Cooling device and method for manufacturing a cooling device

Abstract

This method suppresses the reduction in strength of the cooling device when welding together different types of metal components. [Solution] A cooling device is formed by joining a cover 20 made of metal and a heat dissipation part 10 made of a different type of metal to the cover 20 when they are superimposed on each other and a laser beam 152 is irradiated onto the cover 20. The heat dissipation part 10 has a groove 14 recessed on the surface that contacts the cover 20 when it is superimposed on it, so as to be separated from the cover. The part of the cover 20 opposite to the groove 14 melts and enters the groove 14, melting and joining with the part of the heat dissipation part 10 surrounding the groove 14 to form a molten part 50. In the molten part 50, a single-type metal molten part 51 and a dissimilar metal molten part 52 are formed. The single-type metal molten part 51 is the part where the base material of the cover 20 is melted. The dissimilar metal molten part 52 is the part where the base material of the cover 20 and the base material of the heat dissipation part 10 are melted.

Description

Technical Field

[0001] The present invention relates to a cooling device and a method for manufacturing the same.

Background Art

[0002] For example, in Patent Document 1, there is a dissimilar metal joint in which a copper material and an aluminum material are in contact with each other, and a part of the aluminum material is melted and flows into the copper material to form a molten mixed portion. The shape of the molten mixed portion is continuously and linearly formed on the surface of the copper material in contact with the aluminum material, the depth dimension value from the surface is 5 to 30 μm, and the width dimension value of the shape of the molten mixed portion is 10 to 50 μm on the surface of the copper material in contact with the aluminum material. The component concentration of the copper material inside the molten mixed portion and the component concentration of the aluminum material of the copper material near the molten mixed portion are both less than 10%. For example, in Patent Document 2, there is a method for lap welding dissimilar metal members in which a first metal member and a second metal member having a higher melting point and hardness than the first metal member are overlapped and laser welded. The thickness of the first metal member is 0.8 [mm] or more and 2.0 [mm] or less, the thickness of the second metal member is 0.3 [mm] or more and 0.8 [mm] or less, and the penetration depth of the first metal member by irradiating a laser beam from above the second metal member in a state where the second metal member is overlapped on the first metal member is 0.15 [mm] or more and 0.55 [mm] or less, and the laser beam is irradiated under the condition that the value obtained by dividing the penetration depth by the weld bead width, which is the width in a top view of the welded portion, is 0.43 or less.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] For example, the material of the metal component used in the heat dissipation section of a cooling device may differ from the material of the metal component used in other parts of the device. When different metal components are welded together, an intermetallic compound consisting of two or more metals is formed at the joint. This intermetallic compound is generally more brittle than when the same type of metal is welded together. Therefore, cooling devices in which metal components of different materials are joined together tend to have reduced strength. The present invention aims to suppress a decrease in the strength of a cooling device when welding together different types of metal components. [Means for solving the problem]

[0005] The cooling device to which the present invention is applied is a cooling device to which a first member made of metal and a second member made of a different type of metal than the first member are joined by irradiating the first member with laser light while the two members are superimposed, wherein the second member has a recess on the surface that is superimposed on and in contact with the first member that is recessed away from the first member, and the portion of the first member opposite to the recess melts and enters the recess, and is fused together with the surrounding portion of the second member. Here, the melting point of the first component may be lower than that of the second component, thus providing a cooling device. Alternatively, the cooling device may be configured such that the material of the first component is aluminum and the material of the second component is copper. Furthermore, the second member has a flat base portion to which heat generated by the heating element is transferred, and a fin portion that protrudes from the base portion in a direction intersecting the plate surface of the base portion, and the first member is arranged around the second member, and the recess may be a cooling device provided around the fin portion of the base portion of the second member. Furthermore, the shape of the recess may be such that the depth of the recess is shorter than or equal to the width of the recess.

[0006] From another perspective, the method for manufacturing a cooling device to which the present invention applies is a method for manufacturing a cooling device to which a first member made of metal and a second member made of a different type of metal than the first member are joined by irradiating the first member with laser light while the two members are superimposed, comprising the steps of: forming a recess on the surface of the second member that is superimposed on and in contact with the first member, such that it is recessed away from the first member; and irradiating a portion of the first member opposite to the recess with laser light to melt the first member and fusion-join it with the portion surrounding the recess. Here, when irradiating the portion of the first member facing the recess with laser light, the second member and the first member may be arranged in a superimposed state such that the opening of the recess faces in the opposite direction to the direction of gravity, and the laser light may be irradiated in the direction of gravity toward the portion of the first member facing the recess. [Effects of the Invention]

[0007] The present invention aims to suppress a decrease in the strength of a cooling device when welding together different types of metal components. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of a cooling device to which this embodiment is applied. [Figure 2] This is a cross-sectional view of the cooling system (section II-II in Figure 1). [Figure 3] (a) is an enlarged view of area III in Figure 2, illustrating the area where laser welding is performed, and (b) is a diagram showing the state after laser welding has been performed. [Figure 4] This is a diagram illustrating the position where the laser head is moved. [Figure 5] This experimental result shows an example of the relationship between the shape of the groove and the state of the molten area within the groove. [Figure 6]This experimental result shows an example of the relationship between the output (W) of laser light irradiation and shear strength. [Figure 7] This is a photograph showing some of the experimental results from Figure 6. [Figure 8] This photograph shows a comparative example in which a copper plate and an aluminum plate were welded together without forming a groove. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the attached drawings. Figure 1 shows an example of a cooling device 1 to which this embodiment is applied. Figure 2 is a cross-sectional view of the cooling device 1 (cross-sectional view taken along line II-II in Figure 1). The cooling device 1 according to this embodiment comprises a heat dissipation section 10 having a plurality of fins 12, and a cover 20 having through holes 21 for arranging the heat dissipation section 10 inside. The cooling device 1 is a device that attaches a heat-generating element to the heat dissipation section 10 and dissipates the heat generated from the heat-generating element through the plurality of fins 12. The cooling device 1 is used, for example, by arranging it in a case having an internal space through which a coolant flows, so that the coolant flows between the plurality of fins 12. The cover 20 is used to cover the opening of this case. Alternatively, the cooling device 1 may be an air-cooled type that promotes heat dissipation by flowing a gas such as air between the plurality of fins 12 of the heat dissipation section 10. The heat-generating element cooled by the cooling device 1 is not particularly limited, but a semiconductor element can be given as an example.

[0010] In the example shown in FIG. 1, the plurality of fins 12 project from the front side toward the back side with respect to the plane of the drawing. Hereinafter, the direction in which the plurality of fins 12 project may be simply referred to as the protruding direction. The tip side of the fin 12 in the protruding direction (the lower side in FIG. 2) may be referred to as the "first side", and the opposite side of the "first side" in the protruding direction (the upper side in FIG. 2) may be referred to as the "second side". Further, as shown in FIG. 1, the shape of the cooling device 1 when viewed from the protruding direction is rectangular, and the longitudinal direction of this rectangle may be simply referred to as the "longitudinal direction", and the short side direction of this rectangle may be simply referred to as the "short side direction".

[0011] (Heat dissipation part 10) The material of the heat dissipation part 10 is preferably a material with a high thermal conductivity compared to the material of the cover 20. Examples of the material of the heat dissipation part 10 include copper and copper alloys. Further, plating treatment may be performed on part or all of the surface of the heat dissipation part 10. The material for the plating treatment is not particularly limited, but nickel plating treatment can be exemplified to enhance corrosion resistance. The heat dissipation part 10 includes a flat base part 11 and a plurality of fins 12 protruding from the base part 11.

[0012] The base part 11 has a substantially square shape when viewed from the second side in the protruding direction. The base part 11 includes a fin side surface 111 which is the surface on the side where the plurality of fins 12 protrude, and a mounting surface 112 to which the heating element is attached. Further, the base part 11 includes a lower part 13 that overlaps with the upper part 22 of the cover 20 described later.

[0013] The lower part 13 is located at the outer peripheral edge of the heat dissipation part 10 and has a stepped shape that is recessed from the mounting surface 112 toward the first side in the protruding direction. The lower part 13 has a substantially square annular shape when viewed from the second side in the protruding direction and has an upper surface 132 which is the surface facing the second side in the protruding direction. Welding is performed by overlapping the lower part 13 and the upper part 22, and a melted part 50 is formed. A groove 14 for welding is formed in the lower part 13, and the groove 14 will be described in detail using FIG. 3.

[0014] <000009The plurality of fins 12 project in a direction perpendicular to the plate surface of the base portion 11 from the fin side surface 111 of the base portion 11. The plurality of fins 12 are an example of a fin portion and project from a region that is substantially square when the base portion 11 is viewed from the protruding direction. Each fin 12 is in the shape of a flat plate extending in a direction perpendicular to the plate surface of the base portion 11 and in the short side direction of the cooling device 1. The plurality of fins 12 are arranged side by side in the longitudinal direction of the cooling device 1. Note that the shape of the plurality of fins 12 is not particularly limited, and examples of the shape of the fin 12 include columnar shapes such as cylindrical and quadrangular columnar shapes. Also, the shape of the fin 12 is not limited to one, and the plurality of fins 12 may be composed of fins 12 with different shapes.

[0015] (Cover 20) Examples of the material of the cover 20 include aluminum and aluminum alloys, which are lighter than copper. Also, plating treatment may be performed on part or all of the surface of the cover 20. The material for the plating treatment is not particularly limited, but examples include plating treatment with nickel to enhance corrosion resistance. The cover 20 is a plate-shaped member with a rectangular shape when viewed from the second side in the protruding direction, and a substantially square through-hole 21 for arranging the heat radiating portion 10 is formed in the center. Also, in the cover 20, an upper step portion 22 that is recessed from the first side surface of the cover 20 to the second side is formed around the through-hole 21. The upper step portion 22 has an annular shape that is substantially square so that the shape when viewed from the first side in the protruding direction overlaps with the lower step portion 13 of the heat radiating portion 10. The upper step portion 22 has a contact surface 221 that contacts the upper surface 132 of the lower step portion 13. The contact surface 221 is a surface facing the first side in the protruding direction.

[0016] [Manufacturing Method] Next, a manufacturing method of the cooling device 1 (see FIG. 2) will be described with reference to FIGS. 3 and 4. FIG. 3(a) is an enlarged view of the III region in FIG. 2 and is a diagram for explaining the shape before laser welding. FIG. 3(b) is a diagram showing the state after laser welding. Figure 4 is a diagram illustrating the position to which the laser head 151 is moved.

[0017] The manufacturing process for the cooling device 1 involves, in the first step, forming the heat dissipation section 10 and the cover 20 separately. Then, in the second step, stacking the heat dissipation section 10 and the cover 20. Furthermore, in the third step, welding is performed by irradiating with laser light 152.

[0018] In the first step, copper or a copper alloy is formed into the shape of the heat dissipation section 10, and aluminum or an aluminum alloy is formed into the shape of the cover 20. Examples of methods for forming the heat dissipation section 10 and the cover 20 include pressing, forging, casting, and machining. In addition, multiple forming methods may be combined to form the heat dissipation section 10 and the cover 20. For example, as a method for forming the heat dissipation section 10, all parts except the groove 14 of the heat dissipation section 10 may be formed by casting, and the groove 14 may be formed by machining.

[0019] As shown in Figure 3(a), the groove 14 is provided on the upper surface 132 of the lower section 13 and is a rectangular annular groove provided along the lower section 13 when viewed from the second side in the protruding direction. The groove 14 comprises a bottom surface 141 that forms the bottom of the concave groove 14 and a side surface 142 that forms the concave side surface.

[0020] In the second step, as shown in Figure 3(a), the upper surface 132 of the lower section 13 of the heat dissipation section 10 and the contact surface 221 of the upper section 22 of the cover 20 are brought into contact and overlapped. As described above, the groove 14 is located on the upper surface 132 of the lower section 13. Therefore, in the overlapping section of the lower section 13 and the upper section 22, the groove 14 is recessed in the direction away from the contact surface 221. In other words, the opening of the groove 14 is in contact with the contact surface 221. Furthermore, the heat dissipation section 10 and the cover 20 are positioned such that the direction in which the groove 14 is recessed is in the direction of gravity. In other words, the heat dissipation section 10 and the cover 20 are positioned such that the opening of the groove 14 faces in the opposite direction to gravity. Here, facing in the opposite direction to gravity means that the inclination with respect to the vertical is 45° or less.

[0021] In the third step, with the lower section 13 and the upper section 22 superimposed, the laser beam 152 is shone onto the cover 20 in the direction of the groove 14's recess (in this case, the direction of gravity). The laser beam 152 is shone at a position that overlaps with the groove 14 when viewed from the second side in the protruding direction.

[0022] As shown in Figure 3(b), the cover 20 melts due to the laser beam 152 irradiated in the protruding direction, forming a molten portion 50. As shown in Figure 3(b), the molten portion 50 penetrates into the groove 14 and melts the area around the groove 14 by contacting the bottom surface 141 (see Figure 3(a)) and side surface 142 (see Figure 3(a)). In the molten portion 50, a single-metal molten portion 51 and a dissimilar-metal molten portion 52 are formed. The single-metal molten portion 51 is the part where the base material of the cover 20 is melted. The dissimilar-metal molten portion 52 is the part where the base material of the cover 20 and the base material of the heat dissipation portion 10 are melted.

[0023] The dissimilar metal molten area 52 is formed when the base material of the cover 20 melts and enters the groove 14, causing the base material of the heat dissipation section 10 to melt. Although the melting point of aluminum, the base material of the cover 20, is lower than that of copper, the area irradiated by the laser beam 152 can reach a temperature higher than its melting point. Therefore, even in a single-metal molten area 51 of aluminum, which has a lower melting point than copper, it is possible to melt copper, which has a higher melting point. Furthermore, since the laser beam 152 is irradiated from a position facing the bottom surface 141, the energy of the laser beam 152 is easily transferred to the bottom surface 141 of the groove 14, suppressing excessive melting of the side surface 142. Therefore, the formation of the dissimilar metal molten area 52 is suppressed on the side surface 142 compared to the bottom surface 141.

[0024] As shown in Figure 3(b), the molten portion 50 penetrates into the groove 14 and melts the area around the groove 14 by contacting the bottom surface 141 and the side surface 142 of the groove 14. The side surface 142 is positioned perpendicular to the top surface 132, and a dissimilar metal molten portion 52 is formed along the protruding direction. The dissimilar metal molten portion 52 is a layer in which copper and aluminum have molten, and is a region where intermetallic compounds are likely to be generated.

[0025] In the third step, the laser head 151 is moved along the groove 14 (along the perimeter of the base portion 11) while continuously irradiating with laser light 152, as shown in Figure 4, thereby welding the upper portion 22 and the lower portion 13 without changing the irradiation direction of the laser head 151.

[0026] [Effect] Figure 8 is a photograph showing a comparative example in which a copper plate and an aluminum plate are welded together without forming a groove 14. In Figure 8, a copper plate and an aluminum plate are stacked, and welding is performed by irradiating the aluminum plate with laser light. In the illustrated example, the aluminum plate is placed on the upper side of the drawing, and the copper plate is placed on the lower side. In the comparative example in Figure 8, a molten area of ​​dissimilar metals is formed at the contact surface between the copper plate and the aluminum plate. In Figure 8, an example of the direction in which shear force acts is indicated by an arrow. In the example shown in Figure 8, a shear force acts on the molten area by applying a pulling force to the right on the aluminum plate and to the left on the copper plate. In this case, the pulling force to the left and right is likely to be applied to the molten area of ​​dissimilar metals, and the generally brittle intermetallic compound portion is likely to break. On the other hand, in the cooling device 1 of this embodiment, as shown in Figure 3(b), in the molten area 50 of the cooling device 1, a molten area of ​​dissimilar metals 52 of aluminum and copper is likely to be formed at the interface between the side surface 142 and the bottom surface 141. In other words, the formation of a molten area of ​​dissimilar metals 52 is suppressed at the opening of the groove 14, that is, at the position on the surface where the top surface 132 and the contact surface 221 are in contact. As a result, when forces are applied to the heat dissipation section 10 and the cover 20 in different directions along the contact surface 221 (upper surface 132), shear force is easily applied to the single-metal molten section 51. In other words, the application of shear force to the dissimilar-metal molten section 52 formed in the groove 14 is suppressed, and fracture from the intermetallic compound portion is suppressed.

[0027] <Summary> As described above, the cooling device 1 is formed by joining a cover 20 made of aluminum and a heat dissipation part 10 made of copper when the cover 20 is superimposed on the cover 20 and irradiated with laser light 152. Furthermore, the heat dissipation part 10 of the cooling device 1 has a groove 14 recessed on the upper surface 132 of the lower part 13 that is superimposed on and in contact with the cover 20, so as to be separated from the contact surface 221 of the cover 20. In addition, the part of the cover 20 facing the groove 14 melts and enters into the groove 14, and is fused together at the position of the bottom surface 141 and the side surface 142 of the groove 14 in the heat dissipation part 10.

[0028] In the cooling device 1 formed in this manner, the bottom surface 141 and the side surface 142 of the groove 14 are fused together, thus preventing the formation of a dissimilar metal molten portion 52 in a position continuous with the upper surface 132 of the lower portion 13. As a result, even when a shear force is applied to the heat dissipation portion 10 and the cover 20, the relatively strong single-metal molten portion 51 receives the force, increasing the strength against shear force.

[0029] Furthermore, the cooling device 1 according to this embodiment uses copper, which has high heat dissipation performance, for the heat dissipation section 10 and lightweight aluminum for the cover 20, thereby improving heat dissipation performance and reducing weight.

[0030] Comparing the melting points of aluminum and copper, copper has a higher melting point. In this embodiment, the aluminum cover 20 is irradiated with laser light 152. Therefore, compared to the case where the copper of the heat dissipation section 10 is irradiated with laser light 152 to melt it, the energy required for melting can be reduced.

[0031] Furthermore, the cover 20 is positioned around the heat dissipation section 10, and the groove 14 is provided around the base section 11 of the heat dissipation section 10 and the plurality of fins 12. The cooling device 1 of this embodiment achieves high heat dissipation performance and lightweight design by using copper for the heat dissipation section 10 and aluminum for the cover 20.

[0032] In this embodiment, the heat dissipation section 10 has a flat base section 11 to which the heat generated by the heat-generating element is transferred, and a plurality of fins 12 that protrude from the base section 11 in a direction intersecting the plate surface of the base section 11. The cover 20 is arranged around the heat dissipation section 10. The groove 14, which is the position for welding the heat dissipation section 10 and the cover 20, is provided around the area of ​​the base section 11 from which the plurality of fins 12 protrude. By constructing the heat dissipation section 10, which contributes significantly to heat dissipation, from copper, the contribution to heat dissipation can be enhanced. On the other hand, by constructing the area surrounding the multiple fins 12, which contribute less to heat dissipation, from aluminum, weight reduction can be achieved.

[0033] In this embodiment, the manufacturing method of the cooling device 1 involves superimposing a cover 20 made of aluminum and a heat dissipation section 10 made of copper, a different type of metal from the aluminum used for the cover 20, and then irradiating the cover 20 with laser light. In this manufacturing method, in the first step, a groove 14 is formed on the upper surface 132 of the heat dissipation section 10, which is the surface that is superimposed on and in contact with the cover 20, so as to be separated from the contact surface 221 of the cover 20. In the second step, laser light is irradiated onto the cover 20. Here, the laser light is irradiated onto the part of the cover 20 opposite the groove 14, melting the cover 20 and melting the bottom surface 141 and side surface 142 of the groove 14, thereby melting and joining them with the surrounding part of the groove 14.

[0034] In the cooling device 1 manufactured in this manner, the bottom surface 141 and the side surface 142 of the groove 14 are fused together, thus suppressing the formation of a molten dissimilar metal portion 52 at a position along the contact surface 221 of the upper portion 22 between the upper surface 132 of the lower portion 13, which is the surface surrounding the groove 14, and the upper portion 22.

[0035] Furthermore, in the manufacturing method of the cooling device 1 of this embodiment, when irradiating the portion of the cover 20 facing the groove 14 with laser light 152, the heat dissipation portion 10 and the cover 20 are arranged in a state where they are superimposed on each other so that the opening of the groove 14 faces in the opposite direction to the direction of gravity. Then, the laser light 152 is irradiated in the direction of gravity toward the portion of the cover 20 facing the groove 14. When the cover 20 is arranged in this manner and irradiated with laser light 152, the molten portion 50 falls into the groove 14 due to gravity, making it easier to fill the groove 14.

[0036] The inventors conducted experiments to investigate the relationship between the shape of the groove 14 (width H and depth D) and the state of the molten portion 50 in the groove 14. Figure 5 shows an example of experimental results illustrating the relationship between the shape of the groove 14 and the state of the molten portion 50 in the groove 14. The inventors first formed a groove in a copper plate, then placed an aluminum plate on top of it, and welded the copper plate and aluminum plate together by irradiating the groove with laser light from the aluminum plate side. They then took cross-sectional photographs showing the molten state of the copper plate and aluminum plate.

[0037] More specifically, for the aluminum plate, we used an A1100 aluminum plate with a thickness of 2 mm. For the copper plate, we used a C1020 copper plate with a thickness of 2 mm. Then, grooves were formed in the copper plate by cutting. Three samples were created with different groove shapes, each with a width H of 0.5 mm and depths D of 1 mm, 0.5 mm, and 0.25 mm. As shown in Figure 5, when the depth D is 1 mm, the molten portion 50 cannot fill the groove 14, resulting in poor joining. When the depth D is 0.5 mm or 0.25 mm, the molten portion 50 fills the groove 14, resulting in good joining. In other words, when the depth D of the groove 14 is shorter than or equal to the width H, the molten portion 50 fills the groove 14 and good joining is achieved.

[0038] Next, the inventors joined an aluminum plate and a copper plate by changing the output of the laser beam irradiation while keeping the width H and depth D of the grooves provided in the copper plate unchanged, and measured the shear strength. Figure 6 shows an example of experimental results illustrating the relationship between laser beam output (W) and shear strength (MPa). Hereafter, the laser beam output may simply be referred to as "output." Figure 7 is a photograph showing some of the experimental results from Figure 6. The inventors first formed a groove in a copper plate, then placed an aluminum plate on top of it, and welded the copper plate and aluminum plate together by irradiating the groove with laser light from the aluminum plate side. Then, they pulled the copper plate and aluminum plate in directions parallel to their surfaces but in different directions, gradually increasing the pulling force, and recorded the shear force at which the copper plate and aluminum plate separated as the shear strength.

[0039] More specifically, the system underwent two tests each at three different power levels: 800W, 1000W, and 1200W. Three tests were conducted at 900W, and one test at 850W. In this test, the aluminum plate thickness was set to 1 mm. The width H of the groove formed in the copper was set to 0.5 mm and the depth D to 0.25 mm. Furthermore, the wobbling settings for laser irradiation were set to a wobbling diameter of 0.5 mm and a wobbling speed of 1500 mm / s.

[0040] As shown in Figure 6, the shear strengths were 82 MPa and 85 MPa for an output of 800 W. For an output of 850 W, the shear strength was 91 MPa. For an output of 900 W, the shear strengths were 92 MPa, 79 MPa, and 54 MPa. For an output of 1000 W, the shear strengths were 15 MPa and 20 MPa. For an output of 1200 W, the shear strengths were 27 MPa and 29 MPa. As shown in Figure 6, it was found that the shear strength is greater when the output is between 800W and 900W compared to when the output is 1000W and 1200W. Furthermore, when the width H of the groove 14 of the cooling device 1 according to this embodiment is 0.5 mm, the depth D is 0.25 mm, the thickness of the cover 20 is 1.0 mm, the wobbling diameter of the laser beam 152 irradiated onto the cover 20 is 0.5 mm, and the wobbling speed is 1500 mm / s, when the output of the laser beam is in the range of 800W to 900W, the shear strength of the cover 20, the heat dissipation part 10 and the molten part 50 increases, and the strength of the cooling device 1 increases. In addition, it is desirable that the wobbling diameter be, for example, 1.5 times or less the size of the groove H.

[0041] Figure 7 is a photograph showing a cross-section of the cover 20 and heat dissipation section 10 after they have been separated by a shear test. Even when grooves are provided, as the output of the laser beam 152 increases, the fluidity of the molten portion 50 increases, and the copper molten at the bottom surface 141 and side surface 142 of the groove 14 diffuses within the molten portion 50. As a result, the relatively brittle dissimilar metal molten portion 52 spreads within the molten portion 50, reducing its strength. At output levels of 1000W and 1200W, copper melts from the bottom surface 141 and side surface 142, and a large portion of the molten portion 50 becomes the dissimilar metal molten portion 52, resulting in a lower shear strength. On the other hand, in the output range of 800W to 900W, the dissimilar metal molten portion 52 does not spread as much as at output levels of 1000W and 1200W, resulting in a higher shear strength.

[0042] <Other> In this embodiment, the side surface 142 is perpendicular to the top surface 132. However, the side surface 142 does not necessarily have to be perpendicular to the top surface 132 and may be inclined. For example, the shape of the groove 14 may have a trapezoidal or V-shaped cross-section in which the width gradually increases from the bottom surface 141 toward the opening. Alternatively, the groove 14 may have a semicircular cross-section. [Explanation of Symbols]

[0043] 1...Cooling device, 10...Heat dissipation section, 14...Groove, 20...Cover, 50...Melting section, 51...Single-metal melting section, 52...Dissimilar-metal melting section, 132...Top surface, 141...Bottom surface, 142...Side surface, 151...Laser head, 152...Laser beam, 221...Contact surface

Claims

1. A cooling device in which a first member made of metal and a second member made of a different type of metal than the first member are joined together by irradiating the first member with laser light, The second member has a recess on the surface that overlaps with and contacts the first member, such that it is recessed away from the first member. The portion of the first member facing the recess melts and enters the recess, and is fused together with the surrounding portion of the second member. Cooling device.

2. The melting point of the first member is lower than the melting point of the second member. The cooling device according to claim 1.

3. The material of the first component is aluminum. The material of the second component is copper. The cooling device according to claim 2.

4. The second member comprises a flat base portion to which heat generated by the heating element is transferred, and fin portions that protrude from the base portion in a direction intersecting the plate surface of the base portion. The first member is arranged around the second member, The recess is provided on the base portion of the second member around the fin portion. The cooling device according to claim 1.

5. The shape of the recess is such that the depth of the recess is shorter than or equal to the width of the recess. A cooling device according to any one of claims 1 to 4.

6. A method for manufacturing a cooling device, wherein a first member made of metal and a second member made of a different type of metal than the first member are joined together by irradiating the first member with laser light, A step of forming a recess on the surface of the second member that is superimposed on and in contact with the first member, such that it is recessed away from the first member, A step of irradiating the portion of the first member facing the recess with laser light to melt the first member and fuse it with the portion surrounding the recess, A method for manufacturing a cooling device equipped with the following features.

7. When irradiating the portion of the first member facing the recess with laser light, the second member and the first member are arranged in a superimposed state such that the opening of the recess faces in the opposite direction to the direction of gravity, and the laser light is irradiated in the direction of gravity toward the portion of the first member facing the recess. A method for manufacturing a cooling device according to claim 6.

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