Semiconductor device and fuel cell system equipped therewith

Abstract

This technology provides a way to prevent water from coming into contact with electronic components while avoiding the use of expensive sealants. [Solution] The semiconductor device 10 of this disclosure comprises a substrate 20, an electronic component 30 including a power semiconductor element mounted on the substrate 20, a heat sink 40 positioned on the opposite side of the substrate 20 from the side of the electronic component 30 that the substrate 20 is located relative to the electronic component 30 and cooling the electronic component 30, a case 50 fixed to the substrate 20 and surrounding the electronic component 30, and a heat dissipation sheet 60 positioned between the electronic component 30 and the heat sink 40, extending outward from the surface 30p of the electronic component 30 facing the heat sink 40 and in contact with the open end 50a of the case 50.

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor device and a fuel cell system including the same. [Background Art]

[0002] Power modules such as power MOSFET modules and IGBT modules are cooled by a heat sink. A heat dissipation sheet is used to bring the power module and the heat sink into thermal contact with each other. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 8-46093 [Patent Document 2] Japanese Unexamined Patent Publication No. 2001-332670 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In order to prevent water such as condensed water from coming into contact with the power module, a structure has been proposed in which the power module is covered with a case, and a water intrusion path into the case is sealed with a silicone caulking material.

[0005] However, siloxane contained in silicone caulking materials volatilizes to form an insulating coating, which causes problems such as poor ignition of reformer burners, sensitization of combustible gas sensors, poisoning of fuel cell stacks, and poor relay contact failure in control circuits. Therefore, semiconductor devices used in fuel cell systems are required to use expensive siloxane-free caulking materials. In addition, since processing of siloxane-free caulking materials is difficult, the use of siloxane-free caulking materials increases the costs of the caulking process and the repair process. The repair process refers to a process of removing the power module from the heat sink to investigate the cause of a failure when a failure occurs in the semiconductor device.

[0006] In light of the above circumstances, this disclosure provides a technology for preventing water from coming into contact with electronic components while avoiding the use of expensive caulking materials. [Means for solving the problem]

[0007] This disclosure is, circuit board and Electronic components including power semiconductor elements mounted on the substrate, A heat sink is positioned on the opposite side from the side where the substrate is located relative to the aforementioned electronic component, and is used to cool the aforementioned electronic component. A case fixed to the aforementioned substrate and surrounding the aforementioned electronic component, A heat dissipation sheet is disposed between the electronic component and the heat sink, extending outward from the surface of the electronic component facing the heat sink and in contact with the open end of the case, We provide a semiconductor device equipped with the following features. [Effects of the Invention]

[0008] The semiconductor device described herein makes it possible to prevent water from coming into contact with electronic components while avoiding the use of expensive caulking materials. [Brief explanation of the drawing]

[0009] [Figure 1] Cross-sectional view of the semiconductor device of the first embodiment [Figure 2] Configuration diagram of the fuel cell system of the second embodiment [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted.

[0011] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0012] (First Embodiment) Figure 1 is a cross-sectional view of a semiconductor device according to the first embodiment. The semiconductor device 10 comprises a substrate 20, electronic components 30, a heat sink 40, a case 50, and a heat dissipation sheet 60. The electronic components 30 are fixed to the heat sink 40 by fasteners such as screws 32. The substrate 20 and the case 50 are fixed to the heat sink 40 via the electronic components 30.

[0013] The substrate 20 is a circuit board. The substrate 20 is provided with through holes for receiving terminals 30a of electronic components 30. The substrate 20 has a first surface 20p and a second surface 20q. The first surface 20p is the surface facing the heat sink 40. The second surface 20q is the surface opposite the first surface 20p. The second surface 20q of the substrate 20 is sealed with potting material 22. The substrate 20 and the case 50 are fixed to each other via the potting material 22. The potting material 22 is a resin material such as polyurethane.

[0014] The electronic component 30 is mounted on the circuit board 20. Specifically, terminal 30a of the electronic component 30 is soldered to the circuit board 20. This electrically connects the electronic component 30 to the circuit on the circuit board 20. The electronic component 30 includes at least one power semiconductor element. Examples of power semiconductor elements include power MOSFETs, IGBTs, thyristors, and bipolar transistors. The electronic component 30 is either a power module containing multiple power semiconductor elements or a discrete component containing only one power semiconductor element. Preferably, the electronic component 30 is a power module containing multiple power semiconductor elements.

[0015] The surface 30p of the electronic component 30 may be the surface of a heat diffusion plate such as a Cu plate. The surface 30p is the surface facing the heat sink 40.

[0016] The heat sink 40 is arranged on the side opposite to the side where the substrate 20 is located with the electronic component 30 as a reference, and cools the electronic component 30. The heat sink 40 is made of a metal material such as aluminum.

[0017] The case 50 is fixed to the substrate 20 and surrounds the electronic component 30. The case 50 has a shape of a frame surrounding the electronic component 30. An inner surface of the case 50 faces a side surface of the electronic component 30. The case 50 is formed of a resin material such as ABS resin.

[0018] The heat dissipation sheet 60 has a role of conducting heat from the electronic component 30 to the heat sink 40. The heat dissipation sheet 60 is arranged between the electronic component 30 and the heat sink 40, extends outward from a surface 30p of the electronic component 30, and is in contact with an opening end 50a of the case 50. The heat dissipation sheet 60 is affixed to the heat sink 40 with an adhesive.

[0019] According to the present embodiment, the heat dissipation sheet 60 extends outward from the surface 30p of the electronic component 30. With such a configuration, a gap is less likely to be formed between the electronic component 30 and the heat sink 40. Therefore, even if moisture enters the inside of the case 50 through a slight gap between the heat sink 40 and the case 50 as a result of not using a silicone caulking material or a siloxane-free caulking material, water is less likely to enter between the electronic component 30 and the heat sink 40. Therefore, it is possible to prevent defects such as dielectric breakdown from occurring due to water. The heat dissipation sheet 60 also serves as a sealing material. Since it is not necessary to use a silicone caulking material or a siloxane-free caulking material, the caulking process and the repairing process can be eliminated.

[0020] In the present embodiment, the entire surface 30p of the electronic component 30 is covered with the heat dissipation sheet 60. The area of the heat dissipation sheet 60 is larger than the area of the surface 30p of the electronic component 30. With such a configuration, the effect of preventing water from entering between the electronic component 30 and the heat sink 40 is enhanced. In the present embodiment, the entire electronic component 30 is accommodated inside an outer edge 60e of the heat dissipation sheet 60.

[0021] The heat dissipation sheet 60 is formed of a first resin material and has elasticity. According to this configuration, even if the surface 30p of the electronic component 30 has irregularities, the elasticity of the heat dissipation sheet 60 allows the electronic component 30 to be in close contact with the heat dissipation sheet 60. As a result, water can be prevented from penetrating between the electronic component 30 and the heat sink 40. The elasticity of the heat dissipation sheet 60 may be rubber elasticity.

[0022] The first resin material constituting the heat dissipation sheet 60 may be a siloxane-free resin material. Therefore, it is possible to avoid defects such as contact failure caused by volatilization of siloxane. Examples of the first resin material include thermoplastic resins such as acrylic resin, polyamide resin, polyolefin resin, polycarbonate resin, and polyester resin. Acrylic resin is recommended because it has excellent thermal conductivity and excellent elasticity. The first resin material may contain fillers such as metal particles and boron nitride particles.

[0023] A force in a direction approaching the heat sink 40 is applied to the case 50 via the substrate 20 and the electronic component 30. As a result, the opening end 50a of the case 50 bites into the heat dissipation sheet 60. According to this configuration, water can be prevented from penetrating into the interior of the case 50.

[0024] In the present embodiment, the semiconductor device 10 further includes a sealing material 70. The sealing material 70 is adhered to the heat sink 40 with an adhesive. The sealing material 70 is a sheet-shaped member having approximately the same thickness as the heat dissipation sheet 60.

[0025] The opening end 50a of the case 50 includes a first opening end 51 and a second opening end 52. The first opening end 51 is an opening end located on the outer peripheral side of the case 50. The second opening end 52 is an opening end located on the inner peripheral side of the case 50. The second opening end 52 is in contact with the heat dissipation sheet 60. Since the second opening end 52 functions as a rib, the strength and rigidity of the case 50 are improved.

[0026] The second open end 52 branches off from the first open end 51. In the cross-section shown in Figure 1, that is, the cross-section perpendicular to the surface 40p of the heat sink 40, the second open end 52 is the portion that branches off from the first open end 51 in an L-shape. A space 53 is formed between the first open end 51 and the second open end 52. With this configuration, the second open end 52 can be brought into contact with the heat dissipation sheet 60. The second open end 52 is embedded in the heat dissipation sheet 60.

[0027] The sealing material 70 is positioned between the first open end 51 of the case 50 and the heat sink 40. In a direction parallel to the surface 40p of the heat sink 40, the outer edge 60e of the heat dissipation sheet 60 is located between the tip surface of the first open end 51 and the tip surface of the second open end 52. Similarly, the inner edge 70f of the sealing material 70 is located between the tip surface of the first open end 51 and the tip surface of the second open end 52. The first open end 51 of the case 50 and the sealing material 70 form a first sealing structure. The second open end 52 of the case 50 and the heat dissipation sheet 60 form a second sealing structure. The first sealing structure prevents moisture from entering the interior of the case 50. The second sealing structure prevents water from entering between the electronic component 30 and the heat sink 40. According to this embodiment, the area around the electronic component 30 can be double-sealed.

[0028] The outer edge 60e of the heat dissipation sheet 60 is separated from the inner edge 70f of the sealing material 70. However, the outer edge 60e of the heat dissipation sheet 60 may be in contact with the inner edge 70f of the sealing material 70.

[0029] The sealing material 70 is made of a second resin material and is elastic. With this configuration, the elasticity of the sealing material 70 allows the first open end 51 of the case 50 to adhere tightly to the sealing material 70. As a result, water can be prevented from entering the inside of the case 50.

[0030] In this embodiment, a force is applied to the case 50 in a direction that moves it toward the heat sink 40 via the substrate 20 and the electronic components 30. As a result, the first open end 51 bites into the sealing material 70. With this configuration, water can be prevented from entering the inside of the case 50.

[0031] The properties required for the sealing material 70 are different from those required for the heat dissipation sheet 60. Therefore, the composition of the second resin material constituting the sealing material 70 may be different from the composition of the first resin material constituting the heat dissipation sheet 60. From the viewpoint of preventing water from entering the inside of the case 50, it is desirable that the sealing material 70 be made of a material with excellent waterproofing properties.

[0032] In one example, the sealant 70 is made of a resin foam having closed cells. Since resin foam having closed cells has excellent water resistance, it is suitable for use as a sealant 70. Examples of resin foam having closed cells include foamed EPDM. When the sealant 70 is made of a resin foam, the sealant 70 has rubber elasticity.

[0033] Similar to the first resin material constituting the heat dissipation sheet 60, it is desirable that the second resin material constituting the sealing material 70 is also a siloxane-free resin material. It is desirable that the semiconductor device 10 of this embodiment does not use a resin containing siloxane (a resin containing siloxane bonds).

[0034] The semiconductor device 10 may also partially include a sealing structure using a siloxane-free caulking material.

[0035] (Second Embodiment) Figure 2 is a diagram showing the configuration of a fuel cell system according to a second embodiment. The fuel cell system 200 comprises a fuel cell 100 and a power converter 102. The DC power generated by the fuel cell 100 is converted into AC power by the power converter 102 and supplied to facilities 104 such as residences and factories. The power converter 102 includes a semiconductor device 10 as described in the first embodiment. The semiconductor device 10 is, for example, a DC / AC inverter. The semiconductor device 10 may also be a DC / DC converter.

[0036] In the fuel cell system 200, the fuel cell 100 is housed in a casing together with the power converter 102. As described in the first embodiment, the semiconductor device 10 uses only siloxane-free resin as the resin material. Therefore, not only electrical malfunctions such as poor contacts but also poisoning of the fuel cell 100 by siloxanes can be prevented.

[0037] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0038] (Technology 1) circuit board and Electronic components including power semiconductor elements mounted on the substrate, A heat sink is positioned on the opposite side from the side where the substrate is located relative to the aforementioned electronic component, and is used to cool the aforementioned electronic component. A case fixed to the aforementioned substrate and surrounding the aforementioned electronic component, A heat dissipation sheet is disposed between the electronic component and the heat sink, extending outward from the surface of the electronic component facing the heat sink and in contact with the open end of the case, A semiconductor device equipped with [the necessary components].

[0039] The semiconductor device described herein makes it possible to prevent water from coming into contact with electronic components while avoiding the use of expensive caulking materials.

[0040] (Technology 2) The heat dissipation sheet is made of a first resin material and is elastic, as described in Technical 1 for the semiconductor device. With this configuration, even if the surface of the electronic component has irregularities, the elasticity of the heat dissipation sheet allows the electronic component to adhere closely to the heat dissipation sheet.

[0041] (Technology 3) A semiconductor device according to Technology 1 or 2, wherein the electronic component is a power module including a plurality of power semiconductor elements. The technology of this disclosure is suitable for power modules.

[0042] (Technology 4) The semiconductor device according to any one of the technologies 1 to 3, wherein the opening end includes a first opening end located on the outer circumference side of the case and a second opening end located on the inner circumference side of the case, and the second opening end is in contact with the heat dissipation sheet. The strength and rigidity of the case are increased by the second opening end functioning as a rib.

[0043] (Technology 5) The semiconductor device according to Technology 4, wherein the second open end branches off from the first open end. With this configuration, the second open end can be brought into contact with a heat dissipation sheet.

[0044] (Technology 6) A semiconductor device according to Art 4 or 5, further comprising a sealing material disposed between the first open end and the heat sink. Such a configuration allows for double sealing around the electronic components.

[0045] (Technology 7) The sealing material is made of a second resin material and is elastic, as described in Technical Reference 6 for the semiconductor device. With this configuration, the elasticity of the sealing material allows the first open end of the case to adhere closely to the sealing material.

[0046] (Technology 8) The semiconductor device according to Technical Reference 6, wherein the sealing material is composed of a resin foam having closed cells. Since the resin foam having closed cells has excellent water resistance, it is suitable as a sealing material.

[0047] (Technology 9) Fuel cells and A power converter electrically connected to the fuel cell, Equipped with, The power conversion device includes a semiconductor device described in any one of the Art 1 to 8. Fuel cell system. [Industrial applicability]

[0048] The technology disclosed herein is useful for semiconductor devices used in fuel cell systems and the like. [Explanation of symbols]

[0049] 10 Semiconductor Devices 20 circuit boards 20p page 1 20q 2nd side 22 potting material 30 Electronic Components 30a terminal 30p surface 32 screws 40 Heatsink 40p surface 50 cases 50a Open end 51 1st opening end 52 2nd opening end 53 Space 60 Heat dissipation sheets 60e outer edge 70 sealant 70f inner edge 100 fuel cell 102 Power converter 104 facilities 200 Fuel Cell Systems

Claims

1. circuit board and Electronic components including power semiconductor elements mounted on the substrate, A heat sink is positioned on the opposite side from the side where the substrate is located relative to the aforementioned electronic component, and is used to cool the aforementioned electronic component. A case fixed to the aforementioned substrate and surrounding the aforementioned electronic component, A heat dissipation sheet is disposed between the electronic component and the heat sink, extending outward from the surface of the electronic component facing the heat sink and in contact with the open end of the case, A semiconductor device equipped with [the necessary components].

2. The heat dissipation sheet is made of a first resin material and is elastic. The semiconductor device according to claim 1.

3. The aforementioned electronic component is a power module including a plurality of power semiconductor elements. The semiconductor device according to claim 1.

4. The open end includes a first open end located on the outer circumference side of the case and a second open end located on the inner circumference side of the case. The second open end is in contact with the heat dissipation sheet. The semiconductor device according to claim 1.

5. The second open end branches off from the first open end. The semiconductor device according to claim 4.

6. The system further comprises a sealing material disposed between the first open end and the heat sink, The semiconductor device according to claim 4.

7. The sealing material is made of a second resin material and is elastic. The semiconductor device according to claim 6.

8. The sealing material is composed of a resin foam having closed cells. The semiconductor device according to claim 6.

9. Fuel cells and A power converter electrically connected to the fuel cell, Equipped with, The power conversion device includes the semiconductor device described in claim 1. Fuel cell system.

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