Semiconductor device

Abstract

A semiconductor device is provided that can reduce partial discharge, which can occur between a screw fixing a housing to a heat sink and a high-voltage area, and which can improve reliability. The semiconductor device comprises a heat sink and a housing. The heat sink holds the semiconductor element. The housing contains the semiconductor element, which is held above the heat sink. A first screw hole is formed in a lateral surface of the heat sink. A second screw hole, connected to the first screw hole, is formed in the housing. The housing is fastened to the heat sink by a screw inserted into both the first and second screw holes.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a semiconductor device. BACKGROUND TECHNOLOGY

[0002] Power modules containing semiconductor devices for power control have structures in which a heat sink and a housing are each fastened by screws. For example, in a semiconductor device made of metal disclosed in patent document 1, self-tapping screws fasten a resin housing from below through holes in a heat sink to screw holes located above it. This secures the housing to the heat sink. DOCUMENT ACCORDING TO THE STATE OF THE TECHNOLOGY PATENT DOCUMENT

[0003] Patent document 1: Published Japanese patent application no. 2006-32392 SUMMARY: PROBLEM TO BE SOLVED BY THE INVENTION

[0004] If the insulation performance of the resin enclosure around the holes through which the self-tapping screws pass is insufficient in the structure disclosed in patent document 1, a local discharge (referred to hereafter as partial discharge) may occur between a high-voltage sub-area sealed within the resin enclosure and the self-tapping screws.

[0005] The present disclosure has an objective to provide a semiconductor device that can reduce partial discharge that may occur between a screw fixing a housing to a heat sink and a high-voltage sub-area, and that can improve reliability in order to solve the problem. MEANS TO SOLVE THE PROBLEM

[0006] A semiconductor device according to the present disclosure comprises a heat sink and a housing. The heat sink holds a semiconductor element. The housing contains the semiconductor element, which is held above the heat sink. A first screw hole is formed in a lateral surface of the heat sink. A second screw hole, connected to the first screw hole, is formed in the housing. The housing is fastened to the heat sink by a screw inserted into the first and second screw holes. EFFECTS OF INVENTION

[0007] The present disclosure provides a semiconductor device that can reduce partial discharge that may occur between a screw fixing a housing to a heat sink and a high-voltage sub-area in a power module, and which can improve reliability.

[0008] The purpose, features, aspects and benefits of this revelation will become clearer from the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. Figure 1] is a cross-sectional view illustrating the structure of a semiconductor device according to embodiment 1. [ Fig. Figure 2] is a cross-sectional view illustrating part of the structure of a semiconductor device according to embodiment 2. [ Fig. Figure 3] is a top view illustrating part of the structure of a heat sink of a semiconductor device. [ Fig. Figure 4] is a cross-sectional view illustrating part of the structure of a semiconductor device according to embodiment 3. [ Fig. Figure 5] is a cross-sectional view illustrating part of the structure of a semiconductor device. [ Fig. Figure 6] is a top view illustrating part of the structure of a heat sink of a semiconductor device. [ Fig. Figure 7] is a top view illustrating part of the structure of a heat sink of a semiconductor device according to embodiment 4. [ Fig. Figure 8] is a top view illustrating part of the structure of the heat sink of the semiconductor device according to embodiment 4. [ Fig. Figure 9] is a cross-sectional view illustrating the structure of a semiconductor device according to embodiment 5. [ Fig. Figure 10] is a cross-sectional view illustrating the structure of a semiconductor device according to embodiment 6. DESCRIPTION OF EXECUTION FORMS<Ausführungsform 1 >

[0009] Fig. Figure 1 is a cross-sectional view illustrating the structure of a semiconductor device 101 according to embodiment 1. The semiconductor device 101 comprises a heat sink 10, a screw hole 20, an insulating substrate 30, a semiconductor element 40, a terminal 50, a metal wire 60, a housing 70, and a sealing means 80.

[0010] The heat sink 10 holds the semiconductor element 40 arranged on the insulating substrate 30. The heat sink 10 is, for example, a plate made of a metal such as Cu or Al, or a plate made of an Al-SiC composite material. The heat sink 10 has a position-defining sub-area 10A.

[0011] The position-defining sub-area 10A defines a position of the housing 70 in the heat sink 10. The position-defining sub-area 10A according to embodiment 1 comprises a through-hole penetrating an upper surface and a lower surface of the heat sink 10.

[0012] The screw hole 20 is formed in a lateral surface 10B of the heat sink 10. The screw hole 20 extends inwards from the lateral surface 10B of the heat sink 10. The screw hole 20 is a hole for attaching the housing 70 to the heat sink 10 by means of a self-tapping screw 21. The screw hole 20 penetrates a projection 71 of the housing 70 that aligns with the position-defining sub-area 10A. In other words, the screw hole 20 comprises a first screw hole formed in the lateral surface 10B of the heat sink 10 and a second screw hole formed in conjunction with the first screw hole in the housing 70.

[0013] The insulating substrate 30 comprises an insulating layer 31, a circuit surface structure 32, and a heat dissipation surface structure 33. The insulating layer 31 has insulating properties and is made of, for example, a ceramic. Examples of ceramics include Al₂, Si₃N₄, and Al₂O₃. The circuit surface structure 32 is arranged on the upper surface of the insulating layer 31. The heat dissipation surface structure 33 is arranged on the lower surface of the insulating layer 31. The surface circuit structure 32 and the heat dissipation surface structure 33 are made of a metal such as Cu or Al. The heat dissipation surface structure 33 is bonded to the heat sink 10 by a bonding material 91, such as a solder metal, a brazing filler material, or a sintered material. In other words, the heat sink 10 holds the insulating substrate 30.

[0014] The semiconductor element 40 is bonded to the circuit surface structure 32 of the insulating substrate 30 by a bonding material 92. The bonding material 92 is conductive. The bonding material 92 is, for example, a solder metal. The semiconductor element 40 is also referred to as a semiconductor chip. The semiconductor element 40 consists of, for example, a semiconductor such as Si or a wide-bandgap semiconductor such as SiC, GaN, Ga₂O₃, or diamond. The semiconductor element 40 is, for example, a power semiconductor element or an integrated control circuit (IC) for controlling the power semiconductor element. The semiconductor element 40 is, for example, an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a Schottky barrier diode.Alternatively, the semiconductor element 40 can be a backward-conducting IGBT (RC-IGBT) in which an IGBT and a freewheeling diode are formed in a semiconductor substrate.

[0015] Terminal 50 is a conductor configured to connect to an external circuit located outside the semiconductor device 101. Terminal 50 is, for example, a metal frame obtained by machining a plate made of a metal such as copper into a predetermined shape. Although Fig. Figure 1 illustrates a connector 50 as a component separate from housing 70; the connector 50 can be integrally mounted on the housing 70. The connector 50 has a first end and a second end. The first end corresponds to a lower end in Fig. 1 and is bonded to the circuit surface structure 32 of the insulating substrate 30. The first end can, for example, be bonded by a (not illustrated) wire to an (not illustrated) electrode of the semiconductor element 40. The first end of the terminal 50 is bonded to the circuit surface structure 32 or the electrode of the semiconductor element 40 by ultrasonic bonding or a solder metal. The second end corresponds to an upper end in Fig. 1 and is led to an outer surface of the housing 70 and the sealing agent 80. The second end can be connected to an external circuit.

[0016] The metal wire 60 connects two components consisting of the electrode of the semiconductor element 40, the first end of the terminal 50 and the circuit surface structure 32 of the insulating substrate 30.

[0017] The housing 70 has a hollow frame shape. Although the cross-sectional view of Fig. Figure 1 shows a structure to the right of the housing 70, and the housing 70 has a rectangular frame in top view. The housing 70 is positioned on the heat sink 10 such that it encloses the upper surface of the heat sink 10. The housing 70 contains, for example, the insulating substrate 30 and the semiconductor element 40 in an interior enclosed by the frame, that is, within the frame shape. The housing 70 is made of, for example, a resin. The resin is, for example, polyphenylene sulfide (PPS).

[0018] The housing 70 fits together with the position-defining sub-area 10A of the heat sink 10. The housing 70 according to embodiment 1 has a projection 71 that fits with the through-hole of the heat sink 10 contained in the position-defining sub-area 10A. The projection 71 is located on the bottom of the housing 70.

[0019] The housing 70 is fastened to the heat sink 10 by the self-tapping screw 21, which is screwed into the screw hole 20 of the heat sink 10. The end of the self-tapping screw 21 penetrates the projection 71 of the housing 70 from the outside of the housing 70. The end of the self-tapping screw 21 is located within the screw hole 20 formed in the heat sink 10. In other words, the end of the self-tapping screw 21 is neither exposed to the interior of the housing 70, which is filled with the sealant 80, nor does it remain inside the housing 70.

[0020] Furthermore, the housing 70 is bonded to the heat sink 10 by a silicone adhesive 93. Thus, the housing 70 is bonded to the heat sink 10 by the silicone adhesive 93 and the self-tapping screw 21.

[0021] The sealant 80 fills the interior enclosed by the frame of the housing 70. The sealant 80 seals the upper surface of the heat sink 10, the insulating substrate 30, the semiconductor element 40, part of the connector 50, and the metal wire 60. The sealant 80 is a curing material such as a silicone resin or an epoxy resin.

[0022] In a first manufacturing process of the semiconductor device 101, the screw hole 20 of the heat sink 10 (a first screw hole) is formed by removing material from the heat sink 10 when the self-tapping screw 21 is screwed into the heat sink 10. Similarly, the screw hole 20 of the projection 71 of the housing 70 (a second screw hole) is formed by removing resin from the housing 70 when the self-tapping screw 21 is screwed into the housing 70. In this first manufacturing process, the material of the self-tapping screw 21 must be harder than that of the heat sink 10 and the housing 70.

[0023] In a second manufacturing process of the semiconductor device 101, the screw hole 20 is pre-formed, and the self-tapping screw 21 is screwed into the screw hole 20. Although the screw hole 20 can be pre-threaded, it need not be pre-threaded if the material of the self-tapping screw 21 is harder than that of the heat sink 10 and the housing 70. In the former case, a standard screw can be used instead of the self-tapping screw 21. Furthermore, since the material of the self-tapping screw 21 is typically harder than that of the housing 70, the screw hole 20 of the projection 71 of the housing 70 (second screw hole) does not need to be pre-formed. Fig. Figure 1 illustrates the second manufacturing process.

[0024] After the housing 70 is bonded to the heat sink 10, the liquid sealant 80 is injected into the interior of the housing 70. A hardening treatment then cures the sealant 80.

[0025] In the structure described above, the end of the self-tapping screw 21 is not exposed to the interior enclosed by the frame of the housing 70. Furthermore, the end of the self-tapping screw 21 is not located within a resin section forming the housing 70, i.e., within the frame. The end of the self-tapping screw 21 fits into the heat sink 10. Thus, even if the resin section of the housing 70 has a defective section 72, such as a cavity or a crack, partial discharge between a high-voltage section of the semiconductor device 101, which is a power module, and the self-tapping screw 21 is reduced. Consequently, even if the insulation performance of the housing 70 is insufficient, a decrease in the reliability of the semiconductor device 101 is prevented.

[0026] In summary, the semiconductor device 101 according to embodiment 1 comprises the heat sink 10 and the housing 70. The heat sink 10 holds the semiconductor element 40. The housing 70 contains the semiconductor element 40, which is held above the heat sink 10. The first screw hole of screw hole 20 is formed in the lateral surface 10B of the heat sink 10. The second screw hole of screw hole 20, in conjunction with the first screw hole of screw hole 20, is formed in the housing 70. The housing 70 is fastened to the heat sink 10 by the screw screwed into the first and second screw holes of screw hole 20. The screw according to embodiment 1 is the self-tapping screw 21.

[0027] The semiconductor device 101 reduces partial discharge that can occur between a screw fixing the housing 70 to the heat sink 10 and a high-voltage area. Consequently, the semiconductor device 101 is maintained with high reliability.

[0028] Patent document 1 discloses a structure in which a vertical screw hole in a housing is a through-hole, and a sealant fills the top surface of the through-hole as a structure to reduce partial discharge. However, in such a structure, the sealant being cured can escape from the heat sink through a space between the through-hole and the self-tapping screw during the manufacturing process. This leakage of the sealant reduces the manufacturing yield of the semiconductor device.

[0029] The semiconductor device 101 according to embodiment 1 has no through-hole penetrating the interior of the housing 70 to the outside. The semiconductor device 101 reduces partial discharge without any external leakage of the sealing agent 80.

[0030] Since the housing 70 fits together with the position-defining sub-area 10A of the heat sink 10, the housing 70 is easily positioned when it is bonded to the heat sink 10 during the manufacturing process. Consequently, a clamping device for fixing the positions of the heat sink 10 and the housing 70 becomes unnecessary, and processability is improved.

[0031] The semiconductor device 101 comprises a power semiconductor element consisting of a wide-bandgap semiconductor, designated as semiconductor element 40. The improved reliability of the semiconductor device 101 allows operation at high temperatures, increases the breakdown voltage, and reduces losses in a power conversion device, such as an inverter, on which the semiconductor device 101 is to be mounted. <Ausführungsform 2>

[0032] Fig. Figure 2 is a cross-sectional view illustrating part of the structure of a semiconductor device 102 according to embodiment 2. Fig. Figure 3 is a top view illustrating part of the structure of the heat sink 10 of the semiconductor device 102.

[0033] The semiconductor device 102 according to embodiment 2 is one whose manufacturing process is the second manufacturing process described in embodiment 1, and the illustration shows that the screw hole 20 (first screw hole) and the position-defining sub-area 10A in the heat sink 10 are pre-formed. 10C designates a screw hole for fixing the heat sink 10 to an installation target object of the semiconductor device 102.

[0034] The housing 70 is attached to the heat sink 10 by means of the self-tapping screw 21, which is screwed into the screw hole 20, similar to embodiment 1. The end of the self-tapping screw 21 fits into the heat sink 10 and is not exposed to the interior of the housing 70, which is filled with the sealing agent 70.

[0035] This embodiment 2 produces the same advantages as that according to the previously described embodiment 1. <Ausführungsform 3>

[0036] Fig. Figure 4 is a cross-sectional view illustrating the structure of a semiconductor device 103 according to embodiment 3. Fig. Figure 5 is a cross-sectional view illustrating part of the structure of the semiconductor device 103. Fig. Figure 6 is a top view illustrating part of the structure of the heat sink 10 of the semiconductor device 103. The semiconductor device 103 according to embodiment 3 differs from the semiconductor device 101 according to embodiment 1 in the structure of the position-defining sub-area 10A of the heat sink 10 and the housing 70 that fits with the position-defining sub-area 10A.

[0037] The position-defining sub-area 10A comprises a cut-out sub-area arranged in a circumference of the heat sink 10. The cut-out sub-area is formed in the lateral surface 10B of the heat sink 10 such that it overlaps an opening of the screw hole 20.

[0038] The housing 70 has the projection 71, which fits with the cut-out section. The housing 70 is attached to the heat sink 10 by the self-tapping screw 21, which is screwed into the screw hole 20.

[0039] The end of the self-tapping screw 21 penetrates the projection 71 of the housing 70 from the outside of the housing 70. The end of the self-tapping screw 21 fits into the heat sink 10 and is not exposed to the interior of the housing 70, which is filled with the sealant 80.

[0040] The first manufacturing process or the second manufacturing process described in embodiment 1 are usable for a manufacturing process of the semiconductor device 103.

[0041] As described above, since the housing 70 fits together with the position-defining sub-area 10A of the heat sink 10, the housing 70 is easily positioned when it is bonded to the heat sink 10 during the manufacturing process. Consequently, a clamping device for fixing the positions of the heat sink 10 and the housing 70 becomes unnecessary, and processability is improved. <Ausführungsform 4>

[0042] Fig. 7 and Fig. Figures 8 are top views, each illustrating a part of the structure of the heat sink 10 of a semiconductor device according to embodiment 4. As shown in Fig. 7 and Fig. As illustrated in Figure 8, the semiconductor device according to embodiment 4 differs from the semiconductor device 101 according to embodiment 1 and the semiconductor device 103 according to embodiment 3 in the structure of the heat sink 10.

[0043] The heat sink 10 according to embodiment 4 comprises a first region 11 and a second region 12. The first region 11 consists of AlSiC. The second region 12 consists of Al. The semiconductor element 40 is arranged such that, in plan view, it overlaps the first region 11. The screw hole 20 and the position-defining subregion 10A are formed in the second region 12.

[0044] The housing 70 is attached to the heat sink 10 by the self-tapping screw 21, which is screwed into the screw hole 20. The material of the self-tapping screw 21 is harder than Al, meaning that the material of the heat sink 10 in the second area 12 is harder.

[0045] The first or second manufacturing process described in embodiment 1 is applicable for the fabrication of a semiconductor device. The first manufacturing process is easily applicable by using Al as the material of the heat sink 10 in the second region 12, which is softer than a general material of the cutting screw 21.

[0046] Since the semiconductor element 40 in the semiconductor device according to embodiment 4 is arranged above the first region 11, which consists of AlSiC, the heat dissipation properties are improved. Because the screw hole 20 is located in the second region 12, which consists of Al, a material softer than AlSiC, forming and securing the screw hole 20 using the self-tapping screw 21 is simple. In other words, the heat sink 10, in which the screw hole 20 is formed beforehand, does not need to be prepared before the screw hole 20 is secured using the self-tapping screw 21. Thus, the machining effort required for manufacturing the heat sink 10 is reduced. <Ausführungsform 5>

[0047] Fig. Figure 9 is a cross-sectional view illustrating the structure of a semiconductor device 105 according to embodiment 5. The semiconductor device 105 according to embodiment 5 differs from the semiconductor device 101 according to embodiment 1 in the structure of the heat sink 10 and the housing 70.

[0048] The housing 70 is arranged in contact with the side surface 10B, in which an inner surface 70A of the frame of the housing 70 is formed as the perimeter of the heat sink 10. For example, the housing 70 can be in contact with the entire side surface 10B, which is at least one of the four side surfaces of the heat sink 10.

[0049] The housing 70 is attached to the heat sink 10 by means of a self-tapping screw 21, which is screwed into the screw hole 20 from an external surface 70B of the frame of the housing 70. The end of the self-tapping screw 21 penetrates the housing 70 from the external surface 70B of the frame of the housing 70. The end of the self-tapping screw 70 is located within the screw hole 20 of the heat sink 10. The end of the self-tapping screw 21 is not exposed to the interior of the housing 70, which is filled with the sealant 80.

[0050] The first manufacturing process or the second manufacturing process described in embodiment 1 are usable for a manufacturing process of the semiconductor device 105.

[0051] This embodiment 5 produces the same advantages as that according to the previously described embodiment 1. <Ausführungsform 6>

[0052] Fig.Figure 10 is a cross-sectional view illustrating the structure of a semiconductor device 106 according to embodiment 6. Embodiment 6 is a particularly preferred embodiment when the second manufacturing process described in embodiment 1 is used.

[0053] The screw hole 20 has a hollow section at its deepest point. For example, the end of the self-tapping screw 21 and a gap at the deepest point of the screw hole 20, which is formed beforehand in the heat sink 10, form the hollow section.

[0054] The heat sink 10 contains chips or shavings 20B inside the screw hole 20, which consist of the same material as that of the heat sink 10 or the housing 70. For example, the shavings 70B are enclosed in the hollow section in the deepest part of the screw hole 20. These shavings 20B are generated during the manufacturing process of the semiconductor device 106.

[0055] The second manufacturing process described in embodiment 1 is used for a manufacturing process of the semiconductor device 106. The screw hole 20 has an opening in the lateral surface 10B of the heat sink 10.

[0056] Next, the self-tapping screw 21 is screwed into the screw hole 20, with the projection 71 of the housing 70 aligning with the position-defining section 10A. As the self-tapping screw 21 is screwed in, materials from the heat sink 10 and the projection 71 of the housing 70 are removed, producing chips of the same material as the housing 70 and chips of the same material as the heat sink 10.

[0057] The end of the cutting screw 21 does not reach the deepest part of the screw hole 20. Thus, the chips 20B produced in the process of forming the screw hole 20 are enclosed in the hollow part at the end of the screw hole 20.

[0058] The end of the self-tapping screw 21 fits inside the heat sink 10 and is not exposed to the interior of the housing 70, which is filled with the sealant 80. Furthermore, since the screw hole 20 is not a through hole, the chips 20B generated during the process of forming the screw hole 20 cannot escape. Because the potential of the self-tapping screw 21 and the heat sink 10 is ground (GND), a partial discharge caused by the chips 20B is prevented.

[0059] Although this revelation is described in detail, the preceding description is illustrative in all aspects and does not limit the revelation. Thus, numerous modifications, which have not yet been illustrated by example, are conceived.

[0060] Embodiments of the present disclosure can be freely combined and suitably modified or omitted. EXPLANATION OF REFERENCE SYMBOLS

[0061] 10 Heat sink, 10A Position-defining sub-area, 10B Side surface, 11 First area, 12 Second area, 20 Screw hole, 20B Chip, 21 Cutting screw, 30 Insulating substrate, 31 Insulating layer, 32 Circuit surface structure, 33 Heat dissipation surface structure, 40 Semiconductor element, 50 Terminal, 60 Metal wire, 70 Housing, 70A Inner surface, 70B External surface, 71 Protrusion, 72 Defective sub-area, 80 Sealing agent, 91 Bonding material, 92 Bonding material, 93 Silicone adhesive, 101 to 103 Semiconductor device, 105, 106 Semiconductor device. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] JP 2006-32392

[0003]

Claims

[1] Semiconductor device comprising: a heat sink that holds a semiconductor element; and a housing that contains the semiconductor element held above the heat sink, wherein a first screw hole is formed in a lateral surface of the heat sink, a second screw hole is formed in conjunction with the first screw hole in the housing and The housing is attached to the heat sink by a screw screwed into the first and second screw holes. [2] Semiconductor device according to claim 1, wherein the screw is a self-tapping screw. [3] Semiconductor device according to claim 1 or 2, wherein the heat sink has a position-defining sub-area that defines a position of the housing in the heat sink, the position-defining sub-area has a through-hole that penetrates an upper surface and a lower surface of the heat sink, or a cut-out sub-area that is arranged in a circumference of the heat sink, and the housing fits together with the position-defining sub-area. [4] Semiconductor device according to any one of claims 1 to 3, wherein the heat sink is made of Cu, Al or AlSiC. [5] Semiconductor device according to any one of claims 1 to 3, wherein the heat sink comprises a first area made of AlSiC and a second area made of Al, the first screw hole is formed in the second area and the screw is made of a material that is harder than Al and with which the first screw hole can be threaded when the screw is screwed into the first screw hole. [6] Semiconductor device according to any one of claims 1 to 5, wherein the housing has a frame shape which, in plan view, encloses an upper surface of the heat sink, and The housing is attached to the side surface of the heat sink by means of a screw inserted from an external surface of the frame shape into the first and second screw holes. [7] Semiconductor device according to any one of claims 1 to 6, wherein the heat sink has a space which can receive chips of the heat sink or of the housing, at a deepest part of the first screw hole. [8] Semiconductor device according to any one of claims 1 to 7, wherein the semiconductor element is a power semiconductor element consisting of a wide bandgap semiconductor. [9] Semiconductor device according to any one of claims 1 to 8, wherein one end of the screw is located inside the screw hole formed in the heat sink.

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