Semiconductor device

Abstract

The present disclosure provides a semiconductor device capable of reducing partial discharge that may occur between a screw that fixes a case to a heat dissipation plate and a high-voltage portion, and capable of improving reliability. The semiconductor device includes a heat dissipation plate and a housing. The heat dissipation plate holds the semiconductor element. The housing accommodates the semiconductor element held above the heat dissipation plate. A first threaded hole is formed in the side face of the heat dissipation plate. And a second threaded hole communicated with the first threaded hole is formed in the shell. The housing is fastened to the heat dissipation plate by a screw screwed into the first threaded hole and the second threaded hole.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor device. Background Art

[0002] A power module that includes a semiconductor device for power control has a structure in which a heat sink and a housing are fastened together by screws. For example, in the semiconductor device disclosed in Patent Document 1, metal self-tapping screws are used to fasten the resin housing from below the through-holes in the heat sink toward above the threaded holes. This secures the resin housing to the heat sink. 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] In the structure disclosed in Patent Document 1, if the insulation performance of the resin case around the hole through which the tapping screw passes is insufficient, local discharge (hereinafter referred to as partial discharge) may occur between the high voltage portion enclosed inside the resin case and the tapping screw.

[0005] The present disclosure aims to solve the above-mentioned technical problems and has an object to provide a semiconductor device that can reduce partial discharge that may occur between screws that fix a housing to a heat sink and a high-voltage portion and improve reliability. Technical solutions used to solve technical problems

[0006] The semiconductor device disclosed herein includes a heat sink and a housing. The heat sink holds a semiconductor element. The housing accommodates the semiconductor element held above the heat sink. A first threaded hole is provided on a side of the heat sink. A second threaded hole is provided in the housing, communicating with the first threaded hole. The housing is secured to the heat sink by screws threaded into the first and second threaded holes. Effects of the Invention

[0007] According to the present disclosure, there is provided a semiconductor device capable of reducing partial discharge that may occur between a screw fixing a housing to a heat dissipation plate and a high voltage portion in a power module and capable of improving reliability.

[0008] The objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a cross-sectional view showing the structure of the semiconductor device according to the first embodiment. Figure 2This is a cross-sectional view showing a portion of the structure of a semiconductor device according to the second embodiment. Figure 3 It is a plan view showing a part of the structure of a heat sink of a semiconductor device. Figure 4 This is a cross-sectional view showing the structure of a semiconductor device according to a third embodiment. Figure 5 is a cross-sectional view showing a portion of the structure of a semiconductor device. Figure 6 It is a plan view showing a part of the structure of a heat sink of a semiconductor device. Figure 7 This is a plan view showing a portion of the structure of a heat sink of a semiconductor device according to a fourth embodiment. Figure 8 This is a plan view showing a portion of the structure of a heat sink of a semiconductor device according to a fourth embodiment. Figure 9 This is a cross-sectional view showing the structure of a semiconductor device according to a fifth embodiment. Figure 10 This is a cross-sectional view showing the structure of a semiconductor device according to a sixth embodiment. DETAILED DESCRIPTION

[0010] <Implementation Method 1> Figure 1 1 is a cross-sectional view showing the structure of a semiconductor device 101 according to Embodiment 1. The semiconductor device 101 includes 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 material 80 .

[0011] The heat sink 10 holds the semiconductor element 40 provided on the insulating substrate 30. The heat sink 10 is formed of a metal such as Cu or Al, or an AlSiC composite material. The heat sink 10 includes a position regulating portion 10A.

[0012] Position regulating portion 10A regulates the position of housing 70 relative to heat sink 10. Position regulating portion 10A in Embodiment 1 includes through holes penetrating upper and lower surfaces of heat sink 10.

[0013] The threaded holes 20 are provided on the side surface 10B of the heat sink 10. The threaded holes 20 extend inward from the side surface 10B of the heat sink 10. The threaded holes 20 are holes used to fasten the housing 70 to the heat sink 10 using self-tapping screws 21. The threaded holes 20 extend through the protrusion 71 of the housing 70 that engages with the positioning portion 10A. In other words, the threaded holes 20 include a first threaded hole provided on the side surface 10B of the heat sink 10 and a second threaded hole provided in the housing 70 to communicate with the first threaded hole.

[0014] The insulating substrate 30 includes an insulating layer 31, a circuit surface pattern 32, and a heat dissipation surface pattern 33. The insulating layer 31 is insulating and is formed, for example, from ceramic. Examples of ceramics include AlN, Si3N4, and Al2O3. The circuit surface pattern 32 is provided on the upper surface of the insulating layer 31. The heat dissipation surface pattern 33 is provided on the lower surface of the insulating layer 31. The circuit surface pattern 32 and the heat dissipation surface pattern 33 are formed from metals such as Cu and Al. The heat dissipation surface pattern 33 is bonded to the heat dissipation plate 10 via a bonding material 91 such as solder, brazing material, or sintered material. In other words, the insulating substrate 30 is held by the heat dissipation plate 10.

[0015] The semiconductor element 40 is bonded to the circuit surface pattern 32 of the insulating substrate 30 via a bonding material 92. The bonding material 92 is conductive. The bonding material 92 is, for example, solder. The semiconductor element 40 is also called a semiconductor chip. The semiconductor element 40 is formed, for example, by a semiconductor such as Si or a so-called wide-bandgap semiconductor such as SiC, GaN, Ga2O3, or diamond. The semiconductor element 40 is a power semiconductor element, a control IC (integrated circuit) for controlling the power semiconductor element, or the like. The semiconductor element 40 is, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a Schottky barrier diode (Japanese: Schottky barrier diode), or the like. Alternatively, the semiconductor element 40 may be an RC-IGBT (reverse-conducting IGBT) in which an IGBT and a reflux diode are formed in one semiconductor substrate.

[0016] The terminal 50 is a conductive body configured to be connected to an external circuit provided outside the semiconductor device 101. The terminal 50 is a metal frame formed by processing a flat plate made of metal such as Cu into a predetermined shape. Figure 1 In the embodiment, the terminal 50 is shown as a component separate from the housing 70, but it can also be integrally mounted to the housing 70. The terminal 50 includes a first end and a second end. The first end corresponds to Figure 1 The lower end portion is bonded to the circuit surface pattern 32 of the insulating substrate 30. The first end can be bonded to the electrode (not shown) of the semiconductor element 40 via a wire (not shown). The circuit surface pattern 32 and the first end of the terminal 50, or the electrode of the semiconductor element 40 and the first end of the terminal 50 are bonded by ultrasonic bonding or soldering. The second end corresponds to Figure 1 The upper end of the second end is led out to the outside of the housing 70 and the sealing material 80. The second end can be connected to an external circuit.

[0017] The metal wire 60 connects, for example, an electrode of the semiconductor element 40 , a first end of the terminal 50 , and two components in the circuit surface pattern 32 of the insulating substrate 30 .

[0018] The housing 70 has a hollow frame shape. Figure 1 While the right side of the housing 70 is omitted in the cross-sectional view, the housing 70 has a rectangular frame when viewed from above. The housing 70 is mounted on the heat sink 10, surrounding the upper surface of the heat sink 10. The housing 70 houses the insulating substrate 30, semiconductor element 40, and other components within the enclosed interior space, i.e., within the frame. The housing 70 is formed, for example, from a resin, such as PPS (polyphenylene sulfide).

[0019] The housing 70 is fitted into the position defining portion 10A of the heat sink 10 . The housing 70 of the first embodiment includes a protrusion 71 that is fitted into the through hole of the heat sink 10 constituting the position defining portion 10A. The protrusion 71 is provided on the lower surface of the housing 70 .

[0020] The housing 70 is secured to the heat sink 10 by self-tapping screws 21 threaded into the threaded holes 20 of the heat sink 10. The tip of the self-tapping screw 21 extends from the outside of the housing 70 through the protrusion 71 of the housing 70. The tip of the self-tapping screw 21 is located inside the threaded holes 20 provided in the heat sink 10. In other words, the tip of the self-tapping screw 21 neither protrudes into the interior space of the housing 70, which is filled with the sealing material 80, nor remains within the housing 70.

[0021] Furthermore, the housing 70 is bonded to the heat sink 10 by the silicone adhesive 93. Thus, the housing 70 is joined to the heat sink 10 by the silicone adhesive 93 and the self-tapping screws 21.

[0022] The sealing material 80 fills the internal space surrounded by the frame of the housing 70. The sealing material 80 seals the upper surface of the heat sink 10, the insulating substrate 30, the semiconductor element 40, a portion of the terminal 50, and the metal wire 60. The sealing material 80 is a curing material such as silicone resin or epoxy resin.

[0023] In the first manufacturing process of semiconductor device 101, as self-tapping screws 21 are screwed into heat sink 10, the material of heat sink 10 is cut, forming threaded holes 20 (first threaded holes) in heat sink 10. Similarly, as self-tapping screws 21 are screwed into housing 70, the resin of housing 70 is cut, forming threaded holes 20 (second threaded holes) in protrusion 71 of housing 70. In this first manufacturing process, the material of self-tapping screws 21 needs to be harder than that of heat sink 10 and housing 70.

[0024] On the other hand, in the second manufacturing process of the semiconductor device 101, the threaded hole 20 is pre-formed and the self-tapping screw 21 is screwed into it. The thread cutting of the threaded hole 20 can be pre-formed, but it does not need to be pre-formed if the material of the self-tapping screw 21 is harder than the material of the heat sink 10 and the housing 70. In the former case, a conventional screw can be used instead of the self-tapping screw 21. In addition, the material of the self-tapping screw 21 is generally harder than the material of the housing 70, so the threaded hole 20 (second threaded hole) in the protrusion 71 of the housing 70 does not need to be pre-formed. Figure 1 The second manufacturing process is shown.

[0025] After the housing 70 and the heat sink 10 are bonded to each other, a liquid sealing material 80 is injected into the space inside the housing 70. The sealing material 80 is then solidified through a curing process.

[0026] In the above structure, the tip of the self-tapping screw 21 does not protrude into the interior space enclosed by the housing 70. Furthermore, the tip of the self-tapping screw 21 is not located within the resin portion forming the housing 70, i.e., the interior of the housing. The tip of the self-tapping screw 21 remains within the heat sink 10. Therefore, even if defective portions 72 such as pores or cracks exist in the resin portion of the housing 70, localized discharge between the high-voltage portion of the semiconductor device 101 (power module) and the self-tapping screw 21 is reduced. This prevents a reduction in the reliability of the semiconductor device 101 even if the insulation performance of the housing 70 is partially insufficient.

[0027] In summary, the semiconductor device 101 of the first embodiment includes a heat sink 10 and a housing 70. The heat sink 10 holds the semiconductor element 40. The housing 70 accommodates the semiconductor element 40 held above the heat sink 10. A first threaded hole 20 is provided on the side surface 10B of the heat sink 10. The housing 70 is provided with a second threaded hole 20 that communicates with the first threaded hole 20. The housing 70 is fastened to the heat sink 10 by screws threaded into the first and second threaded holes 20. The screws in the first embodiment are self-tapping screws 21.

[0028] The semiconductor device 101 described above reduces partial discharge that may occur between the screws that fix the housing 70 to the heat sink 10 and the high-voltage portion. As a result, a semiconductor device 101 with high reliability can be obtained.

[0029] Furthermore, Patent Document 1 discloses a structure for reducing partial discharge in which the longitudinal threaded holes provided in the housing are through-holes, the upper portion of which is filled with a sealing material. However, in this structure, during the manufacturing process, the uncured sealing material may leak out of the heat sink through the gap between the through-holes and the self-tapping screws. This leakage of sealing material degrades the manufacturing yield of the semiconductor device.

[0030] In the semiconductor device 101 of the first embodiment, no through hole is provided that penetrates the interior space and the exterior of the housing 70. The semiconductor device 101 reduces partial discharge without causing the sealing material 80 to leak to the outside.

[0031] Furthermore, by fitting the housing 70 with the positioning portion 10A of the heat sink 10, positioning the housing 70 is facilitated during the manufacturing process when joining the heat sink 10 and the housing 70. Consequently, a jig for securing the position of the heat sink 10 and the housing 70 is no longer necessary, thereby improving workability.

[0032] Semiconductor device 101 includes a power semiconductor element formed of a wide bandgap semiconductor as semiconductor element 40. Improved reliability of semiconductor device 101 enables high-temperature operation, higher withstand voltage, and lower loss in power conversion devices such as inverters in which semiconductor device 101 is mounted.

[0033] <Implementation Method 2> Figure 2 This is a cross-sectional view showing a portion of the structure of the semiconductor device 102 according to the second embodiment. Figure 3 It is a plan view showing a portion of the structure of the heat sink 10 of the semiconductor device 102 .

[0034] Semiconductor device 102 of Embodiment 2 is a semiconductor device manufactured using the second manufacturing process described in Embodiment 1. Screw holes 20 (first screw holes) and position-regulating portions 10A are pre-formed in heat sink 10. Reference numeral 10C denotes a screw hole for securing heat sink 10 to an object on which semiconductor device 102 is to be mounted.

[0035] As in Embodiment 1, housing 70 is fastened to heat sink 10 by self-tapping screws 21 screwed into threaded holes 20 . The tips of self-tapping screws 21 remain inside heat sink 10 and do not protrude into the interior space of housing 70 filled with sealing material 80 .

[0036] In this second embodiment, the same effects as those of the above-mentioned first embodiment can be obtained.

[0037] <Implementation Method 3> Figure 4This is a cross-sectional view showing the structure of a semiconductor device 103 according to a third embodiment. Figure 5 is a cross-sectional view showing a portion of the structure of the semiconductor device 103 . Figure 6 This is a plan view showing a portion of the structure of heat sink 10 of semiconductor device 103. Semiconductor device 103 of the third embodiment differs from semiconductor device 101 of the first embodiment in the structures of positioning portion 10A of heat sink 10 and housing 70 fitted therewith.

[0038] The position regulating portion 10A includes a notch provided at the outer edge of the heat dissipating portion 10. The notch is provided so as to overlap with the opening of the screw hole 20 on the side surface 10B of the heat dissipating plate 10B.

[0039] The housing 70 includes a protrusion 71 that fits into the cutout portion. The housing 70 is fastened to the heat sink 10 by self-tapping screws 21 screwed into the threaded holes 20.

[0040] The tip of the self-tapping screw 21 passes through the protrusion 71 of the housing 70 from the outside. The tip of the self-tapping screw 21 remains inside the heat sink 10 and does not protrude into the interior space of the housing 70 filled with the sealing material 80.

[0041] In the manufacturing process of the semiconductor device 103 , the first manufacturing process or the second manufacturing process described in the first embodiment can be applied.

[0042] As described above, the engagement of the housing 70 with the positioning portion 10A of the heat sink 10 facilitates positioning of the housing 70 during the manufacturing process when joining the heat sink 10 to the housing 70. Consequently, a jig for securing the position of the heat sink 10 and the housing 70 is no longer necessary, improving workability.

[0043] <Implementation Method 4> Figure 7 and Figure 8 FIG. 1 is a top view showing a portion of the structure of the heat sink 10 of the semiconductor device according to the fourth embodiment. Figure 7 and Figure 8 As shown respectively, the semiconductor device of the fourth embodiment is different from the semiconductor device 101 of the first embodiment and the semiconductor device 103 of the third embodiment in the structure of the heat sink 10 .

[0044] The heat sink 10 of the fourth embodiment includes a first region 11 and a second region 12. The first region 11 is formed of AlSiC. The second region 12 is formed of Al. The semiconductor element 40 is arranged so as to overlap with the first region 11 in a plan view. The screw hole 20 and the position-regulating portion 10A are provided in the second region 12.

[0045] The housing 70 is fastened to the heat sink 10 by self-tapping screws 21 screwed into the threaded holes 20. The material of the self-tapping screws 21 is harder than Al, that is, the material of the second region 12 of the heat sink 10.

[0046] The semiconductor device manufacturing process can apply the first manufacturing process or the second manufacturing process described in Embodiment 1. Since the material of the second region 12 of the heat sink 10 is Al, which is softer than the material of the general tapping screws 21 , the first manufacturing process can be easily applied.

[0047] In the semiconductor device of Embodiment 4, semiconductor element 40 is located above first region 11 formed of AlSiC, thereby improving heat dissipation. Screw holes 20 are located in second region 12 formed of Al, which is softer than AlSiC. This makes it easier to form and secure screws 21 with screw holes 20. In other words, there is no need to prepare heat sink 10 with screw holes 20 pre-formed before securing with self-tapping screws 21. This reduces the number of processing steps required to manufacture heat sink 10.

[0048] <Implementation Method 5> Figure 9 1 is a cross-sectional view showing 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 structures of a heat sink 10 and a housing 70 .

[0049] The housing 70 is provided so that the inner surface 70A of the housing 70 contacts the side surface 10B forming the outer edge of the heat sink 10. For example, the housing 70 may contact the entire surface of at least one side surface 10B of the four side surfaces of the heat sink 10.

[0050] The housing 70 is fastened to the heat sink 10 by self-tapping screws 21 screwed into the threaded holes 20 from the outer surface 70B of the housing 70. The tip of the self-tapping screw 21 penetrates the housing 70 from the outer surface 70B of the housing 70. The tip of the self-tapping screw 21 is located inside the threaded holes 20 of the heat sink 10. The tip of the self-tapping screw 21 does not protrude into the interior space of the housing 70, which is filled with the sealing material 80.

[0051] In the manufacturing process of the semiconductor device 105 , the first manufacturing process or the second manufacturing process described in the first embodiment can be applied.

[0052] In this fifth embodiment, the same effects as those of the aforementioned first embodiment can be obtained.

[0053] <Implementation Method 6> Figure 101 is a cross-sectional view showing the structure of a semiconductor device 106 according to Embodiment 6. Embodiment 6 is particularly preferred when the second manufacturing process described in Embodiment 1 is applied.

[0054] The screw hole 20 includes a hollow portion at its innermost portion. The hollow portion is formed by, for example, the tip of the self-tapping screw 21 and a blank portion formed in advance in the innermost portion of the screw hole 20 of the heat sink 10 .

[0055] Heat sink 10 includes shavings 20B made of the same material as heat sink 10 or housing 70 inside screw hole 20. For example, shavings 20B are sealed in the innermost cavity of screw hole 20. Shavings 20B are generated during the manufacturing process of semiconductor device 106.

[0056] The second manufacturing process described in Embodiment 1 is applied to the manufacturing process of the semiconductor device 106 . The screw hole 20 has an opening in the side surface 10B of the heat dissipation plate 10 .

[0057] Next, with the protrusion 71 of the housing 70 engaged with the position-regulating portion 10A, the tapping screw 21 is screwed into the threaded hole 20. As the tapping screw 21 is screwed in, material of the heat sink 10 and the protrusion 71 of the housing 70 is removed, resulting in shavings made of the same material as the housing 70 and shavings made of the same material as the heat sink 10.

[0058] The tip of the self-tapping screw 21 does not reach the innermost part of the threaded hole 20 . Therefore, the shavings 20B generated during the formation of the threaded hole 20 are sealed in the hollow portion at the tip of the threaded hole 20 .

[0059] The tip of the tapping screw 21 remains within the heat sink 10 and does not protrude into the interior space of the housing 70, which is filled with sealing material 80. Furthermore, since the threaded hole 20 is not a through hole, shavings 20B generated during the formation of the threaded hole 20 are not scattered to the outside. The potential of the tapping screw 21 and the heat sink 10 is GND (ground), thus preventing partial discharge caused by these shavings 20B.

[0060] While the present disclosure has been described in detail, the above description is in all aspects illustrative and not restrictive, and it will be understood that numerous modifications not shown are conceivable.

[0061] The present disclosure allows for free combination of various embodiments or for appropriate modification or omission of various embodiments. Explanation of symbols

[0062] 10 heat sink; 10A position defining portion; 10B side surface; 11 first area; 12 second area; 20 threaded hole; 20B shavings; 21 tapping screw; 30 insulating substrate; 31 insulating layer; 32 circuit surface pattern; 33 heat dissipation surface pattern; 40 semiconductor element; 50 terminal; 60 metal wire; 70 housing; 70A inner surface; 70B outer surface; 71 protrusion; 72 defective portion; 80 sealing material; 90 bonding material; 92 bonding material; 93 silicone adhesive; 101 to 103 semiconductor devices; 105 to 106 semiconductor devices.

Claims

1. A semiconductor device, characterized in that: include: a heat sink for holding the semiconductor element; as well as a housing for accommodating the semiconductor element held above the heat sink; A first threaded hole is provided on the side of the heat dissipation plate. The housing is provided with a second threaded hole communicating with the first threaded hole. The housing is fastened to the heat dissipation plate by screws screwed into the first threaded holes and the second threaded holes.

2. The semiconductor device according to claim 1, wherein The screws are self-tapping screws.

3. The semiconductor device according to claim 1 or 2, wherein: The heat sink includes a position regulating portion that regulates the position of the housing relative to the heat sink. The position determining portion includes a through hole penetrating the upper surface and the lower surface of the heat dissipation plate or a notch provided on the outer edge of the heat dissipation plate. The housing is fitted into the position defining portion.

4. The semiconductor device according to any one of claims 1 to 3, wherein The heat sink is made of Cu, Al or AlSiC.

5. The semiconductor device according to any one of claims 1 to 3, wherein The heat sink includes a first region formed of AlSiC and a second region formed of Al, The first threaded hole is provided in the second area, The screw is made of a material that is harder than Al and is capable of cutting threads in the first threaded hole when screwed in.

6. The semiconductor device according to any one of claims 1 to 5, wherein: The housing has a frame shape surrounding the upper surface of the heat sink in a plan view. The housing is fastened to the side surface of the heat dissipation plate by the screws screwed into the first threaded holes and the second threaded holes from the outer surface of the frame shape.

7. The semiconductor device according to any one of claims 1 to 6, wherein: The heat sink includes a space at the innermost portion of the first threaded hole that can accommodate shavings of the heat sink or the housing.

8. The semiconductor device according to any one of claims 1 to 7, wherein: The semiconductor element is a power semiconductor element formed of a wide bandgap semiconductor.

9. The semiconductor device according to any one of claims 1 to 8, wherein: The front end of the screw is located inside the threaded hole provided in the heat dissipation plate.

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