Joint and cooling device

Abstract

To improve the airtightness of the joint between aluminum and copper materials. [Solution] In the joint, a plate-shaped aluminum material and a plate-shaped copper material are stacked on top of each other, and when laser light is irradiated onto the aluminum material, a mixed molten portion is formed where the molten portion of the aluminum material and the molten portion of the copper material are mixed. The Vickers hardness of the mixed molten portion at the interface between the aluminum material and the copper material is 55 HV to 150 HV.

Description

Technical Field

[0001] The present invention relates to a joined body and a cooling device.

Background Art

[0002] Patent Document 1 discloses a dissimilar metal joined body in which a copper material and an aluminum material are in contact with each other. This metal joined body has a molten mixed portion formed by melting a part of the aluminum material and flowing it into the copper material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a joined body of an aluminum material and a copper material, when too much copper is mixed with aluminum in a mixed molten portion where the molten portion of the aluminum material and the molten portion of the copper material are mixed, a large amount of intermetallic compounds may be generated. And in a joined body of an aluminum material and a copper material, cracks occur due to these intermetallic compounds, leading to a decrease in airtightness. An object of the present invention is to improve the airtightness of a joined body of an aluminum material and a copper material.

Means for Solving the Problems

[0005] According to the present invention, the inventions according to the following (1) to (6) are provided. (1) A jointed body (heat dissipation part 2) in which a plate-shaped aluminum material (holding member 15, inner circumference 18) and a plate-shaped copper material (heat sink 10, thin plate part 13) are superimposed on each other, and a laser beam is irradiated onto the aluminum material, thereby forming a mixed molten part (joint part 40) in which the molten part of the aluminum material and the molten part of the copper material are mixed, wherein the Vickers hardness of the mixed molten part at the interface (interface 49) between the aluminum material and the copper material is 55 HV or more and 150 HV or less. (2) The joint according to (1), wherein the depth from the interface to the bottom of the mixed molten portion (bottom 45) (joining depth D) is 150 μm or more and 500 μm or less, and the Vickers hardness of the mixed molten portion at the bottom is 89 HV or more and 330 HV or less. (3) The joint according to (2), wherein the copper material has a recess (recess 135) recessed from the interface, the mixed molten portion is formed by mixing the molten portion of the aluminum material that has melted and entered the recess from the portion of the aluminum material facing the recess, and the molten portion of the copper material that has melted from the portion of the copper material surrounding the recess, and the depth of the recess (depth h) is 150 μm or more and 350 μm or less. (4) The joint according to (1), wherein the depth from the interface to the bottom of the mixed molten portion (bottom 45) (joining depth D) is 0 μm or more and 150 μm or less, and the Vickers hardness of the mixed molten portion at the bottom is 55 HV or more and 150 HV or less. (5) The joint according to (4), wherein when the width of the mixed molten portion at the interface is L and the depth from the interface to the bottom of the mixed molten portion is D, D / L is 0.05 or more and 0.3 or less. (6) A cooling device comprising: a heat sink (heat sink 10) made of copper material having a plurality of fins (fins 12) and a holding member (holding member 15) made of aluminum material that holds the heat sink, and a heat dissipation section (heat dissipation section 2) in which a mixed molten section (joint section 40) is formed by irradiating the holding member with laser light while the molten section of the aluminum material and the molten section of the copper material are superimposed on each other; and a main body section (main body section 3) which houses the fins of the heat sink and has a space (circulation space 35) through which a coolant flows, wherein the Vickers hardness of the mixed molten section at the interface between the aluminum material and the copper material is 55 HV or more and 150 HV or less. [Effects of the Invention]

[0006] According to the present invention, the airtightness of the joint between the aluminum material and the copper material can be improved. [Brief explanation of the drawing]

[0007] [Figure 1] This is an example of a diagram showing the components of a cooling device to which this embodiment is applied, disassembled. [Figure 2] This figure shows an example of a cross-section of a cooling device, specifically an example of a cross-section obtained by cutting the cooling device along the z-direction and the x-direction. [Figure 3] This figure shows an example of a cross-section of a cooling device, specifically an example of a cross-section obtained by cutting the cooling device along the z-direction and the y-direction. [Figure 4] This is a perspective view showing an example of the configuration of a heat dissipation unit to which this embodiment is applied. [Figure 5] This is a view of the heat dissipation section from the -z direction, which will be described later. [Figure 6] This is a cross-sectional view of section VI-VI in Figure 5. [Figure 7] (a) and (b) are diagrams illustrating the method of joining the thin plate portion of the heat sink to the inner circumference portion of the retaining member, and are cross-sectional views of the thin plate portion and the inner circumference portion in an overlapping state. [Figure 8]This diagram illustrates the joint formed between the thin plate portion of the heat sink and the inner circumference portion of the retaining member. [Figure 9] This diagram illustrates the joint formed between the thin plate portion of the heat sink and the inner circumference portion of the retaining member. [Figure 10] This figure shows the correlation between the ratio of copper in a joint formed by mixing molten aluminum and molten copper, and the Vickers hardness of the joint. [Figure 11] This is an enlarged view of the joint portion of the first embodiment shown in Figure 8. [Figure 12] This figure shows an example of a joint used in the embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the attached drawings. Figure 1 is an example of a diagram showing the components of the cooling device 1 to which this embodiment is applied in an exploded view. Figure 2 shows an example of a cross-section of the cooling device 1, and is a diagram showing an example of a cross-section obtained by cutting the cooling device 1 along the z-direction and x-direction, which will be described later. Figure 3 shows an example of a cross-section of the cooling device 1, and is a diagram showing an example of a cross-section obtained by cutting the cooling device 1 along the z-direction and y-direction, which will be described later. The cooling device 1 according to this embodiment comprises a heat dissipation section 2 having a heat sink 10, and a main body section 3 that houses the heat sink 10 and forms a space through which a coolant flows. The cooling device 1 also includes bolts 4 that connect the heat dissipation section 2 and the main body section 3. The cooling device 1 of this embodiment is a liquid-cooled cooling device that cools a semiconductor module 5, which is an example of a heat-generating element, using a cooling liquid flowing through the main body 3 and a heat sink 10 of the heat dissipation unit 2.

[0009] The main body 3 includes a case body 21 with a bottomed recess. The main body 3 also includes an O-ring 23 that seals the space between the case body 21 and the retaining member 15 of the heat dissipation section 2, which will be described later. The main body 3 also includes an inflow pipe 25 for allowing the coolant to flow into the space within the case body 21 and an outflow pipe 26 for allowing the coolant to flow out from the space within the case body 21. Examples of the material of the case body 21 in the present embodiment can include an A6000 series of aluminum alloy such as A6063, an aluminum alloy die-cast such as ADC12, and copper.

[0010] The case body 21 has a flat rectangular bottom 31 and four side walls 32 protruding in a direction perpendicular to the plate surface of the bottom 31 from the peripheral end portions of the bottom 31. A first through-hole 323 penetrating the first side wall 321 is formed in the first side wall 321 among the four side walls 32. Also, a second through-hole 324 penetrating the second side wall 322 is formed in the second side wall 322 facing the first side wall 321 among the four side walls 32. The inflow pipe 25 is fitted into the first through-hole 323, and the outflow pipe 26 is fitted into the second through-hole 324. In addition, on the end surfaces of the four side walls 32 on the heat dissipation part 2 side, a groove 325 into which an O-ring 23 is fitted is provided around the opening of the case body 21. Also, on the end surfaces of the four side walls 32 on the heat dissipation part 2 side, female threads 326 for tightening bolts 4 are formed at the four corners outside the groove 325 respectively.

[0011] FIG. 4 is a perspective view showing an example of the configuration of the heat dissipation part 2 to which the present embodiment is applied. FIG. 5 is a view of the heat dissipation part 2 seen from the -z direction side which will be described later. FIG. 6 is a cross-sectional view of the VI-VI part in FIG. 5. The heat dissipation part 2 includes a heat sink 10 and a holding member 15 for holding the heat sink 10. Also, the heat dissipation part 2 has a joining part 40 for joining the heat sink 10 and the holding member 15. The heat dissipation part 2 is an example of a joined body.

[0012] The heat sink 10 is made of copper. Examples of copper materials include copper or copper alloys, and it is preferable to use high-purity copper. More specifically, examples of copper materials include C1020, C1100, etc. Furthermore, the copper material may or may not have a plating on its surface. Since the heat sink 10 is made of copper, for example, compared to the case where the heat sink 10 is made of a metal material other than copper, it becomes easier to dissipate heat from the semiconductor module 5 into the coolant, and the cooling efficiency of the cooling device 1 is improved.

[0013] The heat sink 10 has a flat base portion 11, a plurality of fins 12 protruding from the base portion 11 in a direction perpendicular to the plate surface, and a thin plate portion 13 provided on the outer circumference of the base portion 11 that is thinner than the base portion 11. The base portion 11 has a rectangular shape. The base portion 11 has a surface 111 on which a plurality of fins 12 protrude, and a back surface 112 on which the semiconductor module 5 is mounted. The base portion 11 also has a side surface 113 that connects the outer periphery of the surface 111 and the back surface 112. In the following, the direction in which the fins 12 protrude from the surface 111 of the base 11 will be referred to as the z-direction. The shorter side of the rectangular base 11 will be referred to as the x-direction, and the longer side of the base 11 will be referred to as the y-direction.

[0014] Each fin 12 is a flat plate-shaped member. Multiple fins 12 extend in the x-direction on the surface 111 of the base 11 and are arranged side by side in the y-direction with gaps in between. In this example, each fin 12 is provided in the x-direction from the inlet pipe 25 to the outlet pipe 26, in other words, parallel to the flow direction of the coolant in the flow space 35, which will be described later.

[0015] The thin plate portion 13 has a thin plate shape. The thin plate portion 13 is provided so as to protrude outward from the side surface 113 of the base portion 11. The thin plate portion 13 is recessed in the z direction compared to the back surface 112 of the base portion 11, and as a result, it is thinner than the base portion 11. In this embodiment, the thin plate portion 13 of the heat sink 10 is an example of a plate-shaped copper material.

[0016] The thickness of the thin plate portion 13 can be exemplified by a range of, for example, 1000 μm to 3000 μm. If the thickness of the thin plate section 13 exceeds 3000 μm, the entire heatsink 10 becomes thicker, and the weight of the heatsink 10 tends to increase. If the thickness of the thin plate portion 13 is less than 1000 μm, the joint portion 40 may penetrate the thin plate portion 13, resulting in insufficient bonding strength between the heat sink 10 and the retaining member 15. Furthermore, the width of the thin plate portion 13, in other words, the length from the side surface 113 of the base portion 11 to the outer edge 131 of the thin plate portion 13, can be exemplified as being in the range of 2000 μm to 5000 μm.

[0017] The retaining member 15 is made of aluminum. Examples of aluminum materials include aluminum or aluminum alloys, and it is preferable to use high-purity aluminum. More specifically, examples of aluminum materials include A1100, A1050, etc. The retaining member 15 is a member that holds the heat sink 10, and has a rectangular opening 16 in the center into which the heat sink 10 is inserted. The retaining member 15 has a flat outer peripheral portion 17 located on the outer periphery and attached to the side wall 32 of the case body 21. The retaining member 15 also has a thin, plate-like inner peripheral portion 18 that surrounds the opening 16 and is thinner than the outer peripheral portion 17.

[0018] The outer periphery 17 has a rectangular outer surface 171 and an inner surface 172, and as a whole, it has a frame-like shape. The outer periphery 17 has a surface 173 that faces the side wall 32 of the case body 21, and a back surface 174 located on the opposite side of the surface 173. In addition, holes 175 for passing bolts 4 are formed at each of the four corners of the outer periphery 17.

[0019] The inner circumference 18 is provided so as to protrude from the inner edge of the outer circumference 17 into the opening 16. The inner circumference 18 is recessed in the -z direction compared to the surface 173 of the outer circumference 17, and is thinner than the outer circumference 17. In this embodiment, the inner circumference 18 of the retaining member 15 is an example of a plate-shaped aluminum material. The inner circumference portion 18 is superimposed on the thin plate portion 13 of the heat sink 10 in the -z direction. In addition, the inner circumference portion 18 is in contact with the thin plate portion 13 of the heat sink 10, and the inner circumference portion 18 and the thin plate portion 13 are facing each other. In the following, the xy plane corresponding to the boundary between the inner circumference 18 and the thin plate portion 13 of the heat dissipation section 2, that is, the position where the inner circumference 18 and the thin plate portion 13 face each other, will be referred to as the boundary surface 49.

[0020] The thickness of the inner circumference 18 can be exemplified by a range of, for example, 1000 μm to 2000 μm. If the thickness of the inner circumference 18 exceeds 2000 μm, a large amount of energy is required when irradiating with laser light to form the joint 40. In addition, it may become difficult to make the joint depth D of the joint 40 (see Figure 8 below) the desired size. Furthermore, if the thickness of the inner circumference 18 is less than 1000 μm, the molten aluminum material constituting the inner circumference 18 is more likely to mix with the molten copper material constituting the thin plate portion 13 at the joint 40, leading to the generation of a large amount of intermetallic compounds between aluminum and copper. This can result in insufficient bonding strength between the heat sink 10 and the retaining member 15. In this example, the width of the inner circumference 18 is equal to the width of the thin plate portion 13 of the heat sink 10. As a result, when the inner circumference 18 and the thin plate portion 13 of the heat sink 10 are superimposed, the inner edge 181 of the inner circumference 18 faces the side surface 113 of the base portion 11 of the heat sink 10. Also, the outer edge 131 of the thin plate portion 13 faces the inner surface 172 of the outer circumference 17.

[0021] The heat sink 10 and the retaining member 15 are joined by a joint 40 formed by irradiating a laser beam from the inner circumference 18 side while the thin plate portion 13 of the heat sink 10 and the inner circumference 18 of the retaining member 15 are superimposed. The joint 40 is formed by mixing a molten portion of aluminum material constituting the inner circumference 18, which has been melted by laser irradiation, with a molten portion of copper material constituting the thin plate portion 13. The configuration of the joint 40 and the method of joining the heat sink 10 and the retaining member 15 by the joint 40 will be explained in detail later.

[0022] The cooling device 1 and semiconductor module 5, configured as described above, are assembled as follows. First, the heat sink 10 of the heat dissipation section 2 and the semiconductor module 5 are brazed together. More specifically, the semiconductor module 5 is brazed to the back surface 112 of the base 11 of the heat sink 10. Then, the heat dissipation unit 2 is placed over the case body 21 so that the semiconductor module 5 is located on the outside and the fins 12 of the heat sink 10 are housed inside the main body 3, and the opening of the case body 21 is covered with the heat dissipation unit 2. When placing the heat dissipation unit 2 over the case body 21, the O-ring 23 is fitted into the groove 325 formed in the case body 21. After placing the heat dissipation unit 2 over the case body 21, the bolts 4 that are passed through the holes 175 formed in the retaining member 15 of the heat dissipation unit 2 are tightened into the female threads 326 formed in the case body 21. As a result, a flow space 35 is formed in the space enclosed between the heat sink 10 of the heat dissipation section 2 and the case body 21 of the main body section 3, through which the coolant flows. In this example, the direction of coolant flow through the flow space 35 is parallel to the x-direction, which is the direction in which the fins 12 of the heat sink 10 extend. The flow space 35 is sealed by an O-ring 23.

[0023] Next, we will explain how to join the heat sink 10 and the retaining member 15. Figures 7(a) and 7(b) illustrate the method of joining the thin plate portion 13 of the heat sink 10 and the inner circumference portion 18 of the holding member 15, and are cross-sectional views of the thin plate portion 13 and the inner circumference portion 18 in an overlapping state. Figures 8 and 9 illustrate the joint 40 formed between the thin plate portion 13 of the heat sink 10 and the inner circumference portion 18 of the holding member 15. The cutting directions of the thin plate portion 13 and the inner circumference portion 18 in Figures 7(a) to 7(b), 8 and 9 are the same as in Figure 6. In addition, Figures 7(a) to 7(b), 8 and 9 are cross-sectional views taken in a plane perpendicular to the direction of movement of the laser head when irradiating with laser light. Hereafter, the cross-sections of the thin plate portion 13, the inner circumference portion 18, and the joint 40 taken in a plane perpendicular to the direction of movement of the laser head when irradiating with laser light may simply be referred to as "cross-sections."

[0024] In this embodiment, when forming the joint 40 by irradiating it with laser light, a first embodiment can be adopted in which a heat sink 10 having a recess 135 formed in the thin plate portion 13 is used, and a second embodiment can be adopted in which a heat sink 10 having a recess 135 not formed in the thin plate portion 13 is used. Figure 7(a) shows the method of joining the heat sink 10 and the retaining member 15 in the first embodiment, and Figure 8 shows the joint 40 formed by the first embodiment. Figure 7(b) shows the method of joining the heat sink 10 and the retaining member 15 in the second embodiment, and Figure 9 shows the joint 40 formed according to the second embodiment.

[0025] As shown in Figure 7(a), the heat sink 10 used in the first embodiment has a recess 135 that is recessed in the z direction on the surface of the thin plate portion 13 facing the inner circumference portion 18 of the holding member 15. The recess 135 is formed continuously in the circumferential direction in the thin plate portion 13 provided along the outer circumference of the heat sink 10. In this embodiment, the cross-sectional shape of the recess 135 is rectangular. The width w and depth h of the recess 135 are determined so that the joint width L and joint depth D of the joint 40, described later, are within a desired range. The width w of the recess 135 can be exemplified as being in the range of 350 μm to 650 μm. The depth h of the recess 135 can be exemplified as being in the range of 150 μm to 350 μm, and is preferably 250 μm. Furthermore, the cross-sectional shape of the recess 135 is not limited to a rectangular shape.

[0026] On the other hand, the heat sink 10 used in the second embodiment does not have a recess 135 (see Figure 7(a)) formed in the thin plate portion 13, as shown in Figure 7(b). In addition, in the heat sink 10 used in the second embodiment, the surface of the thin plate portion 13 facing the inner circumference 18 of the retaining member 15 is flat.

[0027] When joining the heat sink 10 and the retaining member 15, first, the thin plate portion 13 of the heat sink 10 and the inner circumference portion 18 of the retaining member 15 are overlapped. More specifically, the thin plate portion 13 and the inner circumference portion 18 are overlapped so that the -z-direction side surface of the thin plate portion 13 and the z-direction side surface of the inner circumference portion 18 are in contact. The area where the thin plate portion 13 and the inner circumference portion 18 are in contact becomes the interface surface 49, which is the boundary between the copper material constituting the thin plate portion 13 and the aluminum material constituting the inner circumference portion 18. In the first embodiment, by overlapping the thin plate portion 13 and the inner circumference portion 18, the recess 135 formed in the thin plate portion 13 is recessed from the interface surface 49.

[0028] Then, laser light P is irradiated in the z direction from the inner circumference 18 side to the region where the thin plate portion 13 of the heat sink 10 and the inner circumference 18 of the holding member 15 overlap. More specifically, the laser light P is irradiated while moving the laser head (not shown) of the laser device (not shown) in the circumferential direction along the inner circumference 18 which is formed to surround the opening 16 of the holding member 15. In addition, in the first embodiment using a heat sink 10 in which a recess 135 is formed in the thin plate portion 13, the laser light P is irradiated in the circumferential direction along the portion in which the recess 135 is formed. The laser source used when irradiating with laser light P is not particularly limited. Examples of laser sources include solid-state lasers such as YAG lasers, gaseous lasers such as CO2 lasers, fiber lasers using optical fibers as the medium, semiconductor lasers using semiconductors as the medium, disk lasers, and the like.

[0029] When the laser beam P is irradiated, the energy of the laser beam P is converted into heat, causing the copper material constituting the thin plate portion 13 of the heat sink 10 and the aluminum material constituting the inner circumference portion 18 of the holding member 15 to melt. The molten copper material constituting the thin plate portion 13 and the molten aluminum material constituting the inner circumference portion 18 then mix and are rapidly cooled to form the joint portion 40. The joint 40 is an example of a mixed molten portion formed by mixing the molten portion of aluminum material with the molten portion of copper material.

[0030] In the first embodiment, which uses a heat sink 10 with a recess 135 formed in the thin plate portion 13, the portion of the aluminum material constituting the inner circumference 18 that faces the recess 135 in the thin plate portion 13 melts and enters the recess 135. Then, the molten portion of the aluminum material that has entered the recess 135 mixes with the molten portion of the copper material that has melted in the portion of the thin plate portion 13 surrounding the recess 135, forming a joint portion 40. On the other hand, in a second embodiment using a heat sink 10 in which the recess 135 is not formed in the thin plate portion 13, the molten portion of the aluminum material in the vicinity of the interface 49 of the inner circumference portion 18 and the molten portion of the copper material in the vicinity of the interface 49 of the thin plate portion 13 are mixed. This forms a joint portion 40.

[0031] Next, the configuration of the joint 40 will be described in detail. As described above, the joint 40 is formed by mixing the molten aluminum material and the molten copper material. In such a joint 40, if the ratio of copper to aluminum becomes too high, brittle intermetallic compounds may be formed. If a large amount of intermetallic compounds are formed in the joint 40, cracks may occur in the joint 40 due to the intermetallic compounds, which may lead to a decrease in the airtightness of the joint 40. For example, if the proportion of copper at the interface surface 49 of the joint 40 exceeds 10 wt%, intermetallic compounds are more likely to form at the joint 40, which can easily lead to a decrease in the airtightness of the joint 40. On the other hand, if the copper content at the interface 49 of the joint 40 is less than 1.4 wt%, the molten aluminum material and the molten copper material will not mix sufficiently, resulting in a lower joint strength at the joint 40, and in some cases, areas where the thin plate portion 13 and the inner circumference portion 18 are not joined may occur. In this case as well, a decrease in airtightness at the joint 40 is likely to occur.

[0032] Figure 10 shows the correlation between the ratio of copper in the joint 40, formed by mixing molten aluminum and molten copper, and the Vickers hardness of the joint 40. In Figure 10, the horizontal axis represents the ratio of copper (wt%) in the joint 40, and the vertical axis represents the Vickers hardness (HV) of the joint 40. As shown in Figure 10, the joint 40 formed by mixing the molten aluminum material and the molten copper material tends to have a higher Vickers hardness as the proportion of copper increases. In this embodiment, by utilizing the correlation between the ratio of copper in the joint 40 and its Vickers hardness, the Vickers hardness of the joint 40 is set within a predetermined range, thereby suppressing a decrease in airtightness in the joint 40.

[0033] The joint 40 of the first embodiment will now be described. Figure 11 is an enlarged view of the joint 40 of the first embodiment shown in Figure 8. In the first embodiment, the joint 40 has a Vickers hardness of 55 HV or more and 150 HV or less at the interface 49. Here, the Vickers hardness at the interface 49 of the joint 40 can be obtained using the cross-section of the joint 40 as follows. First, at the interface 49, the center of the joint 40 is defined as point M1. Also, at the interface 49, points M2 and M3 are defined as points 100 μm inward from both ends of the joint 40, respectively. The Vickers hardness is then measured for each of points M1, M2, and M3, and the average value is taken as the Vickers hardness of the joint 40 at the interface 49. The measurement conditions for Vickers hardness will be described in detail in the examples below.

[0034] In the first embodiment, by having a Vickers hardness of 55 HV or more and 150 HV or less at the interface surface 49 of the joint 40, the ratio of copper at the interface surface 49 can be set to a range in which intermetallic compounds are less likely to be generated at the joint 40. This suppresses a decrease in airtightness at the joint 40. Furthermore, it suppresses the movement of liquid from one side to the other of the joint 40 along the interface 49 between the thin plate portion 13 and the inner circumference portion 18. More specifically, when the heat dissipation portion 2 (see Figure 2) is applied to the cooling device 1 (see Figure 2), leakage of the coolant from the flow space 35 (see Figure 2) to the outside of the cooling device 1 is suppressed.

[0035] Furthermore, in the first embodiment, the joint portion 40 preferably has a joint depth D, which is the depth from the interface 49 to the bottom portion 45 of the joint portion 40, of 150 μm or more and 500 μm or less, and a Vickers hardness of 89 HV or more and 330 HV or less at the bottom portion 45. Here, the bottom portion 45 is the intersection point of a straight line A, which is parallel to the z-direction and passes through point M1, the center of the joint portion 40 at the boundary surface 49, and the outer edge of the joint portion 40.

[0036] Furthermore, the Vickers hardness at the bottom portion 45 can be obtained using the cross-section of the joint portion 40 as follows. First, assuming that the length of the diagonal of the indentation formed by pressing a diamond indenter into the joint 40 is d, point N1 is defined as a position 3d away from the bottom 45 in the -z direction. Furthermore, on the plane where point N1 is at the same position in the z direction, points N2 and N3 are defined as positions 100 μm inward from both ends of the joint 40, respectively. Then, the Vickers hardness is measured for each of points N1, N2, and N3, and the average value is defined as the Vickers hardness of the joint 40 at the bottom 45.

[0037] In the joint 40 of the first embodiment, when the joint depth D is 150 μm or more and 500 μm or less, the copper content tends to be higher at the bottom 45 compared to the interface 49. When the joint depth D is 150 μm or more and 500 μm or less, in order to suppress the decrease in airtightness at the joint 40, it is preferable that the copper content at the bottom 45 be 4.3 wt% or more and 27 wt% or less. In the first embodiment, the Vickers hardness at the bottom 45 of the joint 40 is set to 89 HV or more and 330 HV or less, so that the proportion of copper at the bottom 45 can be set to a range that suppresses the area where intermetallic compounds are generated to the vicinity of the bottom 45 and reduces the amount of intermetallic compounds. This suppresses a decrease in airtightness at the joint 40.

[0038] Next, the joint portion 40 of the second embodiment will be described. The joint 40 of the second embodiment, like the first embodiment, has a Vickers hardness of 55 HV or more and 150 HV or less at the interface 49. The method for measuring the Vickers hardness at the interface 49 is the same as for the joint 40 of the first embodiment. In the second embodiment, by having a Vickers hardness of 55 HV or more and 150 HV or less at the interface surface 49 of the joint 40, the ratio of copper at the interface surface 49 can be set to a range in which intermetallic compounds are less likely to form at the joint 40. This suppresses a decrease in airtightness at the joint 40.

[0039] Furthermore, in the second embodiment, the joint portion 40 preferably has a joint depth D, which is the depth from the interface 49 to the bottom 45 of the joint portion 40, that is 0 μm or more and 150 μm or less, and a Vickers hardness at the bottom 45 that is 55 HV or more and 150 HV or less. The method for measuring the Vickers hardness at the bottom 45 is the same as for the joint portion 40 in the first embodiment. Note that when the joint depth D is 0 μm, the bottom 45 coincides with the interface 49, so the Vickers hardness at the bottom 45 is equal to the Vickers hardness at the interface 49. The Vickers hardness at the interface 49 of the joint portion 40, the Vickers hardness at the bottom 45 of the joint portion 40, and the definition of the bottom 45 are the same as in the first embodiment.

[0040] In the second embodiment, since no recess 135 (see Figure 7(a)) is formed in the thin plate portion 13, the bonding depth D of the joint portion 40 formed by irradiation with laser light P tends to be smaller than in the first embodiment. When the bonding depth D is small, the distance between the interface 49 and the bottom portion 45 is short, so it is preferable that the Vickers hardness at the bottom portion 45 of the joint portion 40 is about the same as the Vickers hardness at the interface 49. In the second embodiment, the Vickers hardness at the bottom 45 of the joint 40 is 55 HV or more and 150 HV or less, so that the ratio of copper at the bottom 45 can be set to a range in which intermetallic compounds are less likely to be generated in the joint 40. This suppresses a decrease in airtightness at the joint 40.

[0041] Furthermore, in the second embodiment, when the width of the joint portion 40 at the interface surface 49 is defined as the joint width L, it is preferable that the ratio of the joint depth D to the joint width L (D / L) is 0.05 or more and 0.3 or less. In the second embodiment, the reduction in airtightness at the joint 40 is suppressed by having a ratio (D / L) of the joint depth D to the joint width L of the joint 40 of 0.05 or more and 0.3 or less.

[0042] In this embodiment, by changing the conditions under which the laser beam P is irradiated when joining the heat sink 10 and the holding member 15, the Vickers hardness at the interface 49 of the joint 40 and the Vickers hardness at the bottom 45 can be set to the above-mentioned range. Examples of conditions when irradiating with laser light P include the intensity of the laser light P, the speed at which the laser head is moved, and the temperatures of the heat sink 10 and the holding member 15. Furthermore, the Vickers hardness at the interface 49 of the joint 40 and at the bottom 45 may be adjusted by changing the thickness of the inner circumference 18 of the retaining member 15, which is an example of an aluminum material. Furthermore, in the first embodiment, the Vickers hardness at the interface 49 of the joint 40 and the Vickers hardness at the bottom 45 may be adjusted by changing the width w, depth h, cross-sectional shape, etc., of the recess 135 formed in the thin plate portion 13 of the heat sink 10. [Examples]

[0043] Next, the present invention will be described in more detail using examples. Note that the present invention is not limited to the following examples. Figure 12 shows an example of a joint used in the examples. (Preparation of test specimens) As a plate-shaped aluminum material, an aluminum plate 210 made of A1100 with dimensions of 30 mm x 70 mm and a thickness of 1.0 mm or 2.0 mm was used. As a plate-shaped copper material, a copper plate 220 made of C1020 with dimensions of 30 mm x 70 mm and a thickness of 1.5 mm was used, with a hole 225 with a diameter of 6 mm formed in the center. The copper plate 220 was prepared in two forms: a first form in which a recess 135 (see Figure 7(a)) with a width w of 500 μm and a depth h of 250 μm was formed in the circumferential direction, and a second form in which the recess 135 was not formed.

[0044] Then, the aluminum plate 210 and the copper plate 220 were placed on top of each other, and a laser beam was irradiated onto the aluminum plate 210 side while moving the laser head in the circumferential direction to form a joint 40. This resulted in a joined body in which the aluminum plate 210 and the copper plate 220 were joined by the joint 40. More specifically, the joint 40 was formed by different conditions for irradiating with laser light for each case, using the copper plate 220 of the first embodiment and the copper plate 220 of the second embodiment, and multiple joined bodies were obtained. In each of the resulting joints, the total circumferential length of the joint 40 was 200 mm.

[0045] (Method for evaluating airtightness) Helium gas was flowed through the holes 225 in the copper plate 220 of the resulting joint at a pressure of 0.2 MPa, and it was confirmed whether or not helium gas leaked from the joint 40 or from between the aluminum plate 210 and the copper plate 220. Joints that did not leak helium gas were evaluated as good, and joints that leaked helium gas were evaluated as poor.

[0046] (Measurement of Vickers hardness) For the joints whose airtightness was evaluated, the Vickers hardness of the joint 40 was measured using the following method. First, the joint was cut by a plane perpendicular to the direction of movement of the laser head when the laser beam was irradiated, exposing the cross-section of the joint 40 to create a test specimen. Then, for each test specimen's joint 40, the Vickers hardness was measured at points M1, M2, and M3 (see Figure 11) as described above, and the average value was taken as the Vickers hardness at the interface 49 (see Figure 11) of the joint 40. In addition, for each test specimen's joint 40, the Vickers hardness was measured at points N1, N2, and N3 (see Figure 11) as described above, and the average value was taken as the Vickers hardness at the bottom 45 of the joint 40. Vickers hardness was measured according to the method described in JIS Z2244. The test force was 0.01 N, and the holding time was 10 seconds.

[0047] (Evaluation results) In both the first and second embodiments, the joints that were evaluated as having good airtightness had a Vickers hardness of 55 HV or more and 150 HV or less at the interface surface 49 of the joint 40. This confirmed that a Vickers hardness of 55 HV to 150 HV at the interface surface 49 of the joint 40 can suppress a decrease in airtightness at the joint 40.

[0048] Furthermore, among the joints that received a good evaluation of airtightness, the joint of the first embodiment had a joint depth D of 150 μm or more and 500 μm or less, and a Vickers hardness of 89 HV or more and 330 HV or less at the bottom 45 of the joint 40. This confirmed that, in the first embodiment, when the joint depth D of the joint 40 is 150 μm or more and 500 μm or less, and the Vickers hardness at the bottom 45 is 89 HV or more and 330 HV or less, the decrease in airtightness at the joint 40 can be suppressed.

[0049] Furthermore, among the joints that were evaluated as having good airtightness, the joint of the second embodiment had a joint depth D of 0 μm or more and 150 μm or less, and a Vickers hardness of 55 HV or more and 150 HV or less at the bottom 45 of the joint 40. This confirmed that in the second embodiment, when the joint depth D of the joint 40 is 0 μm or more and 150 μm or less, and the Vickers hardness at the bottom 45 is 55 HV or more and 150 HV or less, the decrease in airtightness at the joint 40 can be suppressed. Furthermore, in this second embodiment of the joint, the ratio of the joint depth D to the joint width L of the joint portion 40 (D / L) was 0.05 or more and 0.3 or less.

[0050] Although embodiments and examples of the present invention have been described above, the present invention is not limited to the embodiments and examples described above. Various modifications and combinations are permitted as long as they do not contradict the spirit of the present invention. [Explanation of Symbols]

[0051] 1...Cooling device, 2...Heat dissipation section, 3...Main body, 10...Heat sink, 11...Base, 12...Fin, 13...Thin plate section, 15...Holding member, 16...Opening, 17...Outer circumference, 18...Inner circumference, 40...Joint, 45...Bottom, 49...Interface

Claims

1. A joined body in which a plate-shaped aluminum material and a plate-shaped copper material are stacked on top of each other, and a laser beam is irradiated onto the aluminum material, thereby forming a mixed molten portion where the molten portion of the aluminum material and the molten portion of the copper material are mixed, The Vickers hardness of the mixed molten portion at the interface between the aluminum material and the copper material is 55 HV or more and 150 HV or less. zygote.

2. The depth from the interface to the bottom of the mixed molten portion is 150 μm or more and 500 μm or less. The Vickers hardness of the mixed molten portion at the bottom is 89 HV or more and 330 HV or less. The joint according to claim 1.

3. The copper material has a recess that is recessed from the interface, The mixed molten portion is formed by mixing the molten portion of the aluminum material, which has melted and entered the recess, with the molten portion of the copper material, which has melted the portion surrounding the recess. The depth of the recess is 150 μm or more and 350 μm or less. The joint according to claim 2.

4. The depth from the interface to the bottom of the mixed molten portion is 0 μm or more and 150 μm or less. The Vickers hardness of the mixed molten portion at the bottom is 55 HV or more and 150 HV or less. The joint according to claim 1.

5. When the width of the mixed molten portion at the interface is L, and the depth from the interface to the bottom of the mixed molten portion is D, then D / L is 0.05 or more and 0.3 or less. The joint according to claim 4.

6. A heat sink made of copper material having multiple fins and a holding member made of aluminum material that holds the heat sink are superimposed, and when laser light is shone onto the holding member, a mixed molten portion is formed in which the molten portion of the aluminum material and the molten portion of the copper material are mixed, forming a heat dissipation section. The heat sink comprises a main body that houses the fins of the heat sink and has a space formed inside through which a coolant flows, The Vickers hardness of the mixed molten portion at the interface between the aluminum material and the copper material is 55 HV or more and 150 HV or less. Cooling device.

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