Cooler and semiconductor device

Abstract

To provide a cooler capable of suppressing local corrosion at given points in a refrigerant passage.SOLUTION: A cooler (2) includes: a top plate (20) formed with a heat dissipation surface (20a) on one side; a bottom plate (21) thicker than the top plate placed facing the top plate; multiple fins (22) provided to the bottom plate; and a peripheral wall (23) formed to surround the perimeter of the multiple fins along the outer perimeter of the bottom plate. The multiple fins and the peripheral wall are joined to the heat dissipation surface of the top plate. The refrigerant passage is formed by the space surrounded by the top plate, the bottom plate, the multiple fins and the peripheral wall. The potential on the top plate side is higher than the potential on the bottom plate side.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cooler and a semiconductor device. [Background technology]

[0002] General-purpose heat exchangers (coolers) are made of metal materials with good thermal conductivity, such as aluminum alloys (see Patent Documents 1 and 2). For example, Patent Document 1 describes a manufacturing method for a so-called fin-tube type heat exchanger. In Patent Document 1, an extruded flat tube made of an aluminum alloy and a fin are joined with a brazing material. In Patent Document 2, a corrugated plate is disposed between a pair of plate members, and the plate members and the corrugated plate are joined with a brazing material.

[0003] Also, an example of a device to be cooled by a cooler is a semiconductor device, which has a substrate on which semiconductor elements such as an IGBT (Insulated Gate Bipolar Transistor), a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and an FWD (Free Wheeling Diode) are provided, and is used in an inverter device or the like.

[0004] For this type of semiconductor device, those with an integrated cooler have been proposed (see, for example, Patent Documents 3-4). A semiconductor element is placed on a predetermined circuit board (which may be called an insulating board) and mounted on the cooler via a bonding material such as solder. For example, the cooler includes a top plate on which the semiconductor element and the like are mounted, heat dissipation fins, a bottom plate, an inlet and an outlet for the coolant, and the like. The top plate, heat dissipation fins, and bottom plate are bonded together with a brazing material or the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-070658 [Patent Document 2] JP 2009-293888 A [Patent Document 3] JP 2013-036098 A [Patent Document 4] JP 2017-005181 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, a refrigerant (cooling water) flows inside the cooler. The flow of the refrigerant can cause corrosion on the inner surface of the cooler. As the corrosion progresses, there is a risk that a hole will form in the cooler, causing the refrigerant to leak out.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide a cooler and a semiconductor device that are capable of suppressing localized corrosion at predetermined locations in a coolant passage. [Means for solving the problem]

[0008] A cooler of one embodiment of the present invention comprises a top plate having a heat dissipation surface formed on one side, a bottom plate arranged opposite the top plate and thicker than the top plate, a plurality of fins provided on the bottom plate, and a peripheral wall portion formed to surround the outer periphery of the plurality of fins along the outer periphery of the bottom plate, wherein the plurality of fins and the peripheral wall portion are joined to the heat dissipation surface of the top plate, a flow path for a refrigerant is formed by the space surrounded by the top plate, the bottom plate, the plurality of fins, and the peripheral wall portion, and the electric potential on the top plate side is higher than the electric potential on the bottom plate side.

[0009] Furthermore, a semiconductor device according to one embodiment of the present invention comprises the above-mentioned cooler and a semiconductor element arranged on the other surface of the top plate via an insulating substrate, and the multiple fins are arranged directly below the semiconductor element. Effect of the Invention

[0010] According to the present invention, it is possible to suppress localized corrosion at a predetermined location of a refrigerant passage. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a semiconductor device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the cooler according to the present embodiment, seen from above with the top plate omitted. [Diagram 3] FIG. 11 is a cross-sectional view of a semiconductor device according to a comparative example. [Figure 4] FIG. 11 is a plan view of a cooler according to a modified example, seen from below with the bottom plate omitted. [Diagram 5] FIG. 2 is a partially enlarged view of FIG. [Figure 6] FIG. 11 is a cross-sectional view of a semiconductor device according to a modified example. [Figure 7] FIG. 13 is a cross-sectional view of a semiconductor device according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A semiconductor device to which the present invention can be applied will be described below. Fig. 1 is a cross-sectional view of the semiconductor device according to the present embodiment. Fig. 2 is a plan view of the cooler according to the present embodiment, with the top plate omitted, as viewed from above. Note that the semiconductor device shown below is merely an example, and can be modified as appropriate without being limited thereto.

[0013] In the following figures, the longitudinal direction (the direction in which multiple phases are arranged) of the semiconductor device (cooler) is defined as the X direction, the lateral direction of the semiconductor device (cooler) as the Y direction, and the height direction (thickness direction of the substrate) as the Z direction. The illustrated X, Y, and Z axes are perpendicular to each other and form a right-handed system. In some cases, the X direction may be called the left-right direction, the Y direction as the front-back direction, and the Z direction as the up-down direction. These directions (front-back, left-right, up-down directions) are terms used for convenience of explanation, and the corresponding relationship with each of the XYZ directions may change depending on the mounting posture of the semiconductor device. For example, the heat dissipation surface side (cooler side) of the semiconductor device is called the bottom side, and the opposite side is called the top side. In this specification, plan view means the case where the top or bottom of the semiconductor device is viewed from the Z direction.

[0014] A semiconductor device 1 according to this embodiment is applied to a power conversion device such as a power control unit, and is a power semiconductor module constituting an inverter circuit. As shown in Figures 1 and 2, the semiconductor device 1 is configured by arranging a plurality of insulating substrates 3 on the upper surface of a top plate 20, and arranging a semiconductor element 4 on the upper surface of each insulating substrate 3. The plurality of insulating substrates 3 and the semiconductor element 4 are surrounded by a frame-shaped case member 5. The inner space of the case member 5 is filled with a sealing resin 6.

[0015] 1, two insulating substrates 3 and two semiconductor elements 4 are arranged side by side in the Y direction, but the present invention is not limited to this configuration. For example, a plurality of insulating substrates 3 and semiconductor elements 4 may be arranged side by side not only in the Y direction but also in the X direction. In this case, an inverter circuit is formed by the plurality of insulating substrates 3 and semiconductor elements 4.

[0016] The top plate 20 constitutes a part of the cooler 2, and is formed of a plate-like body that is rectangular in plan view and has a predetermined thickness. The cooler 2 includes, for example, the top plate 20, a bottom plate 21, and a plurality of fins 22 and a peripheral wall portion 23 provided on the bottom plate 21. The configuration of the cooler 2 will be described later.

[0017] A heat dissipation surface 20a is formed on the lower surface, which is one surface of the top plate 20. The heat dissipation surface 20a is a surface that dissipates heat from the semiconductor elements, and tips of a plurality of fins 22, which will be described later, are joined to the heat dissipation surface 20a. The heat dissipation surface 20a is also a surface that comes into direct contact with a refrigerant.

[0018] An insulating substrate 3 is disposed on the top surface, which is the other surface of the top plate 20, via solder S. The solder S can be substituted with other binders such as sintered materials. The insulating substrate 3 is formed, for example, of a DCB (Direct Copper Bonding) substrate, an AMB (Active Metal Brazing) substrate, or a metal-based substrate. Specifically, the insulating substrate 3 has an insulating plate 30, a heat sink 31 disposed on the lower surface of the insulating plate 30, and a circuit board 32 disposed on the upper surface of the insulating plate 30. The insulating substrate 3 is formed, for example, in a rectangular shape when viewed from above.

[0019] The insulating plate 30 is formed of an insulating material such as a ceramic material such as alumina (Al2O3), aluminum nitride (AlN), silicon nitride (Si3N4), a resin material such as epoxy, or an epoxy resin material using a ceramic material as a filler. The insulating plate 30 may be called an insulating layer or an insulating film.

[0020] The heat sink 31 has a predetermined thickness in the Z direction, and is formed so as to cover the entire lower surface of the insulating plate 30. The heat sink 31 is formed of a metal plate having good thermal conductivity, such as copper or aluminum.

[0021] A circuit board 32 is formed on the upper surface of the insulating plate 30. Although one circuit board 32 is shown per insulating plate 30 in Fig. 1 for convenience, more circuit boards 32 may be formed on the upper surface of the insulating plate 30. These circuit boards 32 are metal layers of a predetermined thickness made of copper foil or the like, and are formed in islands on the insulating plate 30 while being electrically insulated from each other.

[0022] The semiconductor element 4 is disposed on the upper surface of the circuit board 32 via solder S. The solder S may be substituted with other binders such as a sintered material. The semiconductor element 4 is formed, for example, in a rectangular shape when viewed from above. The semiconductor element 4 is disposed at locations corresponding to the multiple fins 22, as will be described in detail later.

[0023] The semiconductor element 4 is disposed on the upper surface of the circuit board 32 via solder S and electrically connected. For convenience, one semiconductor element 4 is shown per circuit board 32 in Fig. 1, but more semiconductor elements 4 may be disposed on the circuit board 32. The semiconductor element 4 is formed in a square (rectangular) shape in a plan view using a semiconductor substrate such as silicon carbide (SiC), gallium nitride (GaN), diamond, or the like.

[0024] As the semiconductor element 4, a switching element such as an IGBT (Insulated Gate Bipolar Transistor) or a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or a diode such as an FWD (Free Wheeling Diode) may be used. As the semiconductor element 4, a reverse conducting (RC)-IGBT element in which an IGBT and an FWD are integrated, or a power MOSFET element, or a reverse blocking (RB)-IGBT having sufficient withstand voltage against reverse bias, may also be used.

[0025] The shape, number, and location of the semiconductor elements 4 can be changed as appropriate. The semiconductor elements 4 in this embodiment are vertical switching elements having functional elements such as transistors formed on a semiconductor substrate, but are not limited thereto and may be horizontal switching elements.

[0026] The case member 5 is joined to the upper surface of the top plate 20 via, for example, an adhesive (not shown). The case member 5 has a shape that follows the outer shape of the top plate 20. The case member 5 is formed in a rectangular frame shape with an opening in the center. The insulating substrate 3 and the semiconductor element 4 described above are housed in the central opening. That is, the insulating substrate 3 and the semiconductor element 4 are surrounded by the frame-shaped case member 5.

[0027] Further, although details will be described later, the inner space of the case member 5 is filled with a sealing resin 6. That is, the case member 5 defines a space for accommodating a plurality of insulating substrates 3, the semiconductor elements 4, and the sealing resin 6. Such a case member 5 is formed of, for example, a thermoplastic resin. The case member 5 is formed of, for example, a PPS resin (polyphenylene sulfide resin), a PBT resin (polybutylene terephthalate resin), or the like.

[0028] Although not shown, main terminals (P terminal, N terminal, M terminal, etc.) for external connection and control terminals for control are provided on the case member 5. These terminals are integrally formed with the case member 5, for example.

[0029] As described above, the sealing resin 6 is filled into the space defined by the frame-shaped case member 5. This seals the insulating substrate 3 and the semiconductor element 4 mounted thereon in the space. The sealing resin 6 is made of, for example, a thermosetting resin. Specifically, the sealing resin 6 preferably contains at least one of epoxy, silicone, urethane, polyimide, polyamide, and polyamideimide. For example, an epoxy resin mixed with a filler is suitable for the sealing resin 6 in terms of insulation, heat resistance, and heat dissipation.

[0030] Next, a detailed configuration of the cooler 2 will be described. As shown in Figures 1 and 2, the cooler 2 is formed into an integrated box shape by joining a top plate 20 and a bottom plate 21. The cooler 2 is made of a material with good heat dissipation properties, such as an aluminum alloy.

[0031] As described above, the top plate 20 has a rectangular shape in a plan view and is formed of a plate-like body of a predetermined thickness. The outer shape of the top plate 20 corresponds to the outer shape of the case member 5. That is, the longitudinal direction of the top plate 20 extends in the left-right direction (X direction) of the semiconductor device 1, and the lateral direction of the top plate 20 extends in the front-rear direction (Y direction) of the semiconductor device 1. The top plate 20 has one surface (lower surface) and the other surface (upper surface). One surface forms a heat dissipation surface that dissipates heat from the semiconductor element 4. The other surface forms a bonding surface for the insulating substrate 3.

[0032] In this embodiment, the multiple insulating substrates 3 and semiconductor elements 4 are arranged in a central region on the upper surface of the top plate 20. For example, the multiple insulating substrates 3 and semiconductor elements 4 are arranged side by side in the X direction or the Y direction. In FIG. 1, the insulating substrates 3 and the semiconductor elements 4 are arranged two by two in the Y direction, but this configuration is not limited to this. The insulating substrates 3 and the semiconductor elements 4 may also be arranged side by side in the X direction. In this embodiment, the central region on the lower surface side (heat dissipation surface side) of the top plate 20 on which the multiple insulating substrates 3 and semiconductor elements 4 are arranged may be referred to as a heat dissipation region.

[0033] The bottom plate 21 has the same rectangular shape as the top plate 20 in a plan view, and is disposed directly below the top plate 20 with a predetermined gap therebetween. The bottom plate 21 is formed of a plate-like body that is thicker than the top plate 20. The bottom plate 21 is preferably formed of the same material as the top plate 20, that is, an aluminum alloy.

[0034] A plurality of fins 22 are provided on the upper surface of the bottom plate 21. The fins 22 may be, for example, pin fins in a rectangular column shape extending in the Z direction. The plurality of fins 22 may be arranged at a predetermined pitch in the X direction, the Y direction, or a direction intersecting the XY directions. The plurality of fins 22 may be made of the same metal material as the bottom plate 21 and may be provided integrally with the bottom plate 21. In other words, the fins 22 are used as a heat sink.

[0035] More specifically, the fin 22 is formed in a diamond shape in a plan view, and the opposing direction of a pair of diagonally opposing corners coincides with the X-direction or the Y-direction. The fin 22 protrudes a predetermined length toward the positive side of the Z-direction. One end of the fin 22 is connected to the upper surface of the bottom plate 21, and the other end is connected to the lower surface (heat dissipation surface) of the top plate 20. The fin 22 may be connected to the top plate 20 or the bottom plate 21 via a bonding material B described later. The configuration of the fin 22 provided on the bottom plate 21 is not limited to this and can be changed as appropriate. For example, a configuration in which a plurality of cylindrical pins are provided, or a configuration in which a plurality of blade-shaped fins 22 extending in the front-rear direction or the left-right direction are arranged in parallel to each other may be used. The fin 22 may be provided on the bottom plate 21 by brazing, implantation, cutting, or plastic processing.

[0036] The multiple fins 22 form a fin assembly 24 that is generally rectangular in shape as a whole. The longitudinal direction of the fin assembly 24 coincides with the longitudinal direction of the bottom plate 21. Note that the external shape of the fin assembly 24 is not limited to this, and may be chamfered or deformed.

[0037] A peripheral wall portion 23 that surrounds the outer periphery of the multiple fins 22 (fin assembly 24) is provided on the upper surface of the bottom plate 21. The peripheral wall portion 23 protrudes from the upper surface of the bottom plate 21 to the positive side in the Z direction by a predetermined height. The peripheral wall portion 23 is formed in a rectangular frame shape along the outer periphery of the bottom plate 21. The protruding height of the peripheral wall portion 23 is preferably equal to the protruding height of the fins 22.

[0038] The bottom plate 21 and the peripheral wall portion 23 may be integrally formed. That is, the bottom plate 21 and the peripheral wall portion 23 form a box-shaped cooler case that is open at the top. The top plate 20 forms a lid portion that closes the opening of the cooler case.

[0039] The top plate 20 is joined to the peripheral wall portion 23 and the tips (upper ends) of the plurality of fins 22 by brazing or the like. This closes the upper opening of the cooling case. In this manner, a flow path for the refrigerant is formed by the space surrounded by the top plate 20, the bottom plate 21, the plurality of fins 22, and the peripheral wall portion 23. For example, cooling water is used as the refrigerant, and its physical properties can be changed as appropriate. The joining structure between the top plate 20 and the cooling case will be described later.

[0040] The space surrounded by the top plate 20, the bottom plate 21, and the peripheral wall portion 23 is divided into three spaces (first header portion R1, fin accommodating portion R2, and second header portion R3). Specifically, the first header portion R1 forms a space that is continuous with a refrigerant inlet 25, which will be described later. The fin accommodating portion R2 forms a space in which the above-mentioned multiple fins 22 are accommodated. The second header portion R3 forms a space that is continuous with a refrigerant outlet 26, which will be described later.

[0041] The first header portion R1 and the second header portion R3 are disposed to face each other with the fin accommodating portion R2 in between in the Y direction. That is, the first header portion R1 forms a refrigerant flow path upstream of the fin accommodating portion R2, and the second header portion R3 forms a refrigerant flow path downstream of the fin accommodating portion R2. A liquid is used as the refrigerant. Note that various liquids can be used as the refrigerant.

[0042] 2, an inlet 25 and an outlet 26 of the coolant for the cooler 2 are formed at predetermined positions of the bottom plate 21. The inlet 25 and the outlet 26 are formed as through holes penetrating the bottom plate 21 in the thickness direction. Specifically, the inlet 25 and the outlet 26 are disposed so as to face each other diagonally with the multiple fins 22 interposed therebetween in the Y direction. For example, in the first header portion R1, the inlet 25 is disposed offset toward the negative side in the X direction. In contrast, in the second header portion R3, the outlet 26 is disposed offset toward the positive side in the X direction.

[0043] Further, the inlet 25 and the outlet 26 have an elongated hole shape that is long in the X direction in a plan view. For example, the shape of the inlet 25 and the outlet 26 is an ellipse that is short on the short side of the cooler 2 and long on the long side. Note that the shapes and arrangements of the inlet 25 and the outlet 26 are not limited thereto and can be changed as appropriate.

[0044] The semiconductor device 1 thus configured is attached to a flat mounting surface 71 of a flange 70 having a connection port for a hose (not shown) via a packing such as an O-ring 72. At this time, the lower surface of the bottom plate 21 is in contact with the mounting surface 71. In Fig. 1, for example, a groove 73 for the O-ring 72 is formed on the flange 70 side. The O-ring 72 ensures sealing between the mounting surface 71 and the lower surface of the bottom plate 21.

[0045] In a water-cooled cooler, the coolant flows in a space (a flow path of the coolant) formed inside. For example, various types of cooling water are used as the coolant. Therefore, it is expected that the inner surface of the cooler will corrode due to contact with the coolant for a long period of time. Here, the cooler according to the present embodiment will be described with reference to the comparative example of FIG. 1 and FIG. 3. FIG. 3 is a cross-sectional view of a semiconductor device according to the comparative example. Note that the comparative example differs from the present embodiment only in that a plurality of fins and a peripheral wall portion are provided on the top plate. Therefore, the same reference numerals are used for configurations with the same names as those in the present embodiment, and description will be omitted as appropriate.

[0046] 1, the cooler 2 according to this embodiment has a plurality of fins 22 provided on an upper surface of a bottom plate 21. In addition, the plurality of fins 22 and a peripheral wall portion 23 are provided on the upper surface of the bottom plate 21 so as to surround the outer periphery of the plurality of fins 22. The bottom plate 21, the plurality of fins 22, and the peripheral wall portion 23 may be integrally formed.

[0047] 1, a box-shaped cooler case with an opening at the top is formed by a bottom plate 21 and a peripheral wall portion 23. A top plate 20 forms a lid portion that closes the opening of the cooler case. The top plate 20 is joined to the peripheral wall portion 23 and the tips (upper ends) of the multiple fins 22 by brazing or the like. More specifically, the top plate 20 is joined to the peripheral wall portion 23 and the multiple fins 22 via a joining material B.

[0048] 3, the cooler 2 according to the comparative example has a plurality of fins 22 provided on the lower surface of the top plate 20. In addition, a peripheral wall portion 23 is provided on the lower surface of the top plate 20 so as to surround the outer periphery of the plurality of fins 22. The top plate 20, the plurality of fins 22, and the peripheral wall portion 23 may be integrally formed.

[0049] 3, a box-shaped cooler case that is open downward is formed by the top plate 20 and the peripheral wall portion 23. The bottom plate 21 forms a lid portion that closes the opening of the cooler case. The bottom plate 21 is joined to the peripheral wall portion 23 and the tips (lower ends) of the multiple fins 22 by brazing or the like. More specifically, the bottom plate 21 is joined to the peripheral wall portion 23 and the multiple fins 22 via a joining material B.

[0050] In the present embodiment and the comparative example, the bonding material B is, for example, a sheet-shaped brazing material. The bonding material B has a predetermined thickness and is arranged in a predetermined range of the bottom plate 21. The bonding material B is made of an aluminum alloy-based metal material similar to the top plate 20 and the bottom plate 21. In addition, the semiconductor element 4 and the insulating substrate 3, which are the objects to be cooled, are arranged on the upper surface of the top plate 20. The thickness of the top plate 20 is set to be smaller than the thickness of the bottom plate 21 from the viewpoint of thermal conductivity. In addition, the semiconductor element 4 is a heat source that generates heat as the device is driven. Therefore, in general, in the cooler 2, the temperature of the top plate 20 is more likely to rise than the bottom plate 21 and the peripheral wall portion 23, and corrosion is more likely to progress on the top plate 20 side than on the bottom plate 21 side and the peripheral wall portion 23 side.

[0051] In the comparative example, in the internal space of the cooler 2, the heat dissipation surface 20a side of the top plate 20 where the metal base material is exposed tends to corrode more easily than the bottom plate 21 side where the bonding material B is arranged. As described above, since the top plate 20 is thinner than the bottom plate 21, if corrosion progresses, there is a risk that holes will be formed in the top plate 20 and the refrigerant will leak out.

[0052] On the other hand, in this embodiment, in the internal space of the cooler 2, the bottom plate 21 side where the metal base material is exposed tends to corrode more easily than the top plate 20 side where the bonding material B is arranged. Thus, the progress of corrosion on the top plate 20 side is suppressed. As described above, since the bottom plate 21 is thicker than the top plate 20, even if corrosion progresses, it is possible to suppress the risk of holes being formed and the refrigerant leaking out.

[0053] The bonding material B used in the present embodiment and the comparative example is made of a material having a higher potential than the base material of the top plate 20 and the bottom plate 21. The inventors of the present invention have found that the tendency of corrosion in the flow path of the refrigerant is that the area with a lower potential is more susceptible to corrosion, and the area with a higher potential inhibits the progress of corrosion. More specifically, by using a bonding material B having a higher potential than the base material metal of the top plate 20 and the bottom plate 21, the progress of corrosion is more advanced on the side where the bonding material B is not placed, and the progress of corrosion on the side where the bonding material B is placed is inhibited. Therefore, the inventors of the present invention have focused on the tendency of corrosion due to the high and low potential in the refrigerant flow path inside the cooler 2, and the thickness of the top plate 20 and the bottom plate 21, and have come up with the present invention.

[0054] That is, the gist of the present invention is to make the electric potential of the top plate 20 side having the heat dissipation surface 20a higher than that of the bottom plate 21 side as viewed from the refrigerant flow path. Specifically, in this embodiment, the cooler 2 includes a top plate 20 having a heat dissipation surface 20a formed on one side, a bottom plate 21 arranged opposite to the top plate 20 and having a thickness greater than that of the top plate 20, a plurality of fins 22 provided on the bottom plate 21, and a peripheral wall portion 23 formed to surround the outer periphery of the plurality of fins 22 along the outer periphery of the bottom plate 21. The plurality of fins 22 and the peripheral wall portion 23 are joined to the heat dissipation surface 20a of the top plate 20, and the space surrounded by the top plate 20, the bottom plate 21, the plurality of fins 22, and the peripheral wall portion 23 forms a refrigerant flow path. In the refrigerant flow path, the electric potential of the top plate 20 side is higher than that of the bottom plate 21 side.

[0055] According to this configuration, a plurality of fins 22 and a peripheral wall portion 23 are provided on the bottom plate 21, and the bottom plate 21 side constitutes a cooler case. In addition, in the space (the flow path of the refrigerant) inside the cooler 2, the top plate 20 side, which is relatively thin, has a higher potential than the bottom plate 21 side. Therefore, the top plate 20 side is less susceptible to corrosion than the bottom plate 21 side. In other words, the bottom plate 21 side, which is relatively thick, is allowed to corrode to a certain extent, while the top plate 20 side, which is thinner than the bottom plate 21, is intended to have a higher potential to make corrosion as difficult as possible. This makes it possible to suppress local corrosion at a predetermined location of the refrigerant passage and to extend the life of the cooler 2.

[0056] In addition, in this embodiment, when joining the multiple fins 22 and the peripheral wall portion 23 to the top plate 20, a bonding material B having a higher potential than the bottom plate 21 is used. With this configuration, the bonding material B is interposed between the tips of the multiple fins 22 and the peripheral wall portion 23 and the top plate 20. In the coolant flow path, the bonding material B is arranged on the top plate 20 side, and the bonding material B is not arranged on the bottom plate 21 side, and the bottom plate 21 is exposed. Therefore, it is possible to generate a potential difference between the top plate 20 side and the bottom plate 21 side by the bonding material B.

[0057] It is preferable that the potential difference between the top plate 20 side and the bottom plate 21 side, that is, the potential difference between the bonding material B and the bottom plate 21, is 50 mV or more. In this case, it is possible to suppress corrosion on the top plate 20 side as much as possible.

[0058] In addition, in this embodiment, the bonding material B covers the entire lower surface (heat dissipation surface) of the top plate 20. In reality, it is sufficient to place the bonding material B only at the joints. However, in this embodiment, the entire heat dissipation surface 20a is covered with the bonding material B, so that the base material of the top plate 20 is not exposed in the flow path of the refrigerant while ensuring the potential difference between the top plate 20 side and the bottom plate 21 side. As a result, it is possible to prevent corrosion of the top plate 20 with the bonding material B. In other words, the bonding material B in the present invention not only has the original function of bonding between members, but also functions as a protective coating to prevent corrosion of the top plate 20.

[0059] In addition, in this embodiment, the bonding material B is composed of a sheet-shaped brazing material. According to this configuration, the sheet-shaped bonding material B is cut in advance to fit the size of the top plate 20, and the bonding material B can be placed between the top plate 20 and the fins 22 and the peripheral wall portion 23. When the bonding material B melts in the furnace, the fins 22 and the peripheral wall portion 23 are bonded to the top plate 20, and the entire lower surface (heat dissipation surface 20a) of the top plate 20 is covered with the brazing material. In this way, by using the sheet-shaped brazing material as the bonding material B, it is possible to simplify the manufacturing process of the cooler 2 (mainly the bonding process and the protective coating formation process). The bonding material B is not limited to a sheet-shaped material, and may be configured to be applied to the entire lower surface of the top plate 20 as a paste-like brazing material.

[0060] In this embodiment, the cooler 2 is preferably made of an aluminum alloy containing aluminum as a main component. For example, the base material of the top plate 20 and the bottom plate 21 is preferably made of a 6000 series aluminum alloy such as A6063. The 6000 series aluminum alloy is made by adding mainly magnesium and silicon to increase the strength of pure aluminum, and has excellent strength and corrosion resistance. For example, the cooler 2 may be made of aluminum as a main component, with silicon at 0.2% to 1.5%, magnesium at 0.35% to 1.5%, copper at 0% to 0.7%, and zinc at 0% to 0.7%. More specifically, the composition of the base material of the top plate 20 and the bottom plate 21 is preferably made of at least copper at a ratio of 2.0% or less. More preferably, copper is 0.2% or less. The composition ratio is expressed in weight percent. The main component refers to a ratio of 80% or more.

[0061] The top plate 20 and the bottom plate 21 are preferably made of an aluminum alloy having the same composition. Alternatively, the top plate 20 and the bottom plate 21 are not limited to being made of an aluminum alloy having the same composition, and may be made of materials having different compositions. In this case, it is preferable to adjust the composition ratio so that the bottom plate 21 and the top plate 20 have the same electric potential, or the top plate 20 has a higher electric potential than the bottom plate 21.

[0062] The brazing material as the bonding material B is preferably formed of a 4000 series aluminum alloy such as A4047. The 4000 series aluminum alloy is mainly composed of aluminum, mainly containing silicon, and has excellent heat resistance and wear resistance. The material of the constituent members of the cooler 2 is not limited to an aluminum alloy, and may be, for example, a copper alloy. For example, the cooler 2 may be composed of aluminum as the main component, with silicon at 4.5% to 13.5%, magnesium at 0% to 1.3%, copper at 0% to 1.3%, and zinc at 0% to 0.25%. The composition of the bonding material B is higher in silicon composition than the base material of the top plate 20 and the bottom plate 21. Also, the composition ratio of magnesium, which has an effect of lowering the electric potential, is small. Furthermore, the composition ratio of copper, which has an effect of raising the electric potential, may be large. Also, the composition ratio of manganese, which has an effect of lowering the electric potential, may be small. More specifically, the composition of the bonding material B is preferably composed of at least silicon at 7.5% or more and zinc at 0.25% or less. The composition ratios are in weight percent. A main component means that it is made up of 80% or more of a material.

[0063] In this embodiment, the semiconductor element 4 is disposed on the upper surface (the other surface) of the top plate 20 via the insulating substrate 3. The multiple fins 22 are disposed directly below the semiconductor element 4. Thus, in this embodiment, the objects to be cooled by the cooler 2 are the semiconductor element 4 and the insulating substrate 3. This is because the semiconductor element 4 is a heat source that generates heat as the device is operated.

[0064] In the semiconductor device 1, the thickness of the top plate 20 is made as small as possible in order to improve the thermal conductivity. More specifically, the thickness of the top plate 20 is preferably 250 μm or more and 5.0 mm or less. By setting the thickness of the top plate 20 within this range, it is possible to effectively dissipate the heat of the semiconductor element 4 from the heat dissipation surface without impairing the thermal conductivity.

[0065] On the other hand, the bottom plate 21 is the side that is fixed to the installation destination, so it needs to have a certain degree of rigidity. Therefore, the bottom plate 21 is formed thicker than the top plate 20 to ensure its rigidity. More specifically, the thickness of the bottom plate 21 is preferably 2.0 mm or more and 10.0 mm or less.

[0066] In addition to the thicknesses of the top plate 20 and bottom plate 21, the thickness of the bonding material B is preferably 50 μm or more and 500 μm or less. By setting the thickness of the bonding material B within this range, it is possible to simultaneously achieve the function of a protective coating that protects the heat dissipation surface of the top plate 20 without impairing thermal conductivity.

[0067] In the above embodiment, the bonding material B is disposed on the lower surface of the top plate 20 with a uniform thickness, but the present invention is not limited to this configuration. The bonding material B may be formed to be partially thick. FIG. 4 is a plan view of a cooler according to a modified example, with the bottom plate omitted, viewed from the bottom. More specifically, in this embodiment, as shown in FIGS. 2 and 4, the bottom plate 21 has a coolant inlet 25 and an outlet 26. The inlet 25 and the outlet 26 are disposed to face each other diagonally across a plurality of fins 22 in a plan view. In this case, it is preferable that the thickness of the bonding material B in the regions 25a, 26b of the top plate 20 facing the inlet 25 and / or the outlet 26 in the Z direction is larger than that of the surrounding area. According to this configuration, the flow rate of the coolant is high near the inlet 25 and the outlet 26 of the coolant. Therefore, from the perspective of the coolant flow path, the top plate 20 facing the inlet 25 and the outlet 26 is in an environment that is prone to corrosion. Therefore, by making the thickness of the bonding material B facing the inlet 25 and the outlet 26 larger than the thickness of the surrounding area, it is possible to effectively prevent the top plate 20 from corroding. Note that the thickness of the bonding material B may be adjusted only at the location corresponding to both the inlet 25 and the outlet 26, or only at the location corresponding to either the inlet 25 or the outlet 26.

[0068] As described above, in this embodiment, a potential difference is provided between the top plate 20 side and the bottom plate 21 side in the cooler 2, thereby suppressing corrosion of the top plate 20 side, which has a relatively small thickness, as much as possible. However, the present invention does not completely prevent corrosion of the inner wall surface of the cooler 2 due to the refrigerant. As described above, in this embodiment, the thicknesses of the top plate 20 and the bottom plate 21 are different in consideration of cooling efficiency (thermal conductivity) and rigidity due to the arrangement of the cooling target (semiconductor element 4, etc.) of the cooler 2. Therefore, the potential of the top plate 20 side, which has a relatively small thickness, is made higher than the potential of the bottom plate 21 side to suppress corrosion of the top plate 20 side as much as possible. In other words, this means that, even if some corrosion is permitted on the bottom plate 21 side, which has a relatively large thickness, corrosion holes large enough to leak the refrigerant are not formed in the bottom plate 21.

[0069] Here, an example of a case where corrosion occurs in the cooler 2 according to the present embodiment will be described with reference to Fig. 5. Fig. 5 is a partially enlarged view of Fig. 1. Note that the corrosion shown in Fig. 5 is merely an example, and is not limited to this. For example, Fig. 5 shows a case where a relatively small corrosion hole is formed on the top plate 20 side as well.

[0070] As shown in FIG. 5, a plurality of corrosion holes 27 (first corrosion holes) of a predetermined size are formed on the upper surface of the bottom plate 21. The depth of the corrosion holes 27 is, for example, 400 μm or more and 1100 μm or less. Meanwhile, a plurality of corrosion holes 28 (second corrosion holes) of a predetermined size are formed on the heat dissipation surface 20a of the top plate 20. The corrosion holes 28 penetrate the bonding material B and partially erode the lower surface (heat dissipation surface 20a) of the top plate 20. The depth of the corrosion holes 28 is shallower than the corrosion holes 27, for example, 100 μm or more and 550 μm or less. More specifically, the corrosion holes 28 are about half as deep as the corrosion holes 27. The number of the corrosion holes 28 is smaller than the number of the corrosion holes 27.

[0071] In this embodiment, the potential of the relatively thin top plate 20 side is increased, making the top plate 20 side more difficult to corrode than the bottom plate 21 side. Conversely, the relatively thick bottom plate 21 side is more likely to corrode than the top plate 20 side. For this reason, the corrosion holes 27 on the bottom plate 21 side are formed larger and more in number than the corrosion holes 28 on the top plate 20 side. As described above, the bottom plate 21 has a sufficient thickness to ensure rigidity, so some corrosion is tolerable. Therefore, a situation in which the bottom plate 21 side causes liquid leakage due to the corrosion holes 27 does not occur.

[0072] On the other hand, the top plate 20 side has the semiconductor element 4 disposed on its upper surface and is likely to become hotter than the bottom plate 21 side, but is less likely to corrode in the first place because it has a higher potential than the bottom plate 21 side. Even if corrosion does occur, the joining material B made of brazing material corrodes first, so even if the corrosion progresses to the base material of the top plate 20, the size of the corrosion hole 28 itself is sufficiently smaller than the corrosion hole 27 on the bottom plate 21 side. Therefore, even on the top plate 20 side, a situation in which liquid leakage occurs due to the corrosion hole 28 does not occur.

[0073] Next, modified examples will be described with reference to Fig. 3, Fig. 6, and Fig. 7. Fig. 6 is a cross-sectional view of a semiconductor device according to a modified example. Fig. 7 is a cross-sectional view of a semiconductor device according to another modified example.

[0074] As described above, in the comparative example shown in FIG. 3, the bonding material B is disposed on the bottom plate 21 side, and the top plate 20 side has a lower potential than the bottom plate 21 side. On the other hand, the layout in FIG. 3 may be kept the same, and the composition of the bonding material B may be adjusted so that the potential on the top plate 20 side is higher than the potential on the bottom plate 21 side. That is, in FIG. 3, the bonding material B on the bottom plate 21 side may have a lower potential than the top plate 20. In this case, since the bonding material B has a lower potential, the bonding material B becomes a sacrificial layer and corrosion progresses before the top plate 20. Then, until the bonding material B is corroded and disappears, the corrosion on the top plate 20 side can be delayed, and it is possible to suppress liquid leakage on the top plate 20 side. However, in this case, since the bonding material B needs to be sufficiently thick, there is a problem such as a measure against peeling at the joint between the top plate 20 and the bottom plate 21. Therefore, as shown in FIG. 1, it is preferable that the bonding material B has a high potential.

[0075] As shown in FIG. 6, the top plate 20 and the bottom plate 21 are joined via a bonding material B, but the lower surface (heat dissipation surface 20a) of the top plate 20 and the upper surface of the bottom plate 21 are not covered with the bonding material B. In this case, the bonding material B may be formed in a rectangular frame shape that follows the shape of the peripheral wall portion 23. In this case, it is preferable that the top plate 20 side has a higher potential than the bottom plate 21 side. Even with this configuration, the bottom plate 21 side corrodes before the top plate 20 side, so that it is possible to delay the corrosion of the top plate 20 side and suppress the liquid leakage on the top plate 20 side. However, in this case, since the workability, rigidity, and heat dissipation of the top plate 20 and the bottom plate 21 are inferior, it is preferable to have a bonding material B with a higher potential as shown in FIG. 1.

[0076] Furthermore, as shown in FIG. 7, both the lower surface (heat dissipation surface 20a) of the top plate 20 and the upper surface of the bottom plate 21 may be covered with the bonding material B. In this case, it is preferable that the top plate 20 side has a higher potential than the bottom plate 21 side. Even with this configuration, the bottom plate 21 side corrodes before the top plate 20 side, so it is possible to delay the corrosion of the top plate 20 side and suppress liquid leakage on the top plate 20 side. However, in this case, it is necessary to make the bonding material B sufficiently thick, which poses a problem such as a measure against peeling at the joint between the top plate 20 and the bottom plate 21. Therefore, it is preferable that the bonding material B on the top plate 20 side has a higher potential as shown in FIG. 1.

[0077] As described above, according to this embodiment, by providing a potential difference between the top plate 20 and the bottom plate 21 of the cooler 2, it is possible to suppress local corrosion on the top plate 20 side.

[0078] In the above embodiment, the inlet 25 and the outlet 26 are disposed to face each other at an angle, but the present invention is not limited to this configuration. For example, the inlet 25 and the outlet 26 may face each other in a direction (Y direction) perpendicular to the longitudinal direction of the cooler 2.

[0079] In the above embodiment, the inlet 25 and the outlet 26 have a long hole shape that is long in the longitudinal direction (X direction), but are not limited to this configuration. The shapes, locations, etc. of the inlet 25 and the outlet 26 can be changed as appropriate.

[0080] Furthermore, in the above embodiment, the number and locations of the semiconductor elements 4 are not limited to the above configuration and can be changed as appropriate.

[0081] Furthermore, in the above embodiment, the number and layout of the circuit boards 32 are not limited to the above configuration, and can be changed as appropriate.

[0082] In the above embodiment, the insulating substrate 3 and the semiconductor element 4 are configured to be rectangular or square in plan view, but are not limited to this configuration. These configurations may be formed into polygonal shapes other than those described above.

[0083] Furthermore, although the present embodiment and modifications have been described, other embodiments may be combinations of the above-described embodiments and modifications in whole or in part.

[0084] In addition, the present embodiment is not limited to the above-mentioned embodiment and modification, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological progress or a different derived technology, it may be implemented using that method. Therefore, the claims cover all embodiments that may be included in the scope of the technical idea.

[0085] The features of the above embodiment are summarized below. The cooler in the above embodiment comprises a top plate having a heat dissipation surface formed on one side, a bottom plate arranged opposite the top plate and thicker than the top plate, a plurality of fins provided on the bottom plate, and a peripheral wall portion formed along the outer periphery of the bottom plate to surround the outer periphery of the plurality of fins, the plurality of fins and the peripheral wall portion being joined to the heat dissipation surface of the top plate, a flow path for a refrigerant is formed by the space surrounded by the top plate, the bottom plate, the plurality of fins, and the peripheral wall portion, and the electric potential on the top plate side is higher than the electric potential on the bottom plate side.

[0086] Moreover, the cooler according to the above embodiment further includes a bonding material that bonds the plurality of fins and the peripheral wall portion to the top plate, and the bonding material has a higher potential than the bottom plate side.

[0087] In the cooler according to the above embodiment, the bonding material covers the entire heat dissipation surface in the flow path of the refrigerant.

[0088] In the cooler according to the above embodiment, the bonding material is made of a sheet-shaped brazing material.

[0089] In the cooler according to the above embodiment, the potential difference between the bottom plate side and the bonding material is 50 mV or more.

[0090] In the cooler according to the above embodiment, the base material of the bottom plate is exposed to the flow path of the refrigerant.

[0091] In the cooler according to the above embodiment, the bonding material and the base material of the bottom plate are mainly composed of aluminum, and the bonding material has a higher proportion of silicon and a lower proportion of magnesium than the base material of the bottom plate.

[0092] In the cooler according to the above embodiment, the bonding material has a composition mainly composed of aluminum, with at least 7.5% silicon and 0.25% zinc.

[0093] In the cooler according to the above embodiment, the base material of the bottom plate is mainly composed of aluminum with a copper content of at least 2.0% or less.

[0094] In the cooler according to the above embodiment, a first corrosion pit is formed in the upper surface of the bottom plate.

[0095] Furthermore, in the cooler according to the above embodiment, a second corrosion pit penetrating the bonding material is formed in the heat dissipation surface of the top plate, and the second corrosion pit is smaller than the first corrosion pit.

[0096] In the cooler according to the above embodiment, the bonding material has a thickness of 50 μm or more and 500 μm or less.

[0097] In the cooler according to the above embodiment, the thickness of the top plate is not less than 0.25 mm and not more than 5.0 mm.

[0098] In the cooler according to the above embodiment, the thickness of the bottom plate is not less than 2.0 mm and not more than 10.0 mm.

[0099] In the cooler according to the above embodiment, the base material of the top plate and the base material of the bottom plate are formed of materials having different compositions, and the potential of the base material of the top plate is higher than the potential of the base material of the bottom plate.

[0100] In addition, the semiconductor device of the above embodiment comprises the above-mentioned cooler and a semiconductor element arranged on the other surface of the top plate via an insulating substrate, and the multiple fins are arranged directly below the semiconductor element.

[0101] In addition, in the semiconductor device according to the above embodiment, the bottom plate has an inlet and an outlet for a coolant, the inlet and the outlet are arranged to face each other across the multiple fins, and the thickness of the bonding material facing the inlet and / or the outlet is greater than the surrounding area. [Industrial Applicability]

[0102] INDUSTRIAL APPLICABILITY As described above, the present invention has the effect of being able to suppress localized corrosion at predetermined locations in a coolant passage, and is particularly useful for a water-cooling type cooler and a semiconductor device equipped with the same. [Explanation of symbols]

[0103] 1 Semiconductor device 2 cooler 3. Insulating Substrate 4. Semiconductor elements 5 Case material 6 Sealing resin 20 Tabletop 21 Bottom plate 22 Finn 23 Peripheral wall section 24 Fin assembly 25 Introduction 26 Outlet 27 Corrosion pit (first corrosion pit) 28 Corrosion pit (secondary corrosion pit) 30 Insulating plate 31 Heat sink 32 circuit board 70 Flange 71 Mounting surface 72 O-ring 73 Groove S solder B Bonding material R1 First header section R2 Second header section R3 Fin housing

Claims

1. A top plate having a heat dissipation surface on one side; A bottom plate disposed opposite the top plate and having a greater thickness than the top plate; A plurality of fins provided on the bottom plate; a peripheral wall portion formed along an outer peripheral edge of the bottom plate so as to surround an outer periphery of the plurality of fins; a bonding material that bonds the plurality of fins and the peripheral wall portion to the top plate; Equipped with The plurality of fins and the peripheral wall portion are joined to the heat dissipation surface of the top plate, and a flow path of a coolant is formed by a space surrounded by the top plate, the bottom plate, the plurality of fins, and the peripheral wall portion, the potential of the top plate side is higher than the potential of the bottom plate side, The bonding material is mainly composed of aluminum, and contains at least silicon having a composition ratio of 7.5% or more, zinc having a composition ratio of 0.25% or less, and magnesium, The bottom plate is The main component is aluminum, and the composition ratio of at least silicon is 0.2% or more and 1.5% or less, the composition ratio of magnesium is 0.35% or more and 1.5% or less, the composition ratio of copper is 0% or more and 0.7% or less, and the composition ratio of zinc is 0% or more and 0.7% or less, or A cooler having aluminum as its main component, and at least silicon having a composition ratio of 4.5% or more and 13.5% or less, magnesium having a composition ratio of 0% or more and 1.3% or less, copper having a composition ratio of 0% or more and 1.3% or less, and zinc having a composition ratio of 0% or more and 0.25% or less.

2. A cooler as described in claim 1, wherein the bonding material has a higher potential than the bottom plate side.

3. The cooler according to claim 2 , wherein the bonding material covers the entire heat dissipation surface in the flow path of the refrigerant.

4. The cooler according to claim 2 or 3, wherein the bonding material is a sheet-shaped brazing material.

5. 5. The cooler according to claim 2, wherein a potential difference between the bottom plate side and the bonding material is 50 mV or more.

6. The cooler according to claim 2 , wherein a base material of the bottom plate is exposed to a flow path of the refrigerant.

7. The base material of the bonding material and the base plate is mainly composed of aluminum, 7. The cooler according to claim 2, wherein the bonding material has a higher silicon ratio and a lower magnesium ratio than the base material of the bottom plate.

8. 8. The cooler according to claim 2, wherein the bonding material has a composition mainly composed of aluminum, with at least 7.5% silicon and 0.25% zinc.

9. 9. The cooler according to claim 8, wherein the base material of the bottom plate is mainly composed of aluminum with a copper content of 2.0% or less.

10. The cooler according to claim 2 , wherein a first corrosion pit is formed in an upper surface of the bottom plate.

11. a second corrosion hole penetrating the bonding material is formed on the heat dissipation surface of the top plate; The cooler of claim 10 , wherein the second erosion pitting is smaller than the first erosion pitting.

12. The cooler according to claim 2 , wherein the bonding material has a thickness of 50 μm or more and 500 μm or less.

13. The cooler according to claim 2 , wherein the thickness of the top plate is not less than 0.25 mm and not more than 5.0 mm.

14. The cooler according to claim 2 , wherein the bottom plate has a thickness of 2.0 mm or more and 10.0 mm or less.

15. 15. A cooler as described in claim 2, wherein the base material of the top plate and the base material of the bottom plate are formed of materials having different compositions, and the electric potential of the base material of the top plate is higher than the electric potential of the base material of the bottom plate.

16. A cooler according to any one of claims 2 to 15; a semiconductor element disposed on the other surface of the top plate via an insulating substrate; The semiconductor device, wherein the plurality of fins are disposed directly below the semiconductor element.

17. The bottom plate has an inlet and an outlet for a coolant, The inlet and the outlet are disposed to face each other across the fins, The semiconductor device according to claim 16 , wherein a thickness of the bonding material facing the inlet and / or the outlet is greater than a thickness of a periphery thereof.

Images