Graphene cooling fin with high vertical thermal conductivity and easy compression, preparation method of graphene cooling fin and electronic device

Abstract

The invention provides a graphene cooling fin with high vertical thermal conductivity and easy compression, a preparation method thereof and an electronic device, and relates to the field of heat dissipation materials. The method comprises the following steps: mixing graphene powder, a partially gelatinized polymer, an epoxy adhesive A and a solvent to obtain a mixture; carrying out curing molding on the mixture to obtain graphene sheets; sequentially laminating the graphene sheets in the horizontal direction, coating an epoxy adhesive B between the adjacent graphene sheets, and carrying out hot-pressing curing to obtain a graphene block; performing section slicing on the graphene blocks in the direction perpendicular to the stacking direction of the graphene sheets to obtain middle sheet layers; and performing pore-forming treatment on the middle sheet layer to obtain the graphene cooling fin which is high in vertical heat conduction and easy to compress. According to the method, the raw materials are easy to obtain, the process steps are clear, and the density, porosity, thermal conductivity and compression ratio of the product can be flexibly regulated and controlled by adjusting parameters such as the gel content and the slice thickness so as to meet the requirements of different application scenes.

Description

Technical Field

[0001] This application relates to the field of heat dissipation materials, and in particular to a graphene heat sink with high vertical thermal conductivity and easy compressibility, its preparation method, and electronic devices. Background Technology

[0002] With the development of 5G communication, high-performance computing (HPC), and power electronic devices, the heat flux density of chips has increased dramatically, placing extreme demands on heat dissipation materials. An ideal thermal interface material (TIM) needs to possess two key characteristics: first, high intrinsic thermal conductivity for rapid heat conduction; and second, good compressibility to ensure close contact with the heat dissipation surface under low pressure, thereby reducing interfacial contact thermal resistance.

[0003] In existing technologies, polymer-based composite materials filled with high thermal conductivity fillers (such as graphene and carbon nanotubes) are the mainstream approach. However, to achieve high thermal conductivity, extremely high filler loadings are often required, which leads to a significant increase in material hardness and a decrease in compressibility, resulting in increased interfacial thermal resistance and poor actual heat dissipation. On the other hand, while highly oriented pyrolytic graphite films have extremely high in-plane thermal conductivity, their vertical thermal conductivity is low, and their texture is hard and brittle, making it difficult to effectively fill microscopic irregularities at the interface.

[0004] Therefore, a long-standing technical contradiction exists in this field: the bulk thermal conductivity of a material and its compressive flexibility are usually mutually restrictive. Based on this, developing a novel material that can simultaneously possess high vertical thermal conductivity and maintain low thermal resistance at high compression ratios has become an urgent need for the industry. Summary of the Invention

[0005] The purpose of this application is to provide a graphene heat sink with high vertical thermal conductivity and easy compression, as well as its preparation method and electronic device, to solve the above-mentioned problems.

[0006] To achieve the above objectives, the first aspect of this application provides a method for preparing a graphene heat sink with high vertical thermal conductivity and easy compression, comprising: Graphene powder, partially gelled polymer, epoxy adhesive A, and solvent are mixed to obtain a mixture; the mixture is then cured and molded to obtain a graphene sheet. The graphene sheets are stacked horizontally in sequence, and epoxy adhesive B is coated between adjacent graphene sheets. The mixture is then hot-pressed and cured to obtain a graphene block. The graphene block is sliced ​​in cross-section along a direction perpendicular to the stacking direction of the graphene sheets to obtain the intermediate layer. The intermediate layer is perforated to obtain a graphene heat sink with high vertical thermal conductivity and easy compression.

[0007] Optionally, the partially gelled polymer includes one or more of polyvinyl alcohol, polyacrylic acid, polyethylene oxide, and thermoplastic polyurethane.

[0008] Optionally, the viscosity of the epoxy adhesive A is 500-2000 cps.

[0009] Optionally, the viscosity of the epoxy adhesive B is 20,000-200,000 cps.

[0010] Optionally, the solvent may include water.

[0011] Optionally, the mass ratio of the graphene powder, the partially gelled polymer, and the epoxy adhesive A is 20-60:5-30:10-40.

[0012] Optionally, the thickness of the graphene sheet is 0.1-2 mm; And / or, the number of graphene sheets in the graphene block is 100-1000 layers; And / or, the thickness of the adhesive layer formed by the epoxy adhesive B is 15-25 μm; And / or, the thickness of the intermediate sheet is 0.1-2 mm.

[0013] Optionally, the curing process includes coating and / or calendering; And / or, the hot-press curing temperature is 80-120℃, the pressure is 0.5-1.5MPa, and the time is 0.5-1.5h; And / or, the pore-forming process includes low-temperature pyrolysis and / or solvent extraction; The temperature of the low-temperature pyrolysis is 150-300℃.

[0014] The second aspect of this application provides a graphene heat sink with high vertical thermal conductivity and easy compression, which is prepared by the method for preparing the graphene heat sink with high vertical thermal conductivity and easy compression.

[0015] A third aspect of this application provides an electronic device including the aforementioned highly vertically thermally conductive and easily compressible graphene heat sink.

[0016] Compared with the prior art, the beneficial effects of this application include: The method for preparing a graphene heat sink with high vertical thermal conductivity and easy compressibility provided in this application utilizes a clever physical orientation method of "horizontal stacking → vertical slicing" to redirect the high thermal conductivity direction within the graphene sheet layer to the vertical direction of the product. This achieves vertical thermal conductivity performance far exceeding that of conventional randomly distributed composite materials, reaching over 200 W / m·K. By introducing and subsequently removing "partially gelled polymers," a controllable three-dimensional porous network structure is created within the material. This method uses readily available raw materials and has clear process steps. By adjusting parameters such as gel content and slice thickness, the density, porosity, thermal conductivity, and compressibility of the product can be flexibly controlled to meet the needs of different application scenarios.

[0017] The graphene heat sink provided in this application has high vertical thermal conductivity and is easily compressible. The loose structure in the graphene sheet gives the material excellent compressive elasticity, which allows it to be compressed significantly under low pressure, fully filling the interfacial gaps and significantly reducing contact thermal resistance. The entire material is composed of graphene and epoxy resin, and the interlayer and internal layers are firmly bonded by epoxy adhesive. The structure is intact, avoiding the problem of filler shedding, and has high reliability in long-term use.

[0018] The electronic devices provided in this application have good heat dissipation performance and long service life. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0020] Figure 1 A schematic diagram of a cross-sectional slice of the graphene block provided in this application. Detailed Implementation

[0021] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a method for preparing a graphene heat sink with high vertical thermal conductivity and easy compression, comprising: Graphene powder, partially gelled polymer, epoxy adhesive A, and solvent are mixed to obtain a mixture; the mixture is then cured and molded to obtain a graphene sheet. The graphene sheets are stacked horizontally in sequence, and epoxy adhesive B is coated between adjacent graphene sheets. The mixture is then hot-pressed and cured to obtain a graphene block. The graphene block is sliced ​​in cross-section along a direction perpendicular to the stacking direction of the graphene sheets to obtain the intermediate layer. It is important to note that graphene exhibits directional thermal conductivity, with high horizontal thermal conductivity (generally >1500W) but relatively poor vertical thermal conductivity (only a few W). When stacked graphene sheets are cross-sectioned, they become vertically conductive. Only after slicing can the vertical thermal conductivity target of this application be achieved. The specific slicing steps for easily compressible thermally conductive graphene sheets are illustrated below. Figure 1 As shown; The intermediate layer is perforated to obtain a graphene heat sink with high vertical thermal conductivity and easy compression.

[0022] It is important to note that ordinary graphene is relatively hard compared to ordinary thermal interface materials. Ordinary graphene is difficult to compress and requires significant stress, making it unsuitable for widespread application as a vertical thermal interface material. When graphene is pore-formed, it becomes a porous structure with low compressive stress, primarily addressing the compressive stress issue. Some gelled polymers can be used as pore-forming materials, enabling low-temperature pore formation. Unlike ceramic pore formation, which requires temperatures exceeding thousands of degrees Celsius, epoxy resins cannot withstand such high temperatures.

[0023] In some embodiments, the partially gelled polymer includes one or more of polyvinyl alcohol, polyacrylic acid, polyethylene oxide, and thermoplastic polyurethane.

[0024] In some embodiments, the viscosity of epoxy adhesive A is 500-2000 cps.

[0025] Optionally, the viscosity of epoxy adhesive A can be 500 cps, 1000 cps, 1500 cps, 2000 cps, or any value between 500 and 2000 cps.

[0026] It should be noted that epoxy adhesive A is a low-viscosity epoxy adhesive. Its function is as follows: as the main material, the low-viscosity epoxy adhesive system makes it easy to add graphene, and it has good adhesion to graphene, as well as good toughness and strength, making it less prone to cracking during subsequent orientation and cutting.

[0027] In some embodiments, the viscosity of the epoxy adhesive B is 20,000-200,000 cps.

[0028] Optionally, the viscosity of epoxy adhesive B can be 20,000 cps, 50,000 cps, 100,000 cps, 150,000 cps, 200,000 cps, or any value between 20,000 and 200,000 cps.

[0029] It should be noted that epoxy adhesive B is a high-viscosity epoxy adhesive. Its function is as a layered adhesive, which provides good adhesion to the epoxy adhesive matrix.

[0030] In some embodiments, the solvent includes water.

[0031] In some embodiments, the mass ratio of the graphene powder, the partially gelled polymer, and the epoxy adhesive A is 20-60:5-30:10-40.

[0032] Optionally, the mass ratio of graphene powder, partially gelled polymer and epoxy adhesive A can be (20:5:10), (40:5:10), (60:5:10), (40:15:10), (40:30:10), (40:15:20), (40:15:40), (60:30:40) or any value between 20-60:5-30:10-40.

[0033] It is important to note that too little graphene powder will affect the formation of heat conduction channels, resulting in a low thermal conductivity. Too much graphene powder will make it difficult to add, and the system will be too thick and impractical. Too little gelled polymer will result in insufficient air bubbles and excessive compressive stress. Too much gelled polymer will cause air bubble rupture, making it difficult to form continuous graphene sheets. Too little low-viscosity epoxy adhesive will result in a system that is too thick and impractical. Too much low-viscosity adhesive will result in a low thermal conductivity. In some embodiments, the thickness of the graphene sheet is 0.1-2 mm; Optionally, the thickness of the graphene sheet can be any value between 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, or 0.1-2 mm; And / or, the number of graphene sheets in the graphene block is 100-1000 layers; Optionally, the number of graphene sheets in the graphene block can be 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 or any value between 100 and 1000. And / or, the thickness of the adhesive layer formed by the epoxy adhesive B is 15-25 μm; Optionally, the thickness of the adhesive layer formed by epoxy adhesive B can be any value between 15μm, 20μm, 25μm or 15-25μm; And / or, the thickness of the intermediate sheet is 0.1-2 mm.

[0034] Optionally, the thickness of the intermediate layer can be any value between 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, or 0.1-2 mm.

[0035] In some embodiments, the curing process includes coating and / or calendering; And / or, the hot-press curing temperature is 80-120℃, the pressure is 0.5-1.5MPa, and the time is 0.5-1.5h; Optionally, the hot-press curing temperature can be any value between 80℃, 90℃, 100℃, 110℃, 120℃ or 80-120℃, the pressure can be any value between 0.5 MPa, 1 MPa, 1.5 MPa or 0.5-1.5 MPa, and the time can be any value between 0.5h, 1h, 1.5h or 0.5-1.5h. And / or, the pore-forming process includes low-temperature pyrolysis and / or solvent extraction; The temperature of the low-temperature pyrolysis is 150-300℃.

[0036] Optionally, the temperature for low-temperature pyrolysis can be any value between 150℃, 200℃, 250℃, 300℃, or 150-300℃.

[0037] It should be noted that the temperature of low-temperature pyrolysis is higher than the decomposition temperature or glass transition temperature of some gelled polymers, but much lower than the decomposition temperature of epoxy resin. By pyrolysis or sintering, some gelled polymers are decomposed and volatilized, or they are removed by selective solvent extraction. Finally, a graphene heat sink with abundant micropores and a loose structure is obtained.

[0038] The second aspect of this application provides a graphene heat sink with high vertical thermal conductivity and easy compression, which is prepared by the method for preparing the graphene heat sink with high vertical thermal conductivity and easy compression.

[0039] A third aspect of this application provides an electronic device including the aforementioned highly vertically thermally conductive and easily compressible graphene heat sink.

[0040] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0041] Example 1 This embodiment provides a graphene heat sink with high vertical thermal conductivity and easy compression, and its preparation method. The specific preparation steps are as follows: S1. Mix 40 parts by weight of graphene powder, 20 parts by weight of polyvinyl alcohol (PVA, as a partially gelled polymer), 30 parts by weight of two-component epoxy resin (epoxy adhesive A, purchased from Shanghai Baigao Polymer Materials Co., Ltd., model EP 1708) with an appropriate amount of water to form a slurry, cast it into a film, and preliminarily cure and dry it at 80°C to obtain an initial graphene sheet with a thickness of about 0.2 mm. S2. Constructing the block: Stack 100 layers of the initial graphene sheet, spray a thin layer of 20μm epoxy adhesive B (purchased from Shanghai Baigao Polymer Materials Co., Ltd., model EP 1763) between each layer, and hot-press and cure at 100℃ and 1MPa pressure for 1 hour to form a laminated graphene block. S3. Perpendicular Slicing: Using a diamond wire cutter, the block is sliced ​​into 0.3mm thick sheets and 2mm thick sheets along a direction perpendicular to the surface. The 0.3mm sheet is tested for thermal resistance at 80psi and 80℃, and the 2mm sheet is tested for thermal conductivity at 10psi and 80℃. S4. Remove gel and create pores: Place the slice in a muffle furnace and keep it at 250°C in an air atmosphere for 1 hour to allow PVA to completely decompose and volatilize, thus obtaining the final porous graphene heat sink. Performance testing: The measured vertical thermal conductivity is 210 W / m·K, and the pressure at a compression ratio of 30% is less than 0.5MPa, demonstrating excellent overall performance.

[0042] Example 2 The difference from Example 1 is that the amount of graphene powder added is 60 parts by weight.

[0043] Example 3 The difference from Example 1 is that the amount of polyvinyl alcohol added is changed to 40 parts by weight.

[0044] Example 4 The difference from Example 1 is that the amount of two-component epoxy resin (epoxy adhesive A) added is 40 parts by weight.

[0045] Comparative Example 1 The difference from Example 1 is that the graphene heat sink with high vertical thermal conductivity and easy compression is replaced with a conventional non-oriented, horizontally conductive 0.3×200×200mm sheet with a thermal conductivity of 1500W, purchased from Zhejiang Daoming Superconducting Technology Co., Ltd., model CDGC300.

[0046] Comparative Example 2 The difference from Example 1 is that polyvinyl alcohol is not included.

[0047] Comparative Example 3 The difference from Example 1 is that epoxy adhesive A is replaced with epoxy adhesive B.

[0048] Comparative Example 4 The difference from Example 1 is that epoxy adhesive B is replaced with epoxy adhesive A.

[0049] Comparative Example 5 The difference from Example 1 is that the amount of raw materials is different. In step S1, the amount of graphene powder is 85 parts by weight, the amount of polyvinyl alcohol is 5 parts by weight, and the amount of epoxy adhesive A is 10 parts by weight.

[0050] Comparative Example 6 The difference from Example 1 is that the number of graphene sheets in the graphene block is 2000.

[0051] The thermally conductive graphene sheets prepared above were subjected to performance testing, and the specific testing standards are as follows: Specific gravity after curing: according to the standard in ASTM D792-2007 Test Method for Density and Relative Density of Plastics, the unit is g / cc.

[0052] Thermal conductivity: according to the standard in ASTM D5470-2017, the unit is W / m·K.

[0053] Pressure at 30% compression ratio: unit is MPa.

[0054] The performance test results of the above embodiments and comparative examples are shown in Table 1.

[0055] Table 1 Performance Tests

[0056] Note: Comparative Example 4 has obvious cracks in some places after orientation and cutting, and its appearance and operability are not good; Comparative Example 6 has Π-shaped cracks formed under pressure due to excessive graphene, and its utilization rate is not high, only the middle part can be used.

[0057] analyze: As shown in the above tests, the graphene heat sinks with high vertical thermal conductivity and easy compressibility prepared in Examples 1-4 of this application have excellent vertical thermal conductivity and low compressive stress, which can meet the requirements for higher vertical heat dissipation. In contrast, the conventional horizontally conductive graphene sheet in Comparative Example 1 has a low vertical thermal conductivity, which limits its application. Comparative Example 2, without the addition of gelled polymer, has huge compressive stress, which contradicts the application of thermal interface materials and is difficult to use. Using high-viscosity epoxy adhesives makes it difficult to add graphene, which is not feasible. If low-viscosity epoxy is used to bond graphene sheets, cracks are easily formed in some places after orientation and cutting, resulting in poor appearance and operability. When the amount of graphene is too large, it cannot be added, which is not feasible. When the stacking is too high, under pressure, the unique honeycomb lattice structure of graphene will cause cracks to propagate in a specific direction, forming a shape similar to "Π". This is mainly related to the lattice orientation and interlayer interaction of graphene. After cracks are formed, only the middle part can be used, resulting in low utilization.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0059] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a graphene heat sink with high vertical thermal conductivity and easy compression, characterized in that, include: Graphene powder, partially gelled polymer, epoxy adhesive A, and solvent are mixed to obtain a mixture; the mixture is then cured and molded to obtain a graphene sheet. The graphene sheets are stacked horizontally in sequence, and epoxy adhesive B is coated between adjacent graphene sheets. The mixture is then hot-pressed and cured to obtain a graphene block. The graphene block is sliced ​​in cross-section along a direction perpendicular to the stacking direction of the graphene sheets to obtain the intermediate layer. The intermediate layer is perforated to obtain a graphene heat sink with high vertical thermal conductivity and easy compression.

2. The method for preparing the highly vertically conductive and easily compressible graphene heat sink according to claim 1, characterized in that, The partially gelled polymer includes one or more of polyvinyl alcohol, polyacrylic acid, polyethylene oxide, and thermoplastic polyurethane.

3. The method for preparing the highly vertically conductive and easily compressible graphene heat sink according to claim 1, characterized in that, The viscosity of epoxy adhesive A is 500-2000 cps.

4. The method for preparing the highly vertically conductive and easily compressible graphene heat sink according to claim 1, characterized in that, The viscosity of the epoxy adhesive B is 20,000-200,000 cps.

5. The method for preparing the highly vertically conductive and easily compressible graphene heat sink according to claim 1, characterized in that, The solvent includes water.

6. The method for preparing the highly vertically conductive and easily compressible graphene heat sink according to claim 1, characterized in that, The mass ratio of the graphene powder, the partially gelled polymer, and the epoxy adhesive A is 20-60:5-30:10-40.

7. The method for preparing the highly vertically conductive and easily compressible graphene heat sink according to claim 1, characterized in that, The thickness of the graphene sheet is 0.1-2 mm; And / or, the number of graphene sheets in the graphene block is 100-1000 layers; And / or, the thickness of the adhesive layer formed by the epoxy adhesive B is 15-25 μm; And / or, the thickness of the intermediate sheet is 0.1-2 mm.

8. The method for preparing a highly vertically conductive and easily compressible graphene heat sink according to any one of claims 1-7, characterized in that, The curing process includes coating and / or calendering; And / or, the hot-press curing temperature is 80-120℃, the pressure is 0.5-1MPa, and the time is 0.5-1.5h; And / or, the pore-forming process includes low-temperature pyrolysis and / or solvent extraction; The temperature of the low-temperature pyrolysis is 150-300℃.

9. A graphene heat sink with high vertical thermal conductivity and easy compression, characterized in that, It is prepared by the method for preparing a graphene heat sink with high vertical thermal conductivity and easy compressibility as described in any one of claims 1-8.

10. An electronic device, characterized in that, Including the highly vertically conductive and easily compressible graphene heat sink as described in claim 9.

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