Semiconductor device, power conversion device, and moving object

Abstract

A semiconductor device according to the present disclosure includes: a base plate; a semiconductor chip disposed in a region above the base plate; a case provided on the base plate, surrounding the semiconductor chip, having an outer side surface and an inner side surface on the opposite side to the outer side surface, and having a recess formed in the outer side surface; a nut which is press-fitted into the recess of the housing and in which a screw hole extending in the vertical direction is formed; and the screw is inserted into the nut from the lower part of the bottom plate.

Description

Technical Field

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

[0002] Patent Document 1 discloses a semiconductor device comprising a resin housing with screw holes, an insulating substrate on which a semiconductor chip is mounted, and a heat sink with through-holes in the heat sink and on which the insulating substrate is mounted. Metal tapping screws pass through the heat sink through-holes and the screw holes to engage the resin housing and the heat sink. The space within the screw hole formed between the resin housing and the metal tapping screw is filled with a high-voltage-withstand resin. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-32392 Summary of the Invention Technical problem to be solved by the invention

[0004] As semiconductor devices become increasingly miniaturized and denser, the distance between screws and insulating substrates decreases. Consequently, improvements in partial discharge resistance and dielectric breakdown resistance are needed. For example, when screwing components such as housings and heat sinks together using tapping screws, gaps are likely to form around the screws. This gap can reduce partial discharge resistance.

[0005] In contrast, in Patent Document 1, the gap between the housing and the screw is filled with resin to improve discharge resistance. However, filling with resin increases the number of manufacturing steps and may deteriorate workability.

[0006] An object of the present disclosure is to provide a semiconductor device, a power conversion device, and a mobile object capable of improving discharge resistance. Technical means for solving technical problems

[0007] The semiconductor device involved in the first disclosure includes: a base plate; a semiconductor chip, which is arranged in an area above the base plate; a housing, which is arranged on the base plate, surrounds the semiconductor chip, has an outer side surface and an inner side surface opposite to the outer side surface, and has a recess formed on the outer side surface; a nut, which is pressed into the recess of the housing and has a screw hole extending in the vertical direction; and a screw, which is inserted into the nut from below the base plate.

[0008] The semiconductor device involved in the second disclosure includes: a base plate; a semiconductor chip arranged in an area above the base plate; a housing arranged on the base plate and surrounding the semiconductor chip; a nut, which is a bag nut arranged on the housing in an area surrounded by the housing and opened downward; and a screw inserted into the nut from below the base plate. Effects of the Invention

[0009] In the semiconductor devices according to the first and second disclosures, it is possible to suppress the formation of gaps between the screws and components on the substrate that are exposed to high voltage, thereby improving discharge resistance. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0011] The semiconductor device, power conversion device, and movable body according to each embodiment will be described with reference to the accompanying drawings. Identical or corresponding components will be denoted by the same reference numerals, and duplicate descriptions may be omitted.

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

[0013] like Figure 4 As shown, 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 plate 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. In this way, the semiconductor chip 40 is provided in the area above the base plate 10. Furthermore, metal terminals 35 serving as electrodes and metal wiring 37 serving as wires are provided on the metal pattern 33. Figures 1 to 3 , for convenience, only a portion of the insulating substrate 30 is shown.

[0014] The housing 20 surrounding the semiconductor chip is provided on the base plate 10. Figures 1 to 3 , only a portion of the housing 20 is shown. The housing 20 has an outer side surface 21 and an inner side surface 22 opposite to the outer side surface 21. A recess 24 is formed on the outer side surface 21. The housing 20 has a base portion 23 that protrudes toward the inner side of the area surrounded by the housing 20. The recess 24 is formed in the base portion 23. The area surrounded by the housing 20 is filled with a sealing material 42. The housing 20 is provided with electrodes not shown in the figure. In addition, a cover not shown in the figure is provided on the housing 20. The semiconductor chip 40, the metal pattern 33, the metal terminal 35, and the electrodes of the housing 20 are electrically connected by metal wiring 37, US (Ultrasonic) bonding, etc.

[0015] The nut 51 is pressed into the recess 24 of the housing 20. A screw hole extending in the vertical direction is formed in the nut 51. A through hole 12 for inserting the screw 52 is formed in the base plate 10. In addition, a through hole 25 is formed in the housing 20 to connect the recess 24 and the through hole 12. The screw 52 is inserted into the nut 51 from the bottom of the base plate 10 through the through holes 12 and 25. The screw 52 is, for example, a bolt that is screwed into the nut 51. Thus, as Figure 3 As shown, the housing 20 and the base plate 10 are fastened. The nut 51 is circular in plan view, for example.

[0016] Figure 5 This is a cross-sectional view of a semiconductor device 800 according to a comparative example. Unlike the semiconductor device 100 according to Embodiment 1, the semiconductor device 800 according to the comparative example uses tapping screws 852 to fasten the housing 820 and the base plate 10. In this structure, the use of tapping screws 852 for fastening may create a gap 90 between the tapping screws 852 and the housing 20. Partial discharge occurs when voltage is exchanged between, for example, a protruding portion such as a screw thread and the metal pattern 33, metal terminal 35, or metal wiring 37, which are at high voltage. In the semiconductor device 800 according to the comparative example, gaps 90 are likely to form on the straight line connecting the tapping screws 852 and the high-voltage portion. Therefore, gaps 90 may reduce the partial discharge tolerance.

[0017] In contrast, in this embodiment, the base plate 10 and the housing 20 can be fastened together without cutting the housing 20 with the tapping screws 852. This prevents the formation of a gap 90 between the screws 52 and the housing 20, thereby suppressing the occurrence of partial discharge. Consequently, discharge tolerance can be improved. The gap above the screws 52 and the gap between the screws 52 and the housing 20 in the through-holes 25 are not located on the straight line connecting the screws 52 and the high-voltage portion via the shortest path. Consequently, a decrease in partial discharge tolerance is less likely to occur.

[0018] Figure 6 This is a diagram illustrating the gas 91 within the housing 820 involved in the comparative example. In a housing formed of resin, the larger the volume of the resin portion, the greater the amount of gas generated by the molded resin. The recess 24 is not formed in the housing 820 involved in the comparative example. Therefore, the volume of the housing 820 is large, and bubbles caused by the gas 91 are easily generated. In addition, since there is no recess 24 on the housing 820, a thick block-shaped portion is formed. In the block-shaped portion, the distance from the inside of the housing to the surface is large. Therefore, the gas 91 generated during molding is difficult to escape, and bubbles are more likely to be generated. Therefore, in the semiconductor device 800 involved in the comparative example, bubbles are easily formed on the straight line connecting the tapping screw 852 and the high-voltage portion. Due to these bubbles, the partial discharge tolerance may be reduced.

[0019] Figure 7This is a diagram illustrating the gas 91 in the housing 20 according to Embodiment 1. In this embodiment, a recess 24 is formed in the housing 20. By forming the recess 24, the volume of the housing 20 is reduced. Therefore, when the housing 20 is molded with resin, the generation of bubbles can be suppressed. In addition, in this embodiment, by forming the recess 24 in the base portion 23, the base portion 23 can be formed with a thin plate-like portion. In the plate-like portion, the distance from the inside of the housing 20 to the surface is small. Therefore, the gas 91 generated during molding can easily escape, and bubbles are less likely to be generated. In this way, in this embodiment, the formation of bubbles between the screw 52 and the high-voltage portion can be suppressed. Therefore, the discharge tolerance can be improved.

[0020] Furthermore, in this embodiment, there is no need to fill the gap between the housing and the screw with resin to improve the discharge withstand capability. Therefore, the increase in the number of manufacturing steps can be suppressed, and workability can be improved.

[0021] Nut 51 can be made of an insulator such as resin, while screw 52 can be made of metal. In this case, screw 52 is electrically connected to GND, i.e., base plate 10, and is at GND potential. The combination of screw 52, ​​which is at GND potential, and nut 51, which is non-conductive, effectively suppresses partial discharge in high-voltage areas. Both nut 51 and screw 52 can be made of metal or an insulator such as resin. Alternatively, nut 51 can be metal and screw 52 can be made of resin.

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

[0023] The semiconductor chip 40 can also be formed of a wide-bandgap semiconductor. Examples of wide-bandgap semiconductors include silicon carbide, gallium nitride-based materials, or diamond. Using a wide-bandgap semiconductor in the semiconductor chip 40 can improve energy efficiency in the semiconductor device 100. Furthermore, according to this embodiment, the semiconductor device 100 equipped with the semiconductor chip 40 formed of a wide-bandgap semiconductor can achieve improved discharge resistance and stable operation even when high currents flow.

[0024] The above-described variations can be appropriately applied to the semiconductor devices, power conversion devices, and mobile objects according to the following embodiments. Since the semiconductor devices, power conversion devices, and mobile objects according to the following embodiments have many similarities with the first embodiment, the description will focus on the differences from the first embodiment.

[0025] Implementation method 2. Figure 8 This is a top view of a semiconductor device 200 according to Embodiment 2. In this embodiment, the shapes of the nut 251 and the recess 224 of the housing 220 differ from those of Embodiment 1. The remaining structure is the same as that of Embodiment 1. Nut 251 is polygonal in top view. For example, nut 251 is hexagonal or quadrilateral in top view. Recess 224 of the housing 220 is formed to fit the nut 251. Specifically, the side surface of the housing 220 within the recess 224 is configured to closely contact the nut 251.

[0026] In this embodiment, it is possible to prevent the nut 251 from rotating together. This allows for reliable generation of the tightening torque required to tighten the housing 220 and the base plate 10 .

[0027] Implementation method 3. Figure 9 It is a cross-sectional view of a semiconductor device 300 according to the third embodiment. Figure 10 It is a top view of a semiconductor device 300 according to the third embodiment. Figure 11 This is a cross-sectional view showing a state in which a housing 320 and a base plate 10 are fastened together by screws 52 in a semiconductor device 300 according to a third embodiment. In this embodiment, the structure of the housing 320 and the nut 351 differs from that of the first embodiment. The remaining structure is the same as that of the first embodiment.

[0028] The housing 320 surrounding the semiconductor chip 40 is provided on the base plate 10. Figures 9-11 , only a portion of the housing 320 is shown. The housing 320 includes a sidewall portion 327 extending upward from the upper surface of the substrate 10 and a base portion 323 extending along the upper surface of the bottom plate 10. A nut 351 is provided on the housing 320 in an area surrounded by the housing 320. Specifically, the nut 351 is provided on the base portion 323. The nut 351 is a bag nut with a downward opening.

[0029] The housing 320 is provided with a through hole 25 connected to the through hole 12. The screw 52 is inserted into the nut 351 from the bottom of the base plate 10 through the through holes 12 and 25. The screw 52 is, for example, a bolt that is screwed to the nut 351. Figure 11 As shown, the housing 320 and the base plate 10 are fastened. The nut 351 is circular in plan view, for example.

[0030] In this embodiment, the base plate 10 and the housing 320 can also be fastened together without cutting the housing 320 with the tapping screws 852. This prevents the formation of gaps 90 between the screws 52 and the housing 320, thereby suppressing the occurrence of partial discharge. Consequently, discharge tolerance can be improved.

[0031] Furthermore, unlike the case 820 of the comparative example, the case 320 of this embodiment does not include a thick, block-shaped portion for inserting the tapping screw 852. This reduces the volume of the case 320 and suppresses the generation of bubbles during the resin molding of the case 320. Furthermore, in this embodiment, the base 323 of the case 320 can be formed from a thin, plate-like portion. Consequently, the gas 91 generated during the molding of the case 320 is less likely to escape, suppressing the generation of bubbles.

[0032] Furthermore, by using a bag nut as the nut 351, it is possible to prevent the sealing material 42 from seeping out from between the nut and the screw 52. In this embodiment, the sealing material 42 can be brought into close contact with the bag nut without a gap.

[0033] Implementation method 4. Figure 12 This is a top view of a semiconductor device 400 according to Embodiment 4. In this embodiment, the shape of nut 451 differs from that of nut 351 in Embodiment 3. The remaining structure is the same as that of Embodiment 1. Nut 451 is polygonal in top view. For example, nut 451 is hexagonal or quadrilateral in top view.

[0034] In this embodiment, for example, the side surface or corner of the nut 451 contacts the side surface of the housing 320 to prevent the nut 451 from rotating together. This ensures that the tightening torque required to tighten the housing 320 and the base plate 10 is generated securely.

[0035] Implementation method 5. Figure 13 This is a block diagram of a power conversion device 74 according to Embodiment 5. Power conversion device 74 is, for example, a three-phase inverter. Power conversion device 74 is connected between a power source 70 and a load 75, converting power supplied from power source 70 and supplying it to load 75. Power conversion device 74 includes a main conversion circuit 71 that converts and outputs power; a drive circuit 72 that outputs a drive signal for driving the switching elements of main conversion circuit 71; and a control circuit 73 that outputs a control signal to drive circuit 72 for controlling drive circuit 72.

[0036] In the power conversion device 74 according to the present embodiment, any of the semiconductor devices in Embodiments 1 to 4 is mounted as a switching element of the main conversion circuit 71. This can improve the discharge tolerance of the power conversion device 74.

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

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

[0039] Implementation method 6. Figure 14 This figure illustrates a movable object 78 according to Embodiment 6. A power conversion device 74 including the semiconductor device according to any of Embodiments 1 to 4 is mounted on movable object 78. For example, movable object 78 is an electric train. In this embodiment, by improving the discharge tolerance of power conversion device 74, the service life of movable object 78 can be extended.

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

[0041] 10 Base plate, 12 Through-hole, 20 Housing, 21 Outer side surface, 22 Inner side surface, 23 Base portion, 24 Recessed portion, 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 Housing, 224 Recessed portion, 251 Nut, 300 Semiconductor device, 320 Housing, 323 Base portion, 327 Sidewall portion, 351 Nut, 400 Semiconductor device, 451 Nut, 800 Semiconductor device, 820 Housing, 852 Tapping screw

Claims

1. A semiconductor device, characterized in that: include: Base plate; A semiconductor chip, the semiconductor chip being arranged in a region above the base plate; a housing, the housing being disposed on the bottom plate, surrounding the semiconductor chip, having an outer side surface and an inner side surface opposite to the outer side surface, and having a recess formed on the outer side surface; a nut, which is pressed into the recessed portion of the housing and has a screw hole extending in the up-down direction; and A screw is inserted into the nut from below the base plate.

2. A semiconductor device, characterized in that: include: Base plate; A semiconductor chip, the semiconductor chip being arranged in a region above the base plate; A housing, which is disposed on the base plate and surrounds the semiconductor chip; a nut which is a bag nut disposed on the housing in a region surrounded by the housing and which is open downward; as well as A screw is inserted into the nut from below the base plate.

3. The semiconductor device according to claim 1 or 2, wherein: The nut is formed of an insulator, and the screw is formed of metal.

4. The semiconductor device according to any one of claims 1 to 3, wherein: The nut is polygonal in plan view.

5. The semiconductor device according to any one of claims 1 to 4, wherein: The semiconductor chip is formed of a wide bandgap semiconductor.

6. The semiconductor device according to claim 5, wherein: The wide bandgap semiconductor is silicon carbide, gallium nitride-based material or diamond.

7. A power conversion device, characterized in that: A semiconductor device according to any one of claims 1 to 6 is mounted thereon.

8. A mobile body, characterized in that: A semiconductor device according to any one of claims 1 to 6 is mounted thereon.

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