A graphene thermally conductive pad and a preparation method thereof

Abstract

The present application relates to the field of heat dissipation devices for electronic products, and specifically discloses a graphene thermally conductive gasket and a preparation method thereof. The graphene thermally conductive gasket includes multiple layers of graphene films bonded by an adhesive, and through holes are provided on the graphene films through the upper and lower surfaces, and carbon fiber filaments are penetrated in the through holes, and the carbon fiber filaments are coated with an adhesive. The preparation method is to first apply a first layer of adhesive on the first layer of graphene film, and then stack the second layer of graphene film on the first layer of graphene film and apply the second layer of adhesive, repeating in sequence until the stacking reaches a specified height, and then opening holes in the direction parallel to the graphene film stacking direction, and carbon fiber filaments are penetrated in the holes to obtain a graphene-carbon fiber three-dimensional structure, and the obtained graphene-carbon fiber three-dimensional structure is sliced ​​in the direction parallel to the graphene film stacking direction to obtain a graphene thermally conductive gasket. The graphene thermally conductive gasket of the present application can be used in the field of heat dissipation of electronic devices, and has excellent thermal conductivity and mechanical properties.

Description

Technical Field

[0001] The present application relates to the field of heat dissipation devices for electronic products, and more specifically, to a graphene thermally conductive pad and a preparation method thereof. Background Art

[0002] With the advent of the 5G era, the operating frequency of electronic chips continues to increase, and electronic products are gradually developing in the direction of lightweight and high integration, resulting in a significant increase in the heat generated by the equipment. If the excess heat is not conducted away in time, it will greatly affect the working performance of electronic components. In severe cases, it will cause the life of electronic devices to be reduced or even fail.

[0003] In order to improve the heat dissipation performance of electronic products and conduct the heat generated by electronic devices in a timely manner, the industry has begun to use thermal interface materials as heat-conducting media for heat dissipation. Thermal interface materials are a general term for materials used to coat between heat dissipating devices and heating devices to reduce the contact thermal resistance between them. Traditional thermal interface materials mainly include silicone grease, silicone gel, phase change metal sheets, thermal conductive adhesives, and acrylic resins.

[0004] As an application form of thermal interface material, thermal pads are highly favored in the selection of thermal conductive materials for electronic devices because of their high compressibility, softness and elasticity, and the ability to provide a variety of thickness and size options. However, thermal pads made of traditional thermal interface materials have limited thermal conductivity, generally about 1-10W / (m·k), which is difficult to meet the high heat conduction requirements in the current chip heat dissipation field with high heat flux density. Summary of the invention

[0005] In order to improve the thermal conductivity of a thermally conductive gasket to meet the high heat conduction requirements in the field of chip heat dissipation, the present application provides a graphene thermally conductive gasket and a preparation method thereof.

[0006] In a first aspect, the present application provides a graphene thermally conductive pad, which adopts the following technical solution:

[0007] A graphene thermally conductive gasket comprises a multilayer graphene film, wherein an adhesive is coated between adjacent layers of the graphene film, the graphene film is formed with a plurality of through holes penetrating the upper and lower surfaces of the graphene film, carbon fiber filaments are passed through the through holes, and the carbon fiber filaments are coated with an adhesive.

[0008] The thickness of the graphene film is preferably 200-700 μm; the size of the graphene film is preferably 10*10-200*200 mm, and the height of the graphene film stack is preferably 10-200 mm.

[0009] By adopting the above technical scheme, graphene has good thermal properties, and the thermally conductive gasket made of graphene film as thermal interface material has excellent thermal conductivity. By bonding multiple layers of graphene film with adhesive, it can be stacked to a specified height to make thermally conductive gaskets of different sizes to meet the requirements of electronic devices of different specifications. Since the thermal conductivity of graphene is anisotropic, its thermal conductivity in the horizontal direction within the layer is high, and its thermal conductivity in the interlayer direction is low, so carbon fiber filaments are passed through the stacking direction of the graphene film, and the carbon fiber filaments are coated with adhesive to fix the carbon fiber filaments in the through holes on the graphene film, and the thermal conductivity of the graphene thermally conductive gasket in the interlayer direction is improved by the carbon fiber filaments. Through testing, the thermal conductivity coefficient of the graphene thermally conductive gasket in the present application can exceed 180 W / (m·K) at most, and the thermal conductivity coefficient between layers can exceed 90 W / (m·K) at most, and it has good mechanical properties.

[0010] Optionally, the adhesive is one of acrylic resin, epoxy resin, silicone rubber, phenolic resin, and polyurethane, preferably acrylic resin or silicone rubber.

[0011] Optionally, the thickness of the adhesive coated between the graphene film layers is 10-100 μm.

[0012] By adopting the above technical solution, the adhesive mainly plays the role of bonding two adjacent layers of graphene film to prevent the graphene thermal pad from being delaminated and spread out. When the adhesive thickness exceeds 100μm, the adhesive is too thick to affect the thermal conductivity of the graphene thermal pad in the interlayer direction; when the adhesive thickness is less than 10μm, the adhesive is too thin to achieve a good bonding effect, and the graphene film is easy to be delaminated and spread out.

[0013] Optionally, the through holes are distributed in an array on the graphene film, and the aperture of the through holes is 20-100 μm; the distance between the centers of two adjacent through holes is 50-200 μm.

[0014] Optionally, the carbon fiber filaments are made of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber or viscose-based carbon fiber, and the diameter of the carbon fiber filaments is 5-15 μm, preferably 7-10 μm, and further preferably 7 μm.

[0015] By adopting the above technical solution, since the thermal conductivity performance in the direction between graphene layers is poor and two adjacent graphene films are bonded by adhesive, the heat dissipation effect of the prepared graphene thermal conductive gasket in the direction between graphene film layers is weaker than the heat dissipation effect in the horizontal direction within the layer. The use of carbon fiber filaments can improve the thermal conductivity performance between graphene film layers.

[0016] The aperture size of the through hole will affect the mechanical properties of the graphene thermal pad and the thermal conductivity in the intra-layer direction, and the arrangement density of the through hole will affect the mechanical properties of the graphene thermal pad and the thermal conductivity in the inter-layer direction. If the through hole spacing exceeds 200μm, the carbon fiber filaments are too sparsely distributed on the graphene thermal pad, resulting in poor thermal conduction effect in the inter-layer direction of the graphene film; if the spacing between adjacent through holes is less than 50μm, the through holes are too densely distributed, the difficulty of drilling increases, and it will affect the mechanical properties of the graphene thermal pad, and the graphene film is easy to break. The aperture of the through hole will affect the penetration of the carbon fiber filaments. When the aperture of the through hole is less than 30μm, the penetration of the carbon fiber filaments is more difficult; if the aperture of the through hole is greater than 100μm, on the one hand, it will affect the mechanical properties of the graphite thermal pad, and on the other hand, when the aperture is too large, more adhesive will adhere to the through hole, affecting the thermal conductivity of the graphene thermal pad.

[0017] It should be noted that the aperture and arrangement density of the through holes will restrict each other, and thus jointly affect the mechanical properties and thermal conductivity of the graphene thermal pad. For example, when the aperture of the through hole is 40μm and the center spacing between adjacent through holes is 150μm, the number of through holes that can be opened on a graphene thermal pad with a thickness of 0.2mm and a size of 20*20mm is: about 130 in the width direction and 1 in the thickness direction. That is, about 130 carbon fiber filaments can be arranged inside a graphene thermal pad with a thickness of 0.2mm and a size of 20*20mm.

[0018] In a second aspect, the present application provides a method for preparing a graphene thermally conductive gasket, which adopts the following technical solution:

[0019] A method for preparing a graphene thermally conductive pad comprises the following steps:

[0020] S1, graphene film lamination: coating a layer of adhesive on the first graphene film, then placing the second graphene film on the first graphene film, and further coating a layer of adhesive on the second graphene film, and then laminating the third graphene film, and repeating the lamination process until the target height is reached, and obtaining a graphene film block after the adhesive is cured;

[0021] S2, drilling: drilling a through hole in the graphene film block, wherein the axial direction of the through hole is parallel to the stacking direction of the graphene film;

[0022] S3, perforating the carbon fiber yarn: coating the surface of the rewound carbon fiber yarn with an adhesive and then passing it through the through hole to obtain a graphene-carbon fiber three-dimensional structure;

[0023] S4, slicing: slicing the graphene-carbon fiber three-dimensional structure along a direction parallel to the graphene film stacking to obtain a graphene thermal conductive pad;

[0024] By adopting the above technical scheme, since the graphene thermally conductive pad finally obtained is very thin, during preparation, firstly a large piece of graphene film is laminated, each layer of graphene film is connected to the graphene film of the adjacent layer by an adhesive, until the graphene film is laminated to the target height. Then the carbon fiber filaments are arranged inside the graphene film block by the way of perforated penetration. In order to fix the carbon fiber filaments inside the graphene block, it is necessary to wrap an adhesive on the carbon fiber filaments for connection with the graphene block, finally obtain a graphene-carbon fiber three-dimensional structure, and then slice to obtain the graphene thermally conductive pad.

[0025] Optionally, the method further includes the following steps: S5, cutting, cutting the graphene thermal conductive gasket obtained by slicing in step S4 into specified sizes.

[0026] By adopting the above technical solution, when preparing the graphene thermal conductive gasket, large pieces of graphene film can be stacked first, sliced ​​to obtain large pieces of graphene thermal conductive gasket, and then cut into multiple small pieces, which can improve production efficiency.

[0027] Optionally, the adhesive in step S1 is applied by spraying or scraping, and the adhesive is cured by heat curing, room temperature curing or UV curing, preferably heat curing.

[0028] By adopting the above technical solution, different types of adhesives need to be matched with different types of coating methods. For example, for acrylic resin adhesives, because of their low overall viscosity, spray coating can achieve uniform adhesive coating and can be applied very thinly; while for adhesives with higher viscosity such as silicone rubber, scraping coating is required. The curing method of the adhesive is selected according to the type of adhesive and the instructions for use. In addition, the curing of the adhesive can be performed once for each stacked layer of graphene film, or once after all graphene films are stacked, preferably once after all graphene films are stacked.

[0029] Optionally, the punching method in step S2 is laser punching or mechanical drilling; the slicing method in step S4 is wire cutting, laser cutting, blade cutting or ultrasonic cutting.

[0030] By adopting the above technical solution, different punching methods are selected according to the through-hole aperture size and different application requirements. Laser punching has a fast speed and is suitable for processing small-diameter, large-number and high-density group holes, which can improve the punching efficiency. However, laser punching is a high-intensity heat source to open holes in heating materials. When the focusing energy is too high or the spot is large, it will produce certain thermal effect burns near the through hole on the graphene membrane, affecting the structure and mechanical properties of the graphene membrane; at the same time, the hole formed by laser drilling is a truncated cone hole. When opening a large-diameter through hole, the truncated cone structure will affect the subsequent slicing accuracy. Therefore, when a large-diameter through hole needs to be opened, mechanical drilling can be used. Different slicing methods are selected according to the different thickness of the required slices and specific production needs. In addition, the thickness of the graphene thermal conductive gasket can be adjusted according to the needs of the application environment.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. In this application, graphene film is selected as the main material of the thermal conductive gasket, and carbon fiber filaments are inserted into the inside of the graphene film block along the direction of penetrating the graphene film stack to improve the thermal conductivity between the graphene film layers, so that the finally manufactured graphene thermal conductive gasket has excellent thermal conductivity in the thickness direction and the direction between the graphene film stack layers, and the heat dissipation performance of the graphene thermal conductive gasket is significantly improved;

[0033] 2. The method for preparing a graphene thermally conductive gasket provided in the present application comprises stacking multiple layers of graphene film to a target height and then slicing the layers. The layers can be cut into a specified thickness as required. Meanwhile, the thickness of the stacked graphene films can also be flexibly adjusted as required. The method for preparing a graphene thermally conductive gasket is simple, efficient, and suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the stacking direction and slicing direction of the graphene film in this application.

[0035] Explanation of the accompanying drawings: 1. Graphene film; 2. Adhesive; 3. Carbon fiber filament. DETAILED DESCRIPTION

[0036] The following is combined with Figure 1 The present application is further described in detail with reference to the accompanying drawings and embodiments. Example

[0037] Example 1

[0038] This embodiment discloses a graphene thermally conductive gasket, which is prepared by the following method:

[0039] S1, placing a first layer of graphene film on an operating table, coating a layer of adhesive on the first layer of graphene film, then stacking a second layer of graphene film on the first layer of graphene, and coating a layer of adhesive on the second layer of graphene film and then stacking a third layer of graphene film, and repeating the process until the layers are stacked to a target height, and obtaining a graphene film block after the adhesive is dried;

[0040] S2, opening a plurality of through holes on the graphene film block prepared in S1, wherein the axial direction of the through holes is parallel to the direction of graphene film stacking, and the through holes penetrate the entire graphene film block, and all the through holes are distributed in a matrix on the graphene film;

[0041] S3, inserting carbon fiber filaments into the through holes opened in S2, soaking the carbon fiber filaments in an adhesive before inserting, so that the adhesive is coated on the surface of the carbon fiber filaments, and then inserting the carbon fiber filaments coated with the adhesive into the through holes on the graphene film block, and making the carbon fiber filaments completely fill the through holes in the length direction, and after the adhesive is cured, the carbon fiber filaments are fixed inside the graphene block, thereby obtaining a graphene-carbon fiber three-dimensional structure;

[0042] S4, slicing the graphene-carbon fiber three-dimensional structure obtained in S3 to obtain a graphene thermal conductive pad, referring to Figure 1 The slicing direction is parallel to the stacking direction of the graphene film, and the cutting position is located between two adjacent columns or rows of carbon fiber filaments during slicing. At the same time, the graphene thermal conductive pad obtained by slicing has carbon fiber filaments evenly distributed thereon;

[0043] Among them, the size of the graphene film is 50*50㎜, the thickness is 500μm, and the target height of the graphene film stack is 50㎜.

[0044] The adhesive coated between the graphene film layers is an acrylic resin adhesive with a thickness of 10 μm, the coating method is spraying, the curing method is thermal curing, and the curing temperature is 120°C;

[0045] The through hole diameter is 20μm, the center distance between two adjacent through holes is 50μm, and the hole is opened by laser drilling;

[0046] The slicing method is wire cutting, and the graphene thermal conductive gasket obtained by slicing has a thickness of 2mm and a size of 50*50mm.

[0047] Example 2

[0048] The difference from Example 1 is that the thickness of the acrylic resin adhesive coated between adjacent graphene film layers is 100 μm.

[0049] Example 3

[0050] The difference from Example 1 is that the thickness of the acrylic resin adhesive coated between adjacent graphene film layers is 30 μm.

[0051] Example 4

[0052] The difference from Example 3 is that the diameter of the through hole is 100 μm, and the distance between the centers of adjacent through holes is 200 μm.

[0053] Example 5

[0054] The difference from Example 3 is that the diameter of the through hole is 20 μm, and the distance between the centers of adjacent through holes is 200 μm.

[0055] Example 6

[0056] The difference from Example 3 is that the diameter of the through hole is 100 μm, and the distance between the centers of adjacent through holes is 180 μm.

[0057] Example 7

[0058] The difference from Example 3 is that the diameter of the through hole is 60 μm, and the distance between the centers of adjacent through holes is 120 μm.

[0059] Example 8

[0060] The difference from Example 7 is that the adhesive coated between the graphene film layers is a silicone rubber adhesive, the adhesive thickness is 30 μm, the coating method is scraping, the curing method is thermal curing, and the curing temperature is 80°C.

[0061] Example 9

[0062] The difference between the embodiment and embodiment 7 is that the size of the graphene film is 100*100㎜ and the thickness is 500μm;

[0063] The large graphene thermal conductive gasket obtained by slicing is cut into four pieces to obtain a graphene thermal conductive gasket with a thickness of 2 mm and a size of 50*50 mm.

[0064] Comparative Example

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 7 is that no through holes are provided on the graphene membrane and no carbon fiber filaments are provided.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 7 is that acrylic resin adhesive is poured into the through holes on the graphene film, and no carbon fiber filaments are passed through the through holes.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 3 is that the thickness of the acrylic resin adhesive coated between adjacent graphene film layers is 120 μm.

[0071] Comparative Example 4

[0072] The difference between this comparative example and Example 7 is that the aperture of the through hole is 20 μm, and the center distance between adjacent through holes is 250 μm.

[0073] Comparative Example 5

[0074] The difference between this comparative example and Example 7 is that the diameter of the through hole is 120 μm, and the center distance between adjacent through holes is 150 μm.

[0075] Performance testing

[0076] In each embodiment and comparative example, a graphene thermal pad with a thickness of 2 mm was selected for performance testing. The tensile strength of the graphene thermal pad was tested according to ASTM D412-2006; the compression rebound rate of the thermal pad was tested according to ASTM D575-1991; and the thermal conductivity of the thermal pad was tested according to ASTM D5470.

[0077] The performance test data of the graphene thermally conductive pads in Examples 1-9 and Comparative Examples 1-5 are shown in Table 1 below. Among them, the "thickness direction" refers to the thickness direction of the graphene thermally conductive pads obtained by graphene thermally conductive slicing, that is, Figure 1 The “horizontal direction” is the length direction of the carbon fiber filaments on the graphene thermal pad, that is, the interlayer direction of the graphene film. Figure 1 The Z direction is shown in the figure; the “vertical direction” is the direction perpendicular to the length of the carbon fiber filament in the plane of the graphene thermal pad. Figure 1 Y direction shown in .

[0078] Table 1: Performance test data of Examples 1-9 and Comparative Examples 1-5

[0079]

[0080] Combining Example 7, Comparative Examples 1-2, and the data in Table 1, it can be seen that arranging carbon fiber filaments inside the graphene film stack can effectively improve the thermal conductivity of the graphene film in the interlayer direction. Specifically, by arranging carbon fiber filaments in the interlayer direction of the multi-layer graphene film stack, the interlayer direction of the graphene film stack is connected by the carbon fiber filaments, and the thermal conductivity of the graphene thermal conductive gasket finally prepared in the horizontal direction is significantly increased, effectively improving the thermal conductivity of the graphene thermal conductive gasket in the horizontal direction.

[0081] Combining the data in Examples 1-3, Comparative Example 3 and Table 1, it can be seen that the thickness of the adhesive coated between adjacent graphene film layers will affect the thermal conductivity and mechanical properties of the graphene thermally conductive gasket. Specifically, when the thickness of the adhesive increases, the proportion of the adhesive increases on the graphene thermally conductive gasket of the same size. Based on this, the tensile strength and resilience of the graphene thermally conductive gasket will increase, but at the same time, the thermal conductivity of the graphene thermally conductive gasket in the thickness direction and the horizontal direction will decrease, affecting the thermal conductivity of the graphene thermally conductive gasket. When the thickness of the adhesive is about 30μm, the thermal conductivity and mechanical properties of the graphene thermally conductive gasket can reach a higher level.

[0082] Combined with the data of Example 3, Example 4-7, Comparative Example 4-5 and Table 1, the aperture size of the through hole and the distribution density of the through hole will affect the thermal conductivity and mechanical properties of the graphene thermal pad. Specifically, when the thickness of the adhesive between the graphene film layers is constant and the aperture of the through hole increases, the adhesive attached to the through hole increases, then the tensile strength and rebound rate of the graphene thermal pad will be improved to a certain extent, but its thermal conductivity will decrease, and the thermal conductivity will decrease; in addition, if the aperture of the through hole is constant and the density of the through hole increases, the number of carbon fiber filaments arranged in the graphene thermal pad increases, which will improve the horizontal thermal conductivity of the graphene thermal pad, but at the same time, the thermal conductivity of the graphene thermal pad in the thickness direction will decrease, and the mechanical properties will also decrease. Comprehensively considered, when the aperture of the through hole is about 60μm, and the spacing between the centers of adjacent through holes is about 120μm, the thermal conductivity and mechanical properties of the graphene thermal pad will reach a better balance.

[0083] Combining the data in Examples 7 and 8 and Table 1, it can be seen that when the adhesive between the graphene film layers is acrylic resin adhesive and silicone rubber adhesive, there is no obvious difference in the thermal conductivity of the graphene thermal conductive gaskets obtained. Therefore, the tensile strength and resilience of the graphene thermal conductive gasket obtained by coating the graphene film layer with silicone rubber adhesive are higher.

[0084] Combining the data in Examples 7 and 9 and Table 1, it can be seen that there is no obvious difference in thermal conductivity and mechanical properties between the graphene thermal conductive gasket obtained by directly stacking and slicing small graphene films and the graphene thermal conductive gasket obtained by stacking and slicing large graphene films and then cutting them.

[0085] To summarize, the graphene thermal conductive gasket disclosed in the embodiment of the present application arranges carbon fiber filaments in the stacking direction of the graphene films, and uses the carbon fiber filaments to enhance the thermal conductivity of the graphene thermal conductive gasket in the direction between the stacked layers of the graphene films, thereby further improving the overall thermal conductivity performance of the graphene thermal conductive gasket, and thus preparing a thermal interface product with high thermal conductivity, which has broad application prospects in the field of chip heat dissipation.

[0086] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing a graphene thermally conductive pad, It is characterized in that The following steps are involved: S1, graphene film lamination: coating a layer of adhesive on the first graphene film, then placing the second graphene film on the first graphene film, and further coating a layer of adhesive on the second graphene film, and then laminating the third graphene film, and so on, and the lamination is repeated until the target height is reached, and a graphene film block is obtained after the adhesive is cured; the thickness of the adhesive coated between adjacent layers of the graphene film is 10-100 μm; S2, opening holes: opening through holes penetrating both sides of the graphene membrane block on the graphene membrane block, wherein the axial direction of the through holes is parallel to the stacking direction of the graphene membrane; the aperture of the through holes is 20-100 μm, and the distance between the centers of two adjacent through holes is 50-200 μm; S3, perforating the carbon fiber filaments: coating the surface of the carbon fiber filaments with an adhesive and then perforating the carbon fiber filaments into the through holes to obtain a graphene-carbon fiber three-dimensional structure; the diameter of the carbon fiber filaments is 5-15 μm; the carbon fiber filaments are made of one of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber and viscose-based carbon fiber; S4, slicing: slicing the graphene-carbon fiber three-dimensional structure along a direction parallel to the stacking direction of the graphene film to obtain a graphene thermal conductive gasket of a specified thickness.

2. A method for preparing a graphene thermally conductive pad according to claim 1, Features: The adhesive is silicone rubber, acrylic resin, epoxy resin, phenolic resin or polyurethane.

3. A method for preparing a graphene thermally conductive pad according to claim 1, Features: The thickness of the graphene thermal pad is 0.1-5 mm.

4. A method for preparing a graphene thermally conductive pad according to any one of claims 1 to 3, It is characterized in that The following steps are also included: S5, cutting: cutting the graphene thermal conductive pad obtained by slicing in step S4 into a specified size.

5. A method for preparing a graphene thermally conductive pad according to claim 4, Features: In step S1, the adhesive is applied by spraying or scraping; the adhesive is cured by heat curing, room temperature curing or UV curing.

6. A method for preparing a graphene thermally conductive pad according to claim 4, Features: The hole-making method in step S2 is laser drilling or mechanical drilling; the slicing in step S4 is wire cutting, laser cutting, blade cutting or ultrasonic cutting.

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