Semiconductor device

Abstract

A semiconductor device comprising: a power module 101 having a semiconductor element; a heat dissipation member 200 having one surface to which a power module 101 is fixed and the other surface on which a heat dissipation pin 203 is formed; a frame 109 which has an opening and in which a heat dissipation member is disposed such that the heat dissipation part projects from the opening; a sealing member 106 which seals between the heat dissipation member 200 and the frame 109 in a liquid-tight manner; a cover 107 which is connected to the frame 109 such that the heat dissipation pin 203 is disposed on the inner side, and which forms a flow passage 301 in which a refrigerant flows together with the heat dissipation member 200 and the frame 109; and a projection part which is formed in at least one of the heat dissipation member 200 and the frame 109, which projects toward the other side, and which is covered with the sealing member 106.

Description

Semiconductor Devices

[0001] The present invention relates to a semiconductor device, and more particularly to a semiconductor device used in electric power equipment such as a power converter.

[0002] Power conversion devices using power semiconductor elements as switching elements have high power conversion efficiency and are therefore widely used in consumer, automotive, railway, and substation equipment. For example, Patent Document 1 (Patent Document 1) describes a semiconductor device including multiple power modules and used in the power conversion device. In the semiconductor device described in Patent Document 1, a heat dissipation fin material having heat dissipation fins formed on a heat dissipation base is disposed on the heat dissipation surface side of each of the multiple power modules. A frame having multiple openings is disposed so that the heat dissipation fins are inserted into the openings, and a sealing material is filled between the openings and the heat dissipation base to close the openings. Furthermore, a cover is provided that covers the heat dissipation base and frame to form a flow path through which a refrigerant flows. The power modules are cooled by cooling fins disposed in the refrigerant flow path with the refrigerant.

[0003] Japanese Patent Application Laid-Open No. 2023-73861

[0004] To achieve both heat dissipation and reliability in a semiconductor device, it is desirable for the heat dissipation component to be made of a metal with high thermal conductivity, and for the cover and frame to be made of metal with high rigidity. However, if dissimilar metals come into contact with each other in the refrigerant, galvanic corrosion will occur.

[0005] In the semiconductor device described in Patent Document 1, depending on the processing accuracy and assembly accuracy of the heat dissipation member and the frame, there is a possibility that the heat dissipation member and the frame may come into contact with each other. Therefore, if different metals are used for the heat dissipation member and the frame, there is a concern that they may come into contact in the refrigerant, causing galvanic corrosion and reducing reliability.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to suppress the occurrence of galvanic corrosion even when the frame and the heat dissipation member are made of different metals, thereby improving the reliability of the semiconductor device.

[0007] In one preferred embodiment, the semiconductor device according to the present invention comprises a power module having a semiconductor element, a heat dissipation member having the power module fixed to one surface and a heat dissipation portion formed on the other surface, a frame having an opening and in which the heat dissipation member is arranged so that the heat dissipation portion protrudes from the opening, a sealing member that liquid-tightly seals the space between the heat dissipation member and the frame, a cover that is joined to the frame so that the heat dissipation portion is arranged inside and that forms, together with the heat dissipation member and the frame, a flow path through which a refrigerant flows, and a protrusion formed on at least one of the heat dissipation member and the frame, protruding toward the other and covered by the sealing member.

[0008] According to the present invention, the heat dissipation component and frame of a semiconductor device are prevented from coming into contact in a refrigerant, and even when the frame and heat dissipation component are formed from different metal materials, the occurrence of galvanic corrosion is suppressed, thereby improving the reliability of the semiconductor device.

[0009] 1 is a perspective view showing a semiconductor device according to an embodiment; FIG. 2 is a schematic cross-sectional view taken along dashed line A-A' in FIG. 1; FIG. 3 is a schematic cross-sectional view taken along dashed line B-B' in FIG. 1; FIG. 4 is a schematic view showing the appearance of a heat dissipation member according to an embodiment as viewed from above; FIG. 5 is a schematic view showing the appearance of a heat dissipation member according to an embodiment as viewed from the side; FIG. 6 is a schematic view showing an appearance of a modified heat dissipation member; FIG. 7 is a schematic view showing an appearance of another modified heat dissipation member; FIG. 8 is an enlarged cross-sectional view of a region surrounded by dashed line C in FIG. 3; FIG. 9 is a schematic view showing a manufacturing process of a semiconductor device; FIG. 10 is a schematic view showing a partial cross-section of a semiconductor device according to another embodiment.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments and drawings described below are examples for explaining the present invention, and some details have been omitted or simplified as appropriate for clarity of explanation. Please note that in order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not necessarily be accurately represented.

[0011] FIG. 1 is a perspective view showing a semiconductor device for a power conversion device according to an embodiment.

[0012] The semiconductor device 10 of this embodiment has a structure in which multiple power modules including semiconductor elements are arranged on a printed circuit board 108 and cooled from both sides. The semiconductor elements may be semiconductors such as silicon (Si) or silicon carbide (SiC), and may be semiconductor elements used as switching elements in a power conversion device for converting AC power to DC power. As will be described later, heat dissipation members are fixed to both sides of the power modules arranged on the printed circuit board 108, and the power modules are further covered from the outside by a cover 107. The heat dissipation members are arranged to fit into openings formed in a frame 109, and the cover 107 and the frame 109 are fastened together with screws at multiple locations.

[0013] The cover 107 has an elastic biasing portion 110 formed at a location corresponding to the position of the power module. The inner surface of the elastic biasing portion 110 abuts against a pin-shaped heat dissipation portion formed on the heat dissipation member. A flow path through which a refrigerant for cooling the power module flows is formed between the elastic biasing portion 110 and the heat dissipation member. The refrigerant flows in and out of a flow path inlet / outlet 300 (only one of two flow path inlets / outlets is visible in the figure) that leads to the flow path. The flow path on one side of the power module is connected to the flow path on the other side via piping components, and the refrigerant flows through both flow paths. For example, the refrigerant flowing in through the flow path inlet / outlet 300 enters the flow path covered by the upper cover 107 in the figure, flows from the upper left to the lower right in the figure, turns back through the piping components at the lower right end, flows through the flow path covered by the lower cover 107 toward the upper left in the figure, and flows out from another flow path inlet / outlet (not visible in the figure). The coolant can be, for example, water or an antifreeze solution made by mixing ethylene glycol into water. The power module is molded by sealing components such as semiconductor elements with resin, and cooling is achieved by transferring heat from the conductor plate exposed from the sealing resin to the heat dissipation member, and then releasing the heat from the heat dissipation member to the coolant flowing through the flow path.

[0014] Fig. 2 is a longitudinal cross-sectional view of the semiconductor device 10 taken along dashed line A-A' in Fig. 1. Fig. 3 is a width-wise cross-sectional view of the semiconductor device 10 taken along dashed line B-B' in Fig. 1. For simplification, Fig. 2 omits the illustration of the coolant inlet / outlet portion including the flow path inlet / outlet 300 located to the left of the dashed line.

[0015] The semiconductor device 10 has a configuration that is approximately symmetrical between the top and bottom of the figure, with the printed circuit board 108 sandwiched between them. The power module 101 is disposed in an opening formed in the printed circuit board 108 and is electrically connected to circuit wiring formed on the printed circuit board 108. The lower surface of the power module 101 is aligned with a predetermined reference plane. By aligning the lower surfaces of the power modules 101 with a uniform reference plane, it becomes possible to arrange multiple power modules 101 on one heat dissipation member 200. In this embodiment, as shown in FIG. 3 , four power modules 101 are arranged in the width direction of the semiconductor device 10, and one heat dissipation member 200 is arranged on each of the top and bottom sides of the power modules 101.

[0016] Plate-shaped insulating members 103 are bonded to both the top and bottom surfaces of the power module 101 via adhesive layers 102. The insulating members 103 may be made of, for example, an alumina plate, an alumina-zirconia plate, or a silicon nitride plate. The thermal conductivity of the insulating members 103 is preferably 0.5 W / mK or higher. The insulating members 103 are further connected to the heat dissipation member 200 via adhesive layers 102. For example, the adhesive layers 102 may be made of a silicone adhesive or an epoxy adhesive containing a filler such as zinc oxide or alumina powder. The adhesive layers 102 may also be made of a metal bonding material such as solder or brazing filler. By providing the adhesive layers 102 in this manner, good thermal conduction can be maintained between the power module 101 and the insulating members 103, and between the insulating members 103 and the heat dissipation member 200.

[0017] The heat dissipation member 200 is fixed to the power module 101 on one side via two adhesive layers 102 and an insulating member 103. A plurality of heat dissipation pins 203 are formed on the side of the heat dissipation member 200 opposite the side fixed to the power module. In this embodiment, pin-shaped heat dissipation pins are used as the heat dissipation member. However, the heat dissipation member may be shaped like a fin or a plate, as long as it can increase the surface area of ​​the heat dissipation member 200 in contact with the refrigerant and enhance the heat dissipation effect. The heat dissipation member 200 can be formed using a metal material with high thermal conductivity, such as copper or aluminum. The thermal conductivity of the heat dissipation member 200 is preferably 200 W / mK or higher.

[0018] The heat dissipation member 200 is inserted into an opening formed in the frame 109, so that the inner peripheral surface of the opening of the frame 109 faces the outer peripheral side surface of the base of the heat dissipation member 200. The periphery of the opening on one side of the frame 109 is arranged to face a flange formed on the outer periphery of the heat dissipation member 200 on the power module 101 side. The frame 109 is preferably made of a highly rigid metal material such as stainless steel or copper.

[0019] A sealing member 106 is filled between the heat dissipation member 200 and the frame 109. The sealing member 106 preferably has electrical insulation properties and elasticity. The sealing member 106 is made of, for example, a resin material.

[0020] The semiconductor device 10 is further covered on both the top and bottom sides in the figure with covers 107. As described above, the cover 107 is fixed to the frame 109 at multiple locations, for example, by screws. The portion of the cover 107 facing the heat dissipation member 200 is formed with an elastic biasing portion 110 that protrudes toward the heat dissipation member 200. The elastic biasing portion 110 is biased toward the heat dissipation member 200 so as to closely contact the tip portions of the heat dissipation pins 203 via the elastic member 104. By interposing the elastic member 104, even if the amount of deformation of the elastic biasing portion 110 is insufficient, the gap between the heat dissipation pins 203 and the elastic biasing portion 110 is filled, maintaining close contact and improving cooling performance. The elastic member 104 is preferably formed of an insulating resin material.

[0021] The cover 107 is preferably made of a highly rigid metallic material such as stainless steel or copper, similar to the frame 109. By using a highly rigid material for the cover 107 and the frame 109, plastic deformation of the cover 107 and the frame 109 due to the biasing force on the elastic biasing portion 110 can be suppressed, and the tight contact between the tip of the heat dissipation pin 203 and the elastic biasing portion 110 can be maintained.

[0022] The space formed by the heat dissipation member 200, the cover 107, and the frame 109 becomes a flow path 301 through which the refrigerant flows. The heat dissipation pins 203 are arranged in the flow path 301, and the refrigerant flows between the heat dissipation pins 203. Heat generated in the power module 101 is transferred to the heat dissipation member 200 and dissipated from the heat dissipation pins 203 to the refrigerant in the flow path 301. In this way, the power module 101 is cooled from both sides by the refrigerant flowing through the flow path 301.

[0023] Here, if different metals are used for the heat dissipation member 200, the cover 107, and the frame 109, and these metals have different natural potentials in the refrigerant, contact between the heat dissipation member 200 and the cover 107 or the frame 109 within the flow path 301 may cause galvanic corrosion, in which the metal with a lower potential corrodes due to battery action. In this embodiment, by interposing the elastic member 104 between the heat dissipation pin 203 and the elastic biasing member 110, direct contact between the heat dissipation pin 203 and the elastic biasing member 110 can be prevented, thereby suppressing the occurrence of galvanic corrosion. Furthermore, as described below, a protrusion provided between the heat dissipation member 200 and the frame 109 ensures a clearance between them, and the seal member 106 is filled therein. This also prevents contact between the heat dissipation member 200 and the frame 109 within the flow path 301, thereby suppressing the occurrence of galvanic corrosion.

[0024] 4 is a schematic diagram showing the appearance of the heat dissipation member 200 as seen from above. For convenience, the front side of the drawing of the heat dissipation member 200 is referred to as the top, and the back side of the drawing is referred to as the bottom. FIG. 5 is a schematic diagram showing the appearance of the heat dissipation member 200 as seen from the side.

[0025] The heat dissipation member 200 has a plurality of heat dissipation pins 203 formed on the upper surface of a base portion 201. A flange portion 204 that extends outward from the base portion 201 is formed on the lower bottom surface of the base portion 201. When mounted on the semiconductor device 10, the flange portion 204 is positioned so that its outer peripheral portion faces one surface around the opening of the frame 109. A protrusion portion 202 is formed on each of the outer peripheral side surfaces of the base portion 201.

[0026] In this embodiment, the protrusion 202 has a partially spherical or ellipsoidal shape, and includes a curved portion that gradually moves away from the side surface of the base portion 201 as it goes from the top to the bottom. By providing the protrusion 202 with this shape, when the heat dissipation member 200 is placed on the frame 109, the frame 109 does not make uneven contact with the side surface of the base portion 201, and a clearance is secured between the side surface of the base portion 201 and the frame 109, allowing the heat dissipation member 200 to be placed on the frame 109 with precision.

[0027] The protrusions 202 can be formed by, for example, casting, grinding, etc. The shape of the protrusions 202 is not limited to the partially spherical or ellipsoidal shape described above, and may be, for example, a protrusion 202a shaped like a lying cylinder as shown in Fig. 6, or a protrusion 202b having an inclined surface in which the distance from the side surface of the base portion 201 increases from top to bottom as shown in Fig. 7. The shape of the inclined surface is also not limited to a square as shown in the figure, and may be other shapes such as a trapezoid.

[0028] FIG. 8 is an enlarged cross-sectional view of the area surrounded by the dashed line C in FIG. 3, and in the figure, H1 to H4 indicate the dimensions of each part.

[0029] The height H1 of the protrusion 202, i.e., the distance from the surface of the flange 204 facing the heat dissipation pins 203 to the end of the protrusion 202 on the flow path 301 side, is smaller than the height H2 of the base 201, i.e., the distance from the same surface of the flange 204 to the surface of the base 201 on which the heat dissipation pins 203 are formed. The height H1 of the protrusion 202 is also larger than the distance H4 between the flange 204 and the frame 109 at a location where the flange 204 and the frame 109 face each other, and is smaller than the sum of the thickness H3 of the frame 109 and the distance H4 between the flange 204 and the frame 109. In other words, the protrusion 202 is positioned so that the height H1 from the flange 204 at the end on the flow path 301 side satisfies the relationships H4

[0030] ​A seal member 106 is filled between the frame 109 and the base portion 201 and flange portion 204 of the heat dissipation member 200. The seal member 106 is filled so that the thickness in the vertical direction in the figure near the protrusion 202 is greater than H4. If possible, it is desirable that the thickness of the seal member 106 near the protrusion 202 is greater than the height H1 of the protrusion 202. By filling the seal member 106 in this manner, even if the frame 109 and the protrusion 202 come into contact, the contact area is covered with the seal member 106, and the refrigerant flowing through the flow path 301 can be prevented from reaching the contact area between the frame 109 and the protrusion 202.

[0031] 9A to 9C are schematic diagrams showing partial cross sections of the mounting portion of the power module 101 at a number of steps during the manufacturing process of the semiconductor device 10. FIG.

[0032] In step (A), the heat dissipation member 200 is arranged with the surface facing the power module 101 facing upward. In step (B), an adhesive is applied to the surface of the heat dissipation member 200 facing the power module to form an adhesive layer 102, and a plate-shaped insulating member 103 is mounted thereon. The insulating member 103 is pressed using a press or the like so that the adhesive layer 102 has a predetermined thickness. An upper limit is set for the amount of pressure applied, since excessive pressure may cause cracking or damage to the insulating member 103. The pressure is preferably applied at a pressure of 0.1 MPa to 2 MPa. The pressure makes the thickness of the adhesive layer 102 approximately uniform, and the insulating member 103 and the flow path plane are approximately parallel. Pressurization does not need to be performed all at once; it may be performed multiple times so that the adhesive layer 102 finally has the predetermined thickness.

[0033] In step (C), sealing material 106 is applied to the portion of heat dissipation member 200 that spans base portion 201 and flange portion 204. At this time, a sufficient amount of sealing material 106 is applied so that protrusion portion 202 is covered with sealing material 106. For sealing material 106, an elastic insulating adhesive or rubber material is used, which is a material that can be deformed by stress due to pressure applied in the subsequent manufacturing process or pressure applied by elastic biasing portion 110.

[0034] In step (D), elastic member 104 is placed on the portion of cover 107 that faces the tip of heat dissipation pin 203, which is integrated with frame 109, and the assembly assembled up to step (C) is mounted on cover 107 through the opening of frame 109. At this time, pressure is applied to frame 109 and sealing member 106 so that they come into close contact, and if sealing member 106 is a thermosetting adhesive material, heat treatment is performed in a constant temperature bath.

[0035] In step (E), the power module 101 mounted on the printed circuit board 108 is bonded to the insulating member 103 via the adhesive layer 102 .

[0036] In step (F), an adhesive layer 102 is formed on the surface of the power module 101 opposite to the surface bonded to the insulating member 103 in step (E), and another assembly assembled in steps (A) to (D) is mounted on the power module 101. Then, the covers 107 on both sides of the power module 101 are fastened together with bolts and nuts, and the semiconductor device 10 is assembled.

[0037] In step (D), when the assembled body is passed through the opening of the frame 109, the base portion 201 of the heat dissipation member 200 may come into contact with the frame 109. However, in this embodiment, the protrusions 202 formed on the base portion 201 allow for accurate positioning between the frame 109 and the base portion 201. This ensures a clearance between the frame 109 and the base portion 201, preventing the frame 109 and the base portion 201 from coming into contact with each other. Although the protrusions 202 may come into contact with the frame 109, the areas where the protrusions 202 and the frame 109 may come into contact are located in areas covered by the seal member 106 filled between the heat dissipation member 200 and the frame 109, preventing the contact area from being exposed to the refrigerant in the flow path 301. This prevents galvanic corrosion from occurring even when the protrusions 202 and the frame 109 come into contact with each other.

[0038] According to the first embodiment described above, the protrusions 202 formed on the heat dissipation member 200 ensure a clearance between the heat dissipation member 200 and the frame 109, thereby preventing the two from coming into contact with each other in the flow path 301. Furthermore, the areas where the protrusions 202 and the frame 109 may come into contact are covered by the seal member 106 and are not exposed in the flow path 301, preventing the contact areas from coming into contact with the refrigerant flowing in the flow path 301. This makes it possible to prevent the occurrence of galvanic corrosion and improve the reliability of the semiconductor device, and further makes it possible to improve the reliability of electric power equipment such as a power conversion device in which the semiconductor device is used.

[0039] 10 is a schematic diagram showing a partial cross section of a semiconductor device according to another embodiment. The semiconductor device of this embodiment differs from the above-described embodiment in the arrangement of protrusions formed between the heat dissipation member 200 and the frame 109. The other configuration of the semiconductor device is similar to that of the semiconductor device 10 described with reference to FIGS. 1 to 3, and therefore, in the following, the same components will be designated by the reference numerals used in the above-described embodiment, and duplicated explanations will be omitted.

[0040] The cross section shown in FIG. 10 , like FIG. 8 , is a cross section of a portion corresponding to the portion indicated by dashed line C in FIG. 3 . In this embodiment, instead of the protrusions 202 formed on the side surface of the base portion 201 of the heat dissipation member 200 in the previous embodiment, protrusions 150 are formed on the frame 109. Multiple protrusions 150 are formed on the inner circumferential surface of the opening of the frame 109 so as to surround the base portion 201. For example, if the opening is rectangular, multiple protrusions 150 are formed on each side of the opening so as to protrude from the frame 109 toward the base portion 201. It is desirable that the shape of the protrusions 150 be a partially spherical or ellipsoidal shape protruding from the inner circumferential surface of the frame, such that the portion facing the base portion 201 has a curved surface. This shape allows the frame 109 and the heat dissipation member 200 to be easily aligned with high precision.

[0041] Furthermore, it is preferable that the protrusion 150 be formed on the side of the inner circumferential surface of the opening that is closer to the flange 204. The gap between the frame 109 and the heat dissipation member 200 is filled with the seal member 106 at a position higher than the tip of the protrusion 150, preferably sufficiently to cover the protrusion. By forming the protrusion 150 on the side closer to the flange 204, the contact portion between the protrusion 150 and the heat dissipation member 200 is more reliably covered with the seal member 106, reducing the possibility that the contact portion will be exposed to the refrigerant in the flow path 301, and suppressing the occurrence of galvanic corrosion.

[0042] In this embodiment, as in the previously described embodiment, the possibility of the heat dissipation member coming into contact with the frame or cover within the refrigerant flow path is reduced, thereby suppressing the occurrence of galvanic corrosion and realizing a highly reliable semiconductor device.

[0043] In the above-described embodiment, one protrusion is formed on each side of the cooling member, but multiple protrusions may be provided on one side. Furthermore, the position where the protrusions are formed is not limited to the middle of the side of the cooling member, and they may be formed on a corner that spans two side faces. Furthermore, the flow path through which the coolant flows does not necessarily have to be provided on both sides of the module to be cooled, and may be provided on only one side.

[0044] While the present invention has been described above using representative embodiments as examples, the present invention is not limited to these and can be embodied in various forms without departing from the spirit of the invention as set forth in the claims. Furthermore, the above-described embodiments have been described in detail to make the present invention easier to understand, and the present invention is not necessarily limited to those having all of the described configurations.

[0045] 10: Semiconductor device 101: Power module 102: Adhesive layer 103: Insulating member 104: Elastic member 106: Sealing member 107: Cover 108: Printed circuit board 109: Frame 110: Elastic biasing portion 200: Heat dissipation member 201: Base portion 202: Protrusion portion 203: Heat dissipation pin 204: Flange portion 300: Flow path entrance / exit 301: Flow path

Claims

1. A semiconductor device comprising: a power module having a semiconductor element; a heat dissipation member having the power module fixed to one surface and a heat dissipation portion formed on the other surface; a frame having an opening and in which the heat dissipation member is arranged so that the heat dissipation portion protrudes from the opening; a sealing member that provides a liquid-tight seal between the heat dissipation member and the frame; a cover that is coupled to the frame so that the heat dissipation portion is arranged inside, and that forms, together with the heat dissipation member and the frame, a flow path through which a refrigerant flows; and a plurality of protrusions formed on at least one of the heat dissipation member and the frame, protruding toward the other and covered by the sealing member.

2. The semiconductor device according to claim 1, wherein said heat dissipation member and said frame are made of different metallic materials.

3. A semiconductor device according to claim 2, wherein the heat dissipation member has a plurality of side surfaces facing the frame at the opening, and the plurality of protrusions are provided at least one at each of a plurality of locations corresponding to each of the plurality of side surfaces.

4. The semiconductor device according to claim 2, wherein said protrusion is disposed closer to said power module than the surface of said seal member that comes into contact with the coolant flowing through said flow path.

5. The semiconductor device according to claim 2, wherein the protrusion has a curved surface at a portion facing the other of the heat dissipation member and the frame.

6. The semiconductor device according to claim 2, wherein said frame and said cover are formed of a material having higher rigidity than said heat dissipation member.

7. The semiconductor device according to claim 2, wherein said heat dissipation member is made of a material having a higher thermal conductivity than said frame and said cover.

8. The semiconductor device according to claim 2, wherein said heat sink and said cover are in contact with each other via an elastic member therebetween.

9. The semiconductor device according to claim 8, wherein said sealing member and said elastic member are made of an electrically insulating material.

10. The semiconductor device according to claim 2, wherein the heat dissipation member has a base portion fixed to the power module on one side and having the heat dissipation portion formed on the other side opposite the side fixed to the power module, and a flange portion formed on the outer edge of the one side of the base portion, with the surface of the other side facing the frame, wherein when the height from the surface of the other side of the flange portion to the end of the protrusion on the flow path side is H1, the height from the surface of the other side of the flange portion to the surface of the base portion on the heat dissipation portion side is H2, the height of the frame is H3, and the distance between the flange portion and the frame is H4, the relationships H4<H1<H2 and H4<H1<H4+H3 are satisfied.

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