A power module, a power converter, and a method for manufacturing a power module.

Abstract

The objective is to provide a technology that can suppress the deterioration of reliability at the joint between a metal plate and an insulating substrate in a power module. [Solution] The power module comprises a ceramic substrate 10, semiconductor elements 21 and 22 mounted on the ceramic substrate 10, a metal plate 60s bonded to the ceramic substrate 10 or the semiconductor elements 21 and 22 via a bonding material 30, and a main terminal 62 consisting of a busbar 61 bonded to the metal plate 60s. The coefficient of thermal expansion of the metal plate 60s is smaller than the coefficient of thermal expansion of the busbar 61.

Description

Technical Field

[0006] ,

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

Background Art

[0002] As environmental problems become more serious, power modules are being mounted on products in all fields such as power generation, power transmission, and regeneration of electrical energy. Power modules mounted on power generation facilities or power transmission facilities are particularly required to have high reliability and productivity. In addition, power modules are required to be small and lightweight in order to reduce energy consumption during manufacturing. Since power modules handle large currents and high voltages, bonding with an insulating substrate on which a power semiconductor device is mounted is generally performed using a bus bar such as a copper plate.

[0003] In addition, as the main electrode circuit of a power semiconductor device, wire bonding using a wire such as aluminum has been generally used. However, due to an increase in current capacity and improvement in heat dissipation, a circuit formation method of soldering a bus bar is becoming popular.

[0004] For example, Patent Document 1 discloses a method of sandwiching a metal plate between a bonding portion of an insulating substrate and a bus bar and performing laser welding.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the technology described in Patent Document 1 has the problem that thermal stress occurs at the joint between the metal plate and the insulating substrate due to the difference in the coefficient of linear expansion between the metal plate and the insulating substrate, which reduces the reliability of the joint between the metal plate and the insulating substrate.

[0007] Therefore, the present disclosure aims to provide a technology that can suppress the deterioration of reliability at the joint between a metal plate and an insulating substrate in a power module. [Means for solving the problem]

[0008] The power module according to this disclosure comprises an insulating substrate, a semiconductor element mounted on the insulating substrate, a metal plate bonded to the insulating substrate or the semiconductor element via a bonding material, and an external terminal consisting of an electrode plate bonded to the metal plate, wherein the coefficient of linear expansion of the metal plate is smaller than the coefficient of linear expansion of the electrode plate. [Effects of the Invention]

[0009] According to this disclosure, the coefficient of thermal expansion of the metal plate becomes close to that of the insulating substrate, thereby suppressing the generation of thermal stress caused by the difference in the coefficients of thermal expansion between the metal plate and the insulating substrate. This improves the reliability of the joint between the metal plate and the insulating substrate. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a cross-sectional view of a power module according to Embodiment 1. [Figure 2] Figure 2 is a top view showing the power module according to Embodiment 1 with the sealing resin removed. [Figure 3] Figure 3 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 1. [Figure 4] Figure 4 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 1. [Figure 5] Figure 5 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 1. [Figure 6]FIG. 6 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 1. [Figure 7] FIG. 7 is a cross-sectional view of a power module according to Modification 1 of Embodiment 1. [Figure 8] FIG. 8 is a cross-sectional view of a power module according to Modification 2 of Embodiment 1. [Figure 9] FIG. 9 is a cross-sectional view of a power module according to Modification 3 of Embodiment 1. [Figure 10] FIG. 10 is a cross-sectional view of a power module according to Embodiment 2. [Figure 11] FIG. 11 is a top view showing a state in which the encapsulating resin is removed from the power module according to Embodiment 2. [Figure 12] FIG. 12 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 2. [Figure 13] FIG. 13 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 2. [Figure 14] FIG. 14 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 2. [Figure 15] FIG. 15 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 2. [Figure 16] FIG. 16 is a cross-sectional view of a power module according to Embodiment 3. [Figure 17] FIG. 17 is a top view showing a state in which the encapsulating resin is removed from the power module according to Embodiment 3. [Figure 18] FIG. 18 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 3. [Figure 19] FIG. 19 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 3. [Figure 20] FIG. 20 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 3. [Figure 21] FIG. 21 is a cross-sectional view showing a method for manufacturing a power module according to Embodiment 3. [Figure 22]FIG. 22 is a cross-sectional view of a power module according to a modification of Embodiment 3. [Figure 23] FIG. 23 is a block diagram showing the configuration of a power conversion system to which a power conversion device according to Embodiment 4 is applied.

MODE FOR CARRYING OUT THE INVENTION

[0011] Embodiment 1. Embodiment 1 will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a power module according to Embodiment 1. FIG. 2 is a top view showing a state where the encapsulating resin 70 is removed from the power module according to Embodiment 1.

[0012] As shown in FIGS. 1 and 2, the power module includes a base plate 15, a ceramic substrate 10 as an insulating substrate, semiconductor elements 20, 21, a metal plate 60s, a main terminal 62 as an external terminal, a signal terminal 63, a case 5, wires 40, 41, and an encapsulating resin 70.

[0013] The base plate 15 is a metal plate member formed in a rectangular shape in a top view and plated with nickel on copper. The size of the base plate 15 is 100 mm in width and 75 mm in depth.

[0014] The ceramic substrate 10 is joined to the upper surface of the base plate 15 via solder 30 as a joining material. The ceramic substrate 10 has a base material 10,2, a surface conductor layer 103, and a back surface conductor layer 101. The base material 102 is a plate member made of silicon nitride formed in a rectangular shape in a top view. A copper surface conductor layer 103 is provided on the upper surface of the base material 102, and a copper back surface conductor layer 101 is provided on the lower surface of the base material 102. The size of the base material 102 is 75 mm in width, 58 mm in depth, and 0.32 mm in thickness. The thicknesses of both the surface conductor layer 103 and the back surface conductor layer 101 are 0.8 mm.

[0015] The semiconductor element 20 is an IGBT (Insulated Gate Bipolar Transistor) and is bonded to the upper surface of the surface conductor layer 103 via solder 30. The semiconductor element 20 is made of silicon and has dimensions of 10 mm in width, 10 mm in depth, and 0.2 mm in thickness. The semiconductor element 21 is a diode and is bonded to the upper surface of the surface conductor layer 103 via solder 30. The semiconductor element 21 is made of silicon and has dimensions of 10 mm in width, 8 mm in depth, and 0.2 mm in thickness.

[0016] Furthermore, the semiconductor elements 20 and 21 are not limited to IGBTs and diodes, respectively, but may also be MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs with integrated diodes, or MOSFETs with integrated diodes.

[0017] Solder 30 is composed of 96.5% tin, 3% silver, and 0.5% copper. Its melting point is 217°C.

[0018] Case 5 is made of PPS (Polyphenylene sulfide) resin and is formed in a rectangular frame shape when viewed from above. Case 5 is fitted to the peripheral edge of the upper surface of the base plate 15. The main terminal 62 and signal terminal 63 are integrally formed with case 5 by insert molding.

[0019] The main terminal 62 consists of a busbar 61 which serves as an electrode plate. One end of the main terminal 62, that is, one end of the busbar 61, extends inside the case 5. One end of the busbar 61 is joined to the upper surface of the ceramic substrate 10 via a metal plate 61s.

[0020] The main terminal 62 (or busbar 61) and signal terminal 63 are made of copper, and their dimensions are 1.5 mm in width and 0.6 mm in thickness.

[0021] A metal plate 60s is provided between the busbar 61 and the ceramic substrate 10. The metal plate 60s is joined to the ceramic substrate 10 via solder 30. The metal plate 60s is a laminate of copper 601 and 603 as the first metal and invar 602 as the second metal. More specifically, the metal plate 60s is a three-layer clad material of copper 601, invar 602, and copper 603. The dimensions of the metal plate 60s are 5 mm in width, 4 mm in length, and 1 mm in thickness, and the thickness ratio of copper 601, invar 602, and copper 603 is 1:1:1.

[0022] The busbar 61 and the metal plate 60s are joined by multiple laser welds 61w. The size of the laser welds 61w on the upper surface of the busbar 61 is 1 mm in width and 4 mm in length.

[0023] The signal electrode (not shown) and signal terminal 63 of semiconductor element 20 are connected by an aluminum wire 40 (0.15 mm in diameter). This forms a signal circuit. In addition, the signal electrode (not shown) of semiconductor element 20, the signal electrode (not shown) of semiconductor element 21, and the surface conductor layer 103 of ceramic substrate 10 are connected by an aluminum wire 41 (0.4 mm in diameter). This forms a main circuit.

[0024] The inside of case 5 is sealed with a sealing resin 70 made of silicone gel up to a height of 9 mm from the top surface of the base plate 15.

[0025] Next, a method for manufacturing a power module according to Embodiment 1 will be described. Figures 3 to 6 are cross-sectional views showing the method for manufacturing a power module according to Embodiment 1.

[0026] As shown in Figure 3, a ceramic substrate 10 is placed on a base plate 15 via a sheet solder 30s with a thickness of 0.3 mm, semiconductor elements 20 and 21 are placed on the ceramic substrate 10 via a sheet solder 30s with a thickness of 0.1 mm, and a metal plate 60s is placed on the ceramic substrate 10 via a sheet solder 30s with a thickness of 0.1 mm.

[0027] Next, as shown in Figure 4, the base plate 15, ceramic substrate 10, semiconductor elements 20 and 21, and metal plate 60s are joined together by heating the solder plate 30s to 260°C using a reflow oven.

[0028] Next, as shown in Figure 5, after the case 5 is bonded to the base plate 15 (the adhesive is not shown), the upper surface of the main terminal 62, which consists of busbars 61 placed on the metal plate 60s, is irradiated with laser light 80 to form a laser welded portion 61w, thereby joining the busbars 61 and the metal plate 60s.

[0029] Finally, as shown in Figure 6, after forming the main circuit and signal circuit using wires 40 and 41 by wire bonding, sealing resin 70 is injected into the case 5, and insulating sealing is performed by heat curing the sealing resin 70.

[0030] Although copper was used as the material for the base plate 15, similar effects can be obtained by using aluminum with nickel plating on part of it, aluminum with silicon nitride fibers cast into it (AlSiC), or Cu-W sintered material instead.

[0031] Although silicon was used as the material for semiconductor elements 20 and 21, similar effects can be obtained by using wide-bandgap semiconductors such as silicon carbide or gallium nitride instead.

[0032] As the material for the solder 30, a solder material with 96.5% tin, 3% silver, 0.5% copper and a melting point of 217°C was used. However, similar effects can be obtained by substituting a solder material with 99.3% tin, 0.7% copper and a melting point of 224°C. Furthermore, similar effects can be obtained by replacing the solder 30 placed between the semiconductor element 20 and the ceramic substrate 10 with a silver sintered material or brazing material that has better heat resistance than the solder material.

[0033] Although aluminum wires 40 and 41 were used, similar effects can be obtained by using aluminum alloy wires containing trace amounts of additives such as iron, or copper wires. Similarly, the same effects can be obtained by using aluminum or copper ribbon bonds instead of wires.

[0034] Although silicone gel was used as the sealing resin 70, similar effects can be obtained by using epoxy resin in which silica or alumina filler is dispersed, or by using an epoxy resin mixed with silicone resin.

[0035] A three-layer clad material consisting of copper 601, Invar 602, and copper 603 was used as the metal plate 60s. Compared to copper or aluminum, the three-layer clad material of copper 601, Invar 602, and copper 603 has a smaller coefficient of thermal expansion, which reduces the difference in coefficient of thermal expansion with the ceramic substrate 10, thereby suppressing the decrease in reliability due to thermal stress after joining. Similar effects can be obtained by using a Cu-W alloy, which has a smaller coefficient of thermal expansion than copper, or by plating stainless steel with solderable copper or nickel. In the case of the three-phase clad material, by utilizing the fact that the core material Invar 602 is not wetted by the solder 30, the solder 30 wets up to the lower layer of copper 601, forming a fillet, while preventing the solder 30 joining the lower surface of the metal plate 60s from spreading to the upper surface of the metal plate 60s. This is because if the solder 30 joining the lower surface of the metal plate 60s spreads to the upper surface, there is a concern that it will interfere with laser welding.

[0036] Here, laser welding was used to join the busbar 61 and the metal plate 60s, but similar effects can be obtained with ultrasonic bonding, thermocompression bonding, soldering, brazing, conductive adhesive, or bonding using silver sintered bonding material.

[0037] As described above, in Embodiment 1, the power module comprises a ceramic substrate 10, semiconductor elements 21 and 22 mounted on the ceramic substrate 10, a metal plate 60s joined to the ceramic substrate 10 or the semiconductor elements 21 and 22 via solder 30, and a main terminal 62 consisting of a busbar 61 joined to the metal plate 60s. The coefficient of thermal expansion of the metal plate 60s is smaller than the coefficient of thermal expansion of the busbar 61.

[0038] Therefore, the coefficient of thermal expansion of the metal plate 60s becomes close to that of the ceramic substrate 10, thus suppressing the generation of thermal stress caused by the difference in coefficients of thermal expansion between the metal plate 60s and the ceramic substrate 10. This improves the reliability of the joint between the metal plate 60s and the ceramic substrate 10.

[0039] Furthermore, the metal plate 60s is a laminated material of a first metal and a second metal. Therefore, by using a clad material in which copper 601, 603 (17 ppm / K) is laminated as the first metal and Invar 602 (0 ppm / K) as the second metal in the metal plate 60s, it is possible to reduce the coefficient of thermal expansion to about 10 ppm / K.

[0040] Furthermore, since the first metal contains copper 601 and 603, and the second metal contains invar 602, by making the metal plate 60s a three-layer clad material of copper 601, invar 602, and copper 603, copper 601 and 603, which are solderable and have excellent weldability, are placed on both sides, and invar 602 is exposed on the sides. With this configuration, it is possible to suppress the solder 30 that joins the lower surface of the metal plate 60s from spreading up to the upper surface of the metal plate 60s.

[0041] Furthermore, the metal plate 60s and the busbar 61 are joined by a laser weld 61w. Since laser welding is a joining method that uses localized heating, it can reduce warping and reliability issues caused by thermal stress generated in the main terminal 62 and the ceramic substrate 10.

[0042] Next, a modified example of Embodiment 1 will be described. Figure 7 is a cross-sectional view of a power module according to Modified Example 1 of Embodiment 1.

[0043] As shown in Figure 7, the power module is equipped with a metal plate 60f instead of a metal plate 60s. The metal plate 60f is a three-layer clad material of copper 601, Invar 602, and copper 603, with a thickness ratio of 1:1:1. The dimensions of the metal plate 60f are 5 mm in length and 4 mm in width.

[0044] One end of the metal plate 60f is bent and joined to one end of the busbar 61. More specifically, one end of the metal plate 60f is folded back 180° and joined to one end of the busbar 61. The busbar 61 and the metal plate 60f are shaped to allow butt welding, and by irradiating the gap between them with a laser, it is possible to raise the temperature with relatively low power due to diffuse reflection.

[0045] Figure 8 is a cross-sectional view of a power module according to a modified example 2 of Embodiment 1. As shown in Figure 8, the power module is equipped with a metal plate 60b in place of the metal plate 60s. The metal plate 60b is a three-layer clad material of copper 601, invar 602, and copper 603, with a thickness ratio of 1:1:1. The dimensions of the metal plate 60b are 5 mm in length and 4 mm in width.

[0046] One end of the metal plate 60b is bent and joined to one end of the busbar 61. More specifically, one end of the metal plate 60b is bent upward and joined to the upper bent end of the busbar 61 so as to be in contact with it. The busbar 61 and the metal plate 60b are shaped to allow for overlapping welding, which facilitates the positioning of the metal plate 60b and the visual inspection of the laser-welded area 61w.

[0047] Figure 9 is a cross-sectional view of a power module according to a modification 3 of Embodiment 1. As shown in Figure 9, the power module is an insulating and sealed module using a transfer mold sealing resin 71 with a mold. The power module also has a main terminal 62R instead of a main terminal 62. By using a transfer mold sealing resin 71 with a mold to perform insulating sealing on the module, the case 5 is eliminated, making it possible to manufacture modules suitable for mass production.

[0048] Embodiment 2. Next, Embodiment 2 will be described. Figure 10 is a cross-sectional view of the power module according to Embodiment 2. Figure 11 is a top view showing the power module according to Embodiment 2 with the sealing resin 70 removed. In Embodiment 2, the same reference numerals are used for components that are the same as those described in Embodiment 1, and their descriptions are omitted.

[0049] As shown in Figures 10 and 11, the shape of the busbar 61 in Embodiment 2 is different from that of Embodiment 1. Specifically, one end of the busbar 61 extends onto the semiconductor elements 20 and 21. Between one end of the busbar 61 and the semiconductor elements 20 and 21, there is a metal plate 60s (corresponding to a second metal plate) which is different from the metal plate 60s (corresponding to a first metal plate) that is placed between the busbar 61 and the ceramic substrate 10. In other words, the busbar 61 is bonded not only to the ceramic substrate 10 but also to the semiconductor elements 20 and 21 via the metal plate 60s.

[0050] Next, a method for manufacturing a power module according to Embodiment 2 will be described. Figures 12 to 15 are cross-sectional views showing the method for manufacturing a power module according to Embodiment 2.

[0051] As shown in Figure 12, a ceramic substrate 10 is placed on a base plate 15 via a sheet solder 30s with a thickness of 0.3 mm, and semiconductor elements 20 and 21 are placed on the ceramic substrate 10 via a sheet solder 30s with a thickness of 0.1 mm. Next, a metal plate 60s as a first metal plate is placed on the ceramic substrate 10 via a sheet solder 30s with a thickness of 0.1 mm, and a metal plate 60s as a second metal plate is placed on the semiconductor elements 20 and 21 via a sheet solder 30s with a thickness of 0.1 mm.

[0052] Next, as shown in Figure 13, the base plate 15, ceramic substrate 10, semiconductor elements 20 and 21, and metal plate 60s are joined together by heating the sheet solder 30s to 260°C using a reflow oven.

[0053] Next, as shown in Figure 14, after bonding the case 5 to the base plate 15 (adhesive not shown), the busbars 61 and the metal plate 60s are joined by irradiating the upper surface of the main terminal 62, which consists of busbars 61 placed on the metal plate 60s, with laser light 80 to form a laser welded joint 61w. The main circuit is formed by the busbars 61. Next, the signal circuit is formed by wire bonding using wire 40.

[0054] Finally, as shown in Figure 15, the sealing resin 70 is injected into the case 5, and the sealing resin 70 is heat-cured to perform insulating sealing.

[0055] As described above, in Embodiment 2, one end of the busbar 61 extends onto the semiconductor elements 20 and 21, and a metal plate 60s, different from the metal plate 60s placed between the busbar 61 and the ceramic substrate 10, is placed between the one end of the busbar 61 and the semiconductor elements 20 and 21.

[0056] Therefore, compared to Embodiment 1 in which the main circuit is formed by wire 41, forming the main circuit using copper busbar 61 allows for a larger current to flow through the main circuit, reduces resistance, and thus reduces heat generation. Furthermore, since laser welding is basically a room-temperature joining method, compared to joining the busbar 61 and the metal plate 60s by soldering with overall heating, it is less likely to cause warping due to the difference in linear expansion coefficients between the ceramic substrate 10 and the busbar 61.

[0057] Embodiment 3. Next, Embodiment 3 will be described. Figure 16 is a cross-sectional view of the power module according to Embodiment 3. Figure 17 is a top view showing the power module according to Embodiment 3 with the sealing resin 70 removed. In Embodiment 3, the same reference numerals are used for components that are the same as those described in Embodiments 1 and 2, and their descriptions are omitted.

[0058] As shown in Figures 16 and 17, the power module is equipped with a metal plate 60d instead of a metal plate 60s. The metal plate 60d has a different shape from the metal plate 60s. Specifically, one end of the metal plate 60d extends onto the semiconductor elements 20 and 21 and is bonded to the semiconductor elements 20 and 21. In other words, the metal plate 60d is bonded not only to the ceramic substrate 10 but also to the semiconductor elements 20 and 21, thereby also serving as a busbar 61.

[0059] Next, a method for manufacturing a power module according to Embodiment 3 will be described. Figures 18 to 21 are cross-sectional views showing the method for manufacturing a power module according to Embodiment 3.

[0060] As shown in Figure 18, a ceramic substrate 10 is placed on a base plate 15 via a sheet solder 30s with a thickness of 0.3 mm, and semiconductor elements 20 and 21 are placed on the ceramic substrate 10 via a sheet solder 30s with a thickness of 0.1 mm. Next, a sheet solder 30s with a thickness of 0.1 mm is placed on the ceramic substrate 10, and a sheet solder 30s with a thickness of 0.1 mm is placed on the semiconductor elements 20 and 21, and the same metal plate 60d is placed on top of these sheet solders 30s.

[0061] Next, as shown in Figure 19, the base plate 15, ceramic substrate 10, semiconductor elements 20 and 21, and the same metal plate 60d are joined together by heating the plate solder 30s to 260°C using a reflow oven.

[0062] Next, as shown in Figure 20, after bonding the case 5 to the base plate 15 (adhesive not shown), a laser beam 80 is irradiated onto the upper surface of the main terminal 62, which consists of busbars 61 placed on the same metal plate 60d, to form a laser weld 61w, thereby joining the busbars 61 to the same metal plate 60d. The main circuit is formed by the same metal plate 60d. Next, a signal circuit is formed using wire 40 by wire bonding.

[0063] Finally, as shown in Figure 21, the sealing resin 70 is injected into the case 5, and the sealing resin 70 is heat-cured to perform insulating sealing.

[0064] As described above, in Embodiment 3, one end of the metal plate 60d extends onto the semiconductor elements 20 and 21 and is bonded to the semiconductor elements 20 and 21. Therefore, by having the metal plate 60d also function as a busbar 61 that forms the main circuit, it is possible to reduce warping and reliability issues caused by thermal stress resulting from the difference in linear expansion coefficients between the busbar 61 and the ceramic substrate 10.

[0065] Next, a modified example of Embodiment 3 will be described. Figure 22 is a cross-sectional view of a power module according to a modified example of Embodiment 3.

[0066] As shown in Figure 22, the power module is an insulated and sealed module using a transfer mold sealing resin 71 with a mold. Furthermore, the power module is equipped with a main terminal 62R instead of the main terminal 62. By using a transfer mold sealing resin 71 with a mold to insulate and seal the module, the case 5 is eliminated, enabling the manufacture of modules suitable for mass production.

[0067] Embodiment 4. This embodiment applies the power modules according to Embodiments 1 to 3 described above to a power converter. The application of the power modules according to Embodiments 1 to 3 is not limited to a specific power converter, but below, as Embodiment 4, we will describe the case in which the power modules according to Embodiments 1 to 3 are applied to a three-phase inverter.

[0068] Figure 23 is a block diagram showing the configuration of a power conversion system to which the power conversion device according to Embodiment 4 is applied.

[0069] The power conversion system shown in Figure 23 consists of a power supply 150, a power converter 200, and a load 300. The power supply 150 is a DC power supply and supplies DC power to the power converter 200. The power supply 150 can be composed of various components, such as a DC grid, a solar cell, or a battery, or it may be composed of a rectifier circuit or AC / DC converter connected to an AC grid. Alternatively, the power supply 150 may be composed of a DC / DC converter that converts DC power output from a DC grid into a predetermined power.

[0070] The power converter 200 is a three-phase inverter connected between the power supply 150 and the load 300. It converts the DC power supplied from the power supply 150 into AC power and supplies the AC power to the load 300. As shown in Figure 23, the power converter 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 to the main conversion circuit 201 to control the main conversion circuit 201.

[0071] Load 300 is a three-phase electric motor driven by AC power supplied from power converter 200. Note that Load 300 is not limited to a specific application; it is an electric motor installed in various electrical devices, such as hybrid vehicles, electric vehicles, railway vehicles, elevators, or air conditioning equipment.

[0072] The details of the power converter 200 are described below. The main conversion circuit 201 is equipped with switching elements (not shown) and freewheeling diodes (not shown). By switching, the switching elements convert the DC power supplied from the power supply 150 into AC power, which is then supplied to the load 300. There are various specific circuit configurations for the main conversion circuit 201, but the main conversion circuit 201 according to this embodiment is a two-level three-phase full-bridge circuit and can be composed of six switching elements and six freewheeling diodes antiparallel to each switching element. At least one of each switching element or each freewheeling diode of the main conversion circuit 201 is composed of a power module 202. The power module 202 corresponds to the semiconductor device shown in any of the embodiments 1 to 3 described above. The six switching elements are connected in series in pairs 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. The output terminals of each upper and lower arm, i.e., the three output terminals of the main conversion circuit 201, are connected to the load 300.

[0073] Furthermore, 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 it may be configured as a separate drive circuit from the power module 202. The drive circuit generates a drive signal to drive 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, according to the control signal from the control circuit 203, which will be described later, it outputs a drive signal to turn on the switching element and a drive signal to turn off the switching element to the control electrodes of each switching element. When the switching element is kept in the ON state, the drive signal is a voltage signal (ON signal) that is greater than or equal to the threshold voltage of the switching element, and when the switching element is kept in the OFF state, the drive signal is a voltage signal (OFF signal) that is less than or equal to the threshold voltage of the switching element.

[0074] The control circuit 203 controls the switching elements of the main converter circuit 201 so that the desired power is supplied to the load 300. Specifically, it calculates the time (on time) that each switching element of the main converter circuit 201 should be in the ON state based on the power to be supplied to the load 300. For example, the main converter circuit 201 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 then outputs a control command (control signal) to the drive circuit of the main converter circuit 201 so that an ON signal is output to the switching elements that should be in the ON state at each point in time, and an OFF signal is output to the switching elements that should be in the OFF state. The drive circuit outputs an ON signal or an OFF signal as a drive signal to the control electrode of each switching element according to this control signal.

[0075] In the power conversion device 200 according to this embodiment, the power modules according to embodiments 1 to 3 are used as the switching elements and freewheeling diodes of the main conversion circuit 201, thereby improving reliability.

[0076] In this embodiment, an example of applying the power modules according to Embodiments 1 to 3 to a two-level three-phase inverter has been described. However, the application of the power modules according to Embodiments 1 to 3 is not limited to this, and they can be applied to various power conversion devices. In this embodiment, a two-level power conversion device is used, but a three-level or multi-level power conversion device may also be used. Furthermore, when supplying power to a single-phase load, the power modules according to Embodiments 1 to 3 may be applied to a single-phase inverter. In addition, when supplying power to a DC load, etc., it is also possible to apply the power modules according to Embodiments 1 to 3 to a DC / DC converter or an AC / DC converter.

[0077] Furthermore, the power conversion device to which the power module according to Embodiments 1 to 3 is applied is not limited to cases where the load is an electric motor, but can also be used, for example, as a power supply for electrical discharge machining equipment, laser processing equipment, induction heating cookers, or contactless power supply systems, and can even be used as a power conditioner for solar power generation systems or energy storage systems.

[0078] Furthermore, it is possible to freely combine each embodiment, or to modify or omit each embodiment as appropriate.

[0079] The various aspects of this disclosure are summarized below as an appendix.

[0080] (Note 1) Insulating substrate and A semiconductor element mounted on the insulating substrate, A metal plate bonded to the insulating substrate or the semiconductor element via a bonding material, It comprises an external terminal consisting of an electrode plate joined to the metal plate, A power module wherein the coefficient of thermal expansion of the metal plate is smaller than the coefficient of thermal expansion of the electrode plate.

[0081] (Note 2) The power module as described in Appendix 1, wherein the metal plate is a laminate of a first metal and a second metal having a coefficient of thermal expansion smaller than that of the first metal.

[0082] (Note 3) The power module as described in Appendix 2, wherein the first metal comprises copper and the second metal comprises invar.

[0083] (Note 4) The power module according to any one of the appendices 1 to 3, wherein the metal plate and the electrode plate are joined by a laser weld.

[0084] (Note 5) One end of the electrode plate extends onto the semiconductor element, The power module according to any one of the appendices 1 to 4, wherein a metal plate, different from the metal plate disposed between the electrode plate and the insulating substrate, is disposed between the one end of the electrode plate and the semiconductor element.

[0085] (Note 6) The power module according to any one of the appendices 1 to 4, wherein one end of the metal plate extends onto the semiconductor element and is bonded to the semiconductor element.

[0086] (Note 7) The power module according to any one of the appendices 1 to 4, wherein one end of the metal plate is bent and joined to the one end of the electrode plate.

[0087] (Note 8) A power module described in any one of Appendix 1 to Appendix 7, and a main conversion circuit that converts and outputs the input power, A control circuit that outputs a control signal to the main conversion circuit to control the main conversion circuit, A power conversion device equipped with this device.

[0088] (Note 9) The process involves placing an insulating substrate on a base plate via a bonding material, placing a semiconductor element on the insulating substrate via a bonding material, and placing a metal plate on the insulating substrate via a bonding material. The process involves melting the bonding material to bond the base plate, the insulating substrate, the semiconductor element, and the metal plate, The process involves bonding the case to the base plate, then irradiating the upper surface of the external terminal, which consists of an electrode plate placed on the metal plate, with laser light to form a laser-welded area, thereby joining the electrode plate and the metal plate. A method for manufacturing a power module, comprising the following features.

[0089] (Note 10) A step of placing an insulating substrate on a base plate via a bonding material, and a step of placing a semiconductor element on the insulating substrate via a bonding material, The process involves placing a first metal plate on the insulating substrate via a bonding material, and placing a second metal plate on the semiconductor element via a bonding material, A step of joining the base plate, the insulating substrate, the semiconductor element, and the first and second metal plates by melting the bonding material, The process involves bonding the case to the base plate, then irradiating the upper surface of the external terminal, which consists of electrode plates placed on the first and second metal plates, with laser light to form a laser weld, thereby joining the electrode plates to the first and second metal plates. A method for manufacturing a power module, comprising the following features.

[0090] (Note 11) A step of placing an insulating substrate on a base plate via a bonding material, and a step of placing a semiconductor element on the insulating substrate via a bonding material, The process involves placing a bonding material on the insulating substrate and on the semiconductor element, and then placing the same metal plate on the bonding material. A step of joining the base plate, the insulating substrate, the semiconductor element, and the same metal plate by melting the bonding material, The process involves bonding the case to the base plate, then irradiating the upper surface of the external terminal, which consists of an electrode plate placed on the same metal plate, with laser light to form a laser weld, thereby joining the electrode plate and the same metal plate; A method for manufacturing a power module, comprising the following features. [Explanation of Symbols]

[0091] 5 Case, 10 Ceramic substrate, 20, 21 Semiconductor elements, 30 Bonding material, 60b, 60d, 60f, 60s Metal plates, 61 Busbar, 61w Laser welded section, 62, 62R Main terminals, 200 Power converter, 201 Main converter circuit, 202 Power module, 203 Control circuit.

Claims

1. Insulating substrate and A semiconductor element mounted on the insulating substrate, A metal plate bonded to the insulating substrate or the semiconductor element via a bonding material, It comprises an external terminal consisting of an electrode plate joined to the metal plate, A power module wherein the coefficient of thermal expansion of the metal plate is smaller than the coefficient of thermal expansion of the electrode plate.

2. The power module according to claim 1, wherein the metal plate is a laminate of a first metal and a second metal having a coefficient of thermal expansion smaller than that of the first metal.

3. The power module according to claim 2, wherein the first metal comprises copper and the second metal comprises Invar.

4. The power module according to claim 1, wherein the metal plate and the electrode plate are joined by a laser welding joint.

5. One end of the electrode plate extends onto the semiconductor element, The power module according to claim 1, wherein a metal plate, different from the metal plate disposed between the electrode plate and the insulating substrate, is disposed between the one end of the electrode plate and the semiconductor element.

6. The power module according to claim 1, wherein one end of the metal plate extends onto the semiconductor element and is bonded to the semiconductor element.

7. The power module according to claim 1, wherein one end of the metal plate is bent and joined to the one end of the electrode plate.

8. A power module according to any one of claims 1 to 7, comprising a main conversion circuit that converts and outputs input power, A control circuit that outputs a control signal to the main conversion circuit to control the main conversion circuit, A power conversion device equipped with this device.

9. The process involves placing an insulating substrate on a base plate via a bonding material, placing a semiconductor element on the insulating substrate via a bonding material, and placing a metal plate on the insulating substrate via a bonding material. The process involves melting the bonding material to bond the base plate, the insulating substrate, the semiconductor element, and the metal plate, The process involves bonding the case to the base plate, then irradiating the upper surface of the external terminal, which consists of an electrode plate placed on the metal plate, with laser light to form a laser-welded area, thereby joining the electrode plate and the metal plate. A method for manufacturing a power module, comprising the following features.

10. A step of placing an insulating substrate on a base plate via a bonding material, and a step of placing a semiconductor element on the insulating substrate via a bonding material, The process involves placing a first metal plate on the insulating substrate via a bonding material, and placing a second metal plate on the semiconductor element via a bonding material. A step of joining the base plate, the insulating substrate, the semiconductor element, and the first and second metal plates by melting the aforementioned bonding material, The process involves bonding the case to the base plate, then irradiating the upper surface of the external terminal, which consists of electrode plates placed on the first and second metal plates, with laser light to form a laser weld, thereby joining the electrode plates to the first and second metal plates. A method for manufacturing a power module, comprising the following features.

11. A step of placing an insulating substrate on a base plate via a bonding material, and a step of placing a semiconductor element on the insulating substrate via a bonding material, The process involves placing a bonding material on the insulating substrate and on the semiconductor element, and then placing the same metal plate on the bonding material. A step of joining the base plate, the insulating substrate, the semiconductor element, and the same metal plate by melting the bonding material, The process involves bonding the case to the base plate, then irradiating the upper surface of the external terminal, which consists of an electrode plate placed on the same metal plate, with laser light to form a laser weld, thereby joining the electrode plate and the same metal plate; A method for manufacturing a power module, comprising the following features.

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