Heat sink manufacturing method and heat sink

Abstract

To provide a heat sink manufacturing method and a heat sink which enable the inexpensive manufacture of a heat sink comprising hexagonal or nearly hexagonal pin fins.SOLUTION: The heat sink manufacturing method has: an arrangement process of arranging a metal material on one side of a die in which a plurality of die holes having a hexagonal or nearly hexagonal shape in plan view are formed; a compression process of compressing the metal material toward the die in which a knockout pin is inserted into the die hole from the opposite side of the one side to form pin fins by the inflow of the metal material into the die holes; and a discharge process of pushing up the knockout pin to discharge a forge-molded material in which the pin fins are formed from the die. A tip of the knockout pin is circular in plan view, and a diameter of the tip of the knockout pin is equal to or smaller than a diameter of a hexagonal or nearly hexagonal inscription circle in a minimum area in which the a cross-sectional area of the die hole is smallest.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] A known heat sink has a structure including a plate-shaped base and a plurality of pin fins (heat dissipation fins) provided on one surface of the base (for example, Patent Document 1). The heat sink of Patent Document 1 has a first heat dissipation fin having a meandering shape in a plan view and a second heat dissipation fin having a hexagonal shape. A forging method is known as a method for manufacturing a heat sink with such a structure. As a forging method, a metal material, which is the raw material of the heat sink, is placed on a die having a plurality of holes, and a punch is used to press the metal material toward the die, thereby stretching the metal material in the outer periphery direction of the die to form a base, and at the same time, the metal material is caused to flow into each of the plurality of holes to form pin fins.

[0003] In a forging device, a knockout pin (knock pin) for ejecting the product from the die after forging is set into the die hole for forming the pin fins, but it is common to use a knockout pin with the same shape as the die hole. The reason for this is that if a knockout pin with a shape different from the die hole is used, a gap will be generated between the die hole and the knockout pin, and if the gap is large, defects such as bending or breaking of the knockout pin may occur.

[0004] That is, when forming the second heat dissipation fin of the heat sink in Patent Document 1, it is considered that a die (lower die) having a hexagonal die hole is used to form a long and thin knockout pin that is hexagonal in plan view. If the knockout pin is cylindrical, a method such as centerless grinding can be used, so that it can be manufactured in a relatively short time and the processing is relatively easy, making it possible to manufacture a pin with high accuracy at low cost. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6462737 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when manufacturing knockout pins corresponding to the hexagonal pin fins as in Patent Document 1, they cannot be manufactured by a centerless grinding method, and must be manufactured by a cutting method or the like. In that case, when manufacturing a long and thin pin, the processing is very difficult because deformation (bending) occurs during holding and processing of the product, and the manufacturing takes a long time, so the manufacturing cost becomes very expensive. This leads to an increase in the cost of the mold, and if it is used for molding, the product price becomes high. In addition, there was a demand for a heat sink that can flow the refrigerant uniformly.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a heat sink manufacturing method that enables the inexpensive production of a heat sink with hexagonal or approximately hexagonal pin fins, and a heat sink that is manufactured by the heat sink manufacturing method, is in close contact with a jacket, and is capable of allowing a refrigerant to flow uniformly. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following means.

[0009] (1) A method for manufacturing a heat sink according to one aspect of the present invention includes a placement step of placing a metal material on one side of a die having a plurality of die holes each having a hexagonal or approximately hexagonal shape in plan view; a pressurizing step of applying pressure to the metal material from the opposite side toward the die having a knockout pin inserted into the die hole, thereby causing the metal material to flow into the die hole, and a discharge step of pushing up the knockout pin and discharging the forged material with the pin fins formed thereon from the die; The tip of the knockout pin is circular in a plan view, and the diameter of the tip of the knockout pin is equal to or smaller than the diameter of the inscribed circle of a hexagon or approximately hexagon in a minimum region where the cross-sectional area of ​​the die hole is smallest.

[0010] (2) In the method for manufacturing a heat sink described above in (1), the diameter of the tip of the knockout pin may be equal to or greater than half the diameter of the inscribed circle.

[0011] (3) The difference between the diameter of the tip of the knockout pin and the diameter of the inscribed circle of the knockout pin in (1) or (2) above may be 0.5 mm or less.

[0012] (4) In the method for manufacturing a heat sink according to any one of (1) to (3) above, in the pressurizing step and the ejection step, in addition to the knockout pin, at least one sub-knockout pin having a circular tip shape with a diameter of less than or equal to {(diameter of the inscribed circle-diameter of the tip of the knockout pin)÷2} may be used in the die hole.

[0013] (5) In any of the above methods for manufacturing a heat sink (1) to (4), the diameter of the tip of the knockout pin may be in the range of φ0.2 mm to φ6 mm.

[0014] (6) In any of the above methods for manufacturing a heat sink (1) to (5), the die hole may have a tapered portion whose cross-sectional area decreases continuously from the one side to the opposite side.

[0015] (7) A heat sink according to one aspect of the present invention includes a plate-shaped base and a plurality of pin fins provided on one or both surfaces of the base, The pin fin is hexagonal or approximately hexagonal in a plan view, and the tip of the pin fin includes a circular flat portion and an excess portion that is provided on the outer periphery of the flat portion and abuts against the flat portion.

[0016] (8) In the heat sink of (7) above, the pin fin may have a tapered region at an end portion remote from the base portion, in which a cross-sectional area perpendicular to the axial direction continuously decreases. Effect of the Invention

[0017] According to the present invention, it is possible to provide a heat sink manufacturing method capable of inexpensively manufacturing a heat sink having hexagonal or approximately hexagonal pin fins, and a heat sink manufactured by the heat sink manufacturing method, which is in close contact with a jacket and can allow a refrigerant to flow uniformly. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a perspective view showing an example of a configuration of a heat sink according to an embodiment of the present invention. [Diagram 2] 2(a) is a side view of a pin fin provided on the heat sink of FIG. 1, and FIG. 2(b) is a top view of the pin fin provided on the heat sink of FIG. [Diagram 3] Figure 3(a) is a side view of a pin fin for a modified example of Figure 2(a), Figure 3(b) is a top view of a pin fin for a modified example of Figure 2(b), Figure 3(c) is a side view of a pin fin for another modified example of Figure 2(a), and Figure 3(d) is a top view of a pin fin for another modified example of Figure 2(b). [Figure 4] 4(a) and 4(b) are top views of pin fins according to other modified examples of FIG. [Diagram 5]FIG. 2 is a cross-sectional view showing an example of the configuration of a forging device that can be used in a method for manufacturing a heat sink according to an embodiment of the present invention, illustrating a placement process. [Figure 6] FIG. 1 is a cross-sectional view showing an example of the configuration of a forging device that can be used in a method for manufacturing a heat sink according to one embodiment of the present invention, illustrating the state immediately after pressure is applied to a metal material M in a pressure process. [Figure 7] FIG. 2 is a cross-sectional view showing an example of the configuration of a forging device that can be used in a method for manufacturing a heat sink according to one embodiment of the present invention, illustrating the state in which pressing of metal material M has been completed in the pressing process. [Figure 8] FIG. 2 is a cross-sectional view showing an example of the configuration of a forging device that can be used in a method for manufacturing a heat sink according to an embodiment of the present invention, illustrating a discharging process. [Figure 9] FIG. 9(a) is a schematic diagram showing a case where the gap between the knockout pin and the die is large, and FIG. 9(b) is a schematic diagram showing a problem that may occur in a case such as that shown in FIG. 9(a). [Figure 10] 5 is a schematic diagram showing an example of a relationship between a knockout pin and a through hole of a die used in a method for manufacturing a heat sink according to an embodiment of the present invention. FIG. [Figure 11] 10A and 10B are schematic diagrams showing another example of the relationship between knockout pins and die holes used in the method for manufacturing a heat sink according to one embodiment of the present invention. [Figure 12] 10A to 10C are schematic diagrams showing other examples of the relationship between the knock-out pins and sub-knock-out pins and the die holes used in the method for manufacturing a heat sink according to one embodiment of the present invention. [Figure 13] Figures 13(a) and 13(b) are schematic diagrams showing a case where the gap between the knockout pin and the die is large, and Figure 13(c) is a schematic diagram showing a defect other than those shown in Figures 9(a) and 9(b) that can occur in a case such as that shown in Figures 13(a) and 13(b). [Figure 14] FIG. 14(a) is a perspective view showing a state in which a heat sink according to an embodiment of the present invention is in use, and FIG. 14(b) is a cross-sectional view of FIG. 14(a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a heat sink and a method for manufacturing a heat sink according to an embodiment of the present invention will be described in detail with reference to the drawings. The drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics of the present invention easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and may be modified as appropriate within the scope of the effects of the present invention.

[0020] [heat sink] Fig. 1 is a perspective view showing an example of the configuration of a heat sink according to an embodiment of the present invention, Fig. 2(a) is a side view of a pin fin provided on the heat sink of Fig. 1, and Fig. 2(b) is a top view of the pin fin provided on the heat sink of Fig. 1. The heat sink 10 shown in Figs. 1 and 2 comprises a plate-shaped base portion 2 and a plurality of pin fins 3 provided on one or both surfaces of the base portion 2.

[0021] Fig. 1 shows a heat sink 10 having a plurality of pin fins 3 formed on one surface of a base portion 2, but in the base portion 2, pin fins 3 may also be formed on the surface opposite to the surface on which the pin fins 3 are formed in Fig. 1. Hereinafter, this embodiment will be described using the heat sink 10 shown in Fig. 1 as an example.

[0022] The base portion 2 is a portion that serves as the foundation of the pin fins 3. There are no particular limitations on the shape of the base portion 2. The planar shape of the base portion 2 may be, for example, a rounded shape such as a circle or an oval, or a polygonal shape such as a quadrangle (rectangle, square), hexagon, or octagon. The thickness of the base portion 2 may be, for example, within a range of 0.5 mm to 20 mm. The surface of the base portion 2 facing the pin fin 3 is preferably flat. The surface of the base portion 2 opposite the pin fin 3 side may be flat or may have a step. For example, the surface of the base portion 2 opposite the pin fin 3 side may have a convex or concave portion in the center.

[0023] Each of the multiple pin fins 3 extends in a direction perpendicular to the surface of the base portion 2. The multiple pin fins 3 are, for example, arranged in point symmetry with respect to the center of the base portion 2 in a planar view.

[0024] The tip portion 30 of the pin fin 3 includes a flat portion 31 that is circular in plan view and an excess pad portion 32 that is provided on the outer periphery of the flat portion 31 and stands in contact with the flat portion 31. The excess pad portion 32 is provided so as to protrude from the flat portion 31. The shape of the pin fin 3 corresponds to the shape of a die hole and a knockout pin provided in a die of a forging device, the details of which will be described later.

[0025] The pin fin 3 is hexagonal or approximately hexagonal in plan view. Figures 2(a) and 2(b) show a straight fin that is a regular hexagon in plan view and has the same cross-sectional shape at any position in the axial direction. The shape of the pin fin 3 in plan view does not have to be a regular hexagon, so long as it is hexagonal or approximately hexagonal. The pin fin 3 may also be R-chamfered. When the pin fin 3 is R-chamfered, for example, the ratio of the magnitude of the radius of curvature R to the diameter of the inscribed circle of the hexagon in which the pin fin 3 is viewed in plan (radius of curvature R / diameter of the inscribed circle of the hexagon of the pin fin) can be 45% or less, and preferably 5% to 40%.

[0026] In this specification, the term "approximately hexagonal" is intended to allow for processing errors of a few percent and R-chamfering with respect to a strict hexagon, as long as the effects of the present invention are achieved, and includes those with R-chamfering as described above.

[0027] Fig. 3(a) is a side view of a pin fin according to a modification of Fig. 2(a), Fig. 3(b) is a top view of a pin fin according to a modification of Fig. 2(b), Fig. 3(c) is a side view of a pin fin according to another modification of Fig. 2(a), and Fig. 3(d) is a top view of a pin fin according to another modification of Fig. 2(b). The pin fins 3A and 3B shown in Figs. 3(a) to 3(d) have a tapered region T in which the cross-sectional area perpendicular to the axial direction continuously decreases at the end away from the base portion 2. The pin fin 3A shown in Figs. 3(a) and 3(b) is a tapered fin consisting of the tapered region T, and the pin fin 3B shown in Figs. 3(c) and 3(d) has a structure in which the cross-sectional shape does not change in the region close to the base portion 2, and has a tapered region T only at the end away from the base portion 2. In a pin fin having a tapered region T, the ratio of the radius of curvature R to the diameter of the inscribed circle of the hexagon when the pin fin 3 is viewed in a plan view is designed to be a value based on the diameter of the inscribed circle of the pin fin at the point where the cross-sectional area perpendicular to the axial direction is the largest.

[0028] 4(a) and 4(b) are top views of a pin fin according to another modification of FIG. 2. The pin fin 3D shown in FIG. 4(a) has a flat portion 31 corresponding to a knockout pin, which will be described later, at the center of the tip portion 30 in a plan view, and further has at least one preliminary flat portion 33 corresponding to a sub-knockout pin, which will be described later, and the flat portion 31 and the preliminary flat portion 33 are surrounded by an excess portion 32. The flat portion 31 and the preliminary flat portion 33 are configured to have the same height in the axial direction, for example. The pin fin 3E shown in FIG. 4(b) has a plurality of preliminary flat portions 33. The number of the preliminary flat portions 33 is preferably three or more, more preferably four or more, and even more preferably six, corresponding to each apex. The preliminary flat portions 33 are preferably formed symmetrically with respect to the center of the cross section of the pin fin in a plan view.

[0029] [Heat sink manufacturing method] Next, a method for manufacturing a heat sink according to one embodiment of the present invention will be described. The method for manufacturing a heat sink according to one embodiment of the present invention includes a placement step of placing a metal material on one side of a die having a plurality of die holes each having a hexagonal or approximately hexagonal shape in plan view, a pressurizing step of applying pressure to the metal material from the opposite side toward the die having knockout pins inserted into the die holes to cause the metal material to flow into the die holes to form pin fins, and a discharge step of pushing up the knockout pins to discharge the forging material with the pin fins formed thereon from the die.

[0030] Fig. 5 is a cross-sectional view showing an example of the configuration of a forging device that can be used in a method for manufacturing a heat sink according to an embodiment of the present invention, and shows a state of an arrangement step. First, with reference to Fig. 5, a forging device 100 will be described.

[0031] The forging apparatus 100 shown in Fig. 5 has a punch (upper die) 111, a die (lower die) 112, and a die holder 114. The die 112 has a forming hole 112A formed as a recess downward on the upper surface side. In the following figures explaining the manufacturing method of a heat sink, for convenience of explanation, the metal material M which is the material of the heat sink is also shown. The material constituting the forging apparatus 100 is composed of aluminum, copper, or the like having high thermal conductivity. When manufacturing a heat sink with the forging apparatus 100, the metal material M may be forged while being heated, or may be cold forged without being heated.

[0032] A plurality of through holes (die holes) 113 (113a, 113b, 113c, 113d) that penetrate in the vertical direction are formed in the bottom wall of the forming hole 112A in the die 112. A knockout pin 118 is arranged in each die hole 113 so as to be slidable in the vertical direction. The punch 111 is movable up and down along the inner wall of the die 112.

[0033] The metal material M may be subjected to annealing treatment (O treatment). Members configured to slide in the die hole 113, etc., may be subjected to material lubrication treatment. Also, they may be subjected to annealing treatment after material lubrication treatment.

[0034] The die holder 114 has an anvil 115, cylindrical knockout pins 118 (118a, 118b, 118c, 118d), a knockout plate 119, and an ejector 120. The anvil 115 has a bottom plate 116 and a cylindrical die support 117 arranged around the bottom plate 116. The bottom plate 116 has an opening in the center into which the ejector 120 is inserted. The knockout pins 118a, 118b, 118c, 118d are inserted into a plurality of die holes 113a, 113b, 113c, 113d of the die 112. The knockout pins 118a, 118b, 118c, 118d are supported by the knockout plate 119. The knockout plate 119 is arranged on the bottom plate 116 and the ejector 120. The ejector 120 is movable in the vertical direction. In accordance with the vertical movement of the ejector 120, the knockout pins 118a, 118b, 118c, and 118d move vertically via the knockout plate 119. Each of the knockout pins 118 has a tip portion F118.

[0035] In FIG. 6, the knockout pin 118 is circular in plan view, and the die hole 113 is hexagonal or approximately hexagonal in plan view.

[0036] In the illustrated example, the die hole 113 and the knock-out pin 118 , more specifically, the inner circumferential surface of the die hole 113 and the upper end surface of the knock-out pin 118 , form a fin forming recess 142 .

[0037] In this example, die holes 113 are formed in die 112 to form fin forming recesses 142, but the present invention is not limited to this, and bottomed holes may be formed in die 112 to form fin forming recesses 142 using the bottomed holes. Furthermore, a portion of fin forming recesses 142 may be formed using die holes 113. For example, half of fin forming recesses 142 may be formed using die holes 113, and the remaining half may be formed using bottomed holes.

[0038] When the punch 111 is driven into the die 112, the space surrounded by the tip surface of the punch 111 and the forming hole 112A of the die 112 is formed as the base forming portion 141, and the space between the outer peripheral surface of the punch 111 and the inner peripheral surface of the forming hole 112A above the outer periphery of the base forming portion 141 is formed as the burr forming portion 143.

[0039] An example of a process for producing a heat sink by performing a forging process using such forging apparatus 100 will be described with reference to Figs.

[0040] A preparation step may be carried out prior to the placement step. In the preparation process, first, the die 112 is placed on the die support 117 of the die holder 114. Next, the knockout pins 118a, 118b, 118c, 118d are inserted into the through holes 113a, 113b, 113c, 113d of the die 112, and the knockout pins 118a, 118b, 118c, 118d are pushed in until they contact the knockout plate 119. Next, the position of the knockout plate 119 is adjusted to set the positions of the upper ends of the knockout pins 118a, 118b, 118c, 118d, i.e., the depths of the die holes 113a, 113b, 113c, 113d.

[0041] (Placement process) Next, the arrangement step is performed. In the arrangement step, as described above, the metal material M is arranged on one side of the die 112 in which a plurality of die holes 113 (113a to 113d) are formed, each of which is hexagonal or substantially hexagonal in plan view. Specifically, the metal material M is arranged at the center of the die 112 (the center in the X direction and the Y direction). There is no limitation on the shape of the metal material M as long as it can be accommodated in the forming hole 112A of the die 112. The shape of the metal material M may be a square plate shape (hexahedron), a round plate shape, or an irregular shape. In order to suppress positional deviation in the forming hole 112A of the die 112, it is preferable that the metal material M has a shape close to the shape of the forming hole 112A. In addition, the metal material M may be chamfered. The metal material M may be cut out from a rolled material by trimming or machining. In addition, the metal material M may be manufactured by cutting or cutting out a flat or round extruded material or a square or round continuous cast bar. The metal material M may be subjected to an annealing treatment (O treatment) in order to improve ductility. The metal material M may also be subjected to a lubrication treatment in which a lubricant is applied to the surface. The annealing treatment may be performed after the lubrication treatment.

[0042] (Pressure process) Next, a pressing step is carried out. 6 and 7 are cross-sectional views showing an example of the configuration of a forging device that can be used in a method for producing a heat sink according to an embodiment of the present invention, and are views showing the state of the pressurizing step. Fig. 6 is a view showing the state immediately after the start of pressurizing the metal material M, and Fig. 7 is a view showing the state after pressing the metal material M is completed.

[0043] After the metal material M is set in the forming hole 112A, the punch 111 is lowered to pressurize the metal material M. The pressurizing step may be performed by cold forging without heating the metal material M, but is preferably performed while heating the metal material M to 400 to 600°C. As shown in FIG. 6, immediately after the punch 111 starts pressing the metal material M, the metal material M is divided into metal flowing toward the center (inner diameter direction) and metal flowing toward the outside (outer diameter direction). Of these, the metal flowing toward the center flows into the through hole 113 (fin forming recess 142) in the center. The metal flowing toward the outside flows into the through hole 113 (fin forming recess 142) in the outer periphery and into the flash forming portion 143 between the punch 111 and the inner circumferential surface of the forming hole 112A. Since a sufficient amount of metal flows through the center of the base forming portion 141, the fin forming recess 142 in the center is sufficiently filled with metal.

[0044] Pressurization continues, and when it is completed, as shown in FIG. 7, a forged product 10 having the base portion 2, the pin fins 3, and the burrs 10a is formed.

[0045] (discharge process) Next, the discharge step is carried out. FIG. 8 is a cross-sectional view showing an example of the configuration of a forging device that can be used in a method for producing a heat sink according to an embodiment of the present invention, and shows the ejection process. After the base portion 2 and the pin fins 3 are formed, as shown in Fig. 4, the ejector 120 is moved upward to move the knockout pins 118a, 118b, 118c, and 118d upward via the knockout plate 119, thereby pushing out the pin fins. As a result, the forged material 10 is removed from the die 112.

[0046] Next, in a finishing process, the forged material 10 is subjected to finishing processing such as trimming to remove burrs 10a, thereby obtaining the heat sink 10. Burrs formed on the pin fins 3 may be removed, and excess material 32 may also be removed by grinding or the like. Of the base portion 2 of the heat sink 10, the surface opposite to the surface on which the pin fins 3 are formed may be referred to as the mounting surface S2.

[0047] 9(a), if the gap S between the knock-out pin 118 and the die hole 113 is large, the knock-out pin 118 cannot be stably fixed. In this case, as shown in FIG 9(b), problems such as bending or breaking of the knock-out pin 118 due to the molding load in the pressurizing step may occur.

[0048] Fig. 10 is a schematic diagram showing an example of the relationship between a tip F118 of a knockout pin 118 used in the manufacturing method of a heat sink of this embodiment and a die hole 113. In Fig. 10, the inscribed circle of the hexagonal or approximately hexagonal cross section of the die hole 113 is shown by a two-dot chain line. The tip portion F118 of the knockout pin 118 has a circular shape in plan view. The shape of the die hole 113 corresponds to the shape of the pin fin to be formed. Therefore, the die hole 113 is hexagonal or approximately hexagonal in plan view. From the viewpoint of forming pin fins having a tapered region T as shown in Figures 3(a) to 3(d), the die hole 113 may have a tapered portion whose cross-sectional area continuously decreases in the axial direction.

[0049] The diameter of the tip portion F118 of the knockout pin 118 is equal to or smaller than the diameter of the smallest inscribed circle of the hexagon or approximately hexagon in the smallest region of the die hole 113 where the cross-sectional area is the smallest. The diameter of the tip portion F118 of the knockout pin 118 is, for example, 5% to 100% of the diameter of the smallest inscribed circle, and from the viewpoint of smooth removal, is preferably 40% to 100%, more preferably 50% or more, and even more preferably 75% or more. In addition, the diameter of the tip portion F118 of the knockout pin 118 may be less than 100% of the diameter of the smallest inscribed circle, taking into account the friction between the knockout pin 118 and the die 112. The difference between the diameter of the tip portion F118 of the knockout pin 118 and the diameter of the inscribed circle where the cross-sectional area is the smallest of the die hole 113 is, for example, preferably 3 mm or less, more preferably 2 mm or less, 1.5 mm or less, or 1 mm or less, and even more preferably 0.5 mm or less. In order to suppress deformation of the knockout pin 118 during forging and knocking, it is preferable that the diameter of the tip F118 of the knockout pin 118 is approximately the same as the above-mentioned minimum inscribed circle of the hexagonal or approximately hexagonal die hole 113 (approximately 0.01 to 0.5 mm smaller than the minor axis). The diameter of the tip of the knockout pin and the diameter of the minimum inscribed circle of the die hole can be selected arbitrarily, but in the examples described later, it has been confirmed that the product can be discharged without problems in the discharge process by using a pin with a minimum inscribed circle of the die hole 113 in the range of φ2 mm to φ6 mm and a tip F118 of the knockout pin 118 with a diameter of φ1 mm to φ6 mm. In addition, taking into consideration data that the forged material can be removed from the forging device by pulling the formed forged material, the diameter of the tip F118 of the knockout pin 118 may be φ0.2 mm to φ6 mm.

[0050] 11 and 12 are schematic diagrams showing another example of the relationship between the knockout pin and the die hole used in the manufacturing method of the heat sink according to the embodiment of the present invention. FIG. 11(a) shows a state in which the minimum inscribed circle of the die hole 113 and the diameter of the tip portion F118 of the knockout pin 118 are substantially the same. As shown in FIG. 11(a), the die hole 113 may be substantially hexagonal in plan view. When using the die hole 113 having such a shape in plan view to manufacture a heat sink having pin fins having a substantially hexagonal shape in plan view, R chamfering is not required. As shown in FIG. 11(b), the die hole 113 may be a hexagon other than a regular hexagon in plan view, or a hexagon other than a regular hexagon that has been chamfered. Even when such a die hole is used to form pin fins having a shape corresponding to the die hole, it is preferable that the diameter of the tip portion F118 of the knockout pin 118 satisfies the above relationship with the diameter of the minimum inscribed circle of the die hole 113.

[0051] 12(a) to 12(c), in addition to knockout pin 118, at least one sub-knockout pin having a circular tip shape with a diameter of less than or equal to {(diameter of the inscribed circle-diameter of the tip of the knockout pin)÷2} is used. Tip F118X of the sub-knockout pin is shown in Figures 12(a) to 12(c).

[0052] In the example shown in Fig. 12(a), one sub-knockout pin is used in addition to the knock-out pin 118, in the example shown in Fig. 12(b), three sub-knockout pins are used in addition to the knock-out pin 118, and in the example shown in Fig. 12(c), six knock-out pins are used in addition to the knock-out pin 118. As shown in Figs. 12(b) and 12(c), it is preferable that two or more sub-knockout pins are provided symmetrically with respect to the center of the die hole 113 in a plan view in addition to the knock-out pin 118. It is also preferable that the tip portion F118X of the sub-knockout pin is provided so as to contact two sides of the knock-out pin 118 and the die hole 113. Such an arrangement of the sub-knockout pins improves stability during the ejection process described below.

[0053] Figures 13(a) and 13(b) are schematic diagrams showing a case where the gap between the knockout pin and the die is large, and Figure 13(c) is a schematic diagram showing a defect other than that shown in Figures 9(a) and 9(b) that may occur in the case of Figures 13(a) and 13(b). Figure 13(a) shows the state during the preparation process, Figure 13(b) shows the state during the pressurization process, and Figure 13(c) shows the state at the start of the ejection process.

[0054] 13(a) to 13(c), when a knockout pin 118 is used in which the diameter of the inscribed circle is small relative to the diameter of the die hole and the gap between the die 112 and the die hole 113 is large, the knockout pin 118 sinks into the pin fin 3 in the ejection process, and the tip portion F118 of the knockout pin 118 is surrounded by and fixed to the excess metal portion 32 in the radial direction. On the other hand, when the ratio of the diameter of the inscribed circle of the hexagonal or approximately hexagonal tip portion F118 of the knockout pin 118 to the diameter of the die hole 113 is high, even if the excess metal portion 32 is formed in the forged material, the tip portion F118 of the knockout pin 118 is not fixed to the raw material material, and the raw material material can be smoothly ejected.

[0055] Moreover, the planar shape of each of the pin fins 3 formed in the heat sink 10 according to this embodiment is all hexagonal or approximately hexagonal. Of n-gons inscribed in a circle of the same diameter, a regular n-gon has the longest side length. Therefore, in the heat sink 10 according to this embodiment, the surface area of ​​the pin fins 3 can be increased, and high cooling performance is exhibited. Also, it is known that three types of regular polygons, an equilateral triangle, a square, and a regular hexagon, have high uniformity in the distance between the opposing sides separated from each other and can be arranged symmetrically. Of these, when an equilateral triangle and a square are adopted as the planar shape of the pin fin, it cannot be said that they have good fluidity for the fluid due to the size of their angles. In contrast, a regular hexagon is less likely to cause contraction and can be cooled efficiently.

[0056] Furthermore, in the method for manufacturing a heat sink according to this embodiment, since a die hole 113 that is hexagonal or approximately hexagonal in plan view and a knockout pin that is circular in plan view are used, excess metal portions 32 are formed in the pin fins of the formed heat sink.

[0057] Fig. 14(a) is a perspective view showing a state of a heat sink according to an embodiment of the present invention when in use, and Fig. 14(b) is a cross-sectional view of Fig. 14(a). As shown in Fig. 14(a) and Fig. 14(b), the heat sink 10 is used by being fitted into the jacket 60 and fixed with bolts 41, 43 and nuts 42, 44. The heat sink 10 is used by mounting a heating element 70 on a mounting surface S2 corresponding to the rear surface of the base portion 2. An O-ring 45 is provided between the heat sink 10 and the jacket 60 in order to ensure the airtightness of the internal space.

[0058] 14(a) and 14(b) show a configuration in which the surface of the heat sink 10 on the side on which the pin fins 3 are not provided has a stepped structure, but the surface of the heat sink 10 on the side on which the pin fins 3 are not provided may have a flat shape. The configuration having a stepped structure as shown in the drawings can be realized by cutting using a machining machine.

[0059] In conventional heat sinks, the tips of the pin fins are arranged so as not to come into contact with the bottom surface of the jacket (jacket bottom surface). This is because if the pin fins and the jacket bottom surface come into contact, excessive force may be applied to the pin fins due to variations within the dimensional tolerances of the pin fins and the jacket, causing the pin fins to bend, or a gap may be created between the heat sink and the jacket, resulting in the risk of the coolant leaking from the internal space surrounded by the heat sink and the jacket to the external space. In addition, if the pin fins and the jacket bottom surface are spaced apart, the fluid introduced as the coolant will be unevenly distributed on the pin fins compared to the vicinity of the base part of the heat sink. In this case, the heat generating element provided on the base part cannot be efficiently cooled.

[0060] In contrast, the heat sink 10 according to the present embodiment has a flat portion 31 and an excess metal portion 32 at the tip of the pin fin 3. Compared to a pin fin with a flat tip, the heat sink 10 according to the present embodiment has a low tip strength, and when pressure is applied while in contact with another member, the excess metal portion 32 is crushed or can be deformed so that only the excess metal portion 32 is bent. Therefore, the heat sink according to the present embodiment has a lower risk as described above compared to a conventional heat sink with a flat tip, and at least the excess metal portion 32 of the pin fin 3 can be provided so as to contact the jacket bottom surface S60. The excess metal portion 32 is provided at a position corresponding to a corner of a hexagon or approximately hexagon when the pin fin 3 is viewed in a plan view, and when the diameter of the knockout pin 118 is less than the diameter of the smallest inscribed circle of the pin fin 3, the excess metal portion 32 is structured to surround the entire outer periphery of the flat portion 31.

[0061] A fluid coolant is introduced into the space defined by the heat sink 10 and the jacket bottom surface S60 through an inlet 61, and the fluid is discharged through an outlet 62. The heat generating element 70 provided on the mounting surface S2 of the heat sink 10 is cooled by the fluid through the pin fins 3. Due to the above structure, the heat sink 10 according to this embodiment has no gaps between the pin fins 3 and the jacket bottom surface S60 through which the fluid can flow. Therefore, the heat sink 10 according to this embodiment can uniformly flow the fluid coolant in the space defined between the heat sink 10 and the jacket 60. That is, the heat sink 10 according to this embodiment can efficiently cool the heat generating element mounted thereon.

[0062] Furthermore, in the manufacturing method of the heat sink according to the above embodiment, when forming pin fins that are hexagonal or approximately hexagonal in plan view, by using circular knockout pins rather than hexagonal columnar knockout pins, it is possible to significantly reduce the cost of producing the mold and make the product price cheaper. EXAMPLES

[0063] [Example 1-1] First, a 30x30x7.5t six-sided workpiece of an alloy (A6063) containing aluminum as the main component was prepared as the forging material. The corners of the 30x30 were chamfered to give C5 so that the six-sided workpiece could be inserted into a die.

[0064] The die has a die hole that is approximately hexagonal in plan view. The cross-sectional area of ​​the die hole is constant in the axial direction. The size of the die hole in plan view was adjusted so that the diameter of the inscribed circle of the die hole was φ2 mm. The die hole was approximately hexagonal in plan view, and a regular hexagon was used that was chamfered. The chamfering was performed with a length R of 0.1 times the diameter of the inscribed circle of the hexagon. The die used had seven die holes. Specifically, one die hole was provided at the center of the die in plan view, and six die holes were provided around it, and the die holes were arranged point-symmetrically so that the distance between the centers of the die holes provided at the center of the plan view and the die holes provided around it was 9 mm.

[0065] As the knockout pins of the forging device as shown in FIG. 4, a knockout plate with seven straight fins of a hexagonal shape in plan view was prepared. In plan view, the knockout pins were arranged so as to be point-symmetrical with respect to the center of the plan view. Specifically, one knockout pin was arranged at the center of the plan view, and six knockout pins were arranged at equal distances so as to have sides parallel to the six sides constituting the knockout pin. In other words, among the knockout pins arranged in the circumferential direction, the angle between the center of the plan view of two adjacent knockout pins and the center of the plan view of the knockout plate was designed to be 60°. As the size of the knockout pin, a knockout pin with a diameter of φ2 mm was prepared.

[0066] That is, in Example 1-1, a forging device was used in which the diameter of the tip of the knockout pin was 100% of the diameter of the inscribed circle of the approximately hexagon in the minimum region where the cross-sectional area of ​​the die hole was the smallest. In addition, the surface of the forging device was lubricated with a water-soluble lubricant.

[0067] A heat sink was produced using the forging device. When producing the heat sink, the temperature of the forging material (material temperature) was 400°C, and the temperature of the die (die temperature) was 200°C. When forging, the material was pressed against the die until the tips of the pin fins formed were 10 mm or more. That is, in this example, a forged material was formed in which pin fins with a length of 10 mm were formed by forging.

[0068] [Example 1-2] A heat sink was produced in the same manner as in Example 1-1, except that a knockout pin that was circular in plan view and had a diameter of φ1.5 was used. That is, in Example 1-2, a forging device was used in which the diameter of the tip of the knockout pin was 75% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0069] [Examples 1-3] A heat sink was produced in the same manner as in Example 1-1, except that a knockout pin that was circular in plan view and had a diameter of φ1 was used. That is, in Example 1-3, a forging device was used in which the diameter of the tip of the knockout pin was 50% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0070] [Reference example 1] A heat sink was produced in the same manner as in Example 1-1, except that a knockout pin that was circular in plan view and had a diameter of φ0.5 was used. That is, in Reference Example 1, a forging device was used in which the diameter of the tip of the knockout pin was 25% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0071] [Example 2-1] A heat sink was produced in the same manner as in Example 1-1, except that the diameter of the inscribed circle of the die hole, which is a regular hexagon in plan view, was changed to φ4, and accordingly a knockout pin was used that was circular in plan view and had a diameter of φ4. That is, in Example 2-1, a forging device was used in which the diameter of the tip of the knockout pin was 100% of the diameter of the inscribed circle of the approximately hexagon in the minimum region where the cross-sectional area of ​​the die hole is the smallest.

[0072] [Example 2-2] A heat sink was produced in the same manner as in Example 2-1, except that a knockout pin that was circular in plan view and had a diameter of φ3 was used. That is, in Example 2-2, a forging device was used in which the diameter of the tip of the knockout pin was 75% of the diameter of the approximately hexagonal inscribed circle in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0073] [Example 2-3] A heat sink was produced in the same manner as in Example 2-1, except that a knockout pin that was circular in plan view and had a diameter of φ2 was used. That is, in Example 2-3, a forging device was used in which the diameter of the tip of the knockout pin was 50% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0074] [Reference example 2] A heat sink was produced in the same manner as in Example 2-1, except that a knockout pin that was circular in plan view and had a diameter of φ1 was used. That is, in Reference Example 2, a forging device was used in which the diameter of the tip of the knockout pin was 25% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0075] [Example 3-1] A heat sink was produced in the same manner as in Example 1-1, except that the diameter of the inscribed circle of the die hole, which is a regular hexagon in plan view, was changed to φ6, and accordingly a knockout pin was used that was circular in plan view and had a diameter of φ6. That is, in Example 3-1, a forging device was used in which the diameter of the tip of the knockout pin was 100% of the diameter of the inscribed circle of the approximately hexagon in the minimum region where the cross-sectional area of ​​the die hole is the smallest.

[0076] [Example 3-2] A heat sink was produced in the same manner as in Example 3-1, except that a knockout pin that was circular in plan view and had a diameter of φ4.5 was used. That is, in Example 3-2, a forging device was used in which the diameter of the tip of the knockout pin was 75% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0077] [Example 3-3] A heat sink was produced in the same manner as in Example 3-1, except that a knockout pin that was circular in plan view and had a diameter of φ3 was used. That is, in Example 3-3, a forging device was used in which the diameter of the tip of the knockout pin was 50% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0078] [Reference example 3] A heat sink was produced in the same manner as in Example 3-1, except that a knockout pin that was circular in plan view and had a diameter of φ1.5 was used. That is, in Reference Example 3, a forging device was used in which the diameter of the tip of the knockout pin was 25% of the diameter of the inscribed circle of the approximately hexagonal shape in the minimum region where the cross-sectional area of ​​the die hole was the smallest.

[0079] [evaluation] In the above-mentioned Examples 1-1 to 3-3 and Reference Examples 1 to 3, the ejection properties of the forged material in the ejection step during the production of the heat sink were evaluated.

[0080] [result] The conditions of the above Examples 1-1 to 3-3 and Reference Examples 1 to 3 are summarized in Table 1. In the "Dischargeability" column, a symbol "◯" is indicated if the forged material formed in the discharge step after the pressurizing step could be discharged smoothly without adhering to the forging device, and a symbol "×" is indicated if the pin fins of the forged material formed in the discharge step adhered to the members of the forging device and the material could not be discharged smoothly.

[0081] [Table 1]

[0082] In Examples 1-1 to 3-3, the forged material could be discharged without adhering to the forging device, but in Reference Examples 1 to 3, the excess material at the tip of the pin fin was embedded in the knockout pin, and the forged product could not be discharged smoothly from the die. However, even in Reference Examples 1 to 3, the forged material could be removed from the forging device by pulling it. [Explanation of symbols]

[0083] 2 Base part, 3,3A,3B,3C,3D,3E pin fin, 10 Forged molded material 10a burr, 30 tip portion, 31 flat portion, 32 excess portion, 33 spare flat portion, 100 forging device, 111 punch (upper die), 112 die (lower die), 112A molding hole, 113, 113a, 113b, 113c, 113d through holes (die holes), 114 die holder, 115 anvil, 116 bottom plate, 117 die support, 118, 118a, 118b, 118c, 118d knockout pins, 119 knockout plate, 120 ejector, 141 base molding part, 142 fin forming recess, 143 flash forming portion, M metal material, R radius of curvature, T taper area

Claims

1. a placement step of placing a metal material on one side of a die having a plurality of die holes each having a hexagonal or substantially hexagonal shape in plan view; a pressurizing step of pressing the metal material against the die having a knockout pin inserted into the die hole from the opposite side of the one side, thereby causing the metal material to flow into the die hole, thereby forming pin fins; and a discharge step of pushing up the knockout pin and discharging the forging material having the pin fins formed thereon from the die. The tip of the knockout pin is circular in a plan view, A method for manufacturing a heat sink, wherein the diameter of the tip of the knockout pin is equal to or smaller than the diameter of an inscribed circle of a hexagon or approximately hexagon in a minimum region where the cross-sectional area of ​​the die hole is smallest.

2. The method for manufacturing a heat sink according to claim 1 , wherein a diameter of the tip of the knockout pin is equal to or greater than half a diameter of the inscribed circle.

3. The method for manufacturing a heat sink according to claim 1 , wherein a difference between a diameter of the tip of the knockout pin and a diameter of the inscribed circle is 0.5 mm or less.

4. 2. The method for manufacturing a heat sink according to claim 1, wherein in the pressurizing step and the ejection step, in addition to the knockout pin, at least one sub-knockout pin having a circular tip shape with a diameter of less than or equal to {(diameter of the inscribed circle-diameter of the tip of the knockout pin)÷2} is further used in the die hole.

5. The method for manufacturing a heat sink according to claim 1 , wherein a diameter of a tip of the knockout pin is in a range of φ0.2 mm to φ6 mm.

6. The method for manufacturing a heat sink according to claim 1 , wherein the die hole has a tapered portion whose cross-sectional area continuously decreases from the one side to the opposite side.

7. A plate-shaped base portion and a plurality of pin fins provided on one or both surfaces of the base portion, The pin fin is hexagonal or substantially hexagonal in a plan view, The tip of the pin fin includes a circular flat portion and an excess portion provided on the outer periphery of the flat portion and extending upright from the flat portion.

8. The heat sink of claim 7 , wherein the pin fin has a tapered region at an end remote from the base portion, the cross-sectional area perpendicular to the axial direction of the pin fin decreasing continuously.

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