JP7345774B2 - How to manufacture a heat sink - Google Patents

Description

The present invention relates to a heat sink and a method of manufacturing the heat sink.

For example, Patent Document 1 discloses a boiling cooling device (heat sink) using a micro heat transfer device. In such a boiling cooling device, heat generated from a power electronics component that is a heat source is cooled by boiling a refrigerant flowing through a cooling passage formed inside.

Special Publication No. 2004-509450

In recent years, high-performance and small-sized electronic components have been developed, and there is a need to quickly cool down the high heat generated from such high-performance and small-sized components (heat sources). However, in the conventional heat sink as described above, when the refrigerant boils, many large bubbles are generated in the refrigerant flow path near the heat source, increasing flow resistance and gradually reducing the flow rate of the refrigerant. There is a problem that cooling performance is reduced.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to ensure the cooling performance of a heat sink when cooling a high-temperature heat source.

In order to achieve the above object, the present invention provides, as a first means related to a heat sink, a heat sink that cools the heat of a heat source by a refrigerant flowing inside, comprising a plurality of refrigerant channels through which the refrigerant flows, A configuration is adopted in which a refrigerant flow path that is closer to the heat source has a larger hydraulic diameter than a refrigerant flow path that is farther from the heat source.

As a second means related to the heat sink, a configuration is adopted in which the refrigerant flow path has a circular or polygonal cross-sectional shape perpendicular to the flow direction of the refrigerant in the first means.

As a third means related to the heat sink, a configuration is adopted in which the refrigerant flow path is formed in the first or second means, and a plurality of refrigerant flow path layers are laminated.

As a first means according to the method for manufacturing a heat sink, a first groove is formed on a first surface closest to the heat source, and a hydraulic diameter smaller than the first groove is formed on a second surface opposite to the surface closest to the heat source. A configuration is adopted in which a channel plate in which a second groove is formed and a top plate provided for the first surface and the second surface are joined by diffusion bonding.

As a second means according to the method for manufacturing a heat sink, in the first means, the first groove and the second groove are formed by any one of extrusion molding, rolling processing, and cutting processing. adopt.

A third method of manufacturing a heat sink includes a plurality of flow path plates in which refrigerant flow paths through which a refrigerant flows are formed, and each of the plurality of flow path plates has a refrigerant flow path that is close to the heat source. A configuration is adopted in which the shape is set so that the hydraulic diameter is larger than that of the refrigerant flow path located far from the heat source, and the plurality of flow path plates are joined together by diffusion bonding.

According to the present invention, the shape of the refrigerant flow path is set so that the closer it is to the heat source, the larger the hydraulic diameter becomes. In the refrigerant flow path close to the heat source, large bubbles are likely to occur due to the high temperature, but by increasing the hydraulic diameter, it is possible to prevent the refrigerant flow rate from decreasing and ensure the refrigerant flow rate. . A refrigerant flow path that is far from the heat source has a smaller temperature rise than a refrigerant flow path that is closer to the heat source, and flow resistance due to bubble generation is less likely to occur. Since the refrigerant flows selectively through channels with low flow resistance, the hydraulic diameter of the refrigerant channel far from the heat source is set small to match the flow resistance that occurs in the refrigerant channel near the heat source when it is strongly heated. By setting the flow resistance, it is possible to prevent the refrigerant from detouring to a refrigerant flow path far from the heat source. Therefore, it is possible to ensure the cooling performance of the heat sink when cooling a high-temperature heat source.

FIG. 1 is a schematic cross-sectional view of a power semiconductor unit equipped with a heat sink according to a first embodiment of the present invention. FIG. 1 is a schematic perspective view of a heat sink according to a first embodiment of the present invention. It is a schematic perspective view of the heat sink based on 2nd Embodiment of this invention. It is a schematic perspective view which shows the modification of the heat sink based on 1st Embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a heat sink according to the present invention will be described below with reference to the drawings.

[First embodiment]
A heat sink 1 according to this embodiment is included in a power semiconductor unit 100. The power semiconductor unit 100 includes a power semiconductor chip 110, a circuit board 120, and a heat sink 1, as shown in FIG.

Power semiconductor chip 110 is bonded to circuit board 120 with solder layer 111 . This power semiconductor chip 110 is a semiconductor chip whose electrodes are connected to external terminals (not shown). Note that the power semiconductor chip 110 generates a large amount of heat when energized.

The circuit board 120 is a board on which the power semiconductor chip 110 is mounted and an electronic circuit including electronic components is formed. This circuit board 120 is bonded with the surface opposite to the surface to which the power semiconductor chip 110 is bonded fully in contact with the heat sink 1 .

The heat sink 1 is a substantially rectangular parallelepiped-shaped member made of a highly thermally conductive metal (for example, aluminum). As shown in FIG. 2, the heat sink 1 is configured by laminating a first coolant channel layer 2, a second coolant channel layer 3, and a third coolant channel layer 4. The first refrigerant flow path layer 2 is a substantially rectangular plate member with one side in contact with the circuit board 120, and a plurality of (three in this embodiment) first refrigerant flow paths R1 are formed inside. There is. The first refrigerant flow paths R1 penetrate through the inside of the first refrigerant flow path layer 2, and are formed in straight lines so as to be parallel to each other. Further, the first refrigerant flow path R1 has a circular cross-sectional shape in a direction perpendicular to the flow direction of the flow path.

The second refrigerant flow path layer 3 is a substantially rectangular plate member similar to the first refrigerant flow path layer 2, and is in contact with the surface of the first refrigerant flow path layer 2 that is opposite to the surface that is in contact with the circuit board 120. It is set in. The second refrigerant flow path layer 3 has a plurality of (three in this embodiment) second refrigerant flow paths R2 formed therein. The second refrigerant flow path R2 penetrates the inside of the second refrigerant flow path layer 3, and is formed in a straight line so as to be parallel to each other. Further, the second refrigerant flow path R2 has a circular cross-sectional shape in a direction perpendicular to the flow direction of the flow path.

The third refrigerant flow layer 4 is a substantially rectangular plate member similar to the first refrigerant flow layer 2, and has a surface opposite to the surface of the second refrigerant flow layer 3 that is in contact with the first refrigerant flow layer 2. is placed in contact with the The third refrigerant flow path layer 4 has a plurality of (three in this embodiment) third refrigerant flow paths R3 formed therein. The third refrigerant flow path R3 passes through the inside of the third refrigerant flow path layer 4, and is formed in a straight line so as to be parallel to each other. Further, the third refrigerant flow path R3 has a circular cross-sectional shape in a direction perpendicular to the flow direction of the flow path.

The first coolant channel layer 2 is located at the shortest distance from the power semiconductor chip 110, which is the heat source, and the third coolant channel layer 4 is located at the farthest distance from the power semiconductor chip 110. The first refrigerant flow path R1, the second refrigerant flow path R2, and the third refrigerant flow path R3 have a shape in which the first refrigerant flow path R1 has the largest hydraulic diameter and the third refrigerant flow path R3 has the smallest hydraulic diameter. It is set. Further, the first refrigerant flow path R1, the second refrigerant flow path R2, and the third refrigerant flow path R3 are shaped so that the closer they are to the heat source, the larger the cross-sectional area of the flow path becomes. Note that the hydraulic diameter D is determined by the following formula (1), where A is the cross-sectional area in the direction orthogonal to the flow direction of the refrigerant, and L is the circumference of the flow path.

In such a heat sink 1, liquid refrigerant flows in one direction in the first refrigerant flow path R1, the second refrigerant flow path R2, and the third refrigerant flow path R3. The heat generated in the power semiconductor chip 110 and the circuit board 120 is first transferred to the first coolant channel layer 2. As a result, in the first refrigerant flow path R1 in the first refrigerant flow path layer 2, the refrigerant is heated and boils to generate bubbles. Then, the refrigerant in the first refrigerant flow path R1 flows downstream in a gas-liquid mixed state containing large air bubbles as the air bubbles connect and grow.

Furthermore, heat is transferred to the second refrigerant flow path layer 3 via the first refrigerant flow path layer 2 . Therefore, the thermal energy transmitted to the second refrigerant channel layer 3 is smaller than the thermal energy transmitted to the first refrigerant channel layer 2. In such a situation, bubbles are generated in the refrigerant flowing through the second refrigerant flow path R2 of the second refrigerant flow path layer 3 due to heating. Bubbles smaller than bubbles in the refrigerant in the first refrigerant flow path R1 are generated in the refrigerant in the second refrigerant flow path R2, and the refrigerant flows downstream in a gas-liquid mixed state.

Furthermore, in the third refrigerant flow layer 4, heat is transferred via the first refrigerant flow layer 2 and the second refrigerant flow layer 3. Therefore, the thermal energy transmitted to the third refrigerant channel layer 4 is smaller than the thermal energy transmitted to the second refrigerant channel layer 3. In this situation, the refrigerant in the third refrigerant flow path R3 of the third refrigerant flow path layer 4 slightly contains bubbles that are smaller than the bubbles in the refrigerant in the first refrigerant flow path R1 and the second refrigerant flow path R2. Then, it flows downstream in a gas-liquid mixed state.

Such a heat sink 1 discharges heat by boiling and flowing the refrigerant flowing through the first refrigerant flow path R1, the second refrigerant flow path R2, and the third refrigerant flow path R3, and removes heat from the power semiconductor chip 110, which is a heat source. and cools down the heat of the circuit board 120.

In this embodiment, since high-temperature heat is transmitted to the first refrigerant flow path R1, bubbles generated in the refrigerant become larger. R1, the second refrigerant flow path R2, and the third refrigerant flow path R3) are shaped so that the hydraulic diameter thereof becomes large. Thereby, it is possible to ensure the flow rate of the refrigerant in the refrigerant flow path (first refrigerant flow path R1) where the temperature of the refrigerant is high and bubbles are likely to occur. That is, since the hydraulic diameter of the second refrigerant flow path R2 and the third refrigerant flow path R3 gradually decreases, the flow resistance increases and the flow rate of the refrigerant tends to decrease. As the flow rate of the refrigerant moving to the second refrigerant flow path R2 and the third refrigerant flow path R3 decreases, the flow rate of the refrigerant moving to the first refrigerant flow path R1 is ensured. Therefore, since it is possible to prevent the flow rate of the refrigerant in the first refrigerant flow path R1 from decreasing, it is possible to ensure the cooling performance of the heat sink 1 even when cooling a high-temperature heat source. In addition, if the hydraulic diameters of the refrigerant flow paths (first refrigerant flow path R1, second refrigerant flow path R2, and third refrigerant flow path R3) are the same, the third refrigerant flow path R3 has smaller bubbles generated in the refrigerant. The flow rate of the refrigerant moving to the first refrigerant flow path R1 will increase, and the flow rate of the refrigerant moving to the first refrigerant flow path R1 will decrease, and there is a possibility that dryout will occur in the first refrigerant flow path R1. There is.

Further, in this embodiment, the cross-sectional shapes of the first refrigerant flow path R1, the second refrigerant flow path R2, and the third refrigerant flow path R3 perpendicular to the refrigerant flow direction are circular. This makes it easier to set the hydraulic diameter, especially the circumference.

Moreover, in this embodiment, the heat sink 1 is configured by laminating a first refrigerant flow path layer 2, a second refrigerant flow path layer 3, and a third refrigerant flow path layer 4. Therefore, since a refrigerant flow path is formed for each layer, the formation thereof can be easily performed.

[Second embodiment]
Next, a modification of the first embodiment will be described as a second embodiment with reference to FIG. 3. Note that the same components as in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

The heat sink 1A according to this embodiment includes a flow path plate 5 and two top plates 6.
The flow path plate 5 is a substantially rectangular parallelepiped-shaped member, and a plurality of (four in this embodiment) first grooves M1 are formed on a first surface 5a (outer surface) disposed at a position closest to the circuit board 120. A plurality of (five in this embodiment) second grooves M2 are formed on the second surface 5b (outer surface) facing the first surface 5a. The plurality of first grooves M1 and second grooves M2 are each formed in a linear shape parallel to each other from one side of each surface to the opposing side. The first groove M1 has a larger width and depth than the second groove M2.

The top plate 6 is fixed in contact with the first surface 5a and the second surface 5b. Of these, the top plate 6 fixed to the first surface 5a is placed in contact with the circuit board 120. The channel plate 5 and the top plate 6 are each made of a metal with high thermal conductivity (for example, aluminum).

Such a heat sink 1A is formed by joining the top plate 6 to the first surface 5a and second surface 5b of the channel plate 5 by diffusion bonding. Further, the first groove M1 and the second groove M2 of the channel plate 5 are each formed by cutting using a vertical milling cutter. As a result, a space surrounded by the first groove M1 of the channel plate 5 and the top plate 6 and a space surrounded by the second groove M2 and the top plate 6 are used as a refrigerant flow path.

Also in the heat sink 1A according to this embodiment, the hydraulic diameter of the refrigerant flow path (first groove M1) that is closer to the heat source is the hydraulic diameter of the refrigerant flow path (second groove M2) that is farther from the heat source. is set larger than . Therefore, it is possible to ensure the flow rate in the refrigerant flow path where the temperature is high and bubbles are likely to occur, and it is possible to prevent the flow rate of the refrigerant from decreasing due to air bubbles. Therefore, even when cooling a high-temperature heat source, it is possible to ensure the cooling performance of the heat sink 1A.

According to the method for manufacturing the heat sink 1A according to the present embodiment, the first groove M1 and the second groove M2 are formed in the channel plate 5, and the top plate 6 is further formed so as to overlap the first groove M1 and the second groove M2. By joining by diffusion bonding, it is possible to tightly join the channel plate 5 and the top plate 6 without performing difficult processing to form a refrigerant channel inside the plate-like member, and it is also possible to Refrigerant channels with different diameters can be easily formed.

Moreover, in this embodiment, the first groove M1 and the second groove M2 are formed by cutting. Thereby, it is possible to easily form the first groove M1 and the second groove M2 in the channel plate 5.

Although preferred embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the above embodiments. The various shapes and combinations of the constituent members shown in the embodiments described above are merely examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

In the first embodiment, the refrigerant flow path has a circular cross-sectional shape, but the present invention is not limited to this. For example, the cross-sectional shape of the refrigerant flow path may be a polygonal shape such as a rectangle, as shown in FIG. Even in this case, by setting the hydraulic diameter to be larger as the distance from the heat source is shorter, it is possible to prevent the flow rate of the refrigerant from decreasing due to air bubbles. In addition, by making the cross-sectional shape polygonal, the refrigerant in a liquid state remains at the corners due to surface tension, so that the cooling performance of the heat sink 1 can be ensured.

Further, in the second embodiment, the first groove M1 and the second groove M2 of the channel plate 5 are formed by cutting, but the present invention is not limited to this. The first groove M1 and the second groove M2 may be formed by extrusion molding or rolling. Further, when rolling the channel plate 5, it is preferable to perform the rolling using a heated rolling roller in a vacuum environment.

Further, in the first and second embodiments described above, the heat sink 1 has a laminated structure, but the present invention is not limited to this. A single heat sink 1 may have refrigerant channels (a first refrigerant channel R1, a second refrigerant channel R2, and a third refrigerant channel R3). In this case, a bonding process such as diffusion bonding can be omitted.

In the embodiment described above, the heat sink 1 is provided in the power semiconductor unit 100, but the present invention is not limited thereto. The heat sink 1 is not limited to the power semiconductor chip 110, and can be applied to cooling components that generate a large amount of heat.

1, 1A... Heat sink 2... First refrigerant channel layer 3... Second coolant channel layer 4... Third coolant channel layer 5... Channel plate 5a... First surface 5b... Second Surface M1...First groove M2...Second groove R1...First refrigerant flow path R2...Second refrigerant flow path R3...Third refrigerant flow path

Claims (2)

A first groove is formed on a first surface closest to the heat source, and a second groove whose shape is set so that the hydraulic diameter is smaller than that of the first groove is formed on a second surface facing the surface closest to the heat source. a flow path plate,
A method for manufacturing a heat sink, comprising: joining a top plate provided to the first surface and the second surface by diffusion bonding. 2. The method of manufacturing a heat sink according to claim 1 , wherein the first groove and the second groove are formed by extrusion molding, rolling, or cutting.

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