Fixed pyrolytic graphite sheet for heat diffusion

Abstract

A thermal diffusion element is provided. The thermal diffusion element comprises a compressible pyrolytic graphite sheet; and a rigid pyrolytic graphite sheet interleaved with the compressible pyrolytic graphite sheet.

Description

Technology Field

[0001] (Cross-reference to related applications)

[0002] This application claims priority to U.S. provisional application No. 17 / 576,437, filed on January 14, 2022, the entirety of which is incorporated by reference herein. Background Technology

[0003] The present disclosure relates to heat diffusion, in particular to a heat spreader equipped with a fixed pyrolytic graphite sheet (PGS).

[0004] A heat diffuser is an assembly used to transfer heat generated by an electronic device or module from the electronic device or module in a first direction and to diffuse the heat in a second direction. In some cases, the heat diffuser comprises 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 diffuses the heat by transferring the heat generated by the module toward the cold plate.

[0005] In conventional thermal diffusers, the thermal diffusion element was provided as a monolithic copper diffuser. Such monolithic copper diffusers tend to be heavy. Consequently, conventional thermal diffusers containing monolithic copper diffusers also tend to be heavy. means of solving the problem

[0006] According to one aspect of the present disclosure, a thermal diffusion element is provided. The thermal diffusion element comprises a compressible pyrolytic graphite sheet; and a rigid pyrolytic graphite sheet interleaved with the compressible pyrolytic graphite sheet.

[0007] According to an additional or alternative embodiment, at least one of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet exhibits an in-plane (n-plane) thermal conductivity of more than about 1000 W / mK, and the density of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet is less than about 10% of the copper density.

[0008] According to an additional or alternative embodiment, the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet are compressed together in the interleaving direction.

[0009] According to an additional or alternative embodiment, the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet are fixed in an interleaving direction.

[0010] According to one aspect of the present disclosure, a heat diffuser is provided, the heat diffuser comprising: a compressible pyrolytic graphite sheet; a hard pyrolytic graphite sheet interleaved with the compressible pyrolytic graphite sheet to form a heat diffusion element for providing heat transfer and diffusing heat; and a clamp for fixing the heat diffusion element and compressing the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet in a direction in which heat is transferred.

[0011] According to an additional or alternative embodiment, at least one of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet exhibits an in-plane thermal conductivity of more than about 1000 W / mK, and the density of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet is less than about 10% of the copper density.

[0012] According to an additional or alternative embodiment, the direction of heat transfer is the interleaving direction of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet.

[0013] According to an additional or alternative embodiment, the seal prevents moisture penetration into at least one of the heat diffusion element and the clamp.

[0014] According to an additional or alternative embodiment, the thermal diffusion element further comprises a cross section comprising a compressible and hard pyrolytic graphite sheet oriented transversely to the rest of the thermal diffusion element.

[0015] According to an additional or alternative embodiment, the heat diffuser further comprises a module and a cooling plate. A heat diffusion element is inserted between the module and the cooling plate to transfer heat from the module to the cooling plate in a first direction and to diffuse heat in a second direction transverse to the first direction. A clamp is positioned and configured to secure the heat diffusion element between the module and the cooling plate and to compress a compressible pyrolytic graphite sheet and a hard pyrolytic graphite sheet in the first direction.

[0016] According to an additional or alternative embodiment, the module includes an electronic element that generates heat.

[0017] According to an additional or alternative embodiment, the first direction is the interleaving direction of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet.

[0018] According to an additional or alternative embodiment, the clamp is adjusted to compress compressible pyrolytic graphite sheets and hard pyrolytic graphite sheets to optimize thermal performance.

[0019] According to an additional or alternative embodiment, the seal prevents moisture penetration into at least one of the heat diffusion element and the clamp.

[0020] According to an additional or alternative embodiment, a monolithic metal element is inserted between the module and the cooling plate along with a thermal diffusion element.

[0021] According to an additional or alternative embodiment, the compressible pyrolytic graphite sheet provides CTE mismatch compliance between the module, monolithic metal element, hard pyrolytic graphite sheet, and cooling plate.

[0022] According to an additional or alternative embodiment, the monolithic metal element defines a pocket in which the thermal diffusion element is disposable, and the height of the pocket is smaller than the height of the thermal diffusion element prior to the compression of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet.

[0023] According to one aspect of the present disclosure, a method for assembling a heat diffuser is provided, the method for assembling the heat diffuser comprising: a step of interleaving a hard pyrolytic graphite sheet and a compressible pyrolytic graphite sheet to form a heat diffusion element to provide heat transfer and diffuse heat; and a step of compressing the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet in a direction in which heat is transferred.

[0024] According to an additional or alternative embodiment, the method further comprises the step of inserting a heat diffusion element between the module and the cooling plate to transfer heat from the module to the cooling plate in a first direction and to diffuse heat in a second direction transverse to the first direction, and the compressing step comprises fixing the heat diffusion element between the module and the cooling plate to compress the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet in the first direction.

[0025] According to an additional or alternative embodiment, the method further includes the step of inserting a monolithic metal element between the module and the cooling plate together with a thermal diffusion element.

[0026] Additional features and benefits are realized through the description of the present disclosure. Other embodiments and aspects of the present disclosure are described in detail herein and are considered to be part of the claimed technical concept. For a better understanding of the benefits and features of the present disclosure, refer to the description and drawings. Brief explanation of the drawing

[0027] For a more complete understanding of the present disclosure, the following brief description taken in connection with the accompanying drawings and detailed description will now be referenced, wherein similar reference numbers indicate similar parts: FIG. 1 is a schematic side view of a heat diffusion element according to an embodiment; FIG. 2 is a schematic side view of a heat diffuser having a heat diffusion element according to an embodiment; FIG. 3 is a graphic drawing of an assembly of the heat diffuser and heat diffusion element of FIG. 2 according to an embodiment. FIG. 4 is a side schematic diagram of a heat diffuser having a heat diffusion element and a cross-section according to an embodiment; FIG. 5 is a side schematic diagram of a heat diffuser having a heat diffusion element according to an alternative embodiment; FIG. 6 is a side schematic diagram of a heat diffuser having a heat diffusion element according to an alternative embodiment; FIG. 7 is a side schematic diagram of a heat diffuser having a heat diffusion element according to an alternative embodiment; Figure 8 is a flowchart illustrating a method for assembling thermal diffusion according to the mode. Specific details for implementing the invention

[0028] As will be explained below, by using highly conductive and lightweight materials in the heat diffuser, heat diffuser performance similar to or better than that of monolithic copper diffusers is provided, while being much lighter in weight. In some cases, highly conductive and lightweight materials are provided as fixed layers of compressible, incompressible, or rigid PGS materials. Fixing the materials together can further reduce weight.

[0029] Referring to FIG. 1, a thermal diffusion element (101) is provided and comprises a compressible pyrolytic graphite sheet (110) and a hard pyrolytic graphite sheet (120). The hard 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 hard pyrolytic graphite sheet (120) exhibits an in-plane thermal conductivity greater than about 1000 W / mK. The compressible pyrolytic graphite sheet (110) and the hard pyrolytic graphite sheet (120) have a much lower density than a metal material such as copper. For example, the density of the hard pyrolytic graphite sheet (120) may be less than about 10% of the density of the metal material. The density of the compressible pyrolytic graphite sheet (110) may be less than about 10% of the density of the metal material, and in some cases less than about 5%. The compressible pyrolytic graphite sheet (110) and the hard pyrolytic graphite sheet (120) can be compressed together in the interleaving direction (A), for example, by a clamp (130). This compression effectively activates the in-plane thermal conductivity of the compressible pyrolytic graphite sheet (110) and the hard pyrolytic graphite sheet (120), so that the heat diffusion element (101) can transfer heat in the first direction (i.e., the interleaving direction (A)) and diffuse heat in the second direction (i.e., the in-plane direction (B)).

[0030] Depending on the embodiment, the hard pyrolytic graphite sheet (120) may have a density of about 1200-1300 kg / m3, and the compressible pyrolytic graphite sheet (110) may have a sponge quality with a density of about 400-500 kg / m3.

[0031] Referring to FIG. 2, a heat diffuser (201) is provided, comprising a module (210) including electronic devices (211) that generate heat upon operation, a heat exchanger or cooling plate (hereinafter "cooling plate") (220) configured to draw and release heat generated from the electronic devices (211), a heat diffusion element (230), and a clamp (240). The heat diffusion element (230) comprises a compressible pyrolytic graphite sheet (231) and a hard pyrolytic graphite sheet (232) interleaved with the compressible pyrolytic graphite sheet (231). At least one of the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) exhibits an in-plane thermal conductivity of more than about 1000 W / mK. The compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) have a much lower density than a metallic material such as copper. For example, the density of the hard pyrolytic graphite sheet (120) may be less than about 10% of the density of the metal material. The density of the compressible pyrolytic graphite sheet (110) may be less than about 10% of the density of the metal material, and in some cases less than about 5%.

[0032] As described above, depending on the embodiment, the hard pyrolytic graphite sheet (232) may have a density of about 1200-1300 kg / m3, and the compressible pyrolytic graphite sheet (231) may have a sponge quality with a density of about 400-500 kg / m3.

[0033] A heat diffusion element (230) is inserted between the module (210) and the cooling plate (220) to provide for transferring heat generated by the electronic device (211) from the module (210) to the cooling plate (220) in a first direction (i.e., the interleaving direction (A) with respect to the interleaving direction of the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232). The heat diffusion element (230) also diffuses heat in a second direction transverse to the first direction (i.e., the in-plane direction (B) with respect to the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232). A clamp (240) may include a screw (241) capable of engaging with at least the cooling plate (220) to pull the cooling plate (220) toward the module (210). The clamp (240) may alternatively include or be provided with various other configurations that serve to pull the cooling plate (220) toward the module (210). In any case, the clamp (240) serves to secure the thermal diffusion element (230) between the module (210) and the cooling plate (220) and to compress the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) in the first direction or interleaving direction (A) (Fig. 3 exemplarily shows only the compressible pyrolytic graphite sheet (231) being compressed; this is done for clarity and is not necessarily the case). This compression of the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) effectively activates the in-plane thermal conductivity of the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232).

[0034] Depending on the embodiments, the clamp (240) may be used to compress the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) to adjust the contact resistance between the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232). This can generally optimize the thermal performance of the thermal diffusion element (230) and optimize the thermal performance and in-plane thermal conductivity of the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232).

[0035] It should be understood that, depending on additional or other embodiments, the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) do not necessarily need to be interleaved with each other in a 1:1 order, and other configurations are possible. These include configurations in which only the compressible pyrolytic graphite sheet (231) is provided and / or configurations in which a plurality of compressible pyrolytic graphite sheets (232) are interleaved with a single hard pyrolytic graphite sheet (232).

[0036] As illustrated in FIG. 2, the heat diffuser (201) may also include a monolithic metal element (250) in which a heat diffusion element (230) is inserted between the module (210) and the cooling plate (220). The monolithic metal element (250) may be formed from a metal material such as copper or other suitable metal or metal alloy. The monolithic metal element (250) may be provided in a number of configurations, but is generally provided as a single element formed to define a pocket (251) in which the heat diffusion element (230) is disposable. In this sense, the monolithic metal element (250) may be engaged with a clamp (240) or may be engaged by a clamp.

[0037] Referring further to FIG. 2, the heat diffuser (201) may include a seal (245). The seal (245) may take any size, shape, and dimension for use with the heat diffuser (201). In some, but not all, cases, the seal (245) may be positioned and configured to prevent moisture from penetrating into the heat diffusion element (230). In some other cases, the seal (245) may also be positioned and configured so that moisture does not flow around the clamp (240) and does not flow into the heat diffusion element (230).

[0038] Referring to FIG. 3 and according to the embodiment, the height (H1) of the pocket (251) may be smaller than the height (H2) of the thermal diffusion element (230) before the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) are compressed. Thus, as described above, the thermal performance of the thermal diffusion element (230) can be optimized by compressing the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) by adjusting the height (H1) of the pocket (251) together with the clamp (240). That is, when the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) are compressed from the height (H2) of the pocket (251) to the height (H1), this degree of compression optimizes the thermal performance of the thermal diffusion element (230).

[0039] Depending on the mode, the degree of compression may be about 5-60% of the height (H2).

[0040] The compressibility of the compressible pyrolytic graphite sheet (231) can provide a coefficient of thermal expansion (CTE) mismatch compliance to at least two of the module (210), monolithic metal element (250), hard pyrolytic graphite sheet (232), and cooling plate (220).

[0041] Referring to FIG. 4 and according to additional embodiments, the thermal diffusion element (230) of FIG. 2 and 3 may be provided in a hybridized configuration, arrangement, and configuration. For example, as shown in FIG. 4, the thermal diffusion element (230) may include a cross section (401) as well as a compressible pyrolytic graphite sheet (231) and a hard pyrolytic graphite sheet (232). This cross section (401) may be provided within the thermal diffusion element (230), but is not necessarily provided, and may include the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232). The compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) of the cross section (401) are oriented laterally or vertically with respect to the rest of the thermal diffusion element (230), or otherwise rotated. In this way, the cross section (401) can function as a via through which heat diffuses in a direction penetrating the thickness (in addition to in-plane heat diffusion of the compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232). The compressible pyrolytic graphite sheet (231) and the hard pyrolytic graphite sheet (232) of the cross section (401) can be compressed (i.e., by the remaining heat diffusion element (230)), and thus can provide a high level of in-plane heat conduction between the module (210) and the cooling plate (220). This cross section (401) can be placed at or near the hot spot of the module (210).

[0042] Although the cross section (401) is shown in FIG. 4 as being sandwiched between a compressible pyrolytic graphite sheet (231) and a hard pyrolytic graphite sheet (232), it should be understood that this is not necessarily required and other embodiments are possible. For example, the cross section (401) may be in direct contact with one or both of the cooling plate (220) and the monolithic metal element (250).

[0043] Referring to FIGS. 5-7 and according to additional embodiments, the monolithic metal element (250) may be formed such that the pocket (251) may have a number of different configurations. For example, while the pocket (251) of FIGS. 2 and 3 is adjacent to the cooling plate (220), the pocket (251) may be adjacent to the module (210) (see FIG. 5), the pocket (251) may be sandwiched on each side by a part (601) of the monolithic metal element (250) (see FIG. 6), or the pocket (251) may extend over the entire range of distance between the module (210) and the cooling plate (220) (see FIG. 7).

[0044] Referring to FIG. 8, a method for assembling a heat diffuser such as the heat diffuser (201) described above is provided. As illustrated in FIG. 8, the method comprises the steps of interleaving a hard pyrolytic graphite sheet and a compressible pyrolytic graphite sheet to form a heat diffusion element for providing heat transfer and diffusing heat (Block 801), and compressing the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet in the direction of heat transfer (Block 802). According to embodiments, the method may further comprise the step of inserting a heat diffusion element between a module and a cooling plate to provide heat transfer from the module to the cooling plate in a first direction and diffusing heat in a second direction transverse to the first direction (Block 803). Additionally, the compressing step may include fixing the heat diffusion element between the module and the cooling plate to compress the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet in the first direction (Block 804). This method may further include the step of inserting a monolithic metal element having a heat diffusion element between the module and the cooling plate (Block 805).

[0045] The technical effect and benefit of the present disclosure is to provide a PGS for cooling plate applications, which has very high conductivity in a planar plane (>1000 W / mK) and a density of about 10% or less of that of typical high-conductivity materials. As a result, thermal diffusion performance is at least comparable to that of copper thermal diffusers, while the weight can be significantly reduced (at least 20 to 30% compared to typical copper designs). When the PGS are fixed together, epoxy-based materials are not required between the PGS. This allows for further weight reduction while improving thermal performance.

[0046] In the claims below, the functional element plus any means or steps corresponding structures, materials, operations, and equivalents means including any structure, material, or operation for performing a function together with other claimed elements as explicitly claimed. The description of this disclosure is presented for illustrative and illustrative purposes, but is not intended to complete or limit the technical concept of the disclosed form. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of this disclosure. Modes are selected and described to best explain the principles and practical applications of this disclosure and to enable those skilled in the art to understand this disclosure in various modes having various modifications suitable for the specific use being considered.

[0047] Although preferred embodiments of the present disclosure have been described, those skilled in the art will understand that various improvements and enhancements may be made now and in the future within the scope of the following claims. These claims should be interpreted to maintain adequate protection for the disclosure originally described.

Claims

Claim 1 As a heat spreading element, the heat spreading element comprises: a compressible pyrolytic graphite sheet; and a hard pyrolytic graphite sheet interleaved with the compressible pyrolytic graphite sheet; wherein the compressible pyrolytic graphite sheet has a weight of 400 to 500 kg / m² 3 Having a density of 1200 to 1300 kg / m², the hard pyrolytic graphite sheet has a density of 1200 to 1300 kg / m² 3 A thermal diffusion element that has a density. Claim 2 A thermal diffusion element according to claim 1, wherein at least one of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet exhibits an in-plane thermal conductivity of greater than 1000 W / mK, and the density of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet is less than 10% of the density of copper. Claim 3 A thermal diffusion element according to claim 1, wherein the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet are compressed together in the interleaving direction. Claim 4 A thermal diffusion element according to paragraph 3, wherein the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet are fixed in an interleaving direction. Claim 5 As a heat spreader, the heat spreader comprises: a compressible pyrolytic graphite sheet; a hard pyrolytic graphite sheet interleaved with the compressible pyrolytic graphite sheet to form a heat diffusion element that provides heat transfer and diffuses heat; and a clamp for fixing the heat diffusion element and compressing the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet in the direction of heat transfer; wherein the compressible pyrolytic graphite sheet has a weight of 400 to 500 kg / m² 3 Having a density of 1200 to 1300 kg / m², the hard pyrolytic graphite sheet has a density of 1200 to 1300 kg / m² 3 A heat diffuser having a density. Claim 6 A heat diffuser according to claim 5, wherein at least one of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet exhibits an in-plane thermal conductivity of greater than 1000 W / mK, and the density of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet is less than 10% of the density of copper. Claim 7 A heat diffuser according to claim 5, wherein the direction in which the heat is transferred is the interleaving direction of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet. Claim 8 A heat diffuser according to claim 5, further comprising a seal to prevent moisture penetration into at least one of the heat diffusion element and the clamp. Claim 9 A heat diffuser according to claim 5, wherein the heat diffusion element further comprises a transverse section comprising a compressible and hard pyrolytic graphite sheet oriented transversely to the remainder of the heat diffusion element. Claim 10 In claim 5, the heat diffuser further comprises a module; and a cooling plate; wherein the heat diffusion element is inserted between the module and the cooling plate to transfer heat in a first direction from the module to the cooling plate and to diffuse heat in a second direction transverse to the first direction, and the clamp is arranged and configured to fix the heat diffusion element between the module and the cooling plate and to compress a compressible pyrolytic graphite sheet and a hard pyrolytic graphite sheet in the first direction. Claim 11 In item 10, the above module is a heat diffuser comprising an electronic element that generates heat. Claim 12 A heat diffuser according to claim 10, wherein the first direction is the interleaving direction of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet. Claim 13 A heat diffuser according to claim 10, wherein the clamp is adjusted to compress a compressible pyrolytic graphite sheet and a hard pyrolytic graphite sheet to optimize thermal performance. Claim 14 A heat diffuser according to claim 10, further comprising a seal to prevent moisture penetration into at least one of the heat diffusion element and the clamp. Claim 15 A heat diffuser according to claim 10, further comprising a monolithic metallic element inserted between the module and the cooling plate together with the heat diffusion element. Claim 16 A heat diffuser in which, in paragraph 15, the compressible pyrolytic graphite sheet provides CTE mismatch compliance between the module, the monolithic metal element, the hard pyrolytic graphite sheet, and the cooling plate. Claim 17 A heat diffuser according to claim 15, wherein the monolithic metal element defines a pocket in which the heat diffusion element is disposable, and the height of the pocket is smaller than the height of the heat diffusion element prior to the compression of the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet. Claim 18 A method for assembling a heat diffuser, wherein the assembly method comprises: a step of interleaving a hard pyrolytic graphite sheet with a compressible pyrolytic graphite sheet to form a heat diffusion element to provide heat transfer and diffuse heat; and a step of compressing the compressible pyrolytic graphite sheet and the hard pyrolytic graphite sheet in a direction in which heat is transferred; wherein the compressible pyrolytic graphite sheet has a weight of 400 to 500 kg / m² 3 Having a density of 1200 to 1300 kg / m², the hard pyrolytic graphite sheet has a density of 1200 to 1300 kg / m² 3 A method of assembling a heat diffuser having a density. Claim 19 A method for assembling a heat diffuser according to claim 18, wherein the method further comprises the step of inserting a heat diffusion element between a module and a cooling plate to transfer heat from the module to the cooling plate in a first direction and diffusing heat in a second direction transverse to the first direction, and the compressing step comprises fixing the heat diffusion element between the module and the cooling plate to compress a compressible pyrolytic graphite sheet and a hard pyrolytic graphite sheet in the first direction. Claim 20 A method for assembling a heat diffuser according to claim 19, further comprising the step of inserting a monolithic metal element between the module and the cooling plate together with a heat diffusion element.

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