Heat sink

Abstract

To provide a heat sink which has high heat radiation performance and can suppress increase of cost to form a heat sink at the same time.SOLUTION: The heat sink includes: a plate-shaped base part; a plurality of first fins projecting from a surface of the base part; and a second fin formed separately from the first fins and joined to end faces of the plurality of first fins.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a heat sink.

Background Art

[0002] The heat sink described in Patent Document 1 has a base plate that is rectangular in a plan view when viewed from the thickness direction and has a heat generating body mounting surface on which a heat generating body is mounted, and a plurality of fins disposed on the back surface of the heat generating body mounting surface of the base plate. The fins protrude from the base plate and are arranged at intervals in a first direction that is parallel to any one side at the outer peripheral edge of the base plate, and have a fin base portion that extends in a second direction orthogonal to the first direction, and a plurality of pins that protrude from the fin base portion and are arranged at intervals in the second direction. The interval Wp between the pins in the second direction is narrower than the interval Wb between the fin base portions in the first direction, and the ratio Hb / Hp of the height Hb of the fin base portion to the height Hp of the pin satisfies 0 < Hb / Hp < 0.20. The manufacturing method of the heat sink described in Patent Document 1 is to produce an extruded shape material by extrusion molding, which includes the base plate and a plurality of fin planned portions that protrude from the base plate, are plate-shaped, and are arranged at intervals in a direction perpendicular to the extrusion direction, and perform cutting on the plurality of fin planned portions along a straight line extending in a direction different from the extrusion direction to form the fins.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When fins are formed by cutting a thick plate-shaped heat-dissipating material, the fins and base plate are integrally formed, resulting in a heat sink with high heat dissipation efficiency. However, cutting reduces material yield due to the generation of chips, which tends to increase the cost of forming the heat sink. To reduce the cost of cutting, some cutting processes are performed on plate-shaped fins formed by extrusion molding. In this case, the shape of the formed fins is limited to those that can be cut from the shape of the plate-shaped fins created by extrusion molding.

[0005] An object of the present invention is to provide a heat sink that has high heat dissipation performance while suppressing an increase in the cost of molding the heat sink. [Means for solving the problem]

[0006] The heat sink to which the present invention is applicable is a heat sink comprising a flat base portion, a plurality of first fins protruding from the plate surface of the base portion, and second fins formed separately from the first fins and joined to the end faces of the plurality of first fins. Here, the second fin may be a fin formed by bending a single metal plate. The second fin may be a corrugated fin formed by bending the metal plate to form a plurality of alternating peaks and valleys. Furthermore, the valleys may be in contact with the end surface of the first fin, and the valleys may be joined to the end surface of the first fin by irradiating the valleys with laser light from the peak side. The first fin may be a pin fin. The pin fin may have a diamond-shaped cross section taken along a plane perpendicular to the direction in which the pin fin protrudes. The first fin may be formed by cutting. The first fin may be formed by forging. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a heat sink with high heat dissipation performance while suppressing an increase in the cost of molding the heat sink. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is an example of an exploded view of components constituting the cooling device according to the embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a cross section of a cooling device. [Figure 3] FIG. 1 is a diagram illustrating an example of a heat sink. [Figure 4] 10A to 10C are diagrams for explaining a manufacturing method of the flat plate portion and the plurality of pin fins. [Figure 5] FIG. 10 is a diagram showing the state in which the pin fins and the corrugated fins are laser-welded together. [Figure 6] FIG. 2 is a diagram showing an example of a welding path. [Figure 7] FIG. 2 is a diagram showing an example of a welded portion. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an example of an exploded view of components constituting a cooling device 1 according to an embodiment. 2 is a diagram showing an example of a cross section of the cooling device 1. Fig. 2 is a cross section of a plane perpendicular to the front-rear direction of the cooling device 1 of Fig. 1.

[0010] [Cooling device 1] The cooling device 1 according to the embodiment includes a heat sink 10 and a case 20 that houses the heat sink 10 and forms a space through which a coolant flows. The cooling device 1 is a liquid-cooling type cooling device that cools a semiconductor module 5 using a coolant that flows through the space within the case 20.

[0011] [Case 20] The case 20 includes a case body 21 having a concave shape with a bottom, and a cover 22 that covers the opening of the case body 21. The case 20 also includes an O-ring 23 that seals the gap between the case body 21 and the cover 22, and bolts 24 that connect the case body 21 and the cover 22. The case 20 also includes an inlet pipe 25 that allows the coolant to flow into the case 20, and an outlet pipe 26 that allows the coolant to flow out of the case 20. The case body 21 and the cover 22 may be made of, for example, an aluminum alloy or copper.

[0012] 1, the direction in which the semiconductor modules 5 are stacked in the cooling device 1 may be referred to as the "vertical direction." In addition, in the vertical direction, the semiconductor module 5 side may be referred to as the "upper side," and the cooling device 1 side may be referred to as the "lower side." In addition, the direction perpendicular to the vertical direction, from the inlet pipe 25 to the outlet pipe 26, may be referred to as the "front-rear direction," and the direction perpendicular to the vertical direction and the front-rear direction may be referred to as the "left-right direction."

[0013] [Case body 21] The case body 21 has a flat rectangular lower surface 31 and four side walls 32 that protrude from the peripheral edges of the lower surface 31 in directions perpendicular to the plate surface of the lower surface 31 . A first through-hole 323 penetrating the first side wall 321 is formed in a first side wall 321 of the four side walls 32. A second through-hole 324 penetrating the second side wall 322 is formed in a second side wall 322 facing the first side wall 321 of the four side walls 32. The outflow pipe 26 is fitted into the first through-hole 323, and the inflow pipe 25 is fitted into the second through-hole 324. In addition, on the upper end surfaces of the four side walls 32, around the opening of the case body 21, there are formed grooves 325 into which the O-ring 23 is fitted, and at each of the four outer corners of the grooves 325, there are formed female threads 326 into which the bolts 24 are tightened.

[0014] [Cover 22] The cover 22 is a flat plate-shaped member. Holes 221 for passing bolts 24 are formed in each of the four corners of the cover 22. The semiconductor module 5 is bonded to an outer surface 223, which is the outer surface of the cover 22. On the other hand, the heat sink 10 is bonded to an inner surface 222, which is the inner surface of the cover 22.

[0015] [Semiconductor Module 5] The semiconductor module 5 has an insulating substrate 51, a wiring layer 52 provided on the insulating substrate 51, and a semiconductor element 53 attached to the wiring layer 52 via a solder layer 54. The semiconductor module 5 also has a heat transfer layer 55 that transfers heat from the insulating substrate 51 to the cooling device 1. In the semiconductor module 5, the heat transfer layer 55 is joined to the outer surface 223 of the cover 22. Examples of methods for joining the heat transfer layer 55 and the cover 22 include brazing, soldering, sintering, bonding with resin, and pasting with thermally conductive grease.

[0016] [Heat sink 10] The heat sink 10 includes a flat plate-shaped portion 11, a plurality of columnar pin fins 12 protruding from the flat plate-shaped portion 11 in a direction perpendicular to the plate surface, and corrugated fins 13 joined to end faces 12C of the pin fins 12. The flat plate-shaped portion 11 is an example of a base portion. The pin fins 12 are an example of first fins, and the corrugated fins 13 are an example of second fins.

[0017] The flat plate-shaped portion 11 has a protruding surface 111, which is the surface from which the pin fins 12 protrude, and a back surface 112, which is the surface behind the protruding surface 111. The flat plate-shaped portion 11 is joined with the back surface 112 in contact with the inner surface 222 of the cover 22. Heat from the semiconductor module 5 is transferred to the flat plate-shaped portion 11 via the cover 22. The flat plate-shaped portion 11 transfers the heat from the semiconductor module 5 to the pin fins 12 provided on the protruding surface 111 side.

[0018] Referring now to FIG. 3, the heat sink 10 will be described in more detail. Fig. 3 is a diagram showing an example of the heat sink 10. Fig. 3 is a perspective view showing the front end of the heat sink 10 in the front-rear direction.

[0019] The pin fins 12 may be, for example, columnar in shape and protruding perpendicularly from the flat plate portion 11. The cross-sectional shape of the pin fins 12 cut along a plane perpendicular to the protruding direction may be, for example, a quadrilateral such as a square, rectangle, or diamond. The cross-sectional shape of the pin fins 12 may be, for example, a circle or an ellipse. In this embodiment, the cross-sectional shape of the pin fins 12 is a diamond.

[0020] The flat plate portion 11 and the plurality of pin fins 12 are integrally formed. For example, the flat plate portion 11 and the plurality of pin fins 12 may be formed by cutting. Alternatively, for example, the flat plate portion 11 and the plurality of pin fins 12 may be integrally formed by forging.

[0021] The corrugated fins 13 are formed separately from the pin fins 12 and are joined to end faces 12C (see FIG. 2) of the pin fins 12. When viewed from the front to back in FIG. 1, the corrugated fins 13 are metal plates bent into a wave shape. In this embodiment, as shown in FIG. 3, the corrugated fins 13 are formed by bending a metal plate to form multiple alternating top portions 13a (described below) and bottom portions 13b (described below).

[0022] The corrugated fins 13 are arranged so that the wavelength direction of the corrugated fins 13 is along the left-right direction of the cooling device 1, and so that the plate surfaces of the corrugated fins 13 are along the front-rear direction of the cooling device 1. For example, the shape of the corrugated fins 13 when viewed from the front-rear direction can be a rectangular wave shape. Also, for example, the shape of the corrugated fins 13 when viewed from the front-rear direction can be a sine wave shape. The corrugated fins 13 are joined to the end faces 12C of the pin fins 12 by, for example, laser welding or brazing.

[0023] The corrugated fin 13 is formed by bending a single metal plate and includes a top portion 13a, a bottom portion 13b, and a connecting portion 13c that connects the top portion 13a and the bottom portion 13b.

[0024] The peak 13a is an example of a mountain portion. The peak 13a extends in the front-rear direction and is connected to the connecting portion 13c at both ends in the left-right direction. In Fig. 3, the peak 13a and the connecting portion 13c have a planar shape, and the peak 13a and the connecting portion 13c are connected so as to be approximately perpendicular to each other.

[0025] The bottom portion 13b is an example of a valley portion. The bottom portion 13b extends in the front-rear direction, and is connected to the connecting portion 13c at both ends in the left-right direction. In Fig. 3, the bottom portion 13b has a planar shape, and the bottom portion 13b and the connecting portion 13c are connected so as to be approximately perpendicular to each other.

[0026] The connecting portion 13c may have a wave-like shape with a wavelength direction in the front-rear direction, and the corrugated fin 13 may be, for example, a wave fin. The corrugated fin 13 may be, for example, an offset fin.

[0027] [Method for manufacturing the heat sink 10] As described above, the pin fins 12 and the corrugated fins 13 are molded separately. Then, the pin fins 12 and the corrugated fins 13 are joined together to manufacture the heat sink 10.

[0028] [Example of cutting work] Next, a method for manufacturing the flat plate portion 11 and the plurality of pin fins 12 will be described with reference to FIG. 4A to 4C are diagrams for explaining a manufacturing method of the flat plate portion 11 and the plurality of pin fins 12. Figures 4A to 4C are diagrams showing a plate-shaped heat dissipating material 90 as viewed from the plate surface. The pin fins 12 are cut out by forming a plurality of grooves with a cutting blade in a plate-shaped heat dissipating material 90 made of a metal with relatively high heat dissipation properties, such as an aluminum alloy or copper. The cutting blade is configured so that multiple blades each having a desired width are provided at a predetermined interval and can simultaneously cut multiple grooves. Note that the configuration of the cutting blade is not particularly limited, and it may be configured so that only one groove can be cut.

[0029] First, as shown in FIG. 4(a), first grooves 7 are cut into the surface of the plate-shaped heat dissipating material 90 using a cutting blade. The dashed lines in FIG. 4(a) indicate the positions where the cutting blade passes. The first grooves 7 are formed at an angle α (α<45 degrees) with the side surface 91 of the heat dissipating material 90. By cutting multiple first grooves 7 in parallel at regular intervals, a first groove group C is formed in the plate-shaped heat dissipating material 90.

[0030] The solid lines in Fig. 4(b) show the state after first grooves 7 have been machined. After first groove group C has been machined in plate-shaped heat dissipative material 90, the cutting blade is turned so as to intersect with first groove group C at an acute angle, as shown by the dashed lines in Fig. 4(b), and second grooves 8 are cut into the surface of heat dissipative material 90. By cutting multiple second grooves 8 in parallel at regular intervals, second groove group D is formed in plate-shaped heat dissipative material 90.

[0031] As shown in FIG. 4(c), the first groove group C and the second groove group D formed in the heat dissipating material 90 form pin fins 12 that protrude between the grooves. The portions of the heat dissipating material 90 that have been scraped away by the cutting blade become the protruding surfaces 111 of the flat plate-shaped portion 11. The end surfaces 12C of these pin fins 12 are diamond-shaped. In other words, the cross-section of the pin fin 12 cut along a plane perpendicular to the direction in which the pin fin 12 protrudes is diamond-shaped. The end surfaces 12C of the pin fin 12 formed in this manner have diagonal lines of different lengths; in FIG. 4(c), the longer diagonal line is shown as diagonal line 12a, and the shorter diagonal line is shown as diagonal line 12b.

[0032] The heat dissipating material 90 carved out by the first groove group C and the second groove group D has a portion of the side surface 91 of the heat dissipating material 90 remaining on the front side in the front-to-rear direction. This remaining side surface 91 is perpendicular to the flow path direction and obstructs the flow of coolant. For this reason, the heat dissipating material 90 of FIG. 4(c) has a pin with an incomplete diamond-shaped cross section carved on the front side in the front-to-rear direction. Furthermore, the heat dissipating material 90 of FIG. 4(c) has a pin with an incomplete diamond-shaped cross section carved on the rear side in the front-to-rear direction to regulate the flow to the outflow pipe 26 (see FIG. 1).

[0033] [Example of a method for joining the pin fins 12 and the corrugated fins 13] Next, an example of a method for joining the pin fins 12 and the corrugated fins 13 will be described with reference to FIGS. Fig. 5 is a diagram showing the state in which the pin fins 12 and the corrugated fins 13 are laser-welded together. Fig. 5 is a diagram showing the heat sink 10 as viewed from the front in the front-to-rear direction. Fig. 6 is a diagram showing an example of a welding path. Fig. 6 is a diagram showing the heat sink 10 of Fig. 5 as viewed in the direction of gravity.

[0034] 5, the back surface 112 of the flat plate portion 11 is placed facing the direction of gravity, and the end surface 12C of the pin fin 12 is placed facing the opposite direction to the direction of gravity. The corrugated fin 13 is then placed with the bottom portion 13b of the corrugated fin 13 in contact with the end surface 12C of the pin fin 12. The laser head 151 then irradiates laser light L from the top portion 13a of the corrugated fin 13 toward the bottom portion 13b, thereby joining the bottom portion 13b to the end surface 12C.

[0035] In Fig. 6, the top 13a of the corrugated fin 13 is located on the near side of the paper, and the bottom 13b is located on the far side of the paper. Also, in Fig. 6, the end surface 12C of the pin fin 12 is shown by a dashed line. Also, in Fig. 6, the diagonals 12a and 12b of the diamond-shaped end surface 12C are shown by a dotted-dash line.

[0036] The corrugated fin 13 is arranged so that the surface of the connecting portion 13c (see FIG. 5) is aligned with the diagonal line 12a of the end face 12C. A first direction M1 and a second direction M2 in FIG. 6 indicate the movement path of the laser head 151 (see FIG. 5). In the first direction M1, the laser head 151 moves in a direction from the front to the rear in the front-to-rear direction. In the second direction M2, the laser head 151 moves in a direction from the rear to the front in the front-to-rear direction.

[0037] The laser head 151 moves relative to the bottom 13b while irradiating the bottom 13b with laser light L from the top 13a side. First, the laser head 151 moves along the bottom 13b in the first direction M1 in FIG. 6 from the front end to the rear end of the corrugated fin 13. After the laser head 151 reaches the rear end of the corrugated fin 13, the laser head 151 moves to the adjacent bottom 13b in the left-right direction. The laser head 151 moves along the bottom 13b in the second direction M2 from the rear end to the front end of the corrugated fin 13. After the laser head 151 reaches the front end of the corrugated fin 13, the laser head 151 moves to the adjacent bottom 13b in the left-right direction and then repeats moving along the bottom 13b in the first direction M1 from the front end to the rear end of the corrugated fin 13.

[0038] In this embodiment, the orientations of the first grooves 7 (see FIG. 4) and the second grooves 8 (see FIG. 4) are inclined with respect to the first direction M1 and the second direction M2, and intersect with each other. For example, at the positions where the first grooves 7 and the first direction M1 intersect, the end faces 12C of the pin fins 12 and the bottoms 13b of the corrugated fins 13 are not in contact with each other. At the positions where the end faces 12C and the bottoms 13b of the corrugated fins 13 are not in contact with each other (hereinafter, sometimes referred to as "non-contact positions"), the irradiation of the laser light L may be stopped when the laser head 151 passes through the non-contact position so that the bottoms 13b do not melt. Furthermore, the moving speed of the laser head 151 may be increased while irradiating the laser light L when passing through the non-contact position so that the melted portion does not penetrate the bottoms 13b.

[0039] FIG. 7 is a diagram showing an example of a welded portion 40. As shown in FIG. A weld 40 is formed by irradiating the bottom 13b of the corrugated fin 13 and the end surface 12C of the pin fin 12 with laser light L (see FIG. 5). When the laser beam L is irradiated onto the bottom portion 13b of the corrugated fin 13, the energy of the laser beam L is converted into heat, melting the corrugated fin 13 and the tip of the pin fin 12, and forming a weld 40.

[0040] As described above, the bottom 13b of the corrugated fin 13 is joined to the end face 12C of the pin fin 12 by irradiating the laser light L onto the bottom 13b from the top 13a side. As described above, in this embodiment, the bottom 13b has a flat shape. The flat surface of the bottom 13b contacts the end face 12C, which increases the contact area compared to when the bottom 13b has a curved surface.

[0041] [Materials of pin fins 12 and corrugated fins 13] The pin fins 12 and the corrugated fins 13 may be made of the following materials, for example. For example, the pin fins 12 and the corrugated fins 13 are made of the same material, such as copper or an aluminum alloy. In this case, the welded joints 40 are formed more satisfactorily than when the pin fins 12 and the corrugated fins 13 are made of different materials. Furthermore, the pin fins 12 may be made of different materials from the corrugated fins 13. In this case, the pin fins 12 and the corrugated fins 13 may be joined together by brazing, for example.

[0042] Furthermore, the pin fins 12 and the corrugated fins 13 are made of different materials, with one being copper and the other being an aluminum alloy, for example. In this case, for example, copper is used on the pin fins 12 closer to the semiconductor module 5 where heat is generated, and an aluminum alloy is used on the corrugated fins 13 that are farther from the semiconductor module 5. By using copper, which has high thermal conductivity, on the pin fins 12 closer to the semiconductor module 5, the heat dissipation effect can be improved.

[0043] As described above in detail, in the pin fins 12 formed by cutting, the flat plate portion 11 and the pin fins 12 are integrally formed, and thermal conductivity between the flat plate portion 11 and the pin fins 12 is high. As a result, the pin fins 12 formed integrally by cutting have a high heat dissipation effect. However, cutting tends to produce chips, which reduces material yield and increases costs. Furthermore, as the height of the pin fins 12 increases, more chips are produced, which reduces material yield. Furthermore, it is difficult to form thin fins using cutting, and pin fins formed by cutting tend to have a small flow path area and increase pressure loss.

[0044] On the other hand, the corrugated fin 13 can be formed by bending a single metal plate and is relatively inexpensive. Furthermore, the corrugated fin 13 can maintain a large flow path area and generally has a lower pressure loss than the pin fin 12. However, since the corrugated fin 13 is formed from a single metal plate, it cannot be formed integrally with the flat plate portion 11. Therefore, the corrugated fin 13 must be joined to the flat plate portion 11 by welding, brazing, or the like, resulting in low thermal conductivity at the joint. Furthermore, the corrugated fin 13 is formed from a metal plate, which has a thin wall thickness and low thermal conductivity.

[0045] By combining these two types of fins, it is possible to provide a heat sink 10 that meets the required heat dissipation effect, pressure loss, etc., while suppressing cost increases. For example, if cost is a major concern, it is possible to reduce the height of the pin fins 12, which have a relatively low yield, and increase the height of the corrugated fins 13. For example, as shown in FIG. 2, it is desirable that the height of the pin fins 12 be 1 / 3 or less of the height of the corrugated fins 13. Furthermore, if heat dissipation is a major concern, it is possible to increase the height of the pin fins 12, which have a relatively high heat transfer coefficient, and decrease the height of the corrugated fins 13. For example, it is desirable that the height of the pin fins 12 be more than 1 / 3 of the height of the corrugated fins 13.

[0046] 6, in the heat sink 10 of this embodiment, the corrugated fins 13 are arranged so that the faces of the connecting portions 13c of the corrugated fins 13 are aligned with the diagonal line 12a of the end faces 12C of the pin fins 12. Because the diagonal line 12a is longer than the diagonal line 12b, the angle across the diagonal line 12a is an acute angle. When a surface at an acute angle faces the direction of the coolant flow, compared to when a surface at an obtuse angle faces the direction of the coolant flow, the obtuse angle faces the direction of the coolant flow, resulting in a greater pressure loss. In the heat sink 10 of this embodiment, when a coolant flows along the faces of the connecting portions 13c, the coolant faces the acute-angled faces of the pin fins 12. On the other hand, if the corrugated fins 13 are arranged so that the faces of the connecting portions 13c of the corrugated fins 13 are aligned with the diagonal lines 12b of the end faces 12C of the pin fins 12, the coolant faces the obtuse-angled faces of the pin fins 12 when the coolant flows along the faces of the connecting portions 13c. Therefore, the pressure loss in the heat sink 10 of this embodiment is smaller than when the corrugated fins 13 are arranged so that the faces of the connecting portions 13c of the corrugated fins 13 are aligned with the diagonal lines 12b of the end faces 12C of the pin fins 12. [Explanation of symbols]

[0047] 1...cooling device, 5...semiconductor module, 10...heat sink, 11...flat plate portion, 12...pin fin, 13...corrugated fin, 13a...top portion, 13b...bottom portion, 13c...connecting portion, 40...welding portion, 151...laser head

Claims

1. A flat base portion; a plurality of first fins protruding from a plate surface of the base portion; second fins formed separately from the first fins and joined to end surfaces of the plurality of first fins; A heat sink comprising:

2. The second fin is formed by bending a single metal plate. The heat sink of claim 1 .

3. The second fin is a corrugated fin formed by bending the metal plate to form a plurality of alternating peaks and valleys. The heat sink of claim 2 .

4. The valleys are brought into contact with the end surface of the first fin, and laser light is irradiated onto the valleys from the peak side, thereby bonding the valleys to the end surface of the first fin. The heat sink of claim 3 .

5. The first fin is a pin fin. The heat sink of claim 1 .

6. The pin fin has a diamond-shaped cross section cut along a plane perpendicular to the protruding direction of the pin fin. The heat sink of claim 5 .

7. The first fin is formed by cutting. The heat sink of claim 6.

8. The first fin is formed by forging. The heat sink of claim 5 .

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