Heat sink and method of manufacturing heat sink

Abstract

To suppress increase of the pressure drop of a fluid passing between fins of a heat sink and increase the cooling performance of the heat sink.SOLUTION: A heat sink 1 includes a planar base part 10, a plurality of fins 11 protruding from a surface 101 that is a plate surface of the base part 10, and a plurality of melting parts 13 each having a convex part formed by a part of the surface 101 melting and solidifying in convex shape.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A heat sink used to cool a heat generating body dissipates heat absorbed from the heat generating body toward a fluid passing between multiple fins. Therefore, increasing the surface area of ​​the fins increases the heat transfer area, thereby improving the cooling performance of the heat sink. For example, increasing the number of fins increases the heat transfer area, but there is a limit to how much the heat sink can do due to size restrictions and the like. In response to this, there are known techniques for increasing the heat transfer area by processing the surface shape of the fins or the shape of the fins themselves (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6526500 [Patent Document 2] JP 2014-75563 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, while it is possible to increase the heat transfer area by modifying the surface shape of the fins or the shape of the fins themselves, this can also reduce the flow rate and flow speed of the fluid passing between the fins, resulting in increased pressure loss of the fluid. This increased pressure loss of the fluid can reduce the cooling performance of the heat sink. An object of the present invention is to improve the cooling performance of a heat sink while suppressing an increase in pressure loss of a fluid passing between the fins of the heat sink. [Means for solving the problem]

[0005] The present invention, which was completed with this objective in mind, is a heat sink characterized by comprising a flat base portion, a plurality of fins protruding from the plate surface of the base portion, and a plurality of molten portions having convex portions in which part of the plate surface has melted and solidified into a convex shape. Here, the convex portion may rise from the plate surface by 100 μm or more in the direction in which the plate surface faces. The convex portion may rise from the plate surface in a direction toward which the plate surface faces by 250 μm or more. Each of the plurality of fusion zones may have a recess recessed from the plate surface. The plurality of fusion zones may be provided between the plurality of fins. Moreover, each of the plurality of fins may be flat, spaced apart from one another, and arranged parallel or approximately parallel to one another to protrude from the base portion. The molten portion may be formed by irradiating with a laser beam. The laser light may be irradiated at an angle with respect to a direction perpendicular to the plate surface. The laser light may be irradiated at an angle of 45 degrees or more and 70 degrees or less with respect to the plate surface. The laser light may be irradiated at an angle of 85 degrees or more and 90 degrees or less with respect to the plate surface. The present invention also relates to a method for manufacturing a heat sink comprising a flat base portion made of a metal material and a number of fins protruding from a plate surface of the base portion, the method being characterized in that laser light is intermittently irradiated to a number of locations on the plate surface between the fins. Here, the laser light may be irradiated at an angle with respect to a direction perpendicular to the plate surface. The laser light may be irradiated at an angle in the range of 45 degrees to 70 degrees with respect to the plate surface. The laser light may be irradiated at an angle in the range of 85 degrees to 90 degrees with respect to the plate surface. Effect of the Invention

[0006] According to the present invention, it is possible to improve the cooling performance of the heat sink while suppressing an increase in pressure loss of a fluid passing between the fins of the heat sink. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing an example of an external configuration of a heat sink according to a first embodiment. [Diagram 2] 1 is a side view showing an example of an external configuration of a heat sink when viewed in a direction perpendicular to the arrangement direction of a plurality of fins. [Diagram 3] 1A is a graph showing the characteristics of a pulsed laser, and FIG. 1B is a diagram showing how a plurality of molten parts are formed on the plate surface of the base part by irradiating the plate surface with laser light from a pulsed laser. [Figure 4] FIG. 2 is a diagram showing an example of a laser beam irradiation angle (left diagram) and an example of a cross section of a molten part formed by irradiation with a laser beam (right diagram). [Diagram 5] FIG. 11 is a plan view showing an example of an external configuration of a heat sink according to a second embodiment. [Figure 6] 1 is a side view showing an example of an external configuration of a heat sink when viewed in a direction in which a plurality of fins are arranged. [Figure 7] FIG. 2 is a diagram showing an example of a laser beam irradiation angle (left diagram) and an example of a cross section of a molten part formed by irradiation with a laser beam (right diagram). [Figure 8] 1A is a diagram showing an example of a plurality of fusion zones arranged in a line in a first direction among a plurality of fusion zones formed on a plate surface of a base part of a heat sink according to a second embodiment, and FIG. 1B is a graph showing a state of unevenness in the up-down direction in a IV-IV cross section of FIG. [Figure 9] 8(A) is a diagram showing one of the multiple fusion zones shown in Fig. 8(A). (B) is a graph showing the state of unevenness in the vertical direction in the VV cross section of (A). (C) is a graph with the horizontal axis representing pressure loss (unit: kPa (kilopascal)) and the vertical axis representing thermal resistance (unit: K / W (Kelvin per watt)). [Figure 10]1A is a graph showing the characteristics of a CW (Continuous Wave Operation) laser, FIG. 1B is a diagram showing how a molten part is formed on the plate surface of the base part by irradiating the CW laser, and FIG. 1C is a cross-sectional view showing an example of the molten part formed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. <First embodiment> (Heat sink 1) FIG. 1 is a perspective view showing an example of an external configuration of a heat sink 1 according to the first embodiment. FIG. 2 is a side view showing an example of the external configuration of the heat sink 1 when viewed in a direction perpendicular to the arrangement direction of the fins 11. As shown in FIG. The heat sink 1 according to the first embodiment is a component that is integrally molded entirely from a metal material and is used to cool a heat generating body (not shown). The heat sink 1 is cooled by contact with a fluid such as a gas or liquid, and as a result, the heat sink 1 cools the heat generating body through heat exchange with the heat generating body.

[0009] As shown in Fig. 1, the heat sink 1 is configured to include a base portion 10, a plurality of fins 11, a plurality of groove portions 12, and a plurality of fusion portions 13. In the following description, the base portion 10 is located below the plurality of fins 11 in the up-down direction of the heat sink 1. A direction perpendicular to the arrangement direction of the plurality of fins 11 is called a first direction, and the arrangement direction of the plurality of fins 11 is called a second direction. One side in the first direction is called a first side, and the other side is called a second side. One side in the second direction is called a third side, and the other side is called a fourth side.

[0010] The base 10 is a flat plate member consisting of one or more layers that serves as the base of the heat sink 1, and transfers heat from a heat generating body to the multiple fins 11. The base 10 has an upper surface 101 in the vertical direction, a lower surface 102 in the vertical direction, a first side surface 103 in the first direction, a second side surface 104 in the first direction, a third side surface 105 in the second direction, and a fourth side surface 106 in the second direction. The multiple fins 11 protrude from the surface 101, and heat from the heat generating body is transferred to the multiple fins 11 via the base 10.

[0011] The fins 11 are flat fins that protrude upward from the surface 101 of the base 10 in the up-down direction and extend in a first direction of the heat sink 1. The fins 11 are arranged in an orderly manner in parallel or approximately parallel fashion while being spaced apart from one another to form a group. The fins 11 absorb heat from a heat generating element via the base 10 and dissipate the heat by contacting a fluid such as cooling air. The fins 11 are formed by a method such as extrusion molding or skiving. The grooves 12 are grooves that are formed between adjacent fins 11 and extend in the first direction. The grooves 12 form passages for passing a fluid such as cooling air.

[0012] The multiple molten parts 13 are formed by melting a part of the surface 101 of the base part 10 by irradiation with laser light and then solidifying. As shown in Figs. 1 and 2, the multiple molten parts 13 are formed between the multiple fins 11. Specifically, the multiple molten parts 13 are formed in a part of the surface 101 of the base part 10 in the multiple groove parts 12. Note that a method of forming the multiple molten parts 13 by irradiating a part of the surface 101 of the base part 10 with laser light will be described later with reference to Fig. 3 and subsequent figures.

[0013] (Method of forming fusion zone 13) FIG. 3(A) is a graph showing the characteristics of a pulsed laser. The graph shown in FIG. 3(A) is a graph in which the horizontal axis represents time (laser irradiation time (unit: S (seconds))) and the vertical axis represents laser output value (unit: W (watts)). As described above, the multiple molten parts 13 are formed by irradiating a part of the surface 101 of the base part 10 with laser light. In this embodiment, a pulsed laser is used as the laser light irradiated to the part of the surface 101 of the base part 10. As shown in the graph in FIG. 3(A), the pulsed laser is a laser in which the laser output is composed of pulses having a predetermined duration, and the pulses are intermittently repeated at a predetermined frequency.

[0014] FIG. 3(B) is a diagram showing a state in which a plurality of molten parts 13 are formed on the plate surface of the base part 10 by irradiation with the laser light of a pulsed laser. FIG. 3(B) shows a state in which a part of the surface 101, which is the plate surface of the base part 10, is viewed from the upper side to the lower side in the vertical direction. When the surface 101 of the base part 10 is irradiated with the laser light of a pulsed laser while the irradiation position is moved, a plurality of molten parts 13 are formed on the surface 101. FIG. 3(B) shows a state in which the laser light of a pulsed laser is irradiated from the first side to the second side in the first direction of the surface 101. When the laser light of the pulsed laser is irradiated, the irradiation position 130 melts, and a part of the region 131 affected by the heat of the pulsed laser among the region around the irradiation position 130 melts. Thereafter, the melted part solidifies to form the molten part 13.

[0015] The size, number, and interval between adjacent melted portions 13 formed on surface 101 of base portion 10 vary depending on the number of times of irradiation with the laser light of the pulsed laser per unit time, the laser output value, the moving speed of the irradiation position, and the like. However, these values ​​are not particularly limited, and any value can be determined so that a plurality of melted portions 13 are formed in a part of surface 101 of base portion 10 in groove portion 12 between fins 11. For example, the number of times of irradiation with the laser light of the pulsed laser per unit time may be 50 times / second, the laser output value may be 1000 (W), and the moving speed of the irradiation position of the laser light may be 10 cm (centimeter) / second.

[0016] Fig. 4 is a diagram showing an example (left diagram) of an irradiation angle of laser beam 300 and an example (right diagram) of a cross section of melted portion 13 formed by irradiation with laser beam 300. Note that Fig. 4 shows an example in which base portion 10 has multiple layers. The molten portion 13 shown in the right diagram of Fig. 4 is formed by irradiating the surface 101 of the base portion 10 with laser light 300 of a pulse laser perpendicularly (i.e., so that the irradiation angle with respect to the surface 101 is 90 degrees) as shown in the left diagram of Fig. 4. Therefore, the center line 400 of the formed molten portion 13 is parallel to the up-down direction, similar to the irradiation angle.

[0017] As shown in the right diagram of FIG. 4, the melted portion 13 formed on the surface 101 of the base portion 10 is configured to include a convex portion 133 formed by solidifying a part melted by irradiation with the laser light 300 of the pulsed laser into a convex shape, and a concave portion 134 formed by solidifying a part melted by irradiation with the laser light 300 of the pulsed laser into a concave shape. The convex portion 133 is a portion formed by a part of the part melted by irradiation with the laser light 300 of the pulsed laser rising upward in the vertical direction from the surface 101 before the laser irradiation due to the impact of the irradiation with the laser light 300 of the pulsed laser. The concave portion 134 is a portion formed by a part of the part melted by irradiation with the laser light 300 of the pulsed laser being depressed downward in the vertical direction from the surface 101 before the laser irradiation due to the impact of the irradiation with the laser light 300 of the pulsed laser.

[0018] Here, a value H1 indicating a difference between the position of the topmost part (the upper end in the vertical direction) of the convex part 133 constituting the molten part 13 and the position of the surface 101 of the base part 10 is about 100 μm (micrometers) to 150 μm. In this manner, the surface 101 of the base part 10 in the plurality of groove parts 12 (see FIG. 1 and FIG. 2) is irradiated with the laser light 300 of the pulse laser to form the molten part 13, so that the unevenness is formed on the surface 101. As a result, the heat transfer area between the fins 11 is increased compared to when the molten part 13 is not formed, and therefore the cooling performance of the heat sink 1 is improved compared to when the molten part 13 is not formed.

[0019] In summary, the heat sink 1 according to the first embodiment shown in FIG. 1 and FIG. 2 described above only needs to have the following configuration, and can take on a variety of different embodiments. In other words, the heat sink 1 is characterized by having a flat base portion 10, a plurality of fins 11 protruding from a surface 101 which is the plate surface of the base portion 10, and a plurality of molten portions 13 having convex portions 133 which are portions of the surface 101 which have melted and solidified into a convex shape.

[0020] As a result, the convex portions 133 are formed on a part of the surface 101 from which the multiple fins 11 protrude, thereby increasing the heat transfer area between the fins 11 and improving the cooling performance of the heat sink 1. Furthermore, since the convex portions 133 are formed at the bottoms of the grooves 12 between the fins 11 that extend high in the vertical direction, the effect on the flow of fluid passing between the fins 11 is smaller than when the surface shape of the fins 11 or the shape of the fins 11 themselves is processed. This makes it possible to suppress an increase in pressure loss.

[0021] Here, the convex portion 133 of the fusion zone 13 may rise by 100 μm or more in the direction in which the surface 101 of the base portion 10 faces (upward in the vertical direction of the base portion 10). As a result, protrusions 133 having a height of 100 μm or more are formed on part of surface 101 from which multiple fins 11 protrude, thereby increasing the heat transfer area between fins 11 and improving the cooling performance of the heat sink 1.

[0022] Each of the multiple fusion zones 13 may have a recess 134 recessed from the surface 101 of the base portion 10 . As a result, the recesses 134 are formed on the surface 101 from which the fins 11 protrude, so that the heat transfer area can be further increased, and as a result, the cooling performance of the heat sink 1 can be further improved.

[0023] Furthermore, a configuration may be adopted in which a plurality of fusion zones 13 are provided between a plurality of fins 11. As a result, convex portions 133 are formed at the bottoms of grooves 12 between fins 11 that extend high in the vertical direction, so that the effect on the flow of fluid passing between fins 11 is smaller than when the surfaces of fins 11 or the shape of fins 11 are processed. As a result, an increase in pressure loss can be suppressed.

[0024] Furthermore, each of the multiple fins 11 may be flat, spaced apart from one another, and provided so as to protrude from the base portion 10 in parallel or approximately parallel to one another. As a result, the fins 11 are flat, spaced apart, and arranged in parallel or approximately parallel fashion, so that the effect on the flow of fluid passing between the fins 11 is smaller than when the surface shape of the fins 11 or the shape of the fins 11 themselves is processed. As a result, an increase in pressure loss can be suppressed.

[0025] The melted portion 13 may also be formed by irradiation with a laser beam 300. This allows even a narrow region such as the bottom portion of the groove portion 12 between the fins 11 to be easily melted by irradiating it with the laser light 300. As a result, the work efficiency during the manufacture of the heat sink 1 is improved.

[0026] Alternatively, the laser light 300 may be irradiated to the surface 101 of the base portion 10 at an angle in the range of 85 degrees or more and 90 degrees or less. This reduces the size of each protrusion 133 compared to when laser light 300 with the same laser output is irradiated at an irradiation angle of less than 85 degrees to the surface 101 of the base portion 10. As a result, the pitch between adjacent protrusions 133 can be made finer, so that by increasing the number of protrusions 133, the heat transfer area between the fins 11 can be increased, thereby improving the cooling performance of the heat sink 1.

[0027] In addition, the manufacturing method of the heat sink 1 according to the first embodiment is a manufacturing method of a heat sink comprising a flat base portion 10 made of a metal material and a plurality of fins 11 protruding from a surface 101 which is the plate surface of the base portion 10, characterized in that laser light 300 is intermittently irradiated to a plurality of portions on the surface 101 between the fins 11.

[0028] As a result, by intermittently irradiating the laser light 300 to the multiple locations, each of the multiple locations melts, and a protrusion 133 protruding from the surface 101 is formed in each of the multiple locations. As a result, a heat sink 1 can be manufactured that has an increased heat transfer area between the fins 11 and improved cooling performance. Furthermore, in this manufacturing method, the protrusion 133 is formed in the bottom of the groove 12 between the fins 11 that extend high in the vertical direction, so that the effect on the flow of the fluid passing between the fins 11 is smaller than when the surface of the fins 11 or the shape of the fins 11 is processed. As a result, a heat sink 1 that can suppress an increase in pressure loss can be manufactured.

[0029] Here, the laser light 300 may be irradiated to the surface 101 of the base portion 10 at an angle in the range of 85 degrees or more and 90 degrees or less. This reduces the size of each protrusion 133 compared to when laser light 300 with the same laser output is irradiated at an irradiation angle of less than 85 degrees to the surface 101 of the base portion 10. As a result, the pitch between adjacent protrusions 133 can be made finer, so that by increasing the number of protrusions 133, the heat transfer area between the fins 11 can be increased, thereby improving the cooling performance of the heat sink 1.

[0030] <Second embodiment> (Heat sink 2) FIG. 5 is a plan view showing an example of the external configuration of a heat sink 2 according to the second embodiment. The heat sink 2 according to the second embodiment has the same configuration as the heat sink 1 according to the above-described first embodiment, except that the irradiation angle of the laser light from the pulsed laser is different.

[0031] That is, the heat sink 2 is configured to include a base portion 20, a plurality of fins 21, a plurality of groove portions 22, and a plurality of molten portions 23, which correspond respectively to the base portion 10, a plurality of fins 11, a plurality of groove portions 12, and a plurality of molten portions 13 of the heat sink 1 of the first embodiment described above.

[0032] The base portion 20 is a member consisting of one or more layers that serves as the base of the heat sink 2, and transfers heat from a heat generating body (not shown) to the multiple fins 21. The multiple fins 21 are flat fins that protrude upward from the surface 201 of the base portion 20 in the vertical direction and extend in a first direction of the heat sink 2. The multiple fins 21 form a group by being arranged in an orderly manner in parallel or approximately parallel while being spaced apart from each other. The multiple fins 21 absorb heat from the heat generating body via the base portion 20, and dissipate the heat by coming into contact with a fluid such as cooling air.

[0033] The multiple grooves 22 are multiple grooves formed between adjacent fins 21 and extending in a first direction. The multiple grooves 22 form passages for passing a fluid such as cooling air. The multiple molten parts 23 are portions formed by melting a part of the surface 201 of the base part 20 by irradiation with laser light and then solidifying. As shown in FIG. 5, the multiple molten parts 23 are formed between the multiple fins 21. Specifically, the multiple molten parts 23 are formed in a part of the surface 201 of the base part 20 in the multiple grooves 22.

[0034] FIG. 6 is a side view showing an example of the external configuration of the heat sink 2 when viewed in the direction in which the fins 21 are arranged. Fig. 7 is a diagram showing an example of the irradiation angle of laser light 300 (left diagram) and an example of a cross section of melted portion 23 formed by irradiation with laser light 300 (right diagram). Note that Fig. 7 shows an example in which base portion 20 is one layer. Moreover, the conditions for irradiation of laser light 300 when forming melted portion 23 according to the second embodiment are the same as those for melted portion 13 according to the first embodiment, except for the irradiation angle. The molten portion 23 is formed by irradiating the surface 201 of the base portion 20 with the laser beam 300 of a pulsed laser at an angle of 60 degrees. Therefore, the center line 500 of the formed molten portion 23 is inclined with respect to the surface 201 in the same manner as the irradiation angle, as shown in FIG.

[0035] As shown in FIG. 6 and the right diagram of FIG. 7, the melted portion 23 formed on the surface 201 of the base portion 20 is configured to include a convex portion 233 formed by solidifying a part melted by irradiation with the laser light 300 of the pulsed laser into a convex shape, and a concave portion 234 formed by solidifying a part melted by irradiation with the laser light 300 of the pulsed laser into a concave shape. The convex portion 233 is a portion formed by a part of the part melted by irradiation with the laser light 300 of the pulsed laser rising upward in the vertical direction from the surface 201 before the laser irradiation due to the impact of the irradiation with the laser light 300 of the pulsed laser. The concave portion 234 is a portion formed by a part of the part melted by irradiation with the laser light 300 of the pulsed laser being depressed downward in the vertical direction from the surface 201 before the laser irradiation due to the impact of the irradiation with the laser light 300 of the pulsed laser.

[0036] A value H2 indicating the difference between the position of the top of the protrusion 233 (the upper end in the vertical direction) constituting the fusion zone 23 and the position of the surface 201 of the base part 20 is about 250 μm to 300 μm. In contrast, as shown in FIG. 4, a value H1 indicating the difference between the position of the top of the protrusion 133 (the upper end in the vertical direction) and the surface 101 of the base part 10 is about 100 μm to 150 μm. That is, since the value H2>the value H1, the heat transfer area between the fins 21 according to the second embodiment is larger than the heat transfer area between the fins 11 according to the first embodiment. Therefore, the cooling performance of the heat sink 2 according to the second embodiment is higher than the cooling performance of the heat sink 1 according to the first embodiment.

[0037] Fig. 8(A) is a diagram showing an example of a plurality of fusion parts 23 arranged in a line in a first direction among a plurality of fusion parts 23 formed on a surface 201 which is a plate surface of a base part 20 of a heat sink 2 according to a second embodiment. Fig. 8(B) is a graph showing a state of unevenness in the up-down direction in a cross section taken along line IV-IV in Fig. 8(A). In Fig. 8(B), the horizontal axis indicates the position in the first direction, and the vertical axis indicates the position in the up-down direction. As shown in Fig. 8(A), a plurality of fusion zones 23 are arranged in a line in a first direction on a surface 201 of a base portion 20 of a heat sink 2. In the graph shown in Fig. 8(B), a line L1 indicates that a protrusion 233 (see Fig. 7) exists in each of the plurality of fusion zones 23 in Fig. 8(A). A line L2 indicates that a recess 234 (see Fig. 7) exists in each of the plurality of fusion zones 23. A line L3 indicates an unwelded portion (surface 201 of a base portion 20).

[0038] Fig. 9(A) is a diagram showing one of the multiple fusion zones 23 shown in Fig. 8(A). Fig. 9(B) is a graph showing the state of unevenness in the up-down direction in the VV cross section of Fig. 9(A). In the graph shown in FIG. 9(B), the length W1 on the horizontal axis indicates the length in the first direction (approximately 1.0 mm (millimeter)) of the convex portion 233 (see FIG. 7) of one of the fusion parts 23. Furthermore, the length W2 indicates the length in the first direction (approximately 1.0 mm (millimeter)) of the concave portion 234 (see FIG. 7) of one of the fusion parts 23. Furthermore, the line L11 indicates the apex (upper end in the vertical direction) of the convex portion 233 of one of the fusion parts 23. Furthermore, the line L12 indicates the deepest portion (lower end in the vertical direction) of the concave portion 234 of one of the fusion parts 23. Furthermore, the line L13 indicates the unwelded portion (surface 201 of the base portion 20).

[0039] FIG. 9(C) is a graph in which the horizontal axis represents pressure loss (unit: kPa (kilopascal)) and the vertical axis represents thermal resistance (unit: K / W (Kelvin per watt)). In the graph shown in FIG. 9(C), curve L21 shows the relationship between pressure loss and thermal resistance when fusion zone 23 (see FIG. 9(A)) is formed. Specifically, curve L21 shows the relationship between pressure loss and thermal resistance at flow rates 211 to 214, which are the volumes of fluid passing through a predetermined position per unit time. The flow rates 211 to 214 increase in that order. Curve L22 shows the relationship between pressure loss and thermal resistance when fusion zone 23 is not formed. Specifically, curve L22 shows the relationship between pressure loss and thermal resistance at fluid flow rates 221 to 224. Each of the flow rates 221 to 224 is the same as each of the flow rates 211 to 214 of curve L21.

[0040] Thermal resistance is a value that indicates how difficult it is for heat to be transmitted. Thermal resistance is calculated by dividing the temperature difference between any two points by the heat flow rate (amount of heat flowing per unit time) that flows between the two points. The higher the thermal resistance, the harder it is for heat to be transmitted, and the lower the thermal resistance, the easier it is for heat to be transmitted. In other words, the higher the thermal resistance, the lower the cooling performance of the heat sink 2, and the lower the thermal resistance, the higher the cooling performance of the heat sink 2.

[0041] As shown in the graph of FIG. 9(C), for example, when comparing the thermal resistance of the flow rate 211 and the flow rate 221, which have the same flow rate, the thermal resistance of the flow rate 211 is about 0.1100 (K / W), and the thermal resistance of the flow rate 221 is about 0.1150 (K / W). Therefore, it can be seen that the thermal resistance can be reduced by about 0.0050 (K / W) by forming the molten part 23. In contrast, when comparing the pressure loss of the flow rate 211 and the flow rate 221, the pressure loss of the flow rate 211 and the flow rate 221 is 0.9 and 0.8 (kPa), respectively, and there is almost no difference. The tendency seen from this comparison is also seen in the comparison between the flow rate 212 and the flow rate 222, which have the same flow rate, the comparison between the flow rate 213 and the flow rate 223, which have the same flow rate, and the comparison between the flow rate 214 and the flow rate 224, which have the same flow rate. That is, it is understood that by forming the molten portion 23 on the surface 201 of the base portion 20, the pressure loss is prevented from increasing and the thermal resistance is reduced.

[0042] <Comparative Example with CW Laser> Figure 10(A) is a graph showing the characteristics of a CW (Continuous Wave Operation) laser (continuous oscillation laser). Figure 10(B) is a diagram showing how a molten part is formed on the plate surface of a flat plate member by irradiation with the CW laser. Figure 10(C) is a cross-sectional view showing an example of the formed molten part. In the above-described first and second embodiments, a pulsed laser is adopted as the laser light irradiated to form the molten part. In contrast, as shown in the graph of Figure 10(A), when a CW laser that continuously oscillates with a certain laser output is used, a molten part as shown in Figures 10(B) and (C) is formed on the plate surface of the flat plate member.

[0043] That is, as shown in Figure 10(B), when the irradiation position is moved from the first side to the second side in the first direction of the flat plate member while irradiating the plate surface of the flat plate member composed of a plurality of layers with the laser light of the CW laser, a part of the irradiation position of the laser light of the CW laser and a part of the heat-affected region (hatched) affected by the heat of the laser light of the CW laser melt. Then, when the melted part solidifies, a single streak of molten part extending in the first direction of the flat plate member is formed. Note that the molten parts shown in Figures 10(B) and (C) are formed by irradiating the laser light of the CW laser perpendicular to the plate surface of the flat plate member (that is, so that the irradiation angle with respect to the plate surface is 90 degrees).

[0044] The pulsed laser adopted in the above-described first and second embodiments has a higher laser output at the peak than the CW laser of Figure 10. For this reason, due to the impact of the irradiation of the laser light, prominent unevenness such as the convex portions 133 and concave portions 134 of the molten part 13 in Figure 4 and the convex portions 233 and concave portions 234 of the molten part 23 in Figure 7 are formed. In contrast, as shown in Figure 10(C), the molten part formed on the flat plate member by irradiation with the laser light of the CW laser does not have convex or concave portions that can be called such in the molten part. For this reason, as shown in the first and second embodiments, it is preferable to form the molten part by irradiating the laser light of the pulsed laser on the plate surface of the base member.

[0045] In summary, the heat sink 2 according to the second embodiment shown in FIGS. 5 to 9 described above only needs to have the following configuration, and can take on a variety of different embodiments. In other words, the heat sink 2 is characterized by having a flat base portion 20, a plurality of fins 21 protruding from a surface 201 which is the plate surface of the base portion 20, and a plurality of molten portions 23 having convex portions 233 which are portions of the surface 201 which have melted and solidified into a convex shape.

[0046] Here, the convex portion 233 of the fusion zone 23 may rise from the surface 201 of the base portion 20 in the direction in which the surface 201 faces (upward in the up-down direction) by 250 μm or more. As a result, a protrusion 233 having a height of 250 μm or more is formed on a portion of the surface 201 from which the multiple fins 21 protrude, thereby further increasing the heat transfer area between the fins 21 and further improving the cooling performance of the heat sink 2.

[0047] Moreover, the laser light 300 may be irradiated at an angle with respect to the vertical direction of the surface 201 of the base portion 20 (the up-down direction of the base portion 20). As a result, the laser beam 300 is irradiated at an acute angle to the surface 201 of the base portion 20, and the force with which the laser beam 300 melts the metal at the irradiated position and causes it to bulge upward in the vertical direction is stronger than when the laser beam 300 is not irradiated at an acute angle. As a result, the bulge of the protrusion 233 formed on the surface 201 can be made larger, so that the heat transfer area between the fins 21 can be increased and the cooling performance of the heat sink 2 can be improved.

[0048] Alternatively, the laser light 300 may be irradiated to the surface 201 of the base portion 20 at an angle in the range of 45 degrees or more and 70 degrees or less. By reducing the irradiation angle of the laser beam 300, it becomes easier to form the convex portion 233, but if the irradiation angle of the laser beam 300 is made too small, there is a risk that the laser beam 300 will irradiate the already formed convex portion 233. On the other hand, by setting the irradiation angle of the laser beam 300 to be 45 degrees or more and 70 degrees or less with respect to the surface 201 of the base portion 20, it becomes easier to form the convex portion 233 and it is possible to reduce the risk that the laser beam 300 will irradiate the already formed convex portion 233.

[0049] In addition, the manufacturing method of the heat sink 2 according to the second embodiment is a manufacturing method of a heat sink comprising a flat base portion 20 made of a metal material and a plurality of fins 21 protruding from a surface 201 which is the plate surface of the base portion 20, characterized in that laser light 300 is intermittently irradiated to a plurality of portions on the surface 201 between the fins 21.

[0050] As a result, by intermittently irradiating the laser light 300 to the multiple locations, each of the multiple locations melts, and a protrusion 233 protruding from the surface 201 is formed in each of the multiple locations. As a result, a heat sink 2 can be manufactured that has an increased heat transfer area between the fins 21 and improved cooling performance. Furthermore, in this manufacturing method, the protrusion 233 is formed in the bottom of the groove 22 between the fins 21 that extend high in the vertical direction, so that the effect on the flow of the fluid passing between the fins 21 is smaller than when the surface of the fins 21 or the shape of the fins 21 is processed. As a result, a heat sink 2 that can suppress an increase in pressure loss can be manufactured.

[0051] Here, the laser light 300 may be irradiated at an angle with respect to the vertical direction of the surface 201 of the base portion 20 (the up-down direction of the base portion 20). This allows the laser light 300 to be irradiated at an acute angle to the surface 201 of the base portion 20. As a result, the protrusions 233 formed on the surface 201 can be made larger, thereby increasing the heat transfer area between the fins 21 and improving the cooling performance of the heat sink 2.

[0052] Alternatively, the laser light 300 may be irradiated to the surface 201 of the base portion 20 at an angle in the range of 45 degrees or more and 70 degrees or less. By reducing the irradiation angle of the laser beam 300, it becomes easier to form the convex portion 233, but if the irradiation angle of the laser beam 300 is made too small, there is a risk that the laser beam 300 will irradiate the already formed convex portion 233. On the other hand, by setting the irradiation angle of the laser beam 300 to be 45 degrees or more and 70 degrees or less with respect to the surface 201 of the base portion 20, it becomes easier to form the convex portion 233 and it is possible to reduce the risk that the laser beam 300 will irradiate the already formed convex portion 233.

[0053] <Other embodiments> Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments. For example, the configuration of the heat sink 1 according to the first embodiment shown in Figures 1 to 4 and the configuration of the heat sink 2 according to the second embodiment shown in Figures 5 to 9 are merely examples for achieving the object of the present invention, and are not particularly limited. Furthermore, the effects of the present invention are not limited to those described in the above-mentioned embodiments.

[0054] In the above embodiment, the base portion is a rectangular flat plate, but is not limited to this shape. For example, the base portion may be a circular or elliptical flat plate.

[0055] In the above embodiment, the fins protruding from the base portion have a flat plate shape, but the shape is not limited to this. For example, the fins may have a cylindrical or prismatic shape.

[0056] Moreover, the irradiation angle of the laser light 300 according to the second embodiment is an angle tilted from a direction perpendicular to the first direction to the first side, as shown in the left diagram of FIG. 7 described above. Therefore, if the irradiation angle of the laser light 300 is tilted too much toward the first side, there is a high risk that the laser light 300 will be irradiated to the already formed convex portion 233. In contrast, the irradiation angle of the laser light 300 may be an angle tilted from a direction perpendicular to the first direction to the second side. In other words, the traveling direction of the irradiation position of the laser light 300 shown in FIG. 7 may be reversed. In this case, even if the irradiation angle of the laser light 300 is tilted significantly toward the second side, there is no high risk that the laser light 300 will be irradiated to the already formed convex portion 233. [Explanation of symbols]

[0057] 1, 2... heat sink, 10, 20... base portion, 11, 21... fins, 12, 22... groove portion, 13, 23... fusion portion, 101, 201... surface, 133, 233... convex portion, 134, 234... concave portion, 300... laser light

Claims

1. A flat base portion; A plurality of fins protruding from a plate surface of the base portion; A plurality of molten parts having convex parts formed by melting and solidifying a part of the plate surface into a convex shape; A heat sink comprising:

2. The convex portion is characterized in that it protrudes from the plate surface in a direction toward the plate surface by 100 μm or more. The heat sink of claim 1 .

3. The convex portion is characterized in that it protrudes from the plate surface in a direction toward the plate surface by 250 μm or more. The heat sink of claim 2 .

4. Each of the plurality of fusion parts has a recess recessed from the plate surface. The heat sink of claim 1 .

5. The plurality of fusion zones are provided between the plurality of fins. A heat sink according to any one of claims 1 to 4.

6. Each of the plurality of fins is flat, spaced apart from one another, and arranged parallel or approximately parallel to one another to protrude from the base portion. The heat sink of claim 5.

7. The melted portion is formed by irradiating a laser beam. The heat sink of claim 1 .

8. The laser light is irradiated at an angle with respect to a direction perpendicular to the plate surface. The heat sink of claim 7.

9. The laser light is irradiated at an angle of 45 degrees or more and 70 degrees or less with respect to the plate surface.

9. The heat sink of claim 8.

10. The laser light is irradiated at an angle of 85 degrees or more and 90 degrees or less with respect to the plate surface. The heat sink of claim 7.

11. A heat sink including a flat base made of a metal material and a plurality of fins protruding from a plate surface of the base, the plate surface between the fins is intermittently irradiated with laser light at a plurality of locations. A method for manufacturing a heat sink comprising the steps of:

12. The laser light is irradiated at an angle with respect to a direction perpendicular to the plate surface. The method for manufacturing the heat sink according to claim 11 .

13. The laser light is irradiated at an angle of 45 degrees or more and 70 degrees or less with respect to the plate surface. The method for manufacturing the heat sink according to claim 12.

14. The laser light is irradiated at an angle of 85 degrees or more and 90 degrees or less with respect to the plate surface. The method for manufacturing the heat sink according to claim 11 .

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