Semiconductor device, power conversion device, and moving body

Abstract

A semiconductor device according to the present disclosure comprises: a base plate; a semiconductor chip that is provided to an area above the base plate; a case that is provided on the base plate, surrounds the semiconductor chip, has an outside surface and an inside surface on the reverse side from the outside surface, and has a recess formed in the outside surface; a nut that is press-fitted into the recess in the case and has a screw hole extending in the vertical direction formed therein; and a screw that is inserted into the nut from below the base plate.

Description

Semiconductor device, power conversion device and mobile body

[0001] The present disclosure relates to a semiconductor device, a power conversion device, and a mobile object.

[0002] Patent Document 1 discloses a semiconductor device having a resin case including a screw hole, an insulating substrate on which a semiconductor chip is mounted, and a heat sink including a heat sink through-hole and carrying the insulating substrate. Metal tapping screws pass through the heat sink through-hole and the screw hole to engage the resin case with the heat sink. A gap in the screw hole formed between the resin case and the metal tapping screw is filled with a high-voltage resin.

[0003] Japanese Patent Application Laid-Open No. 2006-32392

[0004] As semiconductor devices become smaller and denser, the distance between the screw and the insulating substrate becomes shorter. This requires improvements in partial discharge resistance and dielectric breakdown resistance. For example, when a case and a heat sink are fastened together with a tapping screw, air gaps tend to form around the screw. These air gaps may reduce partial discharge resistance.

[0005] In response to this problem, Patent Document 1 improves discharge resistance by filling the gap between the case and the screw with resin. However, filling the resin increases the number of manufacturing steps, which may result in a decrease in workability.

[0006] An object of the present disclosure is to provide a semiconductor device, a power conversion device, and a mobile body that can improve discharge resistance.

[0007] The semiconductor device according to the first disclosure comprises a base plate, a semiconductor chip provided in an area above the base plate, a case provided on the base plate, surrounding the semiconductor chip, having an outer surface and an inner surface opposite the outer surface, and having a recess formed in the outer surface, a nut press-fitted into the recess of the case and having a screw hole extending in the vertical direction, and a screw inserted into the nut from below the base plate.

[0008] The semiconductor device according to the second disclosure comprises a base plate, a semiconductor chip provided in an area above the base plate, a case provided on the base plate and surrounding the semiconductor chip, a nut that is a cap nut that is provided on the case in the area surrounded by the case and opens downward, and a screw inserted into the nut from below the base plate.

[0009] In the semiconductor device according to the first and second disclosures, it is possible to prevent a gap from being formed between the screw and a member on the base plate that is at a high voltage, thereby improving the discharge resistance.

[0010] FIG. 1 is a cross-sectional view of a semiconductor device according to a first embodiment. FIG. 2 is a plan view of a semiconductor device according to a first embodiment. FIG. 3 is a cross-sectional view showing a state in which a case and a base plate are fastened together with screws in the semiconductor device according to the first embodiment. FIG. 4 is a diagram illustrating an insulating substrate according to the first embodiment. FIG. 5 is a cross-sectional view of a semiconductor device according to a comparative example. FIG. 6 is a diagram illustrating gas in a case according to a comparative example. FIG. 7 is a diagram illustrating gas in a case according to the first embodiment. FIG. 8 is a plan view of a semiconductor device according to a second embodiment. FIG. 9 is a cross-sectional view of a semiconductor device according to a third embodiment. FIG. 10 is a plan view of a semiconductor device according to the third embodiment. FIG. 11 is a cross-sectional view showing a state in which a case and a base plate are fastened together with screws in the semiconductor device according to the third embodiment. FIG. 12 is a plan view of a semiconductor device according to a fourth embodiment. FIG. 13 is a block diagram of a power conversion device according to a fifth embodiment. FIG. 14 is a diagram illustrating a moving body according to a sixth embodiment.

[0011] The semiconductor device, power conversion device, and moving body according to each embodiment will be described with reference to the drawings. The same or corresponding components are designated by the same reference numerals, and repeated description may be omitted.

[0012] First Embodiment Fig. 1 is a cross-sectional view of a semiconductor device 100 according to a first embodiment. Fig. 2 is a plan view of the semiconductor device 100 according to the first embodiment. Fig. 3 is a cross-sectional view showing a state in which the case 20 and the base plate 10 are fastened together with screws 52 in the semiconductor device 100 according to the first embodiment. Fig. 4 is a diagram illustrating an insulating substrate 30 according to the first embodiment. In the semiconductor device 100, the insulating substrate 30 is mounted on the base plate 10.

[0013] As shown in FIG. 4 , the insulating substrate 30 includes a conductor layer 31, an insulating layer 32 on the conductor layer 31, and a metal pattern 33 on the insulating layer 32. The insulating layer 32 is formed of, for example, ceramic or resin. A semiconductor chip 40 is provided on the metal pattern 33. The semiconductor chip 40 is, for example, an IGBT (Insulated Gate Bipolar Transistor) chip or a Di (Diode) chip. As described above, the semiconductor chip 40 is provided in an area above the base plate 10. Furthermore, metal terminals 35, which are electrodes, and metal wiring 37, which is wire or the like, are provided on the metal pattern 33. Note that, for convenience, only a portion of the insulating substrate 30 is shown in FIGS. 1 to 3 .

[0014] A case 20 that surrounds the semiconductor chip is provided on the base plate 10. For convenience, only a portion of the case 20 is shown in FIGS. 1 to 3. The case 20 has an outer surface 21 and an inner surface 22 opposite the outer surface 21. A recess 24 is formed in the outer surface 21. The case 20 has a pedestal portion 23 that protrudes inside the area surrounded by the case 20. The recess 24 is formed in the pedestal portion 23. The area surrounded by the case 20 is filled with a sealing material 42. Electrodes (not shown) are provided on the case 20. A lid (not shown) is also provided on the case 20. The semiconductor chip 40, metal pattern 33, metal terminals 35, and electrodes of the case 20 are electrically connected by metal wiring 37, US (Ultrasonic) bonding, or the like.

[0015] A nut 51 is press-fitted into the recess 24 of the case 20. A screw hole extending in the vertical direction is formed in the nut 51. A through hole 12 for inserting a screw 52 is formed in the base plate 10. A through hole 25 connecting the recess 24 and the through hole 12 is also formed in the case 20. The screw 52 is inserted into the nut 51 from below the base plate 10, passing through the through holes 12 and 25. The screw 52 is, for example, a bolt that screws into the nut 51. As a result, the case 20 and the base plate 10 are fastened together, as shown in FIG. 3 . The nut 51 is, for example, circular in plan view.

[0016] FIG. 5 is a cross-sectional view of a semiconductor device 800 according to a comparative example. The semiconductor device 800 according to the comparative example differs from the semiconductor device 100 according to the first embodiment in that the case 820 and the base plate 10 are fastened together by tapping screws 852. In this configuration, fastening by the tapping screws 852 may result in a void 90 being formed between the tapping screws 852 and the case 20. Partial discharge occurs when a voltage is exchanged between, for example, a protruding portion such as a screw thread and the metal pattern 33, the metal terminal 35, the metal wiring 37, or the like, which are at high voltage. In the semiconductor device 800 according to the comparative example, the void 90 is likely to be formed on the line connecting the tapping screws 852 and the high-voltage portion. Therefore, the void 90 may reduce the partial discharge resistance.

[0017] In contrast, in this embodiment, the base plate 10 and the case 20 can be fastened together with the tapping screw 852 without scraping the case 20. This prevents the formation of a gap 90 between the screw 52 and the case 20, thereby suppressing the occurrence of partial discharge. This improves the discharge resistance. Note that the gap above the screw 52 and the gap between the screw 52 and the case 20 at the through hole 25 are not on the straight line that connects the screw 52 and the high-voltage section via the shortest path. This makes it less likely to lead to a decrease in the partial discharge resistance.

[0018] FIG. 6 is a diagram illustrating gas 91 inside case 820 according to the comparative example. In a case made of resin, the larger the volume of the resin portion, the greater the amount of gas generated from the molded resin. Case 820 according to the comparative example does not have a recess 24. Therefore, the volume of case 820 is large, making it easier for voids due to gas 91 to occur. Furthermore, since case 820 does not have a recess 24, a thick block-shaped portion is formed. In the block-shaped portion, the distance from the inside of the case to the surface is large. Therefore, gas 91 generated during molding is difficult to escape, making it even more likely for voids to occur. Therefore, in semiconductor device 800 according to the comparative example, voids are easily formed on the line connecting tapping screw 852 and the high-voltage section. These voids may also reduce the partial discharge resistance.

[0019] FIG. 7 is a diagram illustrating gas 91 inside case 20 according to embodiment 1. In this embodiment, a recess 24 is formed in case 20. By forming recess 24, the volume of case 20 is reduced. Therefore, the generation of voids can be suppressed when molding case 20 from resin. Furthermore, in this embodiment, by forming recess 24 in base portion 23, base portion 23 can be formed as a thin plate-like portion. In the plate-like portion, the distance from the inside of case 20 to the surface is short. Therefore, gas 91 generated during molding can easily escape, and voids are less likely to be generated. In this way, in this embodiment, the formation of voids between screw 52 and the high-voltage portion can be suppressed. Therefore, the discharge resistance can be improved.

[0020] Furthermore, in this embodiment, there is no need to fill the gap between the case and the screw with resin to improve discharge resistance, which prevents an increase in the number of manufacturing steps and improves workability.

[0021] The nut 51 is preferably made of an insulating material such as resin, and the screw 52 is preferably made of metal. In this case, the screw 52 is electrically connected to the base plate 10, which is at GND, and is at GND potential. By combining the screw 52, ​​which is at GND potential, with the non-conductive nut 51 in relation to the high voltage section, partial discharge can be effectively suppressed. Both the nut 51 and the screw 52 may be made of metal, or both may be made of an insulating material such as resin. Alternatively, the nut 51 may be made of metal and the screw 52 may be made of resin.

[0022] As a modification of this embodiment, the semiconductor chip 40 may be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) chip. Furthermore, a plurality of semiconductor chips 40 may be provided within the case 20. The plurality of semiconductor chips 40 may include a plurality of types of semiconductor chips. In this case, the same effects as those of this embodiment are also achieved.

[0023] The semiconductor chip 40 may be formed of a wide bandgap semiconductor. The wide bandgap semiconductor is, for example, silicon carbide, a gallium nitride-based material, or diamond. Using a wide bandgap semiconductor for the semiconductor chip 40 enables energy saving in the semiconductor device 100. Furthermore, according to this embodiment, in the semiconductor device 100 provided with the semiconductor chip 40 formed of a wide bandgap semiconductor, even when a high current flows, the discharge tolerance can be improved and stable operation can be achieved.

[0024] The above-described modifications can be applied as appropriate to the semiconductor devices, power conversion devices, and mobile bodies according to the following embodiments. Note that the semiconductor devices, power conversion devices, and mobile bodies according to the following embodiments have many points in common with the first embodiment, so the following description will focus on the differences from the first embodiment.

[0025] Second Embodiment. Figure 8 is a plan view of a semiconductor device 200 according to a second embodiment. In this embodiment, the shapes of the nut 251 and the recess 224 of the case 220 differ from those of the first embodiment. The other configurations are the same as those of the first embodiment. The nut 251 is polygonal in plan view. The nut 251 is, for example, hexagonal or rectangular in plan view. The recess 224 of the case 220 is shaped to fit the nut 251. In other words, the side of the case 220 at the recess 224 is configured to fit tightly against the nut 251.

[0026] In this embodiment, it is possible to prevent the nut 251 from rotating together with the case 220. This makes it possible to reliably generate the tightening torque required to fasten the case 220 and the base plate 10 together.

[0027] Third Embodiment Fig. 9 is a cross-sectional view of a semiconductor device 300 according to a third embodiment. Fig. 10 is a plan view of the semiconductor device 300 according to the third embodiment. Fig. 11 is a cross-sectional view showing a state in which the case 320 and the base plate 10 are fastened together with screws 52 in the semiconductor device 300 according to the third embodiment. In this embodiment, the configurations of the case 320 and the nuts 351 are different from those of the first embodiment. The other configurations are the same as those of the first embodiment.

[0028] A case 320 that surrounds the semiconductor chip 40 is provided on the base plate 10. For convenience, only a portion of the case 320 is shown in Figures 9 to 11. The case 320 has a sidewall portion 327 that extends upward from the upper surface of the base plate 10, and a pedestal portion 323 that extends along the upper surface of the base plate 10. A nut 351 is provided on the case 320 in an area surrounded by the case 320. Specifically, the nut 351 is provided on the pedestal portion 323. The nut 351 is a cap nut that opens downward.

[0029] A through hole 25 is formed in the case 320 so as to connect to the through hole 12. The screw 52 is inserted into the nut 351 from below the base plate 10, passing through the through holes 12 and 25. The screw 52 is, for example, a bolt that screws into the nut 351. As a result, the case 320 and the base plate 10 are fastened together, as shown in Fig. 11 . The nut 351 is, for example, circular in plan view.

[0030] In this embodiment as well, the base plate 10 and the case 320 can be fastened together by the tapping screw 852 without scraping the case 320. This makes it possible to prevent the occurrence of a gap 90 between the screw 52 and the case 320, thereby suppressing the occurrence of partial discharge. This improves the discharge resistance.

[0031] Furthermore, case 320 of this embodiment does not have a thick block-shaped portion for inserting tapping screw 852, as in case 820 of the comparative example. This allows the volume of case 320 to be reduced, and the occurrence of voids when molding case 320 from resin can be suppressed. Furthermore, in this embodiment, base portion 323 of case 320 can be formed from a thin plate-shaped portion. This makes it difficult for gas 91 generated during molding of case 320 to escape, and the occurrence of voids can be suppressed.

[0032] Furthermore, by using a cap nut as the nut 351, it is possible to prevent the sealant 42 from seeping out from between the nut and the screw 52. In this embodiment, the sealant 42 can be tightly attached to the cap nut without any gaps.

[0033] 12 is a plan view of a semiconductor device 400 according to a fourth embodiment. In this embodiment, the shape of a nut 451 differs from the shape of the nut 351 of the third embodiment. The other configurations are the same as those of the first embodiment. The nut 451 is polygonal in plan view. The nut 451 is, for example, hexagonal or rectangular in plan view.

[0034] In this embodiment, for example, the side surface or corner of the nut 451 comes into contact with the side surface of the case 320, thereby preventing the nut 451 from rotating together with the case 320. This ensures that the tightening torque required to fasten the case 320 and the base plate 10 is generated.

[0035] Fifth Embodiment Fig. 13 is a block diagram of a power conversion device 74 according to a fifth embodiment. The power conversion device 74 is, for example, a three-phase inverter. The power conversion device 74 is connected between a power supply 70 and a load 75, converts power supplied from the power supply 70, and supplies the power to the load 75. The power conversion device 74 includes a main conversion circuit 71 that converts and outputs power, a drive circuit 72 that outputs drive signals that drive switching elements of the main conversion circuit 71, and a control circuit 73 that outputs control signals for controlling the drive circuit 72 to the drive circuit 72.

[0036] In a power conversion device 74 according to the present embodiment, the semiconductor device according to any one of the first to fourth embodiments is mounted as a switching element of a main conversion circuit 71. This makes it possible to improve the discharge resistance of the power conversion device 74.

[0037] The power conversion device 74 may be a two-level, three-level, or multi-level power conversion device. This embodiment can also be applied to a single-phase inverter, a DC / DC converter, or an AC / DC converter.

[0038] The load 75 is, for example, an electric motor. The power conversion device 74 can also be used as a power supply device for, for example, an electric discharge machine, a laser processing machine, an induction heating cooker, or a contactless power supply system. Furthermore, the power conversion device 74 can also be used as a power conditioner for a solar power generation system, a power storage system, or the like.

[0039] Sixth Embodiment Fig. 14 is a diagram illustrating a mobile object 78 according to a sixth embodiment. The mobile object 78 is equipped with a power conversion device 74 having a semiconductor device according to any one of the first to fourth embodiments. The mobile object 78 is, for example, a train. In this embodiment, the discharge tolerance of the power conversion device 74 is improved, thereby enabling the mobile object 78 to have a longer life.

[0040] The technical features described in each embodiment may be used in appropriate combination.

[0041] REFERENCE SIGNS LIST 10 base plate, 12 through hole, 20 case, 21 outer surface, 22 inner surface, 23 base portion, 24 recess, 25 through hole, 30 insulating substrate, 31 conductor layer, 32 insulating layer, 33 metal pattern, 35 metal terminal, 37 metal wiring, 40 semiconductor chip, 42 sealing material, 51 nut, 52 screw, 70 power supply, 71 main conversion circuit, 72 drive circuit, 73 control circuit, 74 power conversion device, 75 load, 78 moving body, 90 gap, 91 gas, 100 semiconductor device, 200 semiconductor device, 220 case, 224 recess, 251 nut, 300 semiconductor device, 320 case, 323 base portion, 327 side wall portion, 351 nut, 400 semiconductor device, 451 nut, 800 semiconductor device, 820 Case, 852 tapping screws

Claims

1. A base plate and a semiconductor chip provided in an area above the base plate; a case provided on the base plate, surrounding the semiconductor chip, the case having an outer surface and an inner surface opposite to the outer surface, the outer surface having a recess formed therein; a nut that is press-fitted into the recess of the case and has a screw hole that extends in the vertical direction; a screw inserted into the nut from below the base plate; A semiconductor device comprising:

2. A base plate and a semiconductor chip provided in an area above the base plate; a case provided on the base plate and surrounding the semiconductor chip; A nut that is a cap nut provided on the case in an area surrounded by the case and opens downward; a screw inserted into the nut from below the base plate; A semiconductor device comprising:

3. 3. The semiconductor device according to claim 1, wherein the nut is made of an insulating material, and the screw is made of a metal.

4. 3. The semiconductor device according to claim 1, wherein the nut is polygonal in plan view.

5. 3. The semiconductor device according to claim 1, wherein the semiconductor chip is made of a wide band gap semiconductor.

6. 6. The semiconductor device according to claim 5, wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material or diamond.

7. 3. A power conversion device comprising the semiconductor device according to claim 1 or 2.

8. 3. A moving object comprising the semiconductor device according to claim 1 or 2 mounted thereon.