Cold plate

Abstract

A cold plate according to one aspect of the present disclosure comprises a base part and a cover part. A plurality of fins are disposed on the base part. The cover part covers the plurality of fins. The base part is joined to the cover part outside a region in which the plurality of fins are disposed. The plurality of fins include a plurality of brazed fins, the tip ends of which are joined to the cover part by a brazing material. The interval between tip ends of the plurality of brazed fins is greater than the interval between the base ends of the plurality of fins.

Description

Cold plate

[0001] This disclosure relates to a cold plate. This application claims priority based on Japanese Patent Application No. 2024-196594 filed in Japan on November 11, 2024, the content of which is incorporated herein by reference.

[0002] Conventionally, the cooling method of air cooling by fans has been the mainstream for computing servers used in data centers, companies, research institutions, etc. On the other hand, semiconductor computing devices for AI, which are expected to expand in the future, generate much higher heat than conventional ones. For such heat sources, a water cooling system with a higher cooling capacity than the air cooling method may be used.

[0003] In a water cooling system, cooling is performed by bringing a cold plate into contact with heat sources such as a CPU (Central Processing Unit) and a GPU (Graphical Processing Unit). The cold plate is formed, for example, by joining a base part where a plurality of fins are arranged and a cover part that covers the plurality of fins.

[0004] Patent Document 1 discloses a technique for joining the base part and the cover part by brazing.

[0005] Japanese Patent Application Laid-Open No. 2018-081997

[0006] In the above-described conventional technology, there is still room for further improvement in terms of further enhancing the joining strength between the base part and the cover part.

[0007] This disclosure provides a technique capable of enhancing the joining strength between the base part and the cover part.

[0008] The cold plate according to one aspect of this disclosure includes a base part and a cover part. The base part has a plurality of fins arranged thereon. The cover part covers the plurality of fins. The base part is joined to the cover part outside the region where the plurality of fins are arranged. The plurality of fins include a plurality of brazed fins whose tip parts are joined to the cover part by a brazing material. The interval at the tip parts between the plurality of brazed fins is wider than the interval at the base end parts between the plurality of fins.

[0009] According to this disclosure, the bonding strength between the base portion and the cover portion can be increased.

[0010] Figure 1 is a schematic plan view of a cold plate according to an exemplary embodiment. Figure 2 is a schematic cross-sectional view taken along the line II-II shown in Figure 1. Figure 3 is a schematic cross-sectional view showing region III shown in Figure 2. Figure 4 is a schematic cross-sectional view showing the configuration of a brazed fin according to another exemplary embodiment (part 1). Figure 5 is a schematic cross-sectional view showing the configuration of a brazed fin according to another exemplary embodiment (part 2). Figure 6 is a schematic cross-sectional view of a cold plate according to another exemplary embodiment (part 3). Figure 7 is a schematic cross-sectional view showing the configuration of a brazed fin according to another exemplary embodiment (part 4). Figure 8 is a schematic cross-sectional view showing the configuration of a brazed fin according to another exemplary embodiment (part 5). Figure 9 is a schematic cross-sectional view showing the configuration of a fin according to another exemplary embodiment (part 6).

[0011] The embodiments for implementing the cold plate according to this disclosure (hereinafter referred to as "Embodiments") will be described in detail below with reference to the drawings. However, this disclosure is not limited by these embodiments. Furthermore, each embodiment can be combined as appropriate, provided that the processing content is not inconsistent. Also, the same parts are denoted by the same reference numerals in each of the following embodiments, and redundant descriptions are omitted.

[0012] Furthermore, in the drawings referenced below, for the sake of clarity, mutually orthogonal X-axis, Y-axis, and Z-axis directions are defined, and a Cartesian coordinate system is shown with the Z-axis direction being vertically upward. Note that the horizontal direction in this disclosure refers to the XY plane direction.

[0013] (Exemplary Embodiment) First, the configuration of the cold plate 100 according to an exemplary embodiment will be described with reference to Figures 1 to 3. Figure 1 is a schematic plan view of the cold plate 100 according to an exemplary embodiment. Figure 2 is a schematic cross-sectional view taken along the line II-II shown in Figure 1. Figure 3 is a schematic cross-sectional view showing region III shown in Figure 2.

[0014] As shown in Figures 1 and 2, the cold plate 100 has a water-cooled jacket structure in which a coolant flow path with fins for heat exchange is formed in the internal space. The coolant is, for example, a refrigerant. As the refrigerant, for example, an antifreeze such as an aqueous solution of ethylene glycol or propylene glycol, or water may be used.

[0015] The cold plate 100 comprises a base portion 10 and a cover portion 20. The base portion 10 and the cover portion 20 are formed of, for example, metal. Specifically, the base portion 10 and the cover portion 20 may be formed of a metal with relatively high thermal conductivity, such as copper or aluminum.

[0016] The base portion 10 has a first surface 11 and a second surface 12 located opposite the first surface 11. The first surface 11 may be a heat receiving surface that receives heat from a heat source such as a CPU or GPU.

[0017] Multiple fins 30 are arranged in the central part of the second surface 12. The multiple fins 30 extend from the second surface 12 in a direction perpendicular to the second surface 12 (negative Z-axis direction). In addition, the multiple fins 30 extend in a direction along one side of the cold plate 100 (in this case, the Y-axis direction) in a plan view, and are arranged parallel to each other at equal intervals in a direction along the other side of the cold plate 100 (in this case, the X-axis direction).

[0018] The multiple fins 30 may be so-called skived fins formed by skiving. In this case, the multiple fins 30 are integral with the base portion 10. "Integrated" means that the multiple fins 30 and the base portion 10 are integrated without the use of separate components such as brazing material. The multiple fins 30 may also be joined to the base portion 10 via a bonding material such as brazing material. As such fins, so-called stacked fins obtained by stacking fins punched out from a metal sheet are known.

[0019] The fin 30, as a skived fin or stacked fin, is thin plate-shaped. However, it is not limited to this. The fin 30 may also be columnar. That is, multiple fins 30 may be pin fins.

[0020] The base portion 10 is joined to the cover portion 20 outside of region A where the multiple fins 30 are arranged. Specifically, "outside of region A" means the horizontally outside of region A.

[0021] In this embodiment, the base portion 10 is rectangular in plan view. However, it is not limited to this; for example, the base portion 10 may be a polygon with pentagons or more sides in plan view, or it may be triangular. Alternatively, the base portion 10 may be circular in plan view.

[0022] The cover portion 20 is joined to the base portion 10. The base portion 10 and the cover portion 20 are joined, for example, by brazing with a brazing material 40. However, the base portion 10 and the cover portion 20 may also be joined by laser welding.

[0023] The cover portion 20, which is joined to the base portion 10, covers the multiple fins 30. Specifically, the cover portion 20 has a first portion 201 which is spaced apart from the base portion 10, and a plurality of second portions 202 which extend from the first portion 201 toward the base portion 10. For example, as shown in Figure 2, when the cold plate 100 is positioned with the first surface 11 of the base portion 10 facing upward, the first portion 201 corresponds to the bottom of the cover portion 20 and covers the multiple fins 30 from below. The second portions 202 correspond to the sides of the cover portion 20 and cover the multiple fins 30 from the sides.

[0024] The cover portion 20 has an opposing surface 21 and a side wall surface 22. The opposing surface 21 is a surface formed by the first portion 201 on the inner surface of the cover portion 20. The opposing surface 21 faces the second surface 12 of the base portion 10, on which a plurality of fins 30 are arranged, at a distance from it. The side wall surface 22 is a surface formed by the second portion 202 on the inner surface of the cover portion 20. The side wall surface 22 extends from the opposing surface 21 toward the base portion 10.

[0025] Furthermore, the cover portion 20 has a joining surface 23. The joining surface 23 is the tip surface of the second portion 202 and faces the second surface 12 of the base portion 10. When the joining surface 23 of the cover portion 20 and the second surface 12 of the base portion 10 are joined, an internal space is formed between the cover portion 20 and the base portion 10. A refrigerant flows through the internal space.

[0026] As shown in Figure 3, the plurality of fins 30 include a plurality of brazed fins 31 whose tip portion 31A is joined to the cover portion 20 by brazing material 50.

[0027] The spacing L1 between the tip portions 31A of multiple brazed fins 31 is wider than the spacing L2 between the base portions 30B (see Figure 2) of multiple fins 30. Specifically, in an exemplary embodiment, the thickness L3 at the tip portion 31A of the brazed fin 31 is thinner than the thickness L4 at the base portion 31B (see Figure 2) of the brazed fin 31. More specifically, in an exemplary embodiment, the brazed fin 31 has a step 31C between the tip portion 31A and the portion other than the tip portion 31A. The tip portion 31A of the brazed fin 31 has a constant thickness L3 from the portion where the step 31C is located toward the brazing material 50.

[0028] The tip portion 31A of the brazed fin 31 has a step 31C on one side in the horizontal direction of the brazed fin 31, but this is not limited to this; for example, the step 31C may be located on both sides in the horizontal direction of the brazed fin 31. The brazed fin 31 having the step 31C can be formed, for example, by cutting or polishing the tip portion of a fin having a certain thickness.

[0029] In the conventional technology described above, brazing the tips of the fins 30 to the cover portion 20 is considered in order to increase the joint strength between the base portion 10 and the cover portion 20. However, if the tips of the fins 30 and the cover portion 20 are simply brazed, there is a risk that the brazing material 50 will crawl up the fins 30 due to capillary action. If the brazing material 50 is interposed between the fins 30, the flow of refrigerant between the fins 30 will be obstructed by the brazing material 50, which may reduce the cooling efficiency of the cold plate 100. Therefore, there is a need for a technology that can increase the joint strength between the base portion 10 and the cover portion 20 while suppressing the decrease in cooling efficiency.

[0030] In contrast, according to the cold plate 100 of an exemplary embodiment, by brazing the fins 30 and the cover portion 20, the bonding strength between the base portion 10 and the cover portion 20 can be increased compared to the case where the base portion 10 and the cover portion 20 are joined only outside the region A where the multiple fins 30 are arranged.

[0031] If the tip portion 31A of the fin 30 and the cover portion 20 are simply brazed together, there is a risk that the brazing material 50 will crawl up the fin 30 due to capillary action. If the brazing material 50 is interposed between the fins 30, the flow of refrigerant between the fins 30 will be obstructed by the brazing material 50, which may reduce the cooling efficiency of the cold plate 100. In contrast, the cold plate 100 according to the exemplary embodiment makes it difficult for capillary action to occur by making the spacing L1 between the tip portions 31A of the multiple brazed fins 31 wider than the spacing L2 between the base portions 30B of the multiple fins 30. As capillary action is reduced, the brazing material 50 is less likely to crawl up the fins 30. In other words, the flow of refrigerant between the fins 30 is less likely to be obstructed by the brazing material 50. Therefore, according to the cold plate 100 according to the exemplary embodiment, it is possible to increase the joint strength between the base portion 10 and the cover portion 20 while suppressing a decrease in cooling efficiency.

[0032] Furthermore, in the exemplary embodiment of the cold plate 100, the thickness L3 at the tip portion 31A of the brazed fin 31 is made thinner than the thickness L4 at the base portion 31B, thereby making the spacing L1 between the tip portions 31A of multiple brazed fins 31 wider than the spacing L2 between the base portions 30B of multiple fins 30. This makes it possible to increase the bonding strength between the base portion 10 and the cover portion 20 while suppressing a decrease in cooling efficiency.

[0033] Furthermore, in the exemplary embodiment of the cold plate 100, a step 31C is provided between the tip portion 31A and the portion other than the tip portion 31A, which allows the brazing material 50 to be blocked by the step 31C. Therefore, even if the brazing material 50 were to crawl up the brazing fin 31, the possibility of the brazing material 50 crawling up towards the base end portion 31B beyond the step 31C can be reduced.

[0034] (Another exemplary embodiment (Part 1)) Next, a cold plate 100 according to another exemplary embodiment (Part 1) will be described with reference to Figure 4. Figure 4 is a schematic cross-sectional view showing the configuration of a brazed fin 31 according to another exemplary embodiment (Part 1). In the following embodiments, the same parts are denoted by the same reference numerals, and redundant explanations are omitted.

[0035] As shown in Figure 4, the tip portion 31A of the brazed fin 31 may have a shape in which the thickness L3 gradually decreases toward the brazing material 50. For example, the tip portion 31A of the brazed fin 31 may be tapered. In this case, the distance L1 between the tip portions 31A of adjacent brazed fins 31 gradually increases toward the brazing material 50. A brazed fin 31 having a tapered tip portion 31A can be formed, for example, by etching the tip portion of a fin having a certain thickness.

[0036] Thus, the cold plate 100 according to another exemplary embodiment (Part 1) has brazing fins 31 in which the thickness L3 of the tip portion 31A gradually decreases toward the brazing material 50, so that capillary action is less likely to occur toward the brazing material 50. For this reason, the cold plate 100 according to another exemplary embodiment (Part 1) can suitably suppress the upward movement of the brazing material 50.

[0037] (Another exemplary embodiment (Part 2)) Next, a cold plate 100 according to another exemplary embodiment (Part 2) will be described with reference to Figure 5. Figure 5 is a schematic cross-sectional view showing the configuration of a brazing fin 31 according to another exemplary embodiment (Part 2). In the following embodiments, the configuration of the brazing fin 31 will be described using the configuration of the brazing fin 31 according to the exemplary embodiment, that is, a configuration in which the brazing fin 31 has a step 31C as an example. However, the configuration of the brazing fin 31 may also be the configuration of the brazing fin 31 according to another exemplary embodiment (Part 1), that is, a configuration in which the thickness L3 at the tip portion 31A gradually thins towards the brazing material 50.

[0038] As shown in Figure 5, a portion of the tip 31A of the brazed fin 31 may be located inside the brazing material 50. For example, the end 31D of the tip 31A of the brazed fin 31 that is on the brazing material 50 side may be located inside the brazing material 50.

[0039] Thus, in the brazed fin 31 according to another exemplary embodiment (part 2), a portion of the tip portion 31A is located inside the brazing material 50, in other words, a portion of the tip portion 31A is embedded in the brazing material 50. In this case, the end face and side surface of the tip portion 31A of the brazed fin 31 are joined to the brazing material 50. Therefore, the brazed fin 31 and the cover portion 20 can be joined more firmly compared to the case where the tip portion 31A of the brazed fin 31 is not embedded in the brazing material 50.

[0040] (Another Exemplary Embodiment (Part 3)) Next, the cold plate 100 according to another exemplary embodiment (Part 3) will be described with reference to FIG. 6. FIG. 6 is a schematic cross-sectional view of the cold plate 100 according to another exemplary embodiment (Part 3).

[0041] As shown in FIG. 6, the side wall surface 22 may have a tapered portion 24 that inclines outward in the in-plane direction of the opposing surface 21 (horizontally outward) as it approaches the opposing surface 21. For example, the side wall surface 22 has the tapered portion 24 connected to the opposing surface 21. Also, the side wall surface 22 has the tapered portion 24 disposed horizontally outward of the tip portion 30A of the fin 30 and the brazing material 50. Thereby, the distance L5 between the side wall surface 22 and the tip portion 30A of the fin 30 gradually increases toward the opposing surface 21. Also, the distance L6 between the side wall surface 22 and the brazing material 50 gradually increases toward the opposing surface 21. Note that the tapered portion 24 may be formed, for example, by cutting the side wall surface 22.

[0042] Thus, since the side wall surface 22 of the cover portion 20 has the tapered portion 24, capillary action between the tip portion 31A of the fin 30 and the side wall surface 22 is less likely to occur. Thereby, the possibility that the brazing material 50 climbs up the side wall surface 22 of the cover portion 20 can be reduced.

[0043] (Another Exemplary Embodiment (Part 4)) Next, the cold plate 100 according to another exemplary embodiment (Part 4) will be described with reference to FIG. 7. FIG. 7 is a schematic cross-sectional view showing the configuration of the brazed fin 31 according to another exemplary embodiment (Part 4).

[0044] As shown in FIG. 7, the fin 30 may have a thin portion 32 with a thickness thinner than that of the base end portion 31B (see FIG. 2) between the tip end portion 31A and the base end portion 31B (see FIG. 2). The thickness L7 of the thin portion 32 is thinner than the thickness L4 of the base end portion 31B. Therefore, the distance L8 between the thin portions 32 of the plurality of brazed fins 31 is wider than the distance L2 between the base end portions 30B (see FIG. 2) of the plurality of fins 30.

[0045] Incidentally, although the thin portion 32 has steps on the side of the brazing material 50 and the base end portion 31B side of the thin portion 32, this is not the only case. For example, it may be formed in a tapered shape, and the thickness of the thin portion 32 may gradually decrease toward the portion where the thickness of the thin portion 32 is the thinnest. Further, the thin portion 32 may be disposed on the short fins 34 (see FIG. 9) described later.

[0046] Thus, since the fin 30 has the thin portion 32 at a portion other than the tip portion 31A, capillary action is less likely to occur at a location other than the tip portion 31A (the location where the thin portion 32 is provided). Therefore, even if the brazing material 50 climbs over the tip portion 31A of the fin 30, the possibility that the brazing material 50 climbs over to the base end portion 31B side rather than the thin portion 32 can be reduced.

[0047] (Another exemplary embodiment (No. 5)) Next, the cold plate 100 according to another exemplary embodiment (No. 5) will be described with reference to FIG. 8. FIG. 8 is a schematic cross-sectional view showing the configuration of the brazed fin 31 according to another exemplary embodiment (No. 5).

[0048] As shown in FIG. 8, the fin 30 may also have a through hole 33 that penetrates the fin 30 in the thickness direction. The through hole 33 may be provided, for example, between the tip portion 31A and the base end portion 31B (see FIG. 2). The through hole 33 may be circular when viewed from the thickness direction of the fin 30. Note that the through hole 33 is not limited to this, and may be a polygon having a plurality of corners. The through hole 33 may be formed in the short fins 34 (see FIG. 9) described later.

[0049] Thus, since the fin 30 has the through hole 33, capillary action is less likely to occur at the position where the through hole 33 is provided. Therefore, even if the brazing material 50 climbs over the tip portion 31A of the fin 30, the possibility that the brazing material 50 climbs over to the base end portion 31B side rather than the through hole 33 can be reduced.

[0050] (Another exemplary embodiment (6)) Next, a cold plate 100 according to another exemplary embodiment (6) will be described with reference to Figure 9. Figure 9 is a schematic cross-sectional view showing the configuration of the fin 30 according to another exemplary embodiment (6).

[0051] As shown in Figure 9, the plurality of fins 30 may include a plurality of short fins 34 other than the brazed fin 31, which are shorter than the brazed fin 31 and have a space between the tip portion 34A and the brazing material 50. In this case, the brazed fin 31 does not necessarily have to have the configuration of the brazed fin 31 according to the exemplary embodiment, i.e., the configuration in which the brazed fin 31 has a step 31C, or the configuration of the brazed fin 31 according to another exemplary embodiment (the first), i.e., the configuration in which the thickness L3 at the tip portion 31A gradually thins towards the brazing material 50.

[0052] The short fin 34 is located between two adjacent brazed fins 31 among the multiple brazed fins 31. Figure 9 shows an example where one short fin 34 is located between two adjacent brazed fins 31, but it is not limited to this, and two or more short fins 34 may be located between two adjacent brazed fins 31. In other words, it is sufficient that at least one short fin 34 is located between two adjacent brazed fins 31 among the multiple brazed fins 31.

[0053] The short fins 34 are not joined to the brazing material 50 because there is a space between the tip portion 34A and the brazing material 50. Therefore, at least every other fin 30 is joined to the brazing material 50.

[0054] In this way, by positioning at least one short fin 34 between two adjacent brazing fins 31, the distance L1 between the tips 31A of the two adjacent brazing fins 31 becomes larger, making it less likely for capillary action to occur at the tips 31A of the brazing fins 31. This suppresses the upward movement of the brazing material 50.

[0055] Furthermore, it is not necessary for a short fin 34 to be positioned between every two adjacent brazed fins 31.

[0056] Furthermore, this technology can also be configured as follows: <Note> (1) A cold plate comprising a base portion on which a plurality of fins are arranged, and a cover portion covering the plurality of fins, wherein the base portion is joined to the cover portion outside the area on which the plurality of fins are arranged, and the plurality of fins include a plurality of brazed fins whose tips are joined to the cover portion by brazing material, and the distance between the tips of the plurality of brazed fins is wider than the distance between the base ends of the plurality of fins. (2) The cold plate according to (1), wherein the thickness of the tips of the brazed fins is thinner than the thickness of the base ends of the brazed fins. (3) The cold plate according to (2), wherein the brazed fins have a step between the tips and the portions other than the tips. (4) The cold plate according to (2), wherein the thickness of the tips of the brazed fins gradually decreases toward the brazing material. (5) The cold plate according to any one of (1) to (4), wherein a part of the tips of the brazed fins is located inside the brazing material. (6) The cold plate according to any one of (1) to (5), wherein the cover portion has an opposing surface that is spaced apart from the surface of the base portion on which the plurality of fins are arranged, and a side wall surface that extends from the opposing surface toward the base portion, and the side wall surface has a tapered portion that slopes outward in the in-plane direction toward the opposing surface as it approaches the opposing surface. (7) The cold plate according to any one of (1) to (6), wherein the fin has a thin-walled portion between the tip portion and the base portion that is thinner than the base portion. (8) The cold plate according to any one of (1) to (7), wherein the fin has a through hole that penetrates the fin in the thickness direction. (9) The cold plate according to any one of (1) to (8), wherein the plurality of fins include a plurality of short fins other than the brazed fins, which are shorter than the brazed fins and have a space between the tip portion and the brazing material, and at least one of the short fins is located between two adjacent brazed fins among the plurality of brazed fins.

[0057] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Indeed, the above embodiments can be embodied in a variety of forms. Furthermore, the above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0058] 10 Base section 20 Cover section 21 Opposing surface 22 Side wall surface 24 Tapered section 30 Fin 30A Tip section 30B Base end section 31 Brazed fin 31A Tip section 31B Base end section 31C Step 32 Thin section 33 Through hole 34 Short fin 34A Tip section 50 Brazing material 100 Cold plate A Area L1 Spacing L2 Spacing L3 Thickness L4 Thickness

Claims

1. A cold plate comprising a base portion on which a plurality of fins are arranged, and a cover portion covering the plurality of fins, wherein the base portion is joined to the cover portion outside the area on which the plurality of fins are arranged, and the plurality of fins include a plurality of brazed fins whose tips are joined to the cover portion with brazing material, and the distance between the tips of the plurality of brazed fins is greater than the distance between the base ends of the plurality of fins.

2. The cold plate according to claim 1, wherein the thickness at the tip of the brazed fin is thinner than the thickness at the base of the brazed fin.

3. The cold plate according to claim 2, wherein the brazed fin has a step between the tip portion and the portion other than the tip portion.

4. The cold plate according to claim 2, wherein the thickness at the tip of the brazed fin gradually decreases toward the brazing material.

5. The cold plate according to claim 1, wherein a portion of the tip of the brazed fin is located inside the brazing material.

6. The cold plate according to claim 1, wherein the cover portion has an opposing surface that is spaced apart from the surface of the base portion on which the plurality of fins are arranged, and a side wall surface that extends from the opposing surface toward the base portion, and the side wall surface has a tapered portion that slopes outward in the direction in the plane of the opposing surface as it approaches the opposing surface.

7. The cold plate according to claim 1, wherein the fin has a thin-walled portion between the tip and the base portion that is thinner than the base portion.

8. The cold plate according to claim 1, wherein the fin has a through hole that penetrates the fin in the thickness direction.

9. The cold plate according to any one of claims 1 to 8, wherein the plurality of fins include a plurality of short fins other than the brazed fins, which are shorter than the brazed fins and have a space between their tip and the brazing material, and at least one of the short fins is located between two adjacent brazed fins among the plurality of brazed fins.

Images