Thin heat sink and manufacturing method thereof

Abstract

To provide a thin heat sink and a manufacturing method that can suppress thermal deformation that occurs when the sheet materials that make up the lightweight thin heat sink are linearly joined and can be easily attached to a frame.SOLUTION: In a thin heat sink 100, a cooling plate portion 13 having a refrigerant flow path 11 is joined to a frame 15. The cooling plate portion 13 is formed by overlapping and linearly joining a pair of sheet materials 17, 19, at least one of which has a protrusion that serves as the refrigerant flow path 11. Linear protrusions are provided on the outer periphery of the sheet materials 17, 19, protruding from the sheet surface along the outer periphery. The linear protrusions may be, for example, flanges 17a to 17d, 19a to 19d.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a thin heat sink and a method for manufacturing the same. [Background technology]

[0002] There has been a demand for improved occupant safety in vehicles, and for this purpose, the strength of vehicle bodies has been improved. On the other hand, against the backdrop of worsening issues such as global warming, efforts to improve the fuel efficiency of automobiles are accelerating. It is known that reducing the weight of vehicle bodies is an effective way to improve fuel efficiency. Battery packs for electric vehicles (EVs, HVs, FCVs, etc.) use thin aluminum coolers, such as aluminum cooling panels and heat sinks, to reduce the vehicle weight. One such thin aluminum cooler structure is a thin heat sink, which consists of a plate with a flow path formed by pressing or other methods, and a mating plate that is overlapped and joined to ensure watertightness of the refrigerant flow path. While brazing is the mainstream method for joining such structures, the application of laser welding, which allows for high-speed welding as described in Patent Documents 1 and 2, would improve productivity and reduce CO2 emissions. Furthermore, friction stir welding (FSW), as described in Patent Document 3, can be used to achieve high-quality and high-strength joining. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-177861 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-274297 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-55317 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when manufacturing a thin heat sink by joining overlapping sheet materials (press-molded bodies) by laser welding or FSW as in the above-mentioned patent documents, the thin sheet materials are linearly joined over a wide area, which causes a problem that the joined body warps due to thermal deformation, making it difficult to assemble it into a frame.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a thin heat sink and a method for manufacturing the same that can suppress thermal deformation that occurs when the sheet materials that make up the lightweight thin heat sink are linearly joined together. [Means for solving the problem]

[0006] The present invention comprises the following configurations. (1) A thin heat sink in which a cooling plate having a refrigerant flow path is joined to a frame, The cooling plate portion is formed by overlapping and linearly joining a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path, The sheet material has linear protrusions on the outer periphery thereof that protrude from the sheet surface along the outer periphery thereof. Thin heat sink. (2) A method for manufacturing a thin heat sink in which a cooling plate portion having a refrigerant flow path is joined to a frame, comprising: the cooling plate portion includes a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path; a linear protrusion is provided on the outer peripheral edge of the sheet material so as to protrude from the sheet surface along the outer peripheral edge; The pair of sheet materials are overlapped with each other and linearly joined; The cooling plate portion to which the pair of sheet materials are joined is joined to the frame. A method for manufacturing a thin heat sink. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress thermal deformation that occurs when the sheet materials that make up a lightweight, thin heat sink are linearly joined together, and to easily assemble the sheet materials to a frame. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view of the thin heat sink. [Figure 2] FIG. 2 is an exploded perspective view of the thin heat sink shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view of the thin heat sink taken along line III-III shown in FIG. [Figure 4] FIG. 4 is a perspective view of the cooling plate portion showing the joining position of the sheet materials. [Figure 5] FIG. 5 is an enlarged cross-sectional view of a part of a thin heat sink in which a cooling plate portion and a frame are joined together. [Figure 6] FIG. 6 is a partially enlarged cross-sectional view of a thin heat sink showing another bonding mode between the cooling plate portion and the frame. [Figure 7] FIG. 7 is a reference diagram showing the state of thermal deformation during welding when the sheet material does not have linear protrusions. [Figure 8] FIG. 8 is a schematic perspective view showing a modified example of the protruding direction of the linear protrusions. [Figure 9] FIG. 9 is a partial cross-sectional view showing another modified example of the linear protrusion in another protruding direction. [Figure 10] FIG. 10 is a partial cross-sectional view showing a modified example of the shape of the linear protrusion. [Figure 11] FIG. 11 is a partial cross-sectional view showing a modified example of the shape of the linear protrusion. [Figure 12] FIG. 12 is an explanatory diagram showing the upper and lower plates of the test material. [Figure 13] FIG. 13 is a graph showing the results of comparing the amount of warpage of the test materials after welding in Test Examples 1 and 2. [Figure 14] FIG. 14 is a photograph of the test material after welding in Test Example 1. [Figure 15] FIG. 15 is a photograph of the test material of Test Example 2 after welding. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The thin heat sink of this embodiment will be described as an aluminum thin cooler used in a battery pack for an electric vehicle (EV, HV, FCV, etc.), but the use is not limited to this.

[0010] <Structure of a thin heat sink> Fig. 1 is a schematic perspective view of the exterior of a thin heat sink 100. Fig. 2 is an exploded perspective view of the thin heat sink 100 shown in Fig. 1. Fig. 3 is a schematic cross-sectional view taken along line III-III of the thin heat sink shown in Fig. 1.

[0011] 1 and 2, the thin heat sink 100 has a cooling plate 13 having a refrigerant flow path 11, and a frame 15 which is an overall rectangular frame body. The cooling plate 13 has a pair of aluminum or aluminum alloy sheet materials 17, 19, preferably with a thickness of 2.0 mm to 2.5 mm. At least one of the sheet materials 17 has protrusions 21 formed in a specific pattern. The frame 15, which is joined to the sheet materials 17, 19, is made of a plurality of extrusions made of, for example, wrought aluminum, and each extrusion is formed into a rectangular frame shape by welding or the like.

[0012] 3, a pair of sheet materials 17, 19 are overlapped with each other and provided with joints 23 on both sides of a protrusion 21, thereby forming a refrigerant flow path 11 as a closed space between the protrusion 21 of the sheet material 17 and the sheet material 19. The joints 23 may be formed by laser welding, in which the sheet materials 17, 19 are heated and melted by irradiation with laser light LD, or alternatively, by friction stir welding. The refrigerant flow path 11 is provided with a refrigerant inlet and a refrigerant outlet (not shown). The refrigerant supplied from the refrigerant inlet of the refrigerant flow path 11 flows through the refrigerant flow path 11 and is discharged from the refrigerant outlet, thereby exchanging heat.

[0013] FIG. 4 is a perspective view of the cooling plate portion 13 showing the joining position of the sheet materials 17, 19. The refrigerant flow path 11 of this configuration has multiple pairs of straight portions 11a extending along the long sides of the sheet materials 17, 19 and folded portions 11b that fold back in the opposite direction at the ends of the straight portions 11a, forming a single continuous flow path. The aforementioned joint portions 23 are formed on both sides of this refrigerant flow path 11 (see also FIG. 3). A plurality of the joint portions 23 are arranged side by side along the straight portions 11a of the refrigerant flow path 11. The joint portions 23 are formed by the aforementioned laser welding or friction stir welding, thereby forming the refrigerant flow path 11 without any gaps.

[0014] 2, flanges 17a, 17b, 17c, and 17d, which are linear protrusions that protrude from the sheet surface along the outer peripheral edge, are provided on the outer peripheral edge of each of the four sides of sheet material 17. Each of flanges 17a to 17d is bent at a right angle or an angle close to a right angle from the sheet surface by a bending process, and is formed so as to extend continuously along the outer peripheral edge.

[0015] Furthermore, flanges 19a, 19b, 19c, and 19d, which are linear protrusions that protrude from the sheet surface along the outer peripheral edge, are provided on the outer peripheral edge of each of the four sides of the sheet material 19. Like the flanges 17a to 17d, each of the flanges 19a to 19d is bent at a right angle or an angle close to a right angle from the sheet surface by a bending process and is formed to extend continuously along the outer peripheral edge.

[0016] As shown in FIG. 3, when the sheet materials 17 and 19 are superimposed on each other, the flanges 17a to 17d and the flanges 19a to 19d are bent to the same side in the thickness direction.

[0017] FIG. 5 is a partially enlarged cross-sectional view of a thin heat sink 100 in which the cooling plate 13 and the frame 15 are joined. The frame 15 is disposed inside flanges 17b, 19b formed on the outer peripheral edges of the sheet materials 17, 19, and a joint 27 that joins the sheet materials 17, 19 is formed on the end surface 15a of the frame 15 that contacts the cooling plate 13. In other words, the joint 27 penetrates the sheet materials 17, 19 and the end surface 15a of the frame 15. When the pair of sheet materials 17, 19 and the frame 15 are joined (line-joined) by laser welding or friction stir welding, the cooling plate 13 and the frame 15 can be joined with high joint strength by the continuous joint 27. The joint 27 may be continuous along the periphery of the frame 15, or may be formed in multiple dispersed locations.

[0018] 6 is a partially enlarged cross-sectional view of the thin heat sink 100 showing another joining configuration between the cooling plate 13 and the frame 15. As shown in FIG. 6, in addition to the above-described joint 27, joint 29 may be formed by penetrating the flanges 17b, 19b and the outer side surface 15b of the frame 15. This joint 29 may be formed continuously along the periphery of the frame 15 by laser welding or friction stir welding, or may be formed in multiple dispersed locations. By forming the joints 27, 29 in different directions from each other, the joining strength between the cooling plate 13 and the frame 15 can be further improved.

[0019] <Linear protrusions prevent thermal deformation during bonding> The thin heat sink 100 having the above-described configuration has linear protrusions consisting of flanges 25a to 17d, 19a to 19d on the outer peripheral edge of the sheet materials 17, 19, which suppresses thermal deformation of the sheet materials 17, 19 that occurs due to laser welding or friction stir welding when joining (linear joining) the sheet materials 17, 19 together, making it easier to assemble them into the frame 15 in the subsequent process.

[0020] FIG. 7 is a reference diagram showing thermal deformation during welding when sheet materials 17 and 19 do not have linear protrusions. FIG. 7 shows a plan view of sheet material 31 without linear protrusions and a side view of the four sides of sheet material 31. As described above, when a joint 23 shown by the dashed lines is formed on sheet material 31 by laser welding or friction stir welding, sheet material 31 is curved with the center of the sheet surface convex due to thermal contraction after heating. When the edges of the opposing sides of sheet material 31 are used as a reference, the center of the sheet surface bends convexly with a warp amount of Δt1, and when the center of the sheet surface is used as a reference, the warp amounts of the edges of the opposing sides are Δt2 and Δt3.

[0021] Such thermal deformation of the sheet material 31 makes it difficult to bond the sheet material 31 to the frame 15. Even if bonding is successful, it can cause distortion in the thin heat sink 100 after bonding. However, in the sheet materials 17 and 19 of this embodiment, linear protrusions consisting of flanges 25a-17d and 19a-19d are provided on the outer peripheral edges of the sheet materials 17 and 19, thereby increasing the section modulus (second moment of area) of the sheet materials 17 and 19 and improving their bending strength. This reduces thermal deformation when bonding the sheet materials 17 and 19 together, thereby preventing the deflection shown in FIG. 7 . As a result, when bonding the sheet materials 17 and 19 to the frame 15, the bonding surface of the outer peripheral edge of the sheet material 19 is flat, allowing for uniform surface contact with the end face 15a of the frame 15 and bonding. This reduces stress generation after forming the bonding portion 27 and prevents distortion of the thin heat sink 100.

[0022] Furthermore, flanges 19a and 19b are sandwiched between flanges 17a and 17b provided on opposing sides, thereby improving the bending rigidity when sheet materials 17 and 19 are overlapped. Similarly, flanges 19c and 19d are sandwiched between flange portions 17c and 17d, thereby improving the bending rigidity when sheet materials 17 and 19 are overlapped, and sandwiching two pairs of sides between the flange portions synergistically improves the bending rigidity.

[0023] <Modification> The above-described configuration of the thin heat sink 100 is one example, and various modifications are possible. For example, instead of providing flanges 17a-17d, 19a-19d that serve as linear protrusions on both of the sheet materials 17, 19, linear protrusions may be provided on only one of the sheet materials. Furthermore, instead of providing linear protrusions on all four sides that form the outer periphery of the sheet material, linear protrusions may be selectively provided on only one of the sides. In this case, it is preferable to provide linear protrusions on the side closest to the joint 23.

[0024] As shown in FIG. 4, the width Wa of the linear protrusion is preferably equal to or greater than the entire length Wb of the joints 23 arranged along the outer periphery.

[0025] FIG. 8 is a schematic perspective view showing a modified example of the protruding direction of the linear protrusions, and FIG. 9 is a partial cross-sectional view showing another modified example of the protruding direction of the linear protrusions. As shown in FIG. 8, the flanges 17a, 19a and flanges 17c, 19c of the sheet materials 17 and 19 may be configured so that their respective bending directions are reversed to one side and the other side of the sheet thickness direction. Also, as shown in FIG. 9, the flanges 17a, 19a may be configured so that their respective bending directions are reversed to the other side of the sheet thickness direction. By bending one flange in the opposite direction to the other flange, the bending rigidity of the sheet materials 17, 19 can be increased while allowing the frame 15 to be configured either to be joined to the sheet material 19 side or to be joined to the sheet material 17 side, thereby improving design flexibility.

[0026] 10 and 11 are partial cross-sectional views showing modified shapes of the linear protrusions. As shown in Fig. 10, the linear protrusions may be flanges formed by bending the plate surface of the sheet material at a right angle, or may be ridges 33 having a convex cross section formed by press molding, or ridges 35 having a curved cross section with a predetermined radius of curvature as shown in Fig. 11. When ridges 33 and 35 are formed by press molding, the linear protrusions can be formed efficiently, and the takt time during manufacturing can be shortened.

[0027] As described above, the cross-sectional shape of the linear protrusions is not limited as long as it increases the section modulus (second moment of area) of the sheet materials 17, 19. For example, they may be convex ridges with end treatment such as hemming. Furthermore, the number of sheet materials 17, 19 constituting the cooling plate 13 is not limited to two, and three or more sheets may be stacked. [Example]

[0028] Next, the amount of warping caused by welding was compared between rectangular test pieces that simulated the cooling plate portion of a thin heat sink and those that did not have a joint formed. The test material used was a 6000 series aluminum alloy plate with a thickness of 1.2 mm as the upper plate and a 6000 series aluminum alloy plate with a thickness of 2.0 mm as the lower plate. The upper and lower plates were rectangular, as shown in Figure 12, with a width W in the short direction. S is 400mm, longitudinal width W L is 700mm.

[0029] The test materials were two types: Test Example 1, which used sheet material (upper and lower plates) with flanges whose outer edges were bent by approximately 10 mm by press molding, and Test Example 2, which was used for comparison, using flat sheet material (upper and lower plates) as is.

[0030] In both Test Examples 1 and 2, the upper and lower plates were laser welded together to form a total of nine joints 23, each with a longitudinal length Wa of 500 mm and a lateral pitch Pt of 40 mm. The test specimens were then welded together and the amount of warpage after welding was measured in the lateral and longitudinal directions. The amount of warpage in the lateral direction was taken as the average value of Δt2 and Δt3 shown in Figure 7. The laser welding conditions were non-penetration welding with an output of 3.2 kW and a welding speed of 4 m / min.

[0031] Fig. 13 shows a comparison of the amount of warpage of the test materials after welding in Test Examples 1 and 2. Fig. 14 is a photograph of the test material after welding in Test Example 1, and Fig. 15 is a photograph of the test material after welding in Test Example 2. As shown in Fig. 13, the average amount of warpage in the lateral direction of Test Example 1 was reduced to about 1 / 4 of that in Test Example 2, and the average amount of warpage in the longitudinal direction of Test Example 1 was reduced to about 1 / 2 of that in Test Example 2. It can also be seen that the test material of Test Example 1 shown in Fig. 14 had less warpage after welding than the test material of Test Example 2 shown in Fig. 15.

[0032] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these are included in the scope of protection sought.

[0033] As described above, the present specification discloses the following: (1) A thin heat sink in which a cooling plate having a refrigerant flow path is joined to a frame, The cooling plate portion is formed by overlapping and linearly joining a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path, The sheet material has linear protrusions on the outer periphery thereof that protrude from the sheet surface along the outer periphery thereof. Thin heat sink. With this thin heat sink, the linear protrusions on the outer periphery of the sheet material make it difficult for the sheet material to undergo thermal deformation when the pair of sheets are linearly joined, making it easier to join the cooling plate to the frame and preventing distortion after joining.

[0034] (2) The thin heat sink according to (1), wherein the linear protrusions are flanges formed by bending the outer peripheral edge of the sheet material. According to this thin heat sink, the flange formed by bending can easily suppress thermal deformation of the sheet material.

[0035] (3) The thin heat sink according to (1), wherein the linear protrusions are ridges having a convex cross section formed on the outer peripheral edge of the sheet material. According to this thin heat sink, the ridges can easily suppress thermal deformation of the sheet material.

[0036] (4) The thin heat sink according to any one of (1) to (3), wherein the sheet materials are linearly joined by laser welding or friction stir welding. According to this thin heat sink, the joints are formed continuously by laser welding or friction stir welding, and the refrigerant flow paths can be reliably formed without gaps.

[0037] (5) The thin heat sink according to any one of (1) to (4), wherein the pair of sheet materials and the frame are joined by laser welding or friction stir welding. According to this thin heat sink, the cooling plate portion and the frame can be joined continuously along the frame by laser welding or friction stir welding, thereby increasing the joining strength between them.

[0038] (6) The thin heat sink according to any one of (1) to (5), wherein the sheet material is made of aluminum or an aluminum alloy. According to this thin heat sink, the use of a light metal allows the thin heat sink to be made lighter.

[0039] (7) A method for manufacturing a thin heat sink in which a cooling plate portion having a refrigerant flow path is joined to a frame, comprising the steps of: the cooling plate portion includes a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path; a linear protrusion is provided on the outer peripheral edge of the sheet material so as to protrude from the sheet surface along the outer peripheral edge; The pair of sheet materials are overlapped with each other and linearly joined; The cooling plate portion to which the pair of sheet materials are joined is joined to the frame. A method for manufacturing a thin heat sink. According to this method of manufacturing a thin heat sink, the linear protrusions provided on the outer periphery of the sheet material make it difficult for the sheet material to undergo thermal deformation when the pair of sheets are linearly joined together, which makes it easier to join the cooling plate to the frame and prevents distortion after joining.

[0040] (8) The method for manufacturing a thin heat sink according to (7), wherein the linear protrusions are flanges formed by bending the outer peripheral edge of the sheet material. According to this method for manufacturing a thin heat sink, the linear protrusions can be formed by a simple bending process.

[0041] (9) The method for manufacturing a thin heat sink according to (7), wherein the linear protrusions are ridges formed by press-molding the outer peripheral edge of the sheet material. According to this method of manufacturing a thin heat sink, linear protrusions can be efficiently formed by press molding, thereby shortening the takt time during manufacturing.

[0042] (10) The method for manufacturing a thin heat sink according to any one of (7) to (9), wherein the sheet materials are joined together by laser welding or friction stir welding. According to this method of manufacturing a thin heat sink, the sheets of material are continuously formed by laser welding or friction stir welding, and the refrigerant flow paths can be reliably formed without gaps.

[0043] (11) The method for manufacturing a thin heat sink according to any one of (7) to (10), wherein the pair of sheet materials and the frame are joined by laser welding or friction stir welding. According to this method of manufacturing a thin heat sink, the cooling plate portion and the frame can be joined continuously along the frame by laser welding or friction stir welding, thereby increasing the joining strength of both. [Explanation of symbols]

[0044] 11 Refrigerant flow path 13 Cooling plate section 15 frames 15a End face 15b Side 17 Sheet material 17a~17d Flange (linear protrusion) 19 Sheet material 19a~19d Flange (linear protrusion) 21 Convex part 23 Joint 27 Joint 29 Joint 33 Convex stripes (linear protrusions) 35 Convex stripes (linear protrusions) 100 Thin Heat Sink

Claims

1. A thin heat sink in which a cooling plate portion having a refrigerant flow path is joined to a frame, The cooling plate portion is formed by overlapping and linearly joining a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path, a linear protrusion protruding from the sheet surface along the outer periphery of the sheet material; The pair of sheet materials each have a flange that serves as the linear protrusion formed by bending the outer peripheral edge portion toward the same side in the plate thickness direction, The flange of one of the sheet materials is sandwiched inside the flange of the other sheet material, The flange on one side of the outer peripheral edge portion of the sheet material is bent in one direction in the plate thickness direction, and the flange on the other side is bent in the other direction in the plate thickness direction. Thin heat sink.

2. A thin heat sink in which a cooling plate portion having a refrigerant flow path is joined to a frame, The cooling plate portion is formed by overlapping and linearly joining a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path, a linear protrusion protruding from the sheet surface along the outer periphery of the sheet material; the linear protrusions are flanges formed by bending the outer periphery of the sheet material, the frame is disposed inside the flange, and the pair of sheet materials and the frame are joined together; Thin heat sink.

3. the sheet material and the frame are joined at an end surface of the frame that contacts the cooling plate portion, and the flange is joined to an outer side surface of the frame; The low-profile heat sink of claim 2 .

4. The sheet materials are linearly joined by laser welding or friction stir welding. The thin heat sink according to claim 1 .

5. The pair of sheet materials and the frame are joined by laser welding or friction stir welding. The thin heat sink according to claim 1 .

6. The sheet material is made of aluminum or an aluminum alloy. The thin heat sink according to any one of claims 1 to 3.

7. A method for manufacturing a thin heat sink in which a cooling plate portion having a refrigerant flow path is joined to a frame, comprising: the cooling plate portion includes a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path; a linear protrusion is provided on the outer peripheral edge of the sheet material so as to protrude from the sheet surface along the outer peripheral edge; the pair of sheet materials each form a flange that becomes the linear protrusion by bending the outer peripheral edge portion toward the same side in the plate thickness direction, The flange of one of the sheet materials is sandwiched between the flange of the other sheet material, The flange on one side of the outer peripheral edge portion of the sheet material is bent in one direction in the thickness direction, and the flange on the other side is bent in the other direction in the thickness direction; The pair of sheet materials are overlapped with each other and linearly joined; The cooling plate portion to which the pair of sheet materials are joined is joined to the frame. A method for manufacturing a thin heat sink.

8. A method for manufacturing a thin heat sink in which a cooling plate portion having a refrigerant flow path is joined to a frame, comprising: the cooling plate portion includes a pair of sheet materials, at least one of which has a protrusion that serves as the refrigerant flow path; a linear protrusion is provided on the outer peripheral edge of the sheet material so as to protrude from the sheet surface along the outer peripheral edge; the linear protrusion is a flange formed by bending the outer circumferential edge of the sheet material, The pair of sheet materials are overlapped with each other and linearly joined; the frame is disposed inside the flange, and the cooling plate portion to which the pair of sheet materials are joined is joined to the frame; A method for manufacturing a thin heat sink.

9. the sheet material and the frame are joined at an end surface of the frame that contacts the cooling plate portion, and the flange is joined to an outer side surface of the frame; The method for manufacturing the thin heat sink according to claim 8 .

10. The sheet materials are joined together by laser welding or friction stir welding. A method for manufacturing the thin heat sink according to any one of claims 7 to 9.

11. The pair of sheet materials and the frame are joined by laser welding or friction stir welding. A method for manufacturing the thin heat sink according to any one of claims 7 to 9.

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