Heat spreader and method for manufacturing the same

Abstract

A heat spreader capable of improving heat transfer efficiency and a method for manufacturing the heat spreader are provided. [Solution] The heat spreader has a flat portion 30 having a first flat surface 31 and a second flat surface 32 opposite the first flat surface 31, a first convex portion 10 surrounded by the first flat surface 31 and protruding from the first flat surface 31 on the side opposite the second flat surface 32, and a second convex portion 20 surrounded by the second flat surface 32 and protruding from the second flat surface 32 on the side opposite the first flat surface 31.

Description

[Technical Field]

[0001] SUMMARY The present disclosure relates to heat spreaders and methods of manufacturing heat spreaders. [Background technology]

[0002] The heat spreader is used to transfer heat generated by the semiconductor chip to a heat sink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-91491 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-135459 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the increase in the amount of heat generated by semiconductor chips, there has been an increasing demand for improved heat transfer efficiency for heat sinks.

[0005] An object of the present disclosure is to provide a heat spreader and a method for manufacturing a heat spreader that can improve heat transfer efficiency. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, a heat spreader is provided having a flat portion having a first flat surface and a second flat surface opposite the first flat surface, a first convex portion surrounded by the first flat surface and protruding from the first flat surface on the side opposite the second flat surface, and a second convex portion surrounded by the second flat surface and protruding from the second flat surface on the side opposite the first flat surface. [Effects of the Invention]

[0007] According to the disclosed technology, heat transfer efficiency can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are diagrams illustrating a heat spreader according to a first embodiment. [Figure 2] 4A to 4C are cross-sectional views (part 1) illustrating a method for manufacturing the heat spreader according to the first embodiment. [Figure 3] 5A to 5C are cross-sectional views (part 2) illustrating the method for manufacturing the heat spreader according to the first embodiment. [Figure 4] 4A and 4B are diagrams (part 1) illustrating a set of molded parts used in the method for manufacturing the heat spreader according to the first embodiment. [Figure 5] 6A and 6B are diagrams (part 2) illustrating a set of molded parts used in the method for manufacturing the heat spreader according to the first embodiment. [Figure 6] 10 is a view (part 3) illustrating a set of molded parts used in the method for manufacturing the heat spreader according to the first embodiment. FIG. [Figure 7] 10A and 10B are diagrams (part 4) illustrating a set of molded parts used in the method for manufacturing the heat spreader according to the first embodiment. [Figure 8] 3A to 3C are cross-sectional views illustrating a method for manufacturing a semiconductor device using the heat spreader according to the first embodiment. [Figure 9] 10A and 10B are diagrams illustrating a heat spreader according to a second embodiment. [Figure 10] 10A and 10B are diagrams illustrating a heat spreader according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following embodiments will be described in detail with reference to the accompanying drawings. Note that in this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals to avoid redundant description. In the following description, an XYZ Cartesian coordinate system is used, and the +Z side, viewed from an arbitrary point, may be referred to as the upper side, upper side, or top, and the -Z side may be referred to as the lower side, lower side, or bottom. The lower surface may be referred to as the one surface or bottom surface, and the upper surface may be referred to as the other surface or top surface. However, this coordinate system is defined for the purpose of explanation and does not limit the orientation of the heat spreader. The heat spreader can be used upside down or positioned at any angle. Furthermore, a planar view refers to viewing an object from the normal direction of one surface of the heat spreader, and a planar shape refers to the shape of the object viewed from the normal direction of one surface of the heat spreader. In this disclosure, a flat surface refers to a surface that is not intentionally curved or has no irregularities. The arithmetic mean roughness Ra of the flat surface is 0.125 μm or less.

[0010] (First embodiment) A first embodiment will be described. The first embodiment relates to a heat spreader.

[0011] [Heat spreader structure] The structure of the heat spreader according to the first embodiment will be described. Fig. 1 is a diagram illustrating the heat spreader according to the first embodiment. Fig. 1(a) is a plan view, and Fig. 1(b) is a cross-sectional view. Fig. 1(b) corresponds to a cross-sectional view taken along line Ib-Ib in Fig. 1(a).

[0012] 1, the heat spreader 1 according to the first embodiment has a flat portion 30, a first protruding portion 10, a second protruding portion 20, an extending portion 40, and a flange portion 60. The heat spreader 1 is formed of, for example, a single metal plate 70. The metal plate 70 contains, for example, copper (Cu). The metal plate 70 may be a copper plate.

[0013] The flat portion 30 has a first flat surface 31 and a second flat surface 32 opposite to the first flat surface 31. The first flat surface 31 is on the −Z side of the second flat surface 32.

[0014] The first protrusion 10 is surrounded by the first flat surface 31 and protrudes from the first flat surface 31 toward the opposite side (-Z side) of the second flat surface 32 (+Z side). The first protrusion 10 has a first curved surface 11. The first curved surface 11 is continuous with the first flat surface 31 and bulges from the first flat surface 31 toward the -Z side. In this embodiment, the entire surface of the -Z side of the first protrusion 10 is the first curved surface 11. The height of the first protrusion 10 relative to the first flat surface 31 is, for example, 0.005 mm or more and 0.5 mm or less. For example, in a plan view, the outer shape of the first protrusion 10 has two straight line portions along the Y axis and two arc portions connecting both ends of the straight line portions in the Y axis direction, and the dimension in the Y axis direction is larger than the dimension in the X axis direction. The outer shape of the first protrusion 10 may be elliptical, rectangular, or circular.

[0015] The second protrusion 20 is surrounded by the second flat surface 32 and protrudes from the second flat surface 32 toward the opposite side (+Z side) from the first flat surface 31 (-Z side). The second protrusion 20 has a second curved surface 21. The second curved surface 21 is continuous with the second flat surface 32 and bulges from the second flat surface 32 toward the +Z side. In this embodiment, the entire surface of the +Z side of the second protrusion 20 is the second curved surface 21. The height of the second protrusion 20 relative to the second flat surface 32 is, for example, 0.005 mm or more and 0.5 mm or less. For example, in a plan view, the outer shape of the second protrusion 20 has two straight line portions along the Y axis and two arc portions connecting both ends of the straight line portions in the Y axis direction, and the dimension in the Y axis direction is larger than the dimension in the X axis direction. The outer shape of the second protrusion 20 may be elliptical, rectangular, or circular.

[0016] The extending portion 40 is connected to the flat portion 30 and extends from the first flat surface 31 to the opposite side (-Z side) from the second flat surface 32 side (+Z side). For example, in a plan view, the extending portion 40 surrounds the first convex portion 10. The extending portion 40 is spaced apart from the first convex portion 10. The height of the extending portion 40 relative to the first flat surface 31 is greater than the height of the first convex portion 10, and is, for example, 0.1 mm or more and 1 mm or less.

[0017] The flange portion 60 extends from a part of the flat portion 30 and the extending portion 40 in a direction away from the first protrusion 10. For example, the extending portion 40 and the flange portion 60 have surfaces flush with each other on the −Z side.

[0018] The heat spreader 1 has a cavity 50 defined by the first flat surface 31, the first curved surface 11, and the side surface of the extension 40 facing the first protrusion 10. The depth of the cavity 50 is, for example, not less than 0.1 mm and not more than 1 mm.

[0019] [Heat spreader manufacturing method] A method for manufacturing the heat spreader 1 according to the first embodiment will now be described. Figures 2 and 3 are cross-sectional views illustrating the method for manufacturing the heat spreader 1 according to the first embodiment. Figures 4 to 7 are views illustrating sets of molded parts used in the method for manufacturing the heat spreader 1 according to the first embodiment. Figures 4(a), 5(a), 6(a), and 7(a) are top views illustrating one of the molded parts, and Figures 4(b), 5(b), 6(b), and 7(b) are bottom views illustrating the other of the molded parts.

[0020] First, as shown in Fig. 2(a), a metal plate 70 is prepared. The metal plate 70 has a first surface 71 and a second surface 72 opposite to the first surface 71. The first surface 71 is on the -Z side of the second surface 72. For example, the first surface 71 and the second surface 72 are flat surfaces.

[0021] Next, as shown in Fig. 2(b), the metal plate 70 is pressed using the formed parts 110 and 120. The material of the formed parts 110 and 120 includes a cemented carbide such as tungsten carbide (WC). Fig. 2(b) corresponds to a cross-sectional view taken along line IIb-IIb in Fig. 4(a) and Fig. 4(b).

[0022] As shown in Figures 2(b) and 4(a), the molded part 110 has a base 117 and a protruding portion 118. A recess 119 is formed at the top of the protruding portion 118. The base 117 has a flat surface 111 that is pressed against the first surface 71. The protruding portion 118 is used to form the recess 51 that will become the basis of the cavity 50 in the metal plate 70, and the outer shape of the protruding portion 118 matches the outer shape of the cavity 50 in a plan view. The protruding portion 118 is surrounded by the flat surface 111 and protrudes from the flat surface 111 on the +Z side. The protruding portion 118 has a convex surface 112. The convex surface 112 is continuous with the flat surface 111 and bulges from the flat surface 111 on the +Z side. The recess 119 is used to form the first protruding portion 10. The recess 119 has a concave surface 114. The concave surface 114 is continuous with the apex of the convex surface 112 and recessed from the apex of the convex surface 112 toward the −Z side.

[0023] As shown in Figures 2(b) and 4(b), the molded part 120 has a flat surface 121 that is pressed against the second surface 72. A recess 129 is formed in the molded part 120. The recess 129 is for forming the second protrusion 20. The recess 129 has a concave surface 124. The concave surface 124 is continuous with the flat surface 121 and is recessed from the flat surface 121 toward the +Z side. The shape of the concave surface 124 matches the shape of the second curved surface 21.

[0024] By press-forming the metal plate 70 using the molded parts 110 and 120, the recessed parts 51 and the first protruding parts 10 are formed on the first surface 71 of the metal plate 70, and the second protruding parts 20 are formed on the second surface 72. In this way, by press-forming the metal plate 70 using the molded parts 110 and 120, the first surface 71 and the second surface 72 are processed simultaneously.

[0025] After the metal plate 70 is pressed using the formed parts 110 and 120, the metal plate 70 is pressed using the formed parts 210 and 220 as shown in Fig. 2(c). The material of the formed parts 210 and 220 includes a cemented carbide such as tungsten carbide (WC). Fig. 2(c) corresponds to a cross-sectional view taken along line IIc-IIc in Figs. 5(a) and 5(b).

[0026] As shown in FIGS. 2(c) and 5(a), the molded part 210 has a base 217 and a protruding portion 218. A recess 219 is formed at the top of the protruding portion 218. The base 217 has a flat surface 211 that is pressed against the first surface 71. The protruding portion 218 is used to enlarge the recess 51 and form the recess 52 in the metal plate 70. In a plan view, the outer shape of the protruding portion 218 matches the outer shape of the cavity 50. The height of the protruding portion 218 is greater than the depth of the cavity 50. The protruding portion 218 is surrounded by the flat surface 211 and protrudes from the flat surface 211 toward the +Z side. The protruding portion 218 has a side wall surface 212 and a flat surface 213. The side wall surface 212 is continuous with the flat surface 211 and is parallel to the Z axis. In a plan view, the shape of the side wall surface 212 matches the shape of the side wall surface of the cavity 50. The flat surface 213 is continuous with the side wall surface 212 and is perpendicular to the Z axis. The shape of the flat surface 213 matches the shape of the first flat surface 31, which is the bottom surface of the cavity 50. The recess 219 has a concave surface 214. The concave surface 214 is continuous with the flat surface 213 and is recessed from the flat surface 213 toward the -Z side. The shape of the concave surface 214 matches the shape of the first curved surface 11.

[0027] As shown in Figures 2(c) and 5(b), the molded part 220 has a flat surface 221 that is pressed against the second surface 72. A recess 229 is formed in the molded part 220. The recess 229 has a concave surface 224. The concave surface 224 is continuous with the flat surface 221 and is recessed from the flat surface 221 toward the +Z side. The shape of the concave surface 224 matches the shape of the second curved surface 21.

[0028] By pressing the metal plate 70 using the molded parts 210 and 220, a recess 52 that is an enlarged version of the recess 51 is formed on the first surface 71 of the metal plate 70.

[0029] After pressing the metal plate 70 using the formed parts 210 and 220, as shown in Fig. 3(a), the metal plate 70 is pressed using the formed parts 310 and 320. The material of the formed parts 310 and 320 includes a cemented carbide such as tungsten carbide (WC). Fig. 3(a) corresponds to a cross-sectional view taken along line IIIa-IIIa in Fig. 6(a) and Fig. 6(b).

[0030] As shown in FIGS. 3(a) and 6(a), the molded part 310 has a base 317 and a protruding portion 318. A recess 319 is formed at the top of the protruding portion 318. The base 317 has a flat surface 311 that is pressed against the first surface 71. The protruding portion 318 is used to form the cavity 50 in the metal plate 70, and the shape of the protruding portion 318 matches the shape of the cavity 50. The height of the protruding portion 318 matches the depth of the cavity 50. The protruding portion 318 is surrounded by the flat surface 311 and protrudes from the flat surface 311 toward the +Z side. The protruding portion 318 has a side wall surface 312 and a flat surface 313. The side wall surface 312 is continuous with the flat surface 311 and is parallel to the Z axis. The shape of the side wall surface 312 matches the shape of the side wall surface of the cavity 50. The flat surface 313 is continuous with the side wall surface 312 and is perpendicular to the Z axis. The shape of the flat surface 313 matches the shape of the first flat surface 31, which is the bottom surface of the cavity 50. The recess 319 has a concave surface 314. The concave surface 314 is continuous with the flat surface 313 and is recessed from the flat surface 313 toward the -Z side. The shape of the concave surface 314 matches the shape of the first curved surface 11.

[0031] As shown in Figures 3(a) and 6(b), the molded part 320 has a flat surface 321 that is pressed against the second surface 72. A recess 329 is formed in the molded part 320. The recess 329 has a concave surface 324. The concave surface 324 is continuous with the flat surface 321 and is recessed from the flat surface 321 toward the +Z side. The shape of the concave surface 324 matches the shape of the second curved surface 21.

[0032] By pressing the metal plate 70 using the molded parts 310 and 320, the thickest part of the metal plate 70 is compressed, so that the thickness of the thickest part of the metal plate 70 matches the thickness of the thickest part of the heat spreader 1, and a cavity 50 is formed in the first surface 71 of the metal plate 70.

[0033] After pressing the metal plate 70 using the formed parts 310 and 320, as shown in Fig. 3(b), the metal plate 70 is pressed using the formed parts 410 and 420. The material of the formed parts 410 and 420 includes a cemented carbide such as tungsten carbide (WC). Fig. 3(b) corresponds to a cross-sectional view taken along line IIIb-IIIb in Figs. 7(a) and 7(b).

[0034] As shown in FIGS. 3(b) and 7(a), the molded part 410 has a base 417 and a protruding portion 418. A recess 419 is formed at the top of the protruding portion 418. The base 417 has a flat surface 411 that is pressed against the first surface 71. The shape of the protruding portion 418 matches the shape of the cavity 50. The protruding portion 418 is surrounded by the flat surface 411 and protrudes from the flat surface 411 toward the +Z side. The protruding portion 418 has a side wall surface 412 and a flat surface 413. The side wall surface 412 is continuous with the flat surface 411 and is parallel to the Z axis. The shape of the side wall surface 412 matches the shape of the side wall surface of the cavity 50. The flat surface 413 is continuous with the side wall surface 412 and is perpendicular to the Z axis. The shape of the flat surface 413 matches the shape of the first flat surface 31, which is the bottom surface of the cavity 50. The recess 419 has a concave surface 414. The concave surface 414 is continuous with the flat surface 413 and is recessed from the flat surface 413 toward the −Z side. The shape of the concave surface 414 matches the shape of the first curved surface 11.

[0035] As shown in Figures 3(b) and 7(b), the molded part 420 has a flat surface 421 that is pressed against the second surface 72. Recesses 428 and 429 are formed in the molded part 420. The recess 428 has a side wall surface 422 and a flat surface 423 that is part of the bottom surface. The side wall surface 422 is continuous with the flat surface 421 and is parallel to the Z axis. The shape of the side wall surface 422 matches the shape of the side wall surface of the flat portion 30. The flat surface 423 is continuous with the side wall surface 422 and is perpendicular to the Z axis. The shape of the flat surface 423 matches the shape of the second flat surface 32. The recess 429 has a concave surface 424. The concave surface 424 is continuous with the flat surface 423 and is concave from the flat surface 423 toward the +Z side. The shape of the concave surface 424 matches the shape of the second curved surface 21.

[0036] Pressing the metal plate 70 using the molding parts 410 and 420 compresses a portion of the thickest part of the metal plate 70, forming the flat portion 30 with the second flat surface 32, the extension portion 40, and the flange portion 60 in the metal plate 70.

[0037] After the metal plate 70 is pressed using the formed parts 410 and 420, a part of the flange portion 60 is cut off as shown in FIG. 3(c).

[0038] In this manner, the heat spreader 1 according to the first embodiment can be manufactured.

[0039] [Method for manufacturing a semiconductor device using a heat spreader] A method for manufacturing a semiconductor device using the heat spreader 1 according to the first embodiment will now be described. Figure 8 is a cross-sectional view illustrating a method for manufacturing a semiconductor device using the heat spreader 1 according to the first embodiment.

[0040] 8(a), a mounting substrate 82 on which a semiconductor chip 80 is mounted is prepared. For example, the semiconductor chip 80 has external terminals 81, and is flip-chip mounted on the mounting substrate 82. An underfill resin layer 83 is provided between the semiconductor chip 80 and the mounting substrate 82.

[0041] Next, the heat spreader 1 is placed on the semiconductor chip 80. At this time, a paste-like first thermal interface material (TIM) 91 is provided between the first protrusion 10 and the semiconductor chip 80, and an adhesive 84 is provided between the extension portion 40 and the flange portion 60 and the mounting substrate 82. For example, the first TIM 91 contains indium (In), and the adhesive 84 contains silicone resin. Thereafter, the heat spreader 1 is pressed toward the mounting substrate 82 to spread the first TIM 91 and adhesive 84, and the first TIM 91 and adhesive 84 are hardened.

[0042] 8(b), the heat sink 88 is placed on the heat spreader 1. At this time, a paste-like second TIM 92 is provided between the heat sink 88 and the second protrusion 20. For example, the second TIM 92 contains indium (In). Thereafter, the heat sink 88 is pressed toward the heat spreader 1 to spread the second TIM 92, thereby hardening the second TIM 92.

[0043] In this manner, the semiconductor device 5 can be manufactured.

[0044] Because the heat spreader 1 has the first protrusions 10, even if air is contained in the paste-like first TIM 91, the air can be easily expelled from the first TIM 91 when the first TIM 91 is spread out. In particular, the first protrusions 10 have the first curved surfaces 11, which makes it easy to expel air. Therefore, air is less likely to remain in the first TIM 91 after hardening, and the efficiency of heat transfer from the semiconductor chip 80 to the heat spreader 1 can be improved.

[0045] Furthermore, because the heat spreader 1 has the second protrusions 20, even if air is contained in the paste-like second TIM 92, the air is easily expelled from the second TIM 92 when the second TIM 92 is spread out. In particular, the second protrusions 20 have the second curved surfaces 21, which makes it easy to expel air. Therefore, air is less likely to remain in the second TIM 92 after hardening, and the efficiency of heat transfer from the heat spreader 1 to the heat sink 88 can be improved.

[0046] Therefore, the heat spreader 1 can improve the efficiency of heat transfer from the semiconductor chip 80 to the heat sink 88.

[0047] Furthermore, in the press working of the metal plate 70 using the molded parts 110 and 120, the first surface 71 and the second surface 72 are processed simultaneously, so that the first convex portion 10 and the second convex portion 20 can be formed simultaneously.

[0048] It is preferable that the area of ​​the second protrusion 20 is larger than the area of ​​the first protrusion 10 in a plan view. When the area of ​​the second protrusion 20 is larger than the area of ​​the first protrusion 10 in a plan view, the heat generated in the semiconductor chip 80 can be widely diffused from the first protrusion 10 to the second protrusion 20 when it is transferred to the heat sink 88 via the heat spreader 1. This allows for better heat transfer characteristics to be obtained.

[0049] In plan view, the first protrusion 10 and the second protrusion 20 may overlap, or the first protrusion 10 may be located inside the second protrusion 20. In these cases, heat from the semiconductor chip 80 on the first protrusion 10 side can be efficiently transferred to the heat sink 88 on the second protrusion 20 side, improving the heat transfer characteristics.

[0050] (Second embodiment) A second embodiment will now be described. The second embodiment differs from the first embodiment mainly in the arrangement of the first protrusions 10. FIG. 9 illustrates a heat spreader according to the second embodiment. FIG. 9(a) is a plan view, and FIG. 9(b) is a cross-sectional view. FIG. 9(b) corresponds to a cross-sectional view taken along line IXb-IXb in FIG. 9(a).

[0051] As shown in FIG. 9, in the heat spreader 2 according to the second embodiment, the center of the first protrusion 10 is offset from the center of the cavity 50 in a plan view.

[0052] The other configuration of the heat spreader 2 is the same as that of the heat spreader 1.

[0053] The second embodiment can also achieve the same effects as the first embodiment. Furthermore, even if the position of the semiconductor chip 80 on the mounting substrate 82 is offset from the position where the adhesive 84 is provided, the distance between the first protrusion 10 and the semiconductor chip 80 can be reduced, and the heat generated in the semiconductor chip 80 can be transferred to the heat spreader 2 with high efficiency.

[0054] (Third embodiment) A third embodiment will now be described. The third embodiment differs from the first embodiment mainly in the configuration of the first protrusions 10 and the second protrusions 20. FIG. 10 illustrates a heat spreader according to the third embodiment. FIG. 10(a) is a plan view, and FIG. 10(b) is a cross-sectional view. FIG. 10(b) corresponds to a cross-sectional view taken along line Xb-Xb in FIG. 10(a).

[0055] As shown in Figure 10, in the heat spreader 3 of the third embodiment, the -Z side surface of the first convex portion 10 has a first curved surface 11 and a flat surface 12, and the +Z side surface of the second convex portion 20 has a second curved surface 21 and a flat surface 22.

[0056] The flat surface 12 is located inside the first flat surface 31 in a plan view and is spaced apart from the first flat surface 31. The first curved surface 11 is located between the first flat surface 31 and the flat surface 12, is connected to the first flat surface 31 and the flat surface 12, and bulges out from the first flat surface 31 toward the -Z side.

[0057] In a plan view, the flat surface 22 is located inside the second flat surface 32 and is spaced apart from the second flat surface 32. The second curved surface 21 is located between the second flat surface 32 and the flat surface 22, is connected to the second flat surface 32 and the flat surface 22, and bulges out from the second flat surface 32 toward the +Z side.

[0058] The other configuration of the heat spreader 3 is the same as that of the heat spreader 1.

[0059] The third embodiment can also achieve the same effects as the first embodiment. Furthermore, since the -Z side surface of the first protrusion 10 has the flat surface 12, the heat spreader 3 can be made less likely to tilt with respect to the semiconductor chip 80. Similarly, since the +Z side surface of the second protrusion 20 has the flat surface 22, the heat sink 88 can be made less likely to tilt with respect to the heat spreader 3.

[0060] The planar shapes, positions, and sizes of the first protrusion 10 and the second protrusion 20 are not restricted to one another and can be selected appropriately depending on the respective positions, sizes, etc. of the semiconductor chip 80 and the heat sink 88. In addition, there may be two or more first protrusions 10 inside the cavity 50.

[0061] Although the preferred embodiments have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0062] 1, 2, 3 Heat spreader 5. Semiconductor Devices 10 First protrusion 11 1st surface 20 Second convex part 21 Second surface 30 Flat area 31 1st flat surface 32 Second flat surface 40 Extension 50 cavities 70 metal plate 80 Semiconductor Chips 82 Mounting board 88 Heatsink 91 1st TIM 92 2nd TIM 110, 120, 210, 220, 310, 320, 410, 420 Molded parts

Claims

1. a flat portion including a first flat surface and a second flat surface opposite to the first flat surface; a first protrusion that is surrounded by the first flat surface and protrudes from the first flat surface toward an opposite side to the second flat surface; a second protrusion that is surrounded by the second flat surface and protrudes from the second flat surface to a side opposite to the first flat surface; A heat spreader having

2. The heat spreader according to claim 1 , further comprising an extension portion that is connected to the flat portion and extends from the first flat surface to a side opposite to the second flat surface.

3. The heat spreader according to claim 2 , wherein the extension portion surrounds the first protrusion in a plan view.

4. The heat spreader according to claim 2 or 3, wherein the flat portion and the extending portion are formed from a single metal plate.

5. the first convex portion has a first curved surface that is continuous with the first flat surface and bulges out from the first flat surface toward an opposite side to the second flat surface, The heat spreader according to claim 1 , wherein the second convex portion has a second curved surface that is continuous with the second flat surface and bulges out from the second flat surface toward an opposite side to the first flat surface.

6. The heat spreader according to claim 1 , wherein an area of ​​the second protrusions is larger than an area of ​​the first protrusions in a plan view.

7. providing a metal plate having a first surface and a second surface opposite the first surface; By pressing the metal plate one or more times, a flat portion including a first flat surface and a second flat surface opposite to the first flat surface; a first protrusion that is surrounded by the first flat surface and protrudes from the first flat surface toward an opposite side to the second flat surface; a second protrusion that is surrounded by the second flat surface and protrudes from the second flat surface to a side opposite to the first flat surface; and forming and the first flat surface is formed on the first surface; The second flat surface is formed on the second surface.

8. The method for manufacturing a heat spreader according to claim 7 , wherein the step of forming the flat portion, the first convex portion, and the second convex portion on the metal plate includes the step of simultaneously processing the first surface and the second surface.

9. The method for manufacturing a heat spreader according to claim 7 or 8, wherein an extension portion that is connected to the flat portion and extends from the first flat surface to a side opposite to the second flat surface is formed by the press working.

10. The method for manufacturing a heat spreader according to claim 9 , wherein the extension portion surrounds the first protrusion portion in a plan view.

11. the first convex portion has a first curved surface that is continuous with the first flat surface and bulges out from the first flat surface toward an opposite side to the second flat surface, The method for manufacturing a heat spreader according to claim 7 or 8, wherein the second convex portion has a second curved surface that is continuous with the second flat surface and bulges out from the second flat surface toward an opposite side to the first flat surface.

12. The method for manufacturing a heat spreader according to claim 7 or 8, wherein an area of ​​the second protrusions is larger than an area of ​​the first protrusions in a plan view.

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