Heat sink and method for manufacturing a heat sink

Abstract

To continuously manufacture a heat sink having a structure in which the height of pin fins can be easily made uniform without using a back pressure mechanism in a closed construction method, and a method capable of continuously manufacturing a heat sink having pin fins of uniform height over a long period of time without using a back pressure mechanism.SOLUTION: A heat sink includes a plate-shaped base portion and a plurality of pin fins provided on one surface of the base portion, the plurality of pin fins are arranged so as to be spaced apart in a first direction and in a second direction perpendicular to the first direction, and in at least one of the first direction and the second direction, and the cross-sectional area of the pin fins located on the outer side is larger than the cross-sectional area of the pin fins located on the central side.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As a heat sink, a structure including a plate-like base portion and a plurality of pin fins provided on one surface of the base portion is known. As a method for manufacturing such a heat sink, a forging method is known. As the forging method, a method is known in which a metal material, which is a raw material of the heat sink, is placed on a die having a plurality of holes, and the metal material is pressed toward the die using a punch, so that the metal material is stretched in the outer peripheral direction of the die to form the base portion and is caused to flow into each of the plurality of holes to form the pin fins. For the forging method using a die, a flash removal method (also referred to as a semi-closed method) and a closed method are known. The flash removal method is a method in which a gap is provided between the punch and the die, and the metal material that has not flowed into the plurality of holes flows out to the outside through the gap. The closed method is a method in which a gap is not provided between the punch and the die, and the metal material is sealed between the punch and the die.

[0003] In order to manufacture a heat sink having pin fins of uniform height using a forging method, it is necessary to uniformly flow the metal material into the plurality of holes of the die. As a method for uniformly filling the metal material into the plurality of holes of the die using the flash removal method, increasing the inflow resistance of the metal material in the holes located on the central side of the die compared to the inflow resistance of the metal material in the holes located on the outer side has been studied (Patent Document 1). Patent Document 1 describes a method for increasing the inflow resistance of the metal material in the holes located on the central side of the die, which is to provide unevenness on the surface of the inflow port (shoulder) of the metal material in the holes located on the central side of the die. Further, as a method for uniformly filling the metal material into the plurality of holes of the die using the closed method, applying back pressure to the tip of the pin has been performed (Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-228618 [Non-patent literature]

[0005] [Non-Patent Document 1] Yoshitaro Shinozaki, "Illustrated Basics of Forging," First Edition, Nikkan Kogyo Shimbun, July 25, 2009, pp. 128-129. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The sealed die method is advantageous because it reduces metal material loss compared to the deburring method, thus reducing the amount of metal material used. However, in the sealed die method, the metal material that flows from the center to the outside hits the inner wall of the die and returns to the center, making it easier for the metal material to flow into the outer holes. This makes it difficult to uniformly fill the center and outside of the die with metal material. In addition, if back pressure is applied to the pin tips, it is necessary to install equipment for applying back pressure in the forging machine, which increases manufacturing costs. In particular, as the number of pins increases (as the surface area of ​​the pin tips increases), it becomes necessary to avoid the need for high back pressure, thus increasing manufacturing costs. Furthermore, high back pressure requires a higher load during forging, which increases the load on the die and may shorten the die's lifespan.

[0007] This invention has been made in view of the circumstances described above, and aims to provide a heat sink with a structure that makes it easy to achieve uniform pin fin heights without using a back pressure mechanism in a sealed construction method, and a method for continuously manufacturing heat sinks with uniform pin fin heights over a long period of time without using a back pressure mechanism. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides the following means.

[0009] (1) A heat sink comprising a plate-shaped base portion and a plurality of pin fins provided on one surface of the base portion, wherein each of the plurality of pin fins is spaced apart in a first direction and a second direction perpendicular to the first direction, and in at least one of the first and second directions, the cross-sectional area of ​​the pin fins located on the outside is larger than the cross-sectional area of ​​the pin fins located on the central side.

[0010] (2) The heat sink according to (1) above, wherein in both the first and second directions, the cross-sectional area of ​​the pin fins located on the outer side is larger than the cross-sectional area of ​​the pin fins located on the central side.

[0011] (3) The heat sink according to (1) or (2) above, wherein the plurality of pin fins are arranged such that the distance between the centers of adjacent pin fins is the same.

[0012] (4) The heat sink according to (1) to (3) above, wherein the cross-sectional area of ​​the pin fins increases in stages from the pin fin located in the center toward the pin fin located outwards.

[0013] (5) The heat sink according to (1) to (3) above, wherein the cross-sectional area of ​​the pin fins increases continuously from the pin fin located in the center toward the pin fin located outwards.

[0014] (6) The heat sink according to (1) to (5) above, wherein the cross-sectional shapes of the multiple pin fins are similar.

[0015] (7) The heat sink according to (1) to (6) above, wherein the cross-sectional shape of each of the multiple pin fins is a circle.

[0016] (8) A heat sink as described in (1) to (7) above, which is a forged product.

[0017] (9) Prepare a die having a plurality of holes, wherein the plurality of holes are arranged at intervals in a first direction and a second direction perpendicular to the first direction, and in at least one of the first direction and the second direction, the cross-sectional area of the holes located on the outer side is larger than the cross-sectional area of the holes located on the central side; arrange a metal material on the central side in the first direction and the second direction of the die, and by pressurizing the metal material toward the die in a sealed state, stretch the metal material in the outer peripheral direction of the die and cause it to flow into the holes. A method for manufacturing a heat sink, including the above steps.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a heat sink having a structure that easily makes the height of pin fins uniform and a method for continuously manufacturing a heat sink having uniform pin fin heights over a long period of time.

Brief Description of the Drawings

[0019] [Figure 1] It is a perspective view of a heat sink according to an embodiment of the present invention. [Figure 2] It is a plan view of the heat sink shown in FIG. 1. [Figure 3] It is a cross-sectional view of a forging apparatus that can be used in the method for manufacturing the heat sink of this embodiment. [Figure 4] It is a conceptual diagram showing the diameters of the holes formed in the die used in Example 1.

Embodiments for Carrying Out the Invention

[0020] 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 appropriate reference to the drawings. In the drawings used in the following description, characteristic parts may be enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may differ from those of the actual product. The materials, dimensions, etc. exemplified in the following description are examples only, and the present invention is not limited to them, and can be implemented with appropriate modifications without changing the essence of the invention.

[0021] [heat sink] Figure 1 is a perspective view of a heat sink according to one embodiment of the present invention, and Figure 2 is a plan view of the heat sink shown in Figure 1. As shown in Figures 1 and 2, the heat sink 1 of this embodiment includes a plate-shaped base portion 2 and a plurality of pin fins 3 provided on one surface of the base portion 2.

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

[0023] Each of the multiple pin fins 3 extends in a direction perpendicular to the surface of the base portion 2 (Z direction). Each of the multiple pin fins 3 is arranged with spacing in a first direction (X direction, also called the row direction) along the surface of the base portion 2 and in a second direction (Y direction, also called the column direction) perpendicular to the first direction. In this embodiment, 11 pin fins 3 are arranged in the first direction and 10 pin fins 3 are arranged in the second direction. The multiple pin fins 3 are arranged in a staggered pattern, alternately offset in the first direction.

[0024] The pin fins 3 arranged in the second direction are configured such that the cross-sectional area of ​​the pin fins 3 located on the outer side is larger than that of the pin fins 3 located on the central side. Furthermore, the largest cross-sectional area among the multiple pin fins 3 arranged in the second direction is larger on the outer side than on the central side in the first direction. In other words, in both the first and second directions, the cross-sectional area of ​​the pin fins 3 located on the outer side is larger than that of the pin fins 3 located on the central side. In this specification, unless otherwise specified, "cross-section of pin fin 3" refers to the surface that appears when the pin fin 3 is cut along the surface of the base portion 2, and "cross-sectional area of ​​pin fin 3" refers to the area of ​​that cross-section. Among the multiple pin fins 3, the one with the largest cross-sectional area has a cross-sectional area of, for example, 1 mm². 2 More than 30mm 2 The following ranges are also acceptable. For example, if the cross-sectional shape of pin fin 3 is a circle, the pin fin with the largest cross-sectional area may have a diameter within the range of 1 mm to 6 mm. The ratio of the cross-sectional area of ​​the central pin fin 3 to the outer pin fin 3 adjacent to the central pin fin 3 may be within the range of 70 / 100 to 90 / 100 as the ratio of the cross-sectional area of ​​the central pin fin 3 to the cross-sectional area of ​​the outer pin fin 3. Also, the ratio of the diameter of the central pin fin 3 to the diameter of the outer pin fin 3 may be within the range of 85 / 100 to 95 / 100 as the ratio of the diameter of the central pin fin 3 to the diameter of the outer pin fin 3.

[0025] The change in the cross-sectional area of ​​pinfin 3 may be gradual or continuous. Gradual means that the cross-sectional area of ​​pinfin 3 increases at intervals of multiple pinfins (for example, 2 to 3 pinfins) as you move outward from the central pinfin 3. Continuous means that the cross-sectional area of ​​pinfin 3 increases by one pinfin at a time as you move outward from the central pinfin 3. The cross-sectional area of ​​pinfin 3 may have both gradual and continuous changes.

[0026] Multiple pin fins 3 are arranged such that each pin fin 3 is adjacent to a maximum of six other pin fins 3. Adjacent pin fins 3 are positioned so that their center-to-center distances are identical. The center-to-center distance is the distance between the centers in the cross-section of the pin fins 3. For example, the distance L between pin fin 3a and pin fin 3b. ab The distance L between pinfin 3a and pinfin 3c. ac The distance L between pinfin 3a and pinfin 3d. ad These are identical (see Figure 2). The center-to-center distance is, for example, within the range of 1.2 to 2 times the diameter of the pin fin with the largest cross-sectional area. The center-to-center distance may also be within the range of 1.2 mm to 10 mm.

[0027] It is preferable that the cross-sectional shapes of the multiple pin fins 3 are similar. However, there are no restrictions on the cross-sectional shape of the pin fins 3. The cross-sectional shape of the pin fins 3 may be a rounded shape such as a circle or an ellipse, a polygonal shape such as a square (rectangle, square, rhombus), hexagon, or octagon, or an irregular shape such as a feather shape.

[0028] The heights of multiple pin fins 3 may be the same. The heights of the pin fins 3 may be, for example, within the range of 3 mm to 10 mm.

[0029] The material used for heat sink 1 can be aluminum, aluminum alloy, copper, copper alloy, iron, iron alloy, etc. Alternatively, a clad material (composite material) made by bonding two or more metals together can be used for heat sink 1. However, the material for heat sink 1 is not limited to these metals or alloys; various metal materials commonly used for heat sinks can be used.

[0030] [Method for manufacturing heat sinks] The heat sink manufacturing method of this embodiment includes a preparation step of preparing a die and a pressurizing step of applying pressure to the die while the metal material is sealed. The pressurizing step can be carried out using a forging apparatus.

[0031] The die prepared in the preparation process has multiple holes. By flowing metal material into these multiple holes, the pin fins of the heat sink are formed. Therefore, the multiple holes in the die are positioned to correspond to the pin fins of the heat sink, which is the purpose of manufacturing. That is, the multiple holes in the die are spaced apart in a first direction and in a second direction perpendicular to the first direction, and are formed such that in at least one of the first and second directions, the cross-sectional area of ​​the holes located on the outside is larger than the cross-sectional area of ​​the holes located on the central side.

[0032] Figure 3 is a cross-sectional view of a forging apparatus that can be used in the heat sink manufacturing method of this embodiment. As shown in Figure 3, the forging apparatus 10 includes a punch 11, a die 12, and a die holder 14. The metal material 100, which is the material for the heat sink, is placed between the punch 11 and the die 12.

[0033] The punch 11 presses the metal material 100 toward the die 12. The die 12 is a die prepared in the preparation process. The die 12 has multiple holes 13a, 13b, and 13c. The multiple holes 13a, 13b, and 13c are arranged such that the cross-sectional area of ​​the holes located on the outside is larger than the cross-sectional area of ​​the holes located on the inside. That is, hole 13c has the smallest cross-sectional area, hole 13b has the next largest cross-sectional area, and hole 13a has the largest cross-sectional area. The punch 11 is movable up and down along the inner wall of the die 12. The distance between the punch 11 and the die 12 is such that the metal material 100 does not flow out, and the metal material 100 can be forged in a sealed state.

[0034] The die holder 14 includes an anvil 15, knock pins 18, a knockout plate 19, and an ejector 20. The anvil 15 has a base plate 16 and a cylindrical die support 17 arranged around the base plate 16. The base plate 16 has an opening in the center into which the ejector 20 is inserted. The knock pins 18 are inserted into multiple holes 13a, 13b, and 13c of the die 12. The knock pins 18 are supported by the knockout plate 19. The knockout plate 19 is positioned on top of the base plate 16 and the ejector 20. The ejector 20 is movable in the vertical direction. As the ejector 20 moves vertically, the knock pins 18 move vertically via the knockout plate 19.

[0035] The heat sink is manufactured using the forging apparatus 10 as follows. First, the die 12 is placed on the die support 17 of the die holder 14. Next, the knock pins 18 are inserted into the holes 13a, 13b, and 13c of the die 12 and pushed in until the knock pins 18 make contact with the knockout plate 19. Then, the position of the knockout plate 19 is adjusted to set the position of the upper end of the knock pins 18, i.e., the depth of the holes 13a, 13b, and 13c.

[0036] Next, the metal material 100 is placed in the center of the die 12 (center in the first and second directions). The shape of the metal material 100 is not limited as long as it can be housed in the cavity of the die 12. The shape of the metal material 100 may be a rectangular plate (hexahedron), a round plate, or an irregular shape. It is preferable that the shape of the metal material 100 is close to the shape of the cavity in order to suppress displacement within the cavity of the die 12. The metal material 100 may also be chamfered. The metal material 100 may be cut from rolled material by trimming or machining. The metal material 100 may also be manufactured by cutting or cutting flat or round extruded material or rectangular or round continuous cast rods. The metal material 100 may be annealed (O treatment) to improve its ductility. The metal material 100 may also be lubricated by applying a lubricant to its surface.

[0037] Next, the metal material 100 is forged by applying pressure to the die 12 using the punch 11 while it is sealed. Forging stretches the metal material 100 in the direction of the outer circumference of the die 12 and causes it to flow into the holes 13a, 13b, and 13c. The holes 13a, 13b, and 13c of the die 12 have a larger cross-sectional area from the inside outwards, allowing for a larger amount of metal material 100 to be filled inside. Therefore, even if the metal material 100 that flows from the center to the outside of the die 12 hits the inner wall of the die and returns to the center, the filling rate of the metal material 100 in the holes 13a, 13b, and 13c remains the same. As a result, pin fins of uniform height can be formed.

[0038] During forging, the metal material 100 may be heated. For example, if the metal material 100 is aluminum or an aluminum alloy, the metal material 100 may be heated to a temperature of 400°C to 600°C. Alternatively, the metal material 100 may be forged (cold forging) without heating.

[0039] After the heat sink having multiple pin fins is formed by forging, the ejector 20 is moved upward, causing the knock pins 18 to move upward via the knockout plate 19 and push the pin fins of the heat sink. This removes the heat sink from the die 12.

[0040] The heat sink 1 of this embodiment, configured as described above, has a structure in which the cross-sectional area of ​​the pin fins 3 located on the outer side is larger than the cross-sectional area of ​​the pin fins 3 located on the central side in both the first direction (row direction) and the second direction (column direction). In other words, the volume of the pin fins 3 per unit space is larger on the outer side than on the central side. When the heat sink 1 of this embodiment is manufactured using a sealed manufacturing method, the cross-sectional area of ​​the holes located on the outer side can be made larger than the cross-sectional area of ​​the holes located on the central side of the die. By doing so, when metal material that has flowed from the central side of the die to the outside hits the inner wall of the die and returns to the central side, the returned metal material can be allowed to flow into the holes on the outside of the die, thereby enabling the metal material to be uniformly filled throughout the holes. Therefore, the height of the pin fins in the heat sink 1 of this embodiment tends to be uniform even without using a back pressure mechanism. In addition, the heat sink 1 of this embodiment has pin fins 3 with a large cross-sectional area that conduct heat well arranged on the outer circumference, making it easy to release heat to the outside.

[0041] Furthermore, in this embodiment, the heat sink 1 is arranged such that the distance between the centers of adjacent pin fins 3 is the same. As a result, the cross-sectional area of ​​the pin fins 3 located on the outer periphery is larger than that of the pin fins 3 located on the central side. This creates a structure where the volume of pin fins 3 per unit space is greater on the outer periphery than on the central side. Therefore, the amount of heat conducted is greater on the outer periphery compared to the central side, making it easier to release heat to the outside.

[0042] In the heat sink 1 of this embodiment, if the cross-sectional area of ​​the pin fins increases in stages from the central pin fin 3 to the outer pin fin 3, there are multiple pin fins 3 with the same cross-sectional area, and the knock pins 18 can be shared in the forging apparatus 10 that manufactures the heat sink 1, making it easier to manage the forging apparatus 10.

[0043] In the heat sink 1 of this embodiment, if the cross-sectional area of ​​the pin fins increases continuously from the central pin fin 3 to the outer pin fin 3, the amount of heat conducted through the pin fins 3 of the heat sink 1 increases continuously from the central side to the outer side, making it easier to release heat to the outside.

[0044] If the cross-sectional shapes of the multiple pin fins are similar, when cooling water is flowed between the pin fins 3 for cooling, the cooling water flows more uniformly and the flow of the cooling water can be easily adjusted, thus allowing the pin fins 3 to be cooled more uniformly.

[0045] The die 12 used in the heat sink manufacturing method of this embodiment has multiple holes 13a, 13b, and 13c, with the central hole 13c having the smallest cross-sectional area and the outer hole 13a having the largest cross-sectional area. Therefore, even when using a sealed manufacturing method, the metal material 100 can be uniformly filled into the entire hole. For this reason, according to the heat sink manufacturing method of this embodiment, it is possible to manufacture a heat sink with uniform pin fin height without using a back pressure mechanism. In addition, since the die 12 has no irregularities on its surface, wear due to long-term continuous use is less likely to occur. For this reason, according to the heat sink manufacturing method of this embodiment, it is possible to continuously manufacture heat sinks with uniform pin fin height over a long period of time. In particular, when the cross-sectional shape of the holes in the die 12 is circular (i.e., when the cross-sectional shape of each of the multiple pin fins 3 of the heat sink 1 is circular), localized stress concentration is less likely to occur in the holes of the die 12 even when a high load is applied when manufacturing the heat sink 1 using a sealed manufacturing method. For this reason, the die 12 is less likely to break over a long period of time, and it becomes possible to continuously manufacture heat sinks with uniform pin fin height over an even longer period of time.

[0046] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims.

[0047] For example, in the heat sink 1 of this embodiment, multiple pin fins 3 were arranged in a staggered pattern, alternately offset in the first direction, but the arrangement of the pin fins 3 is not limited to this. For example, multiple pin fins 3 may be arranged in parallel. Also, in the heat sink 1 of this embodiment, the cross-sectional area of ​​the outer pin fins 3 was larger than that of the central pin fins 3 in both the first and second directions, but the cross-sectional area of ​​the outer pin fins 3 may be larger than that of the central pin fins 3 in at least one of the first and second directions. Furthermore, in the heat sink 1 of this embodiment, the cross-sectional area may change gradually or continuously from the central pin fins 3 to the outer pin fins 3, but the shape may be such that only the outermost pin fin has a larger cross-sectional area.

[0048] Furthermore, although the heat sink 1 in this embodiment is a forged product, it may also be a cast product. In the case of a cast product, molten metal material is supplied to the central side of the die 12, causing the molten metal material to extend outward from the die 12 and to flow into the holes 13a, 13b, and 13c. In addition, the heat sink 1 in this embodiment may also be manufactured by cutting or laser processing. [Examples]

[0049] [Example 1] A die was prepared with 10 holes in the row direction and 11 holes in the column direction, arranged in a staggered pattern in the column direction. The cross-sectional shape of the holes was circular. The distance between the centers of adjacent holes was 3 mm, and the depth of the holes was 7 mm. Figure 4 shows the diameters of the holes formed in the die. In Figure 4, the numbers in the squares represent the diameters of the holes (in mm). The diameter of the hole located at the 6th column (6th from the left in the X direction) x 5th row (5th from the top in the Y direction) is 0.96 mm. The diameters of the 10 holes in the 6th column are largest at the hole in the 5th row, and increase continuously by 1.11 times outward in the row direction (X direction). Similarly, the diameters of the 11 holes in the 5th row are largest at the hole in the 6th column, and increase continuously by 1.11 times outward in the column direction (Y direction). Furthermore, the diameters also increase continuously by 1.11 times diagonally from the hole at the 6th column x 5th row position. In other words, the diameters of the holes formed in the die increase radially from the hole at the 6th column x 5th row position.

[0050] Using the die described above, a heat sink was manufactured by forging. The die was placed on the die holder. Next, a cubic aluminum alloy material (A6063) with dimensions of 40 mm in length, 40 mm in width, and 20 mm in thickness was placed in the center of the die in both the column and row directions. Then, the metal material was forged by pressing it towards the die using a punch. A water-soluble lubricant was applied to the punch and die beforehand. The die temperature was set to 300°C, and the metal material temperature was set to 500°C. The punch press speed was set to 200 mm / second.

[0051] Forging was stopped when the height of the pin fins formed in the outermost holes reached 7 mm, and the formed heatsink was removed from the die. After the heatsink was allowed to cool to room temperature, the height of the pin fins in the center of the heatsink was measured. As a result, the height of the central pin fins was 6.99 mm, which was substantially the same as the height of the outermost pin fins (7 mm).

[0052] [Comparative Example 1] A die was fabricated by forming 10 holes in the row direction and 11 holes in the column direction, all with a diameter of 1.3 mm, in an aluminum alloy material. Then, a heat sink was manufactured in the same manner as in Example 1, except that this die was used. The height of the central pin fin of the obtained heat sink was measured. As a result, the height of the central pin fin was 4.79 mm, which was about 2.21 mm higher than the height of the outermost pin fin (7 mm). [Explanation of Symbols]

[0053] 1 Heatsink 2 Base section 3, 3a, 3b, 3c, 3d pin fins 10 Forging equipment 11 punches 12 dice 13a, 13b, 13c holes 14 Dice Holder 15 Anvil 16 Bottom plate 17 Dice support 18 knock pins 19 Knockout Plates 20 Ejectors 100 Metal materials

Claims

1. It includes a plate-shaped base portion and a plurality of pin fins provided on one surface of the base portion, Each of the aforementioned pin fins is arranged with spacing between them in a first direction and in a second direction perpendicular to the first direction. In at least one of the first and second directions, the cross-sectional area of ​​the pin fin located on the outer side is larger than the cross-sectional area of ​​the pin fin located on the central side. Larger pin fins are arranged radially from the central pin fin, A heat sink characterized in that multiple pin fins with the same cross-sectional area are arranged in a hexagonal shape surrounding the pin fin located on the central side, and multiple pin fins with larger cross-sectional areas are arranged in a hexagonal shape sequentially on the outside of this arrangement.

2. The heat sink according to claim 1, wherein in the two directions, the first and second directions, the cross-sectional area of ​​the pin fins located on the outer side is larger than the cross-sectional area of ​​the pin fins located on the central side.

3. The heat sink according to claim 1 or 2, wherein the plurality of pin fins are arranged such that the distance between the centers of adjacent pin fins is the same.

4. The heat sink according to any one of claims 1 to 3, wherein the cross-sectional area of ​​the pin fins increases in stages from the pin fin located in the center toward the pin fin located toward the outer side.

5. The heat sink according to any one of claims 1 to 3, wherein the cross-sectional area of ​​the pin fins increases continuously from the pin fin located in the center toward the pin fin located outwards.

6. The heat sink according to any one of claims 1 to 5, wherein the cross-sectional shapes of the multiple pin fins are similar.

7. The heat sink according to any one of claims 1 to 6, wherein the cross-sectional shape of each of the multiple pin fins is circular.

8. A heat sink according to any one of claims 1 to 7, which is a forged product.

9. A method for manufacturing a heat sink according to any one of claims 1 to 8, A step of preparing a die having a plurality of holes, wherein the plurality of holes are spaced apart in a first direction and a second direction perpendicular to the first direction, and in at least one of the first and second directions, the cross-sectional area of ​​the outer holes is larger than the cross-sectional area of ​​the central holes. A method for manufacturing a heat sink, comprising the steps of: placing a metal material on the central side of the die in the first and second directions; and applying pressure toward the die while the metal material is sealed, thereby stretching the metal material toward the outer circumference of the die and causing it to flow into the hole.

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