heat sink

Abstract

To provide a heat sink with high heat dissipation.SOLUTION: In a heat sink 1 for cooling a power module, a stage part 10 installed in a cooled body, and a plurality of fins 30 stood from the stage part 10 are provided. Each fin 30 includes a plurality of hollow parts 31 arranged to a height direction of each fin 30. Each hollow part 31 is characterized so that it is communicated to a flow direction of a cooling medium. Both of the fins 30 and 30 are arranged with a predetermined interval. Each fin 30 and the stage part 10 are formed by an another member, respectively and are bonded each other. Each fin 30 is constructed by an extrusion molding material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat sink used for cooling a power module or the like. [Background technology]

[0002] Conventionally, copper or aluminum (including aluminum alloys), which have good thermal conductivity, have been used for heat sinks used to cool power modules. Although aluminum has inferior thermal conductivity to copper, it is widely used because it is easy to process and lightweight. Known heat sink shapes include those with multiple fins standing upright on a base (see, for example, Patent Documents 1 and 2). The heat sink in Patent Document 1 has lattice-shaped raised portions formed on the end faces of the fins, which increases the surface area and thereby improves thermal conductivity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Design Registration No. 823716 [Patent Document 2] Design Registration No. 957514 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been an increasing demand for higher performance and smaller size of power modules, which has led to a demand for higher heat dissipation capabilities from heat sinks. From this perspective, an object of the present invention is to provide a heat sink with high heat dissipation properties. [Means for solving the problem]

[0005] To solve the above problems, the present invention provides a heat sink for cooling a power module, comprising a base portion to be placed on an object to be cooled and a plurality of fins standing up from the base portion, the fins having a plurality of hollow portions aligned in a height direction of the fins, the hollow portions communicating in a flow direction of a cooling medium, The fin and the base are formed from separate members, a recess is formed at the end of the fin on the joining side where the fin is joined to the base, a first protrusion that fits into the inside of the recess of the fin and a pair of second protrusions that are pressed against the side of the joining side end of the fin are formed on the upper surface of the base, and bifurcated legs that form side walls on both sides of the recess are inserted between the first protrusion and the second protrusion and are clamped between the first protrusion and the second protrusion. It is characterized by: According to the heat sink of the present invention, the surface area of ​​the fins is increased by providing hollow portions in the fins, and heat can be dissipated not only from the outside but also from the inside of the fins, thereby improving heat dissipation. Furthermore, because the fins and base are formed from separate materials, the fins and base each have a simple, flat shape, facilitating manufacturing. Furthermore, the fins can be mechanically joined to the base (by crimping), allowing for easy joining. Furthermore, because the lower end of the fin is bifurcated, the fin can be crimped to the base in two places, improving adhesion between the fin and base. This increases the bonding strength between the fin and base, as well as thermal conductivity.

[0006] In the heat sink of the present invention, the fins are preferably arranged at a predetermined interval. With this configuration, the flow of the coolant between the fins becomes smoother, and heat dissipation performance is further improved.

[0010] In the heat sink of the present invention, the fins are preferably made of an aluminum alloy and the base is preferably made of copper. With this configuration, the fins are made of an aluminum alloy, which has excellent formability, making it easy to form complex shapes with hollow spaces, and the base is made of copper, which improves heat diffusion.

[0011] Furthermore, in the heat sink of the present invention, it is preferable that the hollow portion has a rectangular cross section. With such a configuration, the hollow portion can be easily formed and the surface area of ​​the hollow portion can be increased, thereby improving heat dissipation properties. [Effects of the Invention]

[0012] The heat sink according to the present invention has the excellent effect of improving heat dissipation. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing a heat sink according to an embodiment of the present invention; [Figure 2]1A to 1C are diagrams showing a heat sink according to an embodiment of the present invention, in which (a) is a plan view, (b) is a front view, and (c) is a side view. [Figure 3] FIG. 2 is a perspective view showing a base portion of a heat sink according to an embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view showing fins of a heat sink according to an embodiment of the present invention. [Figure 5] 1 is a perspective view showing a crimping jig for joining fins and a base portion of a heat sink according to an embodiment of the present invention. [Figure 6] 1A and 1B are diagrams showing the crimping joining of the fins and base of a heat sink according to an embodiment of the present invention, in which (a) is a front view showing the state before joining, and (b) is a front view showing the state after joining. [Figure 7] 4 is an enlarged front view showing a state in which the fins and the base of the heat sink according to the embodiment of the present invention are joined by crimping; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] A heat sink according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The heat sink according to this embodiment is an air-cooled heat sink for a power module, and cools the power module, which is configured by combining multiple semiconductors. As shown in FIGS. 1 and 2, the heat sink 1 of this embodiment includes a base 10 and multiple fins 30, 30.... The base 10 and the fins 30 are formed as separate members. In this embodiment, the configuration of the heat sink 1 will be described with the front view of FIG. 2(b) as the reference, with the left-right and up-down directions defined as the left-right and up-down directions and the front-to-back direction defined as the direction of the paper. Note that these directions are used to explain the structure of the heat sink 1 and do not limit the installation direction of the heat sink 1.

[0015] The base 10 is a plate-shaped member that supports the fins 30 and is installed on the power module (body to be cooled). The base 10 is made of copper. The base 10 is formed, for example, by forging or rolling a material and then finishing it by cutting. As shown in Figures 1 to 3, the base 10 has a rectangular shape in a plan view. The lower surface of the base 10 is formed flat and serves as a contact surface with the body to be cooled. The lower surface of the base 10 may be adhered to the surface of the power module via a thermally conductive adhesive, or may be pressed against the surface of the power module using means such as screws.

[0016] The upper surface of the base 10 has an uneven shape for fixing the fins 30. A first ridge 11 and a second ridge 12 are formed on the upper surface of the base 10. The first ridge 11 is a part that fits inside the lower end of the fin 30 and rises from the base surface on the upper surface of the base 10. A step 13 that is one step lower than the base surface is formed on both the left and right ends of the base 10. The step 13 makes it easier for the base 10 to engage with a fixing jig (not shown) that fixes the base 10 to the power module.

[0017] The first ridges 11 have a rectangular cross section and extend along the front-to-rear direction of the base 10. The first ridges 11 are formed over the entire length of the base 10 in the front-to-rear direction. The first ridges 11 have a rectangular cross section.

[0018] The second ridges 12 are portions that are pressed against the lower end side surfaces of the fins 30 and are arranged on both the left and right sides of the first ridges 11 at a predetermined interval. For each fin 30, one first ridge 11 and a pair of second ridges 12, 12 on either side form a set, fixing the fin 30 in place. The number of first ridges 11 and pairs of second ridges 12, 12 corresponds to the number of fins 30. Like the first ridges 11, the second ridges 12 have a rectangular cross section and extend along the front-rear direction of the base 10. The second ridges 12 are also formed over the entire length of the base 10 in the front-rear direction. The thickness of the second ridges 12 is smaller than the thickness of the first ridges 11. The height of the second ridges 12 is equal to the height of the first ridges 11. The height of the second ridges 12 may be greater than the height of the first ridges 11. The second ridges 12 are pressed toward the first ridges 11 by a caulking jig 50 (described later), and press against the side surfaces of the lower ends of the fins 30 .

[0019] As shown in Figures 1 and 2, the fins 30 are plate-shaped members that dissipate heat conducted from the base 10 and are joined to the base 10 in an upright state. The fins 30 have a rectangular shape in side view and extend along the front-to-rear direction of the base 10. The fins 30 are made of extruded aluminum alloy material. The extrusion direction of this extruded material is the front-to-rear direction. The front-to-rear length of the fins 30 is equal to the front-to-rear length of the base 10. As also shown in Figure 4, the fins 30 have a plurality of hollow portions 31 arranged in the height direction. The hollow portions 31 have a rectangular cross section and extend along the front-to-rear direction. The front-to-rear direction is the flow direction of the cooling medium (air). The plurality of hollow portions 31 are arranged at equal intervals in the height direction (vertical direction) of the fins 30.

[0020] An upwardly recessed recess 32 is formed at the lower end of the fin 30 (the end on the joining side with the base 10). That is, bifurcated legs 33, 33 are arranged at the lower end of the fin 30. The recess 32 is formed over the entire length of the fin 30 in the front-to-rear direction, and the legs 33, 33 on both left and right sides of the recess 32 also extend over the entire length of the fin 30 in the front-to-rear direction. The recess 32 has a rectangular cross section, and a flat partition plate is formed between the recess 32 and the adjacent hollow portion 31 above the recess 32. This partition plate, the left and right side walls of the adjacent hollow portion 31 above the recess 32, and the legs 33, 33 form an H-shaped cross section at the end of the fin 30 on the joining side with the base 10. The cross-sectional shape of the recess 32 is the same as the cross-sectional shape of the first ridges 11, and the first ridges 11 are fitted into the recess 32. When the first ridges 11 are fitted into the recesses 32, the legs 33 fit between the first ridges 11 and the second ridges 12, and the lower end faces of the legs 33 abut against the base surface of the upper surface of the base 10. That is, at the end of the lower end of the fin 30 that joins with the base 10, the first ridges 11 are located in the center, with the legs 33, 33 located on either side of it, and the second ridges 12, 12 located on either side of them. The side faces of the second ridges 12 and the legs 33 are in surface contact or there is a small gap between them. The second ridges 12 are pressed toward the first ridges 11 and against the side faces of the legs 33 by a crimping jig 50, which will be described later. This results in the fin 30 being crimped and joined to the base 10.

[0021] Next, the crimping jig 50 will be described. As shown in Fig. 5, the crimping jig 50 includes a base portion 51 and a plurality of claw portions 52, 52..., and is formed in a comb-like shape. The base portion 51 is a portion that supports the plurality of claw portions 52, 52..., and extends in the left-right direction. On both left and right ends of the base portion 51, there are formed protruding portions 53 that protrude outward from the support positions of the claw portions 52. A bolt insertion hole 54 is formed in the protruding portion 53. A bolt is inserted into the bolt insertion hole 54 to fix the crimping jig 50 to a press device (not shown).

[0022] The claw portions 52 are inserted between adjacent fins 30 from above the fins 30, 30, and press against the second protrusions 12. The lower ends of the claw portions 52 have a triangular cross section and a pair of inclined surfaces 55, 55 that approach each other as they extend downward. The number of claw portions 52 is the same as the number of gaps between adjacent fins 30, 30 (i.e., the number is one less than the number of fins 30). Outer claw portions 52a, whose thickness is greater than that of the inner claw portion 52, are formed on the outer sides of both left and right ends of the multiple arranged claw portions 52, 52. The outer claw portions 52a press inward the second protrusions 12 located at both left and right ends of the base portion 10, and are provided with inclined surfaces 55 at their lower ends that press the second protrusions 12 inward.

[0023] When the fin 30 is crimped to the base 10 using the crimping jig 50, as shown in FIG. 6A, the crimping jig 50 is lowered from above the fin 30, and the claws 52 are inserted between the fins 30. As shown in FIG. 6B, when the crimping jig 50 is lowered to a predetermined height, the lower ends of the claws 52 are pressed into the gaps between adjacent second projections 12. Then, as shown in FIG. 7, the inclined surfaces 55 of the claws 52 spread the second projections 12 on both the left and right sides, pressing the second projections 12 against the side surfaces of the lower end of the fin 30. Meanwhile, when the second projections 12 on both the left and right ends are pressed inward, stress acts on the outer claws 52a, tending to deform the outer claws 52a outward. However, the large thickness of the outer claws 52a allows them to resist the outward stress and press the second projections 12 inward.

[0024] According to the heat sink 1 of this embodiment, the fins 30 have hollow portions 31, which increases the surface area of ​​the fins 30. Heat can be dissipated not only from the outer surfaces of the fins 30 but also from the inner surfaces of the hollow portions 31, resulting in improved heat dissipation. Furthermore, multiple hollow portions 31 are formed at predetermined intervals in the vertical direction of the fins 30, further increasing the surface area of ​​the fins 30. Furthermore, each hollow portion 31 has a rectangular cross section, which facilitates extrusion molding of the fins 30. Furthermore, because the cooling medium flows through the interior of the fins 30 in addition to between the fins 30, the flow resistance of the cooling medium is reduced. As a result, fans and pumps used to circulate the cooling medium can be made smaller and more energy-efficient.

[0025] The fins 30 are arranged at predetermined intervals in the left-right direction, which allows the coolant to flow smoothly between the fins 30, and further improves heat dissipation.

[0026] Here, a comparative test was performed between the heat sink 1 of this embodiment and a conventional heat sink with fins that does not have a hollow portion. The heat sinks share the same height (89.5 mm), width (98.2 mm), and fin height (80.0 mm). The conventional fins are thinner than the fins 30 of this embodiment and have more fins (21). The heat sink, with a heat-generating element attached, was placed in a wind tunnel, and cooling air was blown at a constant speed and time. The temperature of the heat-generating element and the temperature of the air at the wind tunnel inlet were measured. The thermal resistance values ​​calculated from this temperature and the pressure difference between the upstream and downstream sides of the air in the heat sink were 0.284 (K / W) for the conventional heat sink and 0.242 (K / W) for the heat sink 1 of this embodiment. From these results, it was found that the heat sink 1 of this embodiment had a 14.8% reduction in thermal resistance compared to the conventional heat sink.

[0027] However, because the specifications of the heat generating element (power module), such as the shape of the heat generating element, differ between the test and the actual implementation, it is necessary to predict the cooling performance when the actual specifications are applied based on the test results. Therefore, the performance was predicted using the following steps. First, the test results were compared with the analysis results of the test reproduction model to confirm consistency. Next, the thermal resistance values ​​of the test results and the analysis results were compared to derive the ratio of the test value to the analysis value. Then, based on the ratio, the analysis results of the model that reproduced the original specifications (hereinafter referred to as the chip reproduction model) were corrected to derive the predicted value. As a result of performing these steps, the ratio of the test results to the analysis results (test thermal resistance value / analysis thermal resistance value) was 0.913 for the conventional heat sink, while the ratio of the test results to the analysis results (test thermal resistance value / analysis thermal resistance value) was 0.936 for the heat sink 1 of this embodiment, indicating consistency. Using this ratio, the analysis results of the chip reproduction model were corrected and the cooling performance under the original specifications was predicted.It was predicted that under the specifications actually implemented, the thermal resistance of the heat sink 1 of this embodiment could be reduced by 28.7% compared to the thermal resistance of a conventional heat sink.

[0028] Furthermore, in this embodiment, the fins 30 and the base 10 are formed from separate members and joined together, allowing the fins 30 and the base 10 to have simple shapes and be easily manufactured. The fins 30 and the base 10 are joined by crimping, allowing for easy joining through mechanical joining (crimping). In particular, in this embodiment, the fins 30 can be fixed to the base 10 simply by pressing the crimping jig 50 into the base 10. Furthermore, the first ridges 11 are inserted into the recesses 32 between the legs 33 at the bottom of the fin 30, and the second ridges 12 are formed on the outer left and right sides of the recesses 32. The legs 33 of the fin 30 are crimped and joined between the first ridges 11 and the second ridges 12, thereby improving adhesion between the fin 30 and the base 10. This increases the bond strength between the fin 30 and the base 10 and also improves thermal conductivity.

[0029] The fins 30 are made of an aluminum alloy with excellent formability, making it easy to form a complex shape with the hollow portion 31. In addition, the hollow portion 31 has a rectangular cross section, making it easy to extrude. On the other hand, the base 10 is made of copper, which has excellent thermal conductivity, and therefore has high heat diffusion properties.

[0030] Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to the above-described embodiments, and appropriate design changes are possible within the scope of the present invention. For example, in the above-described embodiments, the fins 30 and the base portion 10 are joined by crimping, but the joining method is not limited to crimping. For example, the fins 30 and the base portion 10 may be joined by other methods, such as brazing or soldering. However, joining by crimping is preferable because it is easy to perform.

[0031] In the above embodiment, the fins 30 and the base 10 are formed separately and joined together, but they can also be molded as a single unit. When the fins 30 and the base 10 are integrated, they are preferably made of an extruded aluminum alloy material, which has excellent formability. [Explanation of symbols]

[0032] 1 heat sink 10 Base 11 First protrusion 12 Second protrusion 30 Finn 31 Hollow part

Claims

1. In a heat sink for cooling a power module, a base portion to be placed on the body to be cooled, and a plurality of fins standing upright from the base portion; The fin has a plurality of hollow portions aligned in a height direction of the fin, the hollow portion communicates in the direction of flow of the cooling medium, The fin and the base are formed of separate members, A recess is formed at an end of the fin on the side where the fin is joined to the base portion, a first protrusion that fits into the recess of the fin and a pair of second protrusions that are pressed against a side surface of the joining end of the fin, The bifurcated legs constituting the side walls on both sides of the recess are inserted between the first protrusion and the second protrusion, and are crimped and joined between the first protrusion and the second protrusion. A heat sink characterized by:

2. The fins are arranged at predetermined intervals. The heat sink according to claim 1 .

3. The fins are made of an aluminum alloy, and the base is made of copper.

3. The heat sink according to claim 1 or 2.

4. The hollow portion has a rectangular cross section. The heat sink according to any one of claims 1 to 3.

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