Semiconductor device, power conversion device and movable body

Abstract

A semiconductor device according to the disclosure includes a base plate, a semiconductor chip disposed in a region above the base plate, a package disposed on the base plate, enclosing the semiconductor chip, having an outer surface and an inner surface on an opposite side of the outer surface, and having a recess formed on the outer surface, a nut pressed into the recess of the package and having a screw hole formed to extend in a vertical direction, and a screw inserted into the nut from below the base plate.

Description

Area

[0001] The present disclosure relates to a semiconductor device, a power conversion device, and a movable body. background

[0002] PTL 1 discloses a semiconductor device including a resin package having a screw hole, an insulating substrate on which a semiconductor chip is mounted, and a heat sink having a heat sink through-hole and on which the insulating substrate is mounted. A metal tapping screw passes through the heat sink through-hole and the screw hole, engaging the resin package with the heat sink. A cavity in the screw hole formed between the resin package and the metal tapping screw is filled with a high-withstand-voltage resin. Citation listPatent literature

[0003] [PTL 1] JP 2006-32392 A SummaryTechnical problem

[0004] With the progressive reduction in size and increase in density of a semiconductor device, the distance between a screw and an insulating substrate becomes shorter. Therefore, it is necessary to improve the partial discharge withstand capability and the dielectric strength. For example, if a case and a heat sink, etc., are screwed together with a self-tapping screw, a void is likely to be created around the screw. There is a possibility that the partial discharge withstand capability will deteriorate due to this void.

[0005] In contrast, in PTL 1, the discharge resistance capability is improved by filling the cavity between the housing and the screw with a resin. However, due to filling the cavity with the resin, the manufacturing processes increase and there is a possibility of deterioration in machinability.

[0006] The present disclosure is directed to providing a semiconductor device, a power conversion device, and a movable body that can improve discharge withstand capability. Solution to the problem

[0007] A semiconductor device according to the first disclosure includes a base plate, a semiconductor chip disposed in a region above the base plate, a package disposed on the base plate, enclosing the semiconductor chip, having an outer surface and an inner surface on an opposite side of the upper surface, and having a recess formed on the outer surface, a nut pressed into the recess of the package and having a screw hole formed to extend in a vertical direction, and a screw inserted into the nut from below the base plate.

[0008] A semiconductor device according to the second disclosure includes a base plate, a semiconductor chip disposed in a region above the base plate, a housing disposed on the base plate and enclosing the semiconductor chip, a nut disposed on the housing in a region surrounded by the housing, the nut being a union nut open downward, and a screw inserted into the nut from below the base plate. Advantageous effects of the invention

[0009] In the semiconductor devices according to the first and second disclosures, it is possible to prevent a void from forming between the screw and a component on the base plate that receives a high voltage. Therefore, it is possible to improve the partial discharge withstand capability. Short description of the drawings Fig. 1 is a cross-sectional view of a semiconductor device according to a first embodiment. Fig. 2 is a plan view of the semiconductor device according to the first embodiment. Fig. 3 is a cross-sectional view illustrating a state in which a case and a base plate are fixed with a screw in the semiconductor device according to the first embodiment. Fig. 4 is a view for explaining 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 view for explaining a gas in a casing according to the comparative example. Fig. 7 is a view for explaining the gas inside the casing 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 the semiconductor device according to the third embodiment. Fig. 11 is a cross-sectional view illustrating a state in which a case and the base plate are fixed with the screw 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 view for explaining a movable body according to a sixth embodiment. Description of the embodiments

[0010] A semiconductor device and a semiconductor device, a power conversion device, and a movable body according to each embodiment will be described with reference to the drawings. Identical or corresponding constituent elements are given the same reference numerals, and repeated descriptions of such constituent elements may be omitted. First embodiment

[0011] 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 illustrating a state in which a case 20 and a base plate 10 are fixed with a screw 52 in the semiconductor device 100 according to the first embodiment. Fig. 4 is a view for explaining 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.

[0012] As in Fig. As illustrated in Figure 4, the insulating substrate 30 includes a conductor layer 31, an insulating layer 32 on the conductor layer 31, and a metal pattern or metal structure 33 on the insulating layer 32. The insulating layer 32 is formed with, for example, ceramic or a resin. A semiconductor chip 40 is arranged on the metal structure 33. The semiconductor chip 40 is, for example, an insulated gate bipolar transistor (IGBT) chip or a diode (Di) chip. In this way, the semiconductor chip is arranged in a region above the base plate 10. Further, a metal terminal 35, which is an electrode, a metal wiring 37, which is a wire, or the like, is arranged on the metal structure 33. Note that in Fig. 1 to 3, for the sake of convenience, only a part of the insulating substrate 30 is illustrated.

[0013] The housing 20 enclosing the semiconductor chip is arranged on the base plate 10. For the sake of convenience, Fig. 1 to 3 illustrate only a part of the housing 20. The housing 20 includes an outer surface 21 and an inner surface 22 on an opposite side of the outer surface 21. A recess 24 is formed on the outer surface 21. The housing 20 has a base portion 23 projecting inward from a region enclosed by the housing 20. The recess 24 is formed in the base portion 23. The region enclosed by the housing 20 is filled with a sealing resin 42. An electrode (not illustrated) is disposed in the housing 20. Further, a lid (not illustrated) is disposed on the housing 20. The semiconductor chip 40, the metal pattern 33, the metal terminal 35, and the electrode of the housing 20 are electrically connected via the metal wiring 37, ultrasonic (US) bonding, or the like.

[0014] A nut 51 is pressed into the recess 24 of the housing 20. A screw hole extending in a vertical direction is formed in the nut 51. A through hole 12 through which a screw 52 is to be inserted is formed in the base plate 10. Furthermore, a through hole 25 connecting the recess 24 and the through hole 12 is formed in the housing 20. The screw 52 is inserted into the nut 51 through the through holes 12 and 25 from below the base plate 10. The screw 52 is, for example, a bolt to be screwed to the nut 51. In this way, as shown in Fig. 3, the housing 20 and the base plate 10 are fastened. The nut 51 has, for example, a circular shape in plan view.

[0015] 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 of the first embodiment in that a case 820 and the base plate 10 are fastened with a tapping screw 852. In this configuration, a cavity 90 may be created between the tapping screw 852 and the case 820 as a result of fastening with the tapping screw 852. A partial discharge occurs by exchanging voltages between a protruding portion such as, for example, a screw thread of the screw and the metal structure 33, the metal terminal 35, the metal wiring 37, or the like that acquires a high voltage.In the semiconductor device 800 according to the comparative example, the cavity 90 is likely to be formed on a line connecting the tapping screw 852 and the high-voltage portion. Thus, there is a possibility that the partial discharge withstand capability deteriorates due to the cavity 90.

[0016] In contrast, in the present embodiment, the base plate 10 and the housing 20 can be fixed without the housing 20 being scratched by the tapping screw 52. Consequently, the generation of the void 90 between the screw 52 and the housing 20 can be prevented, and the occurrence of a partial discharge can be prevented. Therefore, it is possible to improve the discharge resistance capability. Note that a void above the screw 52 and a void between the screw 52 and the housing 20 in the through hole 25 are not on a line that connects the screw 52 and the high-voltage portion with the shortest route. Consequently, this is less likely to result in deterioration of the partial discharge resistance capability.

[0017] Fig. 6 is a view for explaining a gas 91 in a case 820 according to the comparative example. In the case formed with a resin, as the volume of a resin portion increases, an amount of gas generated from a molding resin increases. The recess 24 is not formed in the case 820 according to the comparative example. Consequently, a volume of the case 820 is large, and a void is likely to be generated by the gas 91. Further, there is no recess 24 in the case 820, and thus a block-shaped thick portion is formed. In the block-shaped portion, a distance from the inside of the case to the surface is long. Consequently, the gas 91 generated during formation is less likely to leak, and a void is more likely to be generated.Therefore, in the semiconductor device 800 according to the comparative example, a void is likely to be formed on a line connecting the tapping screw 852 and the high-voltage portion. This void also poses a possibility of deteriorating the partial discharge withstand capability.

[0018] Fig. 7 is a view for explaining the gas 91 inside the casing 20 according to the first embodiment. In the present embodiment, the recess 24 is formed in the casing 20. As a result of forming the recess 24, the volume of the casing 20 decreases. Therefore, it is possible to prevent the generation of a void when the casing 20 is formed with a resin. Further, in the present embodiment, as a result of forming the recess 24 in the base portion 23, the base portion 23 can be formed with a thin plate-like portion. In the thin plate-like portion, a distance from the inside of the casing 20 to the surface is short. Consequently, the gas 91 generated upon formation is likely to escape, and a void is less likely to be generated.In this way, in the present embodiment, it is possible to prevent a void from being formed between the screw 52 and the high-stress portion. Therefore, it is possible to improve the discharge resistance capability.

[0019] Furthermore, in the present embodiment, it is not necessary to fill the cavity between the housing and the screw with resin to improve the discharge resistance capability. Therefore, it is possible to prevent an increase in manufacturing processes and improve workability.

[0020] The nut 51 is preferably formed with an insulating body such as a resin, and the screw 52 is preferably formed with a metal. In this case, the screw 52 is electrically connected to the base plate 10, which is a GND and has a GND potential. By combining the screw 52, which has a GND potential, and the nut 51, which is a non-conductor for the high-voltage portion, it is possible to effectively prevent partial discharge. Both the nut 51 and the screw 52 may be a metal, or both may be an insulating body such as a resin. Further, the nut 51 may be a metal, and the screw 52 may be a resin.

[0021] As a modification of the present embodiment, the semiconductor chip 40 may be a metal oxide semiconductor field-effect transistor (MOSFET) chip. Furthermore, a plurality of semiconductor chips 40 may be arranged in the package 20. The plurality of semiconductor chips may include a plurality of types of semiconductor chips. In this case, too, effects similar to those of the present embodiment can be provided.

[0022] The semiconductor chip 40 may be made of a wide-bandgap semiconductor. The wide-bandgap semiconductor is, for example, silicon carbide, a gallium nitride-based material, or diamond. By using a wide-bandgap semiconductor as the semiconductor chip 40, it is possible to save power of the semiconductor device 100. Furthermore, according to the present embodiment, in the semiconductor device 100 in which the semiconductor chip made of a wide-bandgap semiconductor is arranged, even in a case where a large current flows, it is possible to improve the discharge withstand capability and implement stable operation.

[0023] These modifications can be applied, as appropriate, to semiconductor devices, power conversion devices, and movable bodies according to the following embodiments. Note that the semiconductor devices, power conversion devices, and movable bodies according to the following embodiments are similar to those of the first embodiment in many aspects, and thus, the following mainly describes differences between the semiconductor devices, power conversion devices, and movable bodies according to the following embodiments and those of the first embodiment. Second embodiment

[0024] Fig. 8 is a plan view of a semiconductor device 200 according to a second embodiment. In the present embodiment, shapes of a nut 251 and a recess 224 of the housing 220 are different from those in the first embodiment. The other configurations are similar to the configurations of the first embodiment. The nut 251 has a polygonal shape in plan view. The nut 251 has, for example, a hexagonal or quadrangular shape in plan view. The recess 224 of the housing 220 has a shape corresponding to the nut 251. In other words, a side surface of the housing 220 in the recess 224 is configured to tightly adhere to the nut 251.

[0025] In the present embodiment, it is possible to prevent corotation of the nut 251. This makes it possible to reliably generate a fastening torque required to fasten the housing 220 and the base plate 10. Third embodiment

[0026] 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 illustrating a state in which a housing 320 and the base plate 10 are fixed with the screw 52 in the semiconductor device 300 according to the third embodiment. In the present embodiment, the configurations of the housing 320 and a nut 351 are different from those of the first embodiment. The other configurations are similar to the configurations of the first embodiment.

[0027] The housing 320 enclosing the semiconductor chip 40 is arranged on the base plate 10. For the sake of convenience, Fig. 9 to 11 show only a portion of the housing 320. The housing 320 includes a sidewall portion 327 extending upward from an upper surface of the base plate 10, and a base portion 323 extending along the upper surface of the base plate 10. The nut 351 is disposed on the housing 320 in an area enclosed by the housing 320. Specifically, the nut 351 is disposed on the base portion 323. The nut 351 may be a union nut that is open downward.

[0028] The through hole 325 is formed in the housing 320 so that it connects with the through hole 12. The screw 52 is inserted through the through holes 12 and 325 from below the base plate 10 into the nut 351. The screw 52 is, for example, a bolt to be screwed with the nut 351. In this way, as shown in Fig. 11, the housing 320 and the base plate 10 are fastened. The nut 351 has, for example, a circular shape in plan view.

[0029] Also in the present embodiment, the base plate 10 and the housing 320 can be fixed without the housing 320 being scratched by the self-tapping screw 52. Consequently, the generation of the cavity 90 between the screw 52 and the housing 320 can be prevented, and the occurrence of a partial discharge can be prevented. Therefore, it is possible to improve the discharge resistance capability.

[0030] Furthermore, in the housing 320 of the present embodiment, the block-shaped thick portion for enabling insertion of the self-tapping screw 852 like the housing 820 according to the comparative example is not provided. Therefore, it is possible to reduce a volume of the housing 320 and prevent the generation of a void when the housing 320 is formed with a resin. Furthermore, in the present embodiment, the base portion 323 of the housing 320 can be formed with a thin plate-like portion. Thus, the gas 91 generated when the housing 320 is formed is more likely to escape, and consequently, it is possible to prevent the generation of a void.

[0031] Furthermore, by using a cap nut such as the nut 351, it is possible to prevent the sealing material 42 from exuding from the gap between the nut and the bolt 52. In the present embodiment, it is possible to cause the sealing material 42 to firmly adhere to the cap nut without a gap therebetween. Fourth embodiment

[0032] Fig. 12 is a plan view of a semiconductor device 400 according to a fourth embodiment. In the present embodiment, a shape of a nut 451 differs from the shape of the nut 451 in the third embodiment. Other configurations are similar to the configurations of the first embodiment. The nut 451 has a polygonal shape in plan view. The nut 451 has, for example, a hexagonal or quadrangular shape in plan view.

[0033] In the present embodiment, for example, as a result of a side surface or a corner of the nut 451 coming into contact with a side surface of the housing 320, co-rotation of the nut 451 can be prevented. This makes it possible to reliably generate a fastening torque required to fasten the housing 320 and the base plate 10. Fifth embodiment

[0034] 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, connected between a power supply 70 and a load 75, converts the power supplied by the power supply 70 and supplies the converted power to the load 75. The power conversion device 74 includes a main conversion circuit 71 that converts power and outputs the converted power, a drive circuit 72 that outputs a drive signal for driving a switching device of the main conversion circuit 71, and a control circuit 73 that outputs a control signal for controlling the drive circuit 72 to the drive circuit 72.

[0035] In the power conversion device 74 according to the present embodiment, one of the semiconductor devices of the first to fourth embodiments is mounted as the switching device of the main conversion circuit 71. This can improve the discharge withstand capability of the power conversion device 74.

[0036] The power conversion device 74 may be a two-level, three-level, or multi-level power conversion device. The present embodiment can also be applied to a single-phase inverter, a DC / DC converter, and an AC / DC converter.

[0037] The load 75 is, for example, an electric motor. The present disclosure is not limited to this, and the power conversion device 74 can also be used as, for example, a power supply device of an electrical discharge machine, a laser machine, an induction heating cooking device, and a non-contact power supply system. Furthermore, the power conversion device 74 can also be used as a power conditioner of a photovoltaic system, an electricity storage system, or the like. Sixth embodiment

[0038] Fig.14 is a view for explaining a movable body 78 according to a sixth embodiment. The movable body 78 mounts the power conversion device 74 including one of the semiconductor devices of the first to fourth embodiments. The movable body 78 is, for example, a train. In the present embodiment, by improving the discharge withstand capability of the power conversion device 74, it is possible to extend the service life of the movable body 78.

[0039] Note that the technical features described in the above embodiments can be combined as appropriate. List of reference symbols

[0040] 10 base plate, 12 through hole, 20 housing, 21 outer surface, 22 inner surface, 23 socket portion, 24 recess, 25 through hole, 30 substrate, 31 conductor layer, 32 insulating layer, 33 metal structure, 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 movable body, 90 cavity, 91 gas, 100 semiconductor device, 200 semiconductor device, 220 housing, 224 recess, 251 nut, 300 semiconductor device, 320 housing, 323 socket portion, 327 sidewall portion, 351 Nut, 400 Semiconductor Device, 451 Nut, 800 Semiconductor Device, 820 Housing, 852 Tapping Screw QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2006-32392 A

[0003]

Claims

[1] A semiconductor device comprising: a base plate; a semiconductor chip arranged in a region above the base plate; a housing disposed on the base plate, enclosing a semiconductor chip, having an outer surface and an inner surface on an opposite side of the outer surface, and having a recess formed on the outer surface; a nut pressed into the recess of the housing and having a screw hole formed to extend in a vertical direction; and a screw that is inserted into the nut from below the base plate. [2] A semiconductor device comprising: a base plate; a semiconductor chip arranged in a region above the base plate; a housing arranged on the base plate and enclosing the semiconductor chip; a nut arranged on the housing in an area enclosed by the housing, the nut being a union nut open at the bottom; and a screw that 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 with an insulating body and the screw is formed with a metal. [4] The semiconductor device according to any one of claims 1 to 3, wherein the nut has a polygonal shape in plan view. [5] A semiconductor device according to any one of claims 1 to 4, wherein the semiconductor chip is made of a wide band gap semiconductor. [6] A semiconductor device according to claim 5, wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material, or diamond. [7] A power conversion device in which the semiconductor device according to any one of claims 1 to 6 is mounted. [8] A movable body in which the semiconductor device according to any one of claims 1 to 6 is mounted.

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