Clamp-type pyrolytic graphite sheet for heat diffusion

Abstract

A heat spreading element is provided, the heat spreading element including a compressible pyrolytic graphite sheet and a rigid pyrolytic graphite sheet interleaved with the compressible pyrolytic graphite sheet.

Description

[Technical Field]

[0001] (Reference to Related Application) This application claims priority to U.S. Non-Provisional Patent Application No. 17 / 576,437, filed January 14, 2022, which is incorporated herein by reference in its entirety.

[0002] (Technical field) The present disclosure relates to spreading heat, and more particularly to a heat spreader comprising clamped pyrolytic graphite sheets (PGS). [Background technology]

[0003] A heat spreader is an assembly used to transfer heat generated by an electronic device or module in a first direction away from the electronic device or module and spread the heat in a second direction. In some cases, the heat spreader includes a module, a cold plate or heat exchanger, and a heat spreading element interposed between the module and the cold plate. The heat spreading element transfers the heat generated by the module to the cold plate, spreading the heat in the process.

[0004] In conventional heat spreaders, the heat spreading element is provided by a monolithic copper spreader. These monolithic copper spreaders tend to be heavy. Therefore, conventional heat spreaders that include a monolithic copper spreader also tend to be heavy. Summary of the Invention

[0005] According to an aspect of the present disclosure, a heat spreading element is provided, the heat spreading element including compressible pyrolytic graphite sheets and rigid pyrolytic graphite sheets interleaved with the compressible pyrolytic graphite sheets.

[0006] According to additional or alternative embodiments, at least one of the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet exhibits an in-plane thermal conductivity greater than about 1000 W / mK, and the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet have a density less than about 10% of the density of copper.

[0007] According to additional or alternative embodiments, the compressible pyrolytic graphite sheets and the rigid pyrolytic graphite sheets are compressed together in an interleaved direction.

[0008] According to additional or alternative embodiments, the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet are clamped in an interleaved orientation.

[0009] According to aspects of the present disclosure, a heat spreader is provided that includes a compressible pyrolytic graphite sheet, a rigid pyrolytic graphite sheet interleaved with the compressible pyrolytic graphite sheet to form a heat spreading element that achieves heat transfer and heat spreading, and a clamp for clamping the heat spreading element and compressing the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in the direction of heat transfer.

[0010] According to additional or alternative embodiments, at least one of the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet exhibits an in-plane thermal conductivity greater than about 1000 W / mK, and the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet have a density less than about 10% of the density of copper.

[0011] According to additional or alternative embodiments, the direction of heat transfer is in the direction of interleaving of the compressible pyrolytic graphite sheets and the rigid pyrolytic graphite sheets.

[0012] According to additional or alternative embodiments, the seal prevents moisture from entering at or around the heat spreading element and / or clamp.

[0013] According to additional or alternative embodiments, the heat spreading element further includes a transverse portion including a compressible and rigid pyrolytic graphite sheet oriented transversely relative to the remainder of the heat spreading element.

[0014] According to additional or alternative embodiments, the heat spreader further includes a module and a cold plate. The heat spreading element is interposed between the module and the cold plate to facilitate heat transfer from the module to the cold plate in a first direction and spread heat in a second direction transverse to the first direction. The clamp is positioned and configured to clamp the heat spreading element between the module and the cold plate and compress the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in the first direction.

[0015] According to additional or alternative embodiments, the module includes electronic elements that generate heat.

[0016] According to additional or alternative embodiments, the first direction is a direction of interleaving of the compressible pyrolytic graphite sheets and the rigid pyrolytic graphite sheets.

[0017] According to additional or alternative embodiments, the clamps are adjusted to compress the compressible pyrolytic graphite sheets and the rigid pyrolytic graphite sheets to optimize thermal capacity.

[0018] According to additional or alternative embodiments, the seal prevents moisture from entering at or around the heat spreading element and / or clamp.

[0019] According to additional or alternative embodiments, a monolithic metal element is interposed between the module with the heat spreading element and the cold plate.

[0020] According to additional or alternative embodiments, the compressible pyrolytic graphite sheet provides CTE mismatch compliance between the module, the monolithic metal element, the rigid pyrolytic graphite sheet, and the cold plate.

[0021] According to additional or alternative embodiments, the monolithic metal element defines a pocket in which the heat spreading element is disposable, the height of the pocket being less than the height of the heat spreading element before the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet are compressed.

[0022] According to an aspect of the present disclosure, a method for assembling a heat spreader is provided, comprising interleaving compressible pyrolytic graphite sheets and rigid pyrolytic graphite sheets, and compressing the compressible pyrolytic graphite sheets and the rigid pyrolytic graphite sheets in a direction of heat transfer to form a heat spreading element that provides heat transfer and spreading.

[0023] According to additional or alternative embodiments, the method further includes interposing a heat spreading element between the module and the cold plate to achieve heat transfer from the module to the cold plate in a first direction and spreading heat in a second direction transverse to the first direction, and the compressing includes clamping the heat spreading element between the module and the cold plate to compress the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in the first direction.

[0024] According to additional or alternative embodiments, the method further includes interposing a monolithic metal element between the module and the cold plate along with the heat spreading element.

[0025] Further features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the present disclosure are described in detail herein and are considered part of the claimed technical concept. For a better understanding of the present disclosure, together with its advantages and features, please refer to the description and drawings. For a more complete understanding of the present disclosure, reference is now made to the following brief description taken in conjunction with the accompanying drawings and detailed description, wherein like reference characters represent like parts. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic side view of a heat spreading element according to an embodiment. [Figure 2] 1 is a schematic side view of a heat spreader with a heat spreading element according to an embodiment. [Figure 3] 3 is a graphical illustration of an assembly of the heat spreader and heat spreading element of FIG. 2 according to an embodiment. [Figure 4] 1 is a schematic side view of a heat spreader with a heat spreading element and a cross section according to an embodiment. [Figure 5] 1 is a schematic side view of a heat spreader with a heat spreading element according to an embodiment. [Figure 6] 1 is a schematic side view of a heat spreader with a heat spreading element according to an embodiment. [Figure 7] 1 is a schematic side view of a heat spreader with a heat spreading element according to an embodiment. [Figure 8] 1 is a flow chart illustrating a method for assembling a heat spreader according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0027] As described below, highly conductive, lightweight materials are used in heat spreaders to provide heat spreader performance equal to or better than monolithic copper spreaders, but at much lighter weight. In some cases, the highly conductive, lightweight material is applied as a clamping layer to compressible and incompressible or rigid PGS materials. By clamping the materials together, further weight savings are possible.

[0028] Referring to FIG. 1 , a heat spreading element 101 is provided and includes a compressible pyrolytic graphite sheet 110 and a rigid pyrolytic graphite sheet 120. The rigid pyrolytic graphite sheet 120 is interleaved with the compressible pyrolytic graphite sheet 110. At least one of the compressible pyrolytic graphite sheet 110 and the rigid pyrolytic graphite sheet 120 exhibits an in-plane thermal conductivity of greater than approximately 1000 W / mK. The compressible pyrolytic graphite sheet 110 and the rigid pyrolytic graphite sheet 120 have a much lower density than metallic materials such as copper. For example, the density of the rigid pyrolytic graphite sheet 120 can be less than approximately 10% of the density of the metallic material. The density of the compressible pyrolytic graphite sheet 110 can be less than approximately 10%, or in some cases, less than approximately 5%, of the density of the metallic material. The compressible pyrolytic graphite sheet 110 and the rigid pyrolytic graphite sheet 120 can be compressed together in an interleaving direction A, for example, by clamps 130. This compression effectively activates the in-plane thermal conductivity of the compressible pyrolytic graphite sheet 110 and the rigid pyrolytic graphite sheet 120, allowing the heat spreading element 101 to transfer heat in a first direction (i.e., the interleaving direction A) and spread heat in a second direction (i.e., the in-plane direction B).

[0029] According to an embodiment, the rigid pyrolytic graphite sheet 120 may have a density of about 1200-1300 kg / m 3 , and the compressible pyrolytic graphite sheet 110 may have a spongy nature with a density of about 400-500 kg / m 3 .

[0030] Referring to FIG. 2 , a heat spreader 201 is provided, including a module 210 containing electronic devices 211 that generate heat during operation, a heat exchanger or cold plate (hereinafter referred to as a “cold plate”) 220 configured to absorb and dissipate the heat generated by the electronic devices 211, a heat spreading element 230, and a clamp 240. The heat spreading element 230 includes a compressible pyrolytic graphite sheet 231 and a rigid pyrolytic graphite sheet 232 interleaved with the compressible pyrolytic graphite sheet 231. At least one of the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232 exhibits an in-plane thermal conductivity greater than approximately 1000 W / mK. The compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232 have a much lower density than metallic materials such as copper. For example, the density of the rigid pyrolytic graphite sheet 120 can be less than approximately 10% of the density of the metallic material. The density of the compressed pyrolytic graphite sheet 110 can be less than about 10% of the density of the metallic material, and in some cases less than about 5%.

[0031] As mentioned above, according to an embodiment, the rigid pyrolytic graphite sheet 232 may have a density of about 1200-1300 kg / m3, and the compressible pyrolytic graphite sheet 231 may have a spongy nature with a density of about 400-500 kg / m3.

[0032] The heat spreading element 230 is interposed between the module 210 and the cold plate 220 and transfers heat generated by the electronic device 211 from the module 210 to the cold plate 220 in a first direction (i.e., an interleaving direction A relative to the interleaving direction of the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232). The heat spreading element 230 also spreads heat in a second direction transverse to the first direction (i.e., an in-plane direction B of the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232). The clamp 240 can include a screw 241 that can engage with at least the cold plate 220 to draw the cold plate 220 toward the module 210. The clamp 240 can alternatively include or be provided with various other configurations that serve to draw the cold plate 220 toward the module 210. In either case, clamp 240 serves to sandwich heat spreading element 230 between module 210 and cold plate 220 and compress compressible pyrolytic graphite sheet 231 and rigid pyrolytic graphite sheet 232 in a first or interleaving direction A. (Although FIG. 3 shows only compressible pyrolytic graphite sheet 231 as being compressed, this is for clarity and is not necessarily the case.) This compression of compressible pyrolytic graphite sheet 231 and rigid pyrolytic graphite sheet 232 effectively activates the in-plane thermal conductivity of compressible pyrolytic graphite sheet 231 and rigid pyrolytic graphite sheet 232.

[0033] According to an embodiment, clamp 240 can be used to compress compressible pyrolytic graphite sheet 231 and rigid pyrolytic graphite sheet 232 to adjust the contact resistance between compressible pyrolytic graphite sheet 231 and rigid pyrolytic graphite sheet 232. This can optimize the overall thermal capacity of heat spreading element 230 and the thermal capacity and in-plane thermal conductivity of compressible pyrolytic graphite sheet 231 and rigid pyrolytic graphite sheet 232.

[0034] It should be understood that, according to further or alternative embodiments, the compressible pyrolytic graphite sheets 231 and the rigid pyrolytic graphite sheets 232 need not be interleaved with one another in a 1:1 order, and other configurations are possible, including configurations where only the compressible pyrolytic graphite sheets 231 are provided and / or where multiple compressible pyrolytic graphite sheets 232 are interleaved with a single rigid pyrolytic graphite sheet 232.

[0035] 2, the heat spreader 201 can also include a monolithic metal element 250 interposed between the module 210 with the heat spreading element 230 and the cold plate 220. The monolithic metal element 250 can be formed of a metallic material such as copper or other suitable metal or metal alloy. The monolithic metal element 250 can be provided in a variety of configurations, but is typically provided as a single, integral element formed to define a pocket 251 in which the heat spreading element 230 can be positioned. In this sense, the monolithic metal element 250 can also engage with and be engaged by the clamp 240.

[0036] 2, the heat spreader 201 may also include a seal 245. The seal 245 may be of any size, shape, and dimension for use in the heat spreader 201. In some, but not all, cases, the seal 245 may be positioned and configured to prevent moisture from entering the heat spreading element 230. In some other cases, the seal 245 may also be positioned and configured to prevent moisture from flowing around the clamp 240 and then entering the heat spreading element 230.

[0037] 3 , according to an embodiment, the height H1 of the pocket 251 before the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232 are compressed can be lower than the height H2 of the heat spreading element 230. Therefore, as described above, the height H1 of the pocket 251 can be adjusted together with the clamp 240 to compress the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232 and optimize the thermal capacity of the heat spreading element 230. That is, when the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232 are compressed from the height H2 of the pocket 251 to the height H1, the thermal capacity of the heat spreading element 230 is optimized depending on the degree of compression.

[0038] According to an embodiment, the degree of compression can be about 5-60% of the height H2.

[0039] The compressibility of the compressible pyrolytic graphite sheet 231 allows for coefficient of thermal expansion (CTE) mismatch compliance between at least two or more of the module 210, the monolithic metal element 250, the rigid pyrolytic graphite sheet 232, and the cold plate 220.

[0040] Referring to FIG. 4 and according to yet further embodiments, the heat spreading element 230 of FIGS. 2 and 3 may be provided in a hybrid configuration, arrangement, and formation. For example, as shown in FIG. 4, the heat spreading element 230 may include a compressible pyrolytic graphite sheet 231 and a rigid pyrolytic graphite sheet 232, as well as a cross section 401. This cross section 401 may, but need not, be provided within the heat spreading element 230 and may include the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232. The compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232 of the cross section 401 may be oriented or rotated transversely or perpendicularly relative to the rest of the heat spreading element 230. In this manner, the cross section 401 can function like a via for through-thickness heat spreading (in addition to the in-plane heat spreading of the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232). The compressible pyrolytic graphite sheet 231 and rigid pyrolytic graphite sheet 232 of the cross section 401 are compressible (i.e., by the remainder of the heat spreading element 230), thus enabling a high degree of in-plane thermal conduction between the module 210 and the cold plate 220. This cross section 401 can be placed at or near a hot spot of the module 210.

[0041] 4, the cross section 401 is shown as being sandwiched between the compressible pyrolytic graphite sheet 231 and the rigid pyrolytic graphite sheet 232, but it should be understood that this is not required and other embodiments are possible. For example, the cross section 401 could be in direct contact with one or both of the cold plate 220 and the monolithic metal element 250.

[0042] 5-7, according to further embodiments, the monolithic metal element 250 can be formed such that the pocket 251 can have a number of different configurations. For example, while the pocket 251 in FIGS. 2 and 3 is adjacent to the cold plate 220, the pocket 251 can be adjacent to the module 210 (see FIG. 5), the pocket 251 can be sandwiched on either side by portions 601 of the monolithic metal element 250 (see FIG. 6), or the pocket 251 can extend the entire distance between the module 210 and the cold plate 220 (see FIG. 7).

[0043] Referring to FIG. 8 , a method for assembling a heat spreader, such as heat spreader 201 described above, is presented. As shown in FIG. 8 , the method includes interleaving a rigid pyrolytic graphite sheet with a compressible pyrolytic graphite sheet to form a heat spreading element for heat transfer and heat spreading (block 801) and compressing the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in a heat transfer direction (block 802). According to an embodiment, the method may further include interposing a heat spreading element between the module and a cold plate to transfer heat in a first direction from the module to the cold plate and spread heat in a second direction transverse to the first direction (block 803). Further, the compressing may include clamping the heat spreading element between the module and the cold plate to compress the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in the first direction (block 804). The method may further include interposing a monolithic metal element between the module with the heat spreading element and the cold plate (Block 805).

[0044] The technical effects and advantages of the present disclosure are the provision of PGS in cold plate applications, which are highly conductive (>1000 W / mK) in planar form, with a density approximately 10% or less than typical highly conductive materials. This results in heat spreading capabilities at least comparable to copper heat spreaders, while also providing significant weight savings (at least approximately 20-30% compared to typical copper designs). Clamping the PGS together eliminates the need for epoxy-based materials between the PGS, further reducing weight and improving thermal capabilities.

[0045] The corresponding structure, material, acts, and equivalents of all means or step-plus-function elements in the following claims are intended to include any structure, material, or acts for performing the function as specifically claimed in combination with other claimed elements. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limiting to the technical concepts in the disclosed form. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The selection and description of the embodiments was made to best explain the principles and practical applications of the present disclosure and to enable others skilled in the art to understand the present disclosure in various embodiments with various modifications suitable for the particular use intended.

[0046] While preferred embodiments of the present disclosure have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements that fall within the scope of the following claims, which should be interpreted to maintain the appropriate protection for the disclosure as originally described.

Claims

1. a heat spreading element, a compressible pyrolytic graphite sheet having a density of 400 to 500 kg / m 3 ; and rigid pyrolytic graphite sheets having a density of 1200 to 1300 kg / m 3 interleaved with the compressible pyrolytic graphite sheets. Heat diffusion element.

2. at least one of the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet exhibits an in-plane thermal conductivity greater than about 1000 W / m-K; the density of the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet is less than about 10% of the density of copper; The heat spreading element of claim 1 .

3. The heat spreading element of claim 1 , wherein the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet are compressed together in an interleaving direction.

4. The heat spreading element of claim 3 , wherein the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet are clamped in the interleaving direction.

5. A heat spreader, a compressible pyrolytic graphite sheet having a density of 400 to 500 kg / m 3 ; a rigid pyrolytic graphite sheet having a density of 1200-1300 kg / m 3 interleaved with said compressible pyrolytic graphite sheet to form a heat spreading element for effecting heat transfer and spreading of said heat; a clamp for clamping the heat spreading element and compressing the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in the direction of the heat transfer. Heat spreader.

6. at least one of the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet exhibits an in-plane thermal conductivity greater than about 1000 W / m-K; the density of the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet is less than about 10% of the density of copper; The heat spreader of claim 5 .

7. The heat spreader of claim 5 , wherein the direction in which the heat is transferred is the direction of interleaving of the compressible pyrolytic graphite sheets and the rigid pyrolytic graphite sheets.

8. The heat spreader of claim 5 , further comprising a seal to prevent ingress of moisture into or around at least one of the heat spreading element and the clamp.

9. The heat spreader of claim 5 , wherein the heat spreading element further comprises a transverse portion comprising a compressible and rigid pyrolytic graphite sheet oriented transversely relative to the remainder of the heat spreading element.

10. Modules and a cold plate; and the heat spreading element is interposed between the module and the cold plate, and provides for the transfer of the heat from the module to the cold plate in a first direction and for spreading the heat in a second direction transverse to the first direction; the clamp is positioned and configured to clamp the heat spreading element between the module and the cold plate and compress the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in the first direction. The heat spreader of claim 5 .

11. The heat spreader of claim 10 , wherein the module comprises an electronic component that generates the heat.

12. The heat spreader of claim 10 , wherein the first direction is an interleaving direction of the compressible pyrolytic graphite sheets and the rigid pyrolytic graphite sheets.

13. 11. The heat spreader of claim 10, wherein the clamps are adjusted to compress the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet to optimize thermal capacity.

14. The heat spreader of claim 10 , further comprising a seal to prevent ingress of moisture into or around at least one of the heat spreading element and the clamp.

15. The heat spreader of claim 10 further comprising a monolithic metal element interposed with the heat spreading element between the module and the cold plate.

16. 16. The heat spreader of claim 15, wherein the compressible pyrolytic graphite sheet provides CTE mismatch compliance between the module, the monolithic metal element, the rigid pyrolytic graphite sheet, and the cold plate.

17. the monolithic metal element defines a pocket in which the heat spreading element is disposable; the height of the pocket is less than the height of the heat spreading element before the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet are compressed; The heat spreader of claim 15.

18. 1. A method of assembling a heat spreader, comprising: interleaving compressible pyrolytic graphite sheets having a density of 400-500 kg / m 3 with rigid pyrolytic graphite sheets having a density of 1200-1300 kg / m 3 to form a heat spreading element for transferring and spreading heat; compressing the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet with a clamp in the direction of the heat transfer. method.

19. the method further comprising interposing the heat spreading element between a module and a cold plate to achieve transfer of the heat from the module to the cold plate in a first direction and spreading the heat in a second direction transverse to the first direction; the compressing includes clamping the heat spreading element between the module and the cold plate to compress the compressible pyrolytic graphite sheet and the rigid pyrolytic graphite sheet in the first direction.

20. The method of claim 18.

20. 20. The method of claim 19, further comprising interposing a monolithic metal element between the module and the cold plate along with the heat spreading element.

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