer 13 is made of copper and is provided on the lower surface of the base material 11. The back surface conductor layer 13 forms a surface opposite to the mounting surface in the ceramic substrate 10. Both the front surface conductor layer 12 and the back surface conductor layer 13 have a thickness of 0.8 mm and are formed by film formation by brazing.

[0020] On each surface conductor layer 12 of the two ceramic substrates 10, there are a region where semiconductor elements 21, 22 are mounted and a region for forming a circuit by wire 41. On each surface conductor layer 12 of the two ceramic substrates 10, three sets of the six sets of semiconductor elements 21, 22 that make up the 6-in-1 module are mounted by solder 30. The semiconductor element 21 is a silicon diode, and the size of the semiconductor element 21 is 13 mm in width, 10 mm in depth, and 0.2 mm in thickness. The semiconductor element 22 is a silicon IGBT (Insulated Gate Bipolar Transistor), and the size of the semiconductor element 22 is 13 mm in width, 13 mm in depth, and 0.2 mm in thickness.

[0021] Next, two ceramic substrates 10A, 10B will be described. One ceramic substrate 10A (outer dimensions 35 mm × 65 mm) has one surface conductor layer 12 (outer dimensions 31 mm × 61 mm), and three sets of semiconductor elements 21, 22 are mounted on the one surface conductor layer 12. The other ceramic substrate 10B (outer dimensions 45 mm × 65 mm) has four surface conductor layers 12, and one set of semiconductor elements 21, 22 is mounted on each of the three larger surface conductor layers 12 (outer dimensions 30 mm × 19 mm) among them.

[0022] The main terminals of the semiconductor elements 21, 22 are connected to the external electrodes 61 inserted and formed in the case 5 by aluminum wires 41 (diameter 0.4 mm). The gate electrode 221 of the semiconductor element 22 and the signal electrode 63 inserted and formed in the case 5 are wire-bonded by an aluminum wire 42 (diameter 0.15 mm) to form a circuit.

[0023] The encapsulating resin 82 is composed of an epoxy resin in which a silica filler is dispersed.

[0024] FIG. 3 is a bottom view of the ceramic substrates 10A and 10B included in the power module 202 according to Embodiment 1. As shown in FIG. 3, the back surface conductor layer 13 is formed in a region corresponding to the portions where the semiconductor elements 21 and 22 are mounted. Specifically, the back surface conductor layer 13 is integrally formed without being divided in a region corresponding to the entire portions where the three sets of semiconductor elements 21 and 22 are mounted, and is not formed in other regions. Therefore, as shown in FIG. 1, since there is no back surface conductor layer 13 in the region corresponding to the portion where the wire 41 is directly bonded to the ceramic substrate 10, this region is not bonded to the base portion 70a of the fin base 70. Therefore, in this region, there is a gap between the base material 11 and the base portion 70a of the fin base 70, and this gap is filled with the sealing resin 82. The outer dimensions of the back surface conductor layer 13 of the ceramic substrate 10A are 31 mm × 55 mm, and the outer dimensions of the back surface conductor layer 13 of the ceramic substrate 10B are 31 mm × 61 mm.

[0025] Here, the region corresponding to the portion where the semiconductor elements 21 and 22 are mounted in the back surface conductor layer 13 is the region of the back surface conductor layer 13 facing the semiconductor elements 21 and 22 through the base material 11 and the front surface conductor layer 12.

[0026] Next, another example and yet another example of the ceramic substrate 10 will be described. FIG. 4 is a bottom view showing another example of the ceramic substrates 10A and 10B included in the power module 202 according to Embodiment 1. As shown in FIG. 4, the back surface conductor layer 13 is divided into regions corresponding to the portions where the semiconductor elements 21 and 22 are each mounted. That is, six back surface conductor layers 13 are provided for each ceramic substrate 10. As a result, since the area of each back surface conductor layer 13 becomes smaller, it is possible to suppress the shrinkage cavities that are likely to occur when performing large-area soldering.

[0027] FIG. 5 is a bottom view showing still another example of the ceramic substrates 10A and 10B included in the power module 202 according to Embodiment 1. As shown in FIG. 6, the back surface conductor layer 13 is formed in a region corresponding to the portion where the three sets of semiconductor elements 21 and 22 are mounted. The four corner portions of each back surface conductor layer 13 have an R chamfered shape. This makes it possible to suppress cracks during temperature cycling, which is likely to occur when performing soldering over a large area.

[0028] <Manufacturing Process of Power Module> Next, the manufacturing process of the power module 202 will be described. FIGS. 6(a) to 6(c) are schematic diagrams showing the manufacturing process of the power module 202 according to Embodiment 1.

[0029] As shown in FIG. 6(a), a sheet-like solder 30 having a thickness of 0.2 mm and cut to a predetermined dimension is mounted on the surface conductor layer 12 of the ceramic substrate 10, and the semiconductor elements 21 and 22 are arranged in a positioned state. By heating the assembly with the semiconductor elements 21 and 22 arranged on the surface conductor layer 12 in a reflow furnace, the semiconductor elements 21 and 22 are solder-bonded to the surface conductor layer 12.

[0030] Next, as shown in FIG. 6(b), a sheet-like solder 30 having a thickness of 0.4 mm and the ceramic substrate 10 are arranged in a region excluding the peripheral edge of the base portion 70a of the fin base 70. An adhesive 81 is applied to the peripheral edge of the base portion 70a, and the case 5 is arranged thereon. By heating this assembly in a reflow furnace, the solder bonding between the base portion 70a and the ceramic substrate 10 and the adhesion between the base portion 70a and the case 5 are performed simultaneously.

[0031] Finally, as shown in FIG. 6(c), the semiconductor elements 21 and 22 are joined to the external electrodes 61 by wires 41, and the signal electrode (not shown) of the semiconductor element 22 and the signal electrode 63 are joined by a wire 42. Then, the encapsulating resin 82 is injected, and the encapsulating resin 82 is heat-cured in an oven to manufacture the power module 202.

[0032] <Effect> As described above, the power module 202 according to Embodiment 1 includes semiconductor elements 21 and 22, a ceramic substrate 10 having a mounting surface on which the semiconductor elements 21 and 22 are mounted, and a fin base 70 joined to a surface of the ceramic substrate 10 opposite to the mounting surface. The joining region of the ceramic substrate 10 with the fin base 70 is a region corresponding to the portion where the semiconductor elements 21 and 22 are mounted, and the area of the joining region of the ceramic substrate 10 with the fin base 70 is smaller than the area of the portion where the semiconductor elements 21 and 22 are mounted.

[0033] Therefore, by reducing the area of the joining region of the ceramic substrate 10 with the fin base 70, warping of the fin base 70 caused by thermal stress can be suppressed.

[0034] Further, the ceramic substrate 10 includes a back surface conductor layer 13 that forms a surface opposite to the mounting surface, and the back surface conductor layer 13 is formed in a region corresponding to the portion where the semiconductor elements 21 and 22 are mounted. Therefore, since the area of the back surface conductor layer 13 can be reduced, the power module 202 can be made lighter. From the above, the durability of the power module 202 and the reduction of energy consumption can be achieved.

[0035] Also, in any of FIGS. 3, 4, and 5, the area of the surface conductor layer 12 of the ceramic substrate 10 is larger than the area of the back surface conductor layer 13. That is, on the surface side of the ceramic substrate 10, the area of the copper conductor layer having a large coefficient of linear expansion is larger than that on the back surface side. However, since the semiconductor elements 21 and 22 having a smaller coefficient of linear expansion than the surface conductor layer 12 are mounted on the surface conductor layer 12, the warping of the ceramic substrate 10 is canceled out and reduced.

[0036] Here, three sets of semiconductor elements 21 and 22 are mounted on each of the two ceramic substrates 10A and 10B. From the viewpoints of temperature cycle performance and warpage of each ceramic substrate 10, it is considered effective to reduce the external dimensions of the ceramic substrate 10 as much as possible by using one or two semiconductor elements 21 and 22 mounted on each ceramic substrate 10. However, since the ceramic substrate 10 needs to ensure insulation with respect to the fin base 70, a region (frame region) of only a certain amount of base material 11 is required at the peripheral portion of the ceramic substrate 10. Therefore, if the ceramic substrate 10 is divided too much, the frame region of the entire ceramic substrate 10 becomes large, and the entire power module 202 becomes large. Therefore, it is considered effective to divide the ceramic substrate 10 into two so that the external dimensions can accommodate three sets of semiconductor elements 21 and 22 each.

[0037] <Modification Example 1 of Embodiment 1> Next, a modification example of Embodiment 1 will be described. FIG. 7 is a cross-sectional view of a power module 202 according to Modification Example 1 of Embodiment 1.

[0038] As shown in FIG. 7, the fin base 70 is provided with a convex portion 71 that contacts a region where the fin base 70 is not joined among the surfaces of the ceramic substrate 10 opposite to the mounting surface. Specifically, the convex portion 71 is provided at a position that contacts a region where the back surface conductor layer 13 is not formed on the ceramic substrate 10.

[0039] The height of the convex portion 71 is 1.0 mm. Since the encapsulating resin 82 has poor heat conduction, the provision of the convex portion 71 can reduce the thickness of the encapsulating resin 82 filled in the gap between the base material 11 and the base portion 70a of the fin base 70. As a result, it becomes easier to dissipate the joule heat generated at the joint portion between the wire 41 and the surface conductor layer 12.

[0040] FIG. 8 is a cross-sectional view of the power module 202 according to Modification 2 of Embodiment 1. FIG. 9 is a top view showing the state of the power module 202 according to Modification 2 of Embodiment 1 with the encapsulating resin 82 removed. FIG. 10 is a bottom view of the ceramic substrate 10A included in the power module 202 according to Modification 2 of Embodiment 1. In Modification 2 of Embodiment 1, the same components as those described in Embodiment 1 are denoted by the same reference numerals and the description thereof is omitted.

[0041] As shown in FIGS. 8 and 9, in Modification 2 of Embodiment 1, the power module 202 has a configuration in which three 2-in-1 modules are arranged side by side. The power module 202 includes six sets of semiconductor elements 21 and 22, three ceramic substrates 10A, 10B, and 10C, a case 5, a plurality of external electrodes 61, a plurality of signal electrodes 63, an encapsulating resin 82, and a fin base 70. When the three ceramic substrates 10A, 10B, and 10C are not distinguished, they are simply referred to as the ceramic substrate 10.

[0042] The case 5 has a different size from that of Embodiment 1. The size of the case 5 is 70 mm in width, 120 mm in depth, and 6 mm in thickness.

[0043] The fin base 70 has a different size of the base portion 70a from that of Embodiment 1. The size of the base portion 70a is 70 mm in width, 120 mm in depth, and 3 mm in thickness.

[0044] Each of the three ceramic substrates 10 has two surface conductor layers 12 (outer dimensions: 41 mm × 32 mm). Two sets of semiconductor elements 21 and 22 are mounted on each of the two surface conductor layers 12 of the three ceramic substrates 10.

[0045] As shown in FIG. 10, the back surface conductor layer 13 (outer dimensions 32 mm × 32 mm) is formed in a region corresponding to the portion where the semiconductor elements 21 and 22 are mounted. Specifically, the back surface conductor layer 13 is integrally formed without being divided in a region corresponding to the entire portion where the two sets of semiconductor elements 21 and 22 are mounted, and is not formed in other regions. Therefore, as shown in FIG. 10, since there is no back surface conductor layer 13 in the region corresponding to the portion where the wire 41 is directly joined to the ceramic substrate 10, this region is not joined to the base portion 70a of the fin base 70. Therefore, in this region, there is a gap between the base material 11 and the base portion 70a of the fin base 70, and this gap is filled with the sealing resin 82. Note that the configuration of Modification 2 of Embodiment 1 can also be adopted in Modification 1 of Embodiment 1 and the following Embodiments 2 and 3.

[0046] Here, two sets of semiconductor elements 21 and 22 are mounted on each of the three ceramic substrates 10A, 10B, and 10C. From the viewpoints of the temperature cycle performance and warpage of each ceramic substrate 10, it is considered effective to reduce the outer dimensions of the ceramic substrate 10 as much as possible by using one or two semiconductor elements 21 and 22 mounted on each ceramic substrate 10. However, since a certain amount of the region of only the base material 11 (frame region) is required at the peripheral edge of the ceramic substrate 10 to ensure insulation with respect to the fin base 70, if the ceramic substrate 10 is divided too much, the frame region of the entire ceramic substrate 10 will become large, and the entire power module 202 will become large. Therefore, it is considered effective to use three ceramic substrates 10 so that the outer dimensions can accommodate two sets of semiconductor elements 21 and 22 each.

[0047] <Embodiment 2> Next, the power module 202 according to Embodiment 2 will be described. FIG. 11 is a cross-sectional view of the power module 202 according to Embodiment 2. FIG. 12 is a bottom view of the ceramic substrate 10 included in the power module 202 according to Embodiment 2. In Embodiment 2, the same components as those described in Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0048] As shown in FIGS. 11 and 12, in the second embodiment, the back surface conductor layer 13 is provided on the entire back surface of the base material 11. Therefore, among the back surface conductor layer 13, the region corresponding to the portion where the semiconductor elements 21 and 22 are mounted is joined to the base portion 70a of the fin base 70, and a solder resist 131 made of a UV curable resin is formed in the other regions so as not to be joined to the fin base 70. The solder resist 131 is soldered to the regions other than the region corresponding to the portion where the semiconductor elements 21 and 22 are mounted in the back surface conductor layer 13.

[0049] As described above, in the power module 202 according to the second embodiment, the ceramic substrate 10 includes the back surface conductor layer 13 that forms the surface opposite to the mounting surface, and among the back surface conductor layer 13, a solder resist 131 is formed in the regions other than the region corresponding to the portion where the semiconductor elements 21 and 22 are mounted so as not to be joined to the fin base 70.

[0050] Therefore, the regions of the back surface conductor layer 13 other than the region corresponding to the portion where the semiconductor elements 21 and 22 are mounted are not joined to the base portion 70a of the fin base 70. By reducing the bonding area between the ceramic substrate 10 and the fin base 70, warping of the fin base 70 caused by thermal stress can be suppressed.

[0051] Note that the convex portion 71 of the modification of the first embodiment may be provided so as to contact the region where the solder resist 131 is formed on the ceramic substrate 10. Also in this case, it is possible to improve the heat dissipation of the joule heat generated at the joint portion between the wire 41 and the front surface conductor layer 12.

[0052] <Embodiment 3> Next, the power module 202 according to Embodiment 3 will be described. FIG. 13 is a cross-sectional view of the power module 202 according to Embodiment 3. FIG. 14 is a bottom view of the ceramic substrate 10 included in the power module 202 according to Embodiment 3. In Embodiment 3, the same components as those described in Embodiments 1 and 2 are denoted by the same reference numerals, and the description thereof will be omitted.

[0053] As shown in FIGS. 13 and 14, in Embodiment 3, the back surface conductor layer 13 is divided into a first region 13a which is a region corresponding to the portion where the semiconductor elements 21 and 22 are mounted by the slit 13c and a second region 13b which is the other region. Of the back surface conductor layer 13, the first region 13a is joined to the base portion 70a of the fin base 70, and the second region 13b is not joined to the base portion 70a.

[0054] As described above, in the power module according to Embodiment 3, the ceramic substrate 10 includes the back surface conductor layer 13 that forms the surface opposite to the mounting surface, and the back surface conductor layer 13 is divided into a first region 13a which is a region corresponding to the portion where the semiconductor elements 21 and 22 are mounted by the slit 13c and a second region 13b which is the other region.

[0055] Therefore, the area difference between the front surface conductor layer 12 and the back surface conductor layer 13 can be reduced, and the bonding area with the fin base 70 in the ceramic substrate 10 can be reduced without an additional process such as forming the solder resist 131.

[0056] Note that the convex portion 71 in the modification of Embodiment 1 may be provided so as to contact the second region 13b. Also in this case, it is possible to improve the heat dissipation of the Joule heat generated at the joint portion between the wire 41 and the front surface conductor layer 12.

[0057] <Modifications of Embodiments 1 to 3> In the above description, the base material 11 was described as being made of aluminum nitride, but the same effects can be obtained even if it is made of silicon nitride or alumina. Also, although the front surface conductor layer 12 and the back surface conductor layer 13 were described as being made of copper, the same effects can be obtained even if they are made of aluminum by modifying the surface thereof so that it wets solder, such as by nickel plating.

[0058] Also, although the fin base 70 was described as being made of an aluminum alloy, the same effects can be obtained even if it is made of copper or a copper alloy. Also, although the semiconductor elements 21 and 22 were described as being made of silicon, the same effects can be obtained even if they are wide bandgap semiconductors such as silicon carbide and gallium nitride.

[0059] Also, although the solder 30 was described as being composed of 96.5% tin, 3% silver, and 0.5% copper and having a melting point of 217°C, the same effects can be obtained even if it is composed of 99.3% tin and 0.7% copper and has a melting point of 224°C, or if it is composed of 95% tin and 5% antimony and has a melting point of 240°C.

[0060] Also, even if a part of the solder 30 is replaced with a silver epoxy adhesive, a silver sintered material, or a brazing material, which are bonding materials other than solder, the same effects can be obtained.

[0061] Also, although the wires 41 and 42 were described as being made of aluminum, the same effects can be obtained even if they are made of an aluminum alloy containing a trace amount of an additive such as iron or made of copper.

[0062] Also, instead of forming a circuit by wire bonding using the wires 41 and 42, the same effects can be obtained by performing soldering on the upper surfaces of the semiconductor elements 21 and 22 using a copper frame to form a circuit.

[0063] Also, although the case 5 was described as being made of PPS, it is also possible to improve the heat resistance by replacing it with LCP (Liquid Crystal Polymer).

[0064] Also, although the external electrode 61 and the signal electrode 63 have been described as being made of a copper frame, the same effect can be obtained even if nickel plating is appropriately applied, or if they are replaced with those made of a copper alloy or nickel-plated aluminum.

[0065] Also, although the encapsulating resin 82 has been described as being composed of an epoxy resin in which silica fillers are dispersed, fillers such as alumina may be dispersed instead of the silica fillers, or the same effect can be obtained even if it is composed of a mixture of a silicone resin and an epoxy resin. Further, the same effect can be obtained even if the encapsulating resin 82 is composed only of a silicone resin.

[0066] <Embodiment 4> This embodiment applies the power module 202 according to the above-described Embodiments 1 to 3 to a power conversion device. The application of the power module 202 according to Embodiments 1 to 3 is not limited to a specific power conversion device, but hereinafter, as Embodiment 4, a case where the power module 202 according to Embodiments 1 to 3 is applied to a three-phase inverter will be described.

[0067] FIG. 15 is a block diagram showing the configuration of a power conversion system to which the power conversion device according to Embodiment 4 is applied.

[0068] The power conversion system shown in FIG. 15 is composed of a power source 100, a power conversion device 200, and a load 300. The power source 100 is a DC power source and supplies DC power to the power conversion device 200. The power source 100 can be composed of various things. For example, it can be composed of a DC system, a solar cell, a storage battery, or it may be composed of a rectifier circuit or an AC / DC converter connected to an AC system. Further, the power source 100 may be composed of a DC / DC converter that converts the DC power output from the DC system into a predetermined power.

[0069] The power conversion device 200 is a three-phase inverter connected between the power supply 100 and the load 300. It converts the DC power supplied from the power supply 100 into AC power and supplies the AC power to the load 300. As shown in FIG. 15, the power conversion device 200 includes a main conversion circuit 201 that converts DC power into AC power and outputs it, and a control circuit 203 that outputs a control signal for controlling the main conversion circuit 201 to the main conversion circuit 201.

[0070] The load 300 is a three-phase motor driven by the AC power supplied from the power conversion device 200. Note that the load 300 is not limited to a specific application, but is a motor mounted on various electrical devices, and is used, for example, as a motor for a hybrid vehicle, an electric vehicle, a railway vehicle, an elevator, or an air conditioner.

[0071] Hereinafter, the details of the power conversion device 200 will be described. The main conversion circuit 201 includes a switching element (not shown) and a freewheeling diode (not shown). By switching the switching element, the DC power supplied from the power supply 100 is converted into AC power and supplied to the load 300. There are various specific circuit configurations of the main conversion circuit 201, but the main conversion circuit 201 according to the present embodiment is a two-level three-phase full-bridge circuit, and can be composed of six switching elements and six freewheeling diodes connected in anti-parallel to each switching element. At least any one of the switching elements and the freewheeling diodes of the main conversion circuit 201 is constituted by the power module 202 corresponding to any one of the above-described Embodiments 1 to 3. The six switching elements are connected in series in pairs of two switching elements to form upper and lower arms, and each upper and lower arm constitutes each phase (U phase, V phase, W phase) of the full-bridge circuit. Then, the output terminals of each upper and lower arm, that is, the three output terminals of the main conversion circuit 201, are connected to the load 300.

[0072] The main conversion circuit 201 includes a drive circuit (not shown) for driving each switching element. The drive circuit may be built into the power module 202, or may be configured to include a drive circuit separately from the power module 202. The drive circuit generates a drive signal for driving the switching elements of the main conversion circuit 201 and supplies it to the control electrodes of the switching elements of the main conversion circuit 201. Specifically, in accordance with a control signal from a control circuit 203 described later, a drive signal for turning on the switching element and a drive signal for turning off the switching element are output to the control electrodes of each switching element. When maintaining the switching element in the on state, the drive signal is a voltage signal (on signal) equal to or higher than the threshold voltage of the switching element. When maintaining the switching element in the off state, the drive signal is a voltage signal (off signal) equal to or lower than the threshold voltage of the switching element.

[0073] The control circuit 203 controls the switching elements of the main conversion circuit 201 so that desired power is supplied to the load 300. Specifically, based on the power to be supplied to the load 300, the time (on time) during which each switching element of the main conversion circuit 201 should be in the on state is calculated. For example, the main conversion circuit 201 can be controlled by PWM control that modulates the on time of the switching element according to the voltage to be output. Then, a control command (control signal) is output to the drive circuit included in the main conversion circuit 201 so that an on signal is output to the switching element that should be in the on state and an off signal is output to the switching element that should be in the off state at each time point. The drive circuit outputs an on signal or an off signal to the control electrode of each switching element as a drive signal in accordance with this control signal.

[0074] In the power conversion device according to the present embodiment, since the power module 202 according to Embodiments 1 to 3 is applied as the switching element and the freewheeling diode of the main conversion circuit 201, weight reduction, durability improvement, and reduction of energy consumption can be achieved.

[0075] In this embodiment, an example in which the power module 202 according to Embodiments 1 to 3 is applied to a two-level three-phase inverter has been described. However, the application of the power module 202 according to Embodiments 1 to 3 is not limited to this, and it can be applied to various power conversion devices. In this embodiment, a two-level power conversion device is used, but it may also be a three-level or multi-level power conversion device. When supplying power to a single-phase load, the power module 202 according to Embodiments 1 to 3 may be applied to a single-phase inverter. Further, when supplying power to a DC load or the like, the power module 202 according to Embodiments 1 to 3 can also be applied to a DC / DC converter or an AC / DC converter.

[0076] In addition, the power conversion device to which the power module 202 according to Embodiments 1 to 3 is applied is not limited to the case where the above-described load is an electric motor. For example, it can also be used as a power supply device for a discharge machining machine, a laser processing machine, an induction heating cooker, or a non-contact power supply system. Furthermore, it can also be used as a power conditioner for a solar power generation system, a power storage system, or the like.

[0077] Although this disclosure has been described in detail, the above description is illustrative in all aspects and not limiting. Innumerable modifications that are not illustrated can be conceived.

[0078] It should be noted that the respective embodiments can be freely combined, or the respective embodiments can be appropriately modified or omitted.

[0079] Hereinafter, aspects of the present disclosure will be collectively described as appendices.

[0080] (Appendix 1) A semiconductor element, An insulating substrate having a mounting surface on which the semiconductor element is mounted, A heat dissipation member joined to a surface of the insulating substrate opposite to the mounting surface, and A joining region of the insulating substrate with the heat dissipation member is a region corresponding to a portion where the semiconductor element is mounted. A power module in which the area of the bonding region of the insulating substrate with the heat radiating member is smaller than the area of the portion on which the semiconductor element is mounted.

[0081] (Appendix 2) A plurality of the insulating substrates are provided, A plurality of the semiconductor elements are provided, The plurality of semiconductor elements are six sets of transistors and diodes, The power module according to Appendix 1, wherein two or three sets out of the six sets of the transistors and the diodes are mounted on each of the insulating substrates.

[0082] (Appendix 3) The insulating substrate includes a conductor layer forming a surface on the side opposite to the mounting surface, The power module according to Appendix 1, wherein the conductor layer is formed in a region corresponding to the portion on which the semiconductor element is mounted.

[0083] (Appendix 4) The insulating substrate includes a conductor layer forming a surface on the side opposite to the mounting surface, The power module according to Appendix 1, wherein a solder resist for preventing bonding with the heat radiating member is formed in a region of the conductor layer other than the region corresponding to the portion on which the semiconductor element is mounted.

[0084] (Appendix 5) The insulating substrate includes a conductor layer forming a surface on the side opposite to the mounting surface, The power module according to Appendix 1, wherein the conductor layer is divided by a slit into a region corresponding to the portion on which the semiconductor element is mounted and a region other than that.

[0085] (Appendix 6) The heat radiating member is provided with a convex portion that contacts a region of the surface of the insulating substrate on the side opposite to the mounting surface where the heat radiating member is not bonded. The power module according to Appendix 1.

[0086] (Appendix 7) A main conversion circuit having the power module described in Appendix 1 and converting and outputting the input power, A control circuit that outputs a control signal for controlling the main conversion circuit to the main conversion circuit, A power conversion device comprising the same.

Explanation of Signs

[0087] 10, 10A, 10B, 10C ceramic substrates, 13 back surface conductor layer, 13a first region, 13b second region, 13c slit, 21, 22 semiconductor elements, 70 fin base, 71 convex portion, 131 solder resist, 200 power conversion device, 201 main conversion circuit, 202 power module, 203 control circuit.

Claims

1. A plurality of semiconductor elements, a plurality of insulating substrates each having a surface conductor layer on which the plurality of semiconductor elements are mounted and a back conductor layer on the side opposite to the surface conductor layer, and a heat radiating member joined to the back conductor layer, wherein the joining regions of the plurality of insulating substrates with the heat radiating member are regions corresponding to the portions where the plurality of semiconductor elements are mounted, the area of the surface conductor layer is larger than the area of the back conductor layer, the plurality of semiconductor elements are six sets of transistors and diodes, and a power module in which two or three sets out of the six sets of the transistors and the diodes are mounted on each of the insulating substrates.

2. A semiconductor element, an insulating substrate having a surface conductor layer on which the semiconductor element is mounted and a back conductor layer on the side opposite to the surface conductor layer, and a heat radiating member joined to the back conductor layer, wherein the joining region of the insulating substrate with the heat radiating member is a region corresponding to the portion where the semiconductor element is mounted, the area of the surface conductor layer is larger than the area of the back conductor layer, and a power module in which the back conductor layer is formed in a region corresponding to the portion where the semiconductor element is mounted.

3. A semiconductor element, an insulating substrate having a surface conductor layer on which the semiconductor element is mounted and a back conductor layer on the side opposite to the surface conductor layer, and a heat radiating member joined to the back conductor layer, wherein the joining region of the insulating substrate with the heat radiating member is a region corresponding to the portion where the semiconductor element is mounted, the area of the surface conductor layer is larger than the area of the back conductor layer, and a power module in which a solder resist is formed in a region of the back conductor layer other than the region corresponding to the portion where the semiconductor element is mounted so as not to be joined to the heat radiating member.

4. A semiconductor element, an insulating substrate having a surface conductor layer on which the semiconductor element is mounted and a back conductor layer on the side opposite to the surface conductor layer, and a heat radiating member joined to the back conductor layer, wherein the joining region of the insulating substrate with the heat radiating member is a region corresponding to the portion where the semiconductor element is mounted, the area of the surface conductor layer is larger than the area of the back conductor layer, and a power module in which the back conductor layer is divided by a slit into a region corresponding to the portion where the semiconductor element is mounted and a region other than that.

5. A semiconductor element, An insulating substrate having a surface conductor layer on which the semiconductor element is mounted and a back surface conductor layer on the opposite side of the surface conductor layer, A heat radiating member joined to the back surface conductor layer, and The joining region of the insulating substrate with the heat radiating member is a region corresponding to the portion where the semiconductor element is mounted, The area of the surface conductor layer is larger than the area of the back surface conductor layer, The heat radiating member is provided with a convex portion that contacts a region of the surface of the insulating substrate on the side opposite to the surface conductor layer where the heat radiating member is not joined. A power module.

6. A main conversion circuit that has the power module according to any one of claims 1 to 5 and converts and outputs input power, A control circuit that outputs a control signal for controlling the main conversion circuit to the main conversion circuit, A power conversion device comprising:

7. A semiconductor element, An insulating substrate having a mounting surface on which the semiconductor element is mounted, A heat radiating member joined to a surface of the insulating substrate on the side opposite to the mounting surface, and The joining region of the insulating substrate with the heat radiating member is a region corresponding to the portion where the semiconductor element is mounted, A power module in which the area of the joining region of the insulating substrate with the heat radiating member is smaller than the area of the portion where the semiconductor element is mounted.

8. A plurality of the insulating substrates are provided, A plurality of the semiconductor elements are provided, The plurality of semiconductor elements are six sets of transistors and diodes, The power module according to claim 7, wherein two or three sets of the six sets of the transistors and the diodes are mounted on each of the insulating substrates.

9. The insulating substrate includes a conductor layer that forms a surface on the side opposite to the mounting surface, The power module according to claim 7, wherein the conductor layer is formed in a region corresponding to a portion where the semiconductor element is mounted.

10. The insulating substrate includes a conductor layer that forms a surface on the side opposite to the mounting surface, The power module according to claim 7, wherein a solder resist for preventing joining with the heat radiating member is formed in a region of the conductor layer other than the region corresponding to the portion where the semiconductor element is mounted.

11. The insulating substrate includes a conductor layer that forms a surface on the side opposite to the mounting surface, The power module according to claim 7, wherein the conductor layer is divided by a slit into a region corresponding to a portion on which the semiconductor element is mounted and a region other than that portion.

12. The power module according to claim 7, wherein the heat radiating member is provided with a convex portion that contacts a region of the surface of the insulating substrate opposite to the mounting surface where the heat radiating member is not joined.

13. A power conversion device having the power module according to claim 7, a main conversion circuit that converts input power and outputs the converted power, a control circuit that outputs a control signal for controlling the main conversion circuit to the main conversion circuit, and comprising the above.

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