A self-adhesive graphene heat-conducting gasket and a preparation method thereof

Abstract

This application relates to the field of thermal interface materials technology and discloses a self-adhesive graphene thermal conductive pad and its preparation method. The self-adhesive graphene thermal conductive pad includes a thermally conductive layer and an adhesive layer. The thermally conductive layer includes multiple graphene films and multiple carbon fiber mesh layers spaced apart along the thickness direction. The adhesive layer is disposed on a first surface and a second surface opposite to the first surface of the thermally conductive layer. The adhesive layer has multiple pore structures for reducing thermal resistance, and the pore distribution density of the peripheral region and the central region of the adhesive layer is different. The peripheral region has a first porosity, and the central region has a second porosity. The first porosity is less than the second porosity. This application uses the carbon fiber mesh to naturally form vertical thermal conductive channels. Combined with the gradient porosity design of the adhesive layer, it not only ensures the adhesion reliability of the periphery of the pad but also reduces the thermal resistance of the central region, achieving an efficient balance between adhesion and thermal conductivity.

Description

Technical Field

[0001] This application relates to the field of thermal interface materials technology, and in particular to a self-adhesive graphene thermal pad and its preparation method. Background Technology

[0002] As electronic products become increasingly lightweight and highly integrated, the operating frequency of electronic chips continues to rise, leading to a significant increase in heat generation. Thermal interface materials, as key components for heat dissipation, directly impact the operational stability and lifespan of electronic devices due to their thermal conductivity, ease of assembly, and reliability. Graphene, with its ultra-high theoretical thermal conductivity of up to 5300 W / (m·K), has become a preferred substrate for thermal interface materials, and graphene-based thermal pads are widely used in the heat dissipation of electronic devices.

[0003] However, existing graphene thermal pads have many limitations: their thermal conductivity is anisotropic. While the thermal conductivity within the graphene film is excellent, the interlayer thermal conductivity perpendicular to the film plane is relatively low. Traditional solutions improve interlayer thermal conductivity by creating through-holes and filling them with thermally conductive fillers, but this requires additional complex processes such as laser drilling and filler injection, resulting in high production costs and cumbersome processes. Furthermore, they have poor assembly compatibility. Pure graphene thermal pads have no adhesive surface, making them prone to misalignment during assembly. They also lack effective self-adhesive design, limiting their application scenarios. On the other hand, adhesive backing solutions significantly increase contact thermal resistance and severely reduce thermal conductivity.

[0004] Regarding the aforementioned technologies, existing graphene thermal pads are insufficient to meet the comprehensive heat dissipation and assembly requirements of high-power electronic devices, and a solution that simplifies the process and balances thermal conductivity and self-adhesive properties is urgently needed. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a self-adhesive graphene thermal pad and its preparation method.

[0006] Firstly, this application provides a self-adhesive graphene thermal conductive pad, which adopts the following technical solution: A self-adhesive graphene thermally conductive pad includes: a thermally conductive layer comprising a plurality of graphene films and a plurality of carbon fiber mesh layers spaced apart along the thickness direction; and an adhesive layer disposed on a first surface and a second surface opposite to the first surface of the thermally conductive layer, wherein the adhesive layer is provided with a plurality of pore structures for reducing thermal resistance, and the pore distribution density of the peripheral region and the central region of the adhesive layer is different, the peripheral region has a first porosity, the central region has a second porosity, and the first porosity is less than the second porosity.

[0007] By adopting the above technical solution, the thermal conductive layer adopts a structure in which graphene film and carbon fiber mesh layer are alternately arranged. The carbon fiber mesh layer replaces the traditional through-hole filler processing method, naturally forming vertical thermal conductive channels. No additional laser drilling and filler injection steps are required, which reduces production costs while improving interlayer thermal conductivity. The adhesive layer cleverly balances the viscosity requirement and thermal conduction efficiency through the gradient design of low porosity (high viscosity) in the peripheral area and high porosity (low thermal resistance) in the central area. It solves the contradiction of "increasing thermal resistance when improving viscosity" in traditional uniform thickness adhesive layers, and effectively meets the high heat conduction requirements of highly integrated electronic devices in the 5G era.

[0008] Optionally, the first porosity is 0%-15%, and the second porosity is 30%-50%.

[0009] By adopting the above technical solution, the specific numerical range of gradient porosity was clarified. This range has been verified by the process and can ensure that the low porosity of 0%-15% in the peripheral area meets the bonding and positioning requirements, while the high porosity of 30%-50% in the central area can effectively reduce thermal resistance, thereby increasing the thermal conductivity to 150W / (m・K). At the same time, it controls the overall thermal resistance of the adhesive layer to be reduced by 20%, thus achieving the optimization effect of both adhesion and thermal conductivity.

[0010] Optionally, in the mesh structure of the carbon fiber mesh layer, the shape of a single mesh is selected from the group consisting of triangles, hexagons, squares, and rhombuses, and the opening direction of the mesh is set towards the thickness direction of the heat-conducting layer.

[0011] By adopting the above technical solution, multiple optional shapes of carbon fiber mesh are identified. The mesh openings face the thickness direction of the heat-conducting layer, which can form directional vertical heat-conducting channels and improve the heat conduction efficiency between layers. Multiple mesh shapes can be adapted to the heat conduction requirements of different scenarios, enhancing the flexibility and applicability of the solution.

[0012] Optionally, the carbon fiber mesh layer is prepared by electrospinning, with a fiber diameter of 10-50 μm and a mesh spacing of 100-200 μm.

[0013] By adopting the above technical solution, the preparation process and key dimensional parameters of the carbon fiber mesh layer are defined. Electrospinning is a mature industrial process that can stably prepare a uniform mesh structure. The combination of a fiber diameter of 10-50μm and a mesh spacing of 100-200μm can ensure the structural strength of the mesh to support the heat-conducting layer and form an efficient heat-conducting channel, thereby improving the interlayer thermal conductivity by more than 12%.

[0014] Optionally, the adhesive layer includes a phase change adhesive region and a non-phase change adhesive region. The material of the phase change adhesive region includes an addition-cured silicone adhesive and paraffin carbon nanotube microcapsules. The paraffin carbon nanotube microcapsules are configured to absorb near-infrared light and undergo a phase change. The phase change adhesive region is configured to form a reversible bond based on the phase change of the paraffin carbon nanotube microcapsules.

[0015] By adopting the above technical solution, the phase change bonding area utilizes the photothermal response characteristics of paraffin carbon nanotube microcapsules to achieve the reversible bonding function of the bonding layer, solving the problem that traditional permanent adhesive bonding layers are not conducive to equipment repair; when irradiated with near-infrared light, the microcapsules undergo phase change, causing the adhesiveness to disappear, and the adhesiveness is restored after cooling, which enables the gasket to be reused. The design of setting phase change bonding areas locally takes into account both the overall bonding reliability and the convenience of repair.

[0016] Optionally, the viscosity of the addition-type silicone adhesive is 60-150 mPa・s, and the weight percentage of the paraffin carbon nanotube microcapsules is 2%-8%.

[0017] By adopting the above technical solution, the viscosity range of the addition-cured silicone adhesive and the weight ratio of the microcapsules are limited. This parameter range can ensure that the adhesive has good coatability, while enabling the microcapsules to be uniformly dispersed and stably perform photothermal response function. According to the test, the adhesive retention rate of the gasket is still greater than 90% after being reused 3 times under this ratio, taking into account both adhesive stability and reversibility.

[0018] Optionally, the thickness of the adhesive layer is 1-6 μm.

[0019] By adopting the above technical solution, the thickness of the adhesive layer is controlled within a thin range of 1-6μm. Compared with the traditional adhesive layer thickness of 2-10μm, the material usage is reduced by 15%, which further reduces thermal resistance and avoids affecting the overall thermal conductivity due to excessive adhesive layer thickness. This adapts to the installation space requirements of lightweight and highly integrated electronic products.

[0020] Secondly, this application provides a method for preparing a self-adhesive graphene thermal pad, which adopts the following technical solution: A method for preparing a self-adhesive graphene thermally conductive pad includes the following steps: providing a graphene film and a carbon fiber mesh layer; spaced multiple graphene films and multiple carbon fiber mesh layers to form a thermally conductive layer; providing an addition-type silicone adhesive and a microsphere foaming agent; mixing 0%-0.5% by weight of the microsphere foaming agent into a portion of the addition-type silicone adhesive to form a first foaming adhesive, and mixing 0.8%-2% by weight of the microsphere foaming agent into another portion of the addition-type silicone adhesive to form a second foaming adhesive; and in the phase of the thermally conductive layer... The two surfaces are divided into peripheral and central areas. A multi-nozzle spraying device is used to apply a first foaming adhesive to the peripheral areas of both surfaces and a second foaming adhesive to the central areas of both surfaces to form an adhesive substrate layer. The sprayed adhesive substrate layer is pre-cured at 60℃-100℃ and then cured again at 100℃-150℃ to form an adhesive layer. The microsphere foaming agent expands when heated, so that the peripheral area of ​​the adhesive layer forms a porous structure with a porosity of 0%-15% and the central area forms a porous structure with a porosity of 30%-50%.

[0021] By adopting the above technical solution, the preparation process is clear. By adjusting the addition ratio of microsphere foaming agent and combining it with the partitioned spraying process, the gradient porosity structure of the adhesive layer can be accurately achieved without the need for complex processing equipment. The staged curing process can ensure that the microsphere foaming agent fully expands to form a stable pore structure, thereby achieving a balance between viscosity and thermal resistance. The entire process adopts mature industrial technologies such as spraying and lamination, and all materials are industrial grade, which is conducive to large-scale production and reduces production costs.

[0022] Optionally, the preparation method further includes the steps of: providing paraffin carbon nanotube microcapsules; mixing 2%-8% by weight of paraffin carbon nanotube microcapsules into a partially addition-cured silicone adhesive to obtain a phase change adhesive; and coating the phase change adhesive onto a predetermined phase change bonding area of ​​the adhesive substrate layer so that the obtained adhesive layer has a reversible bonding function.

[0023] By adopting the above technical solution, the preparation and coating steps of phase change adhesive are added to the basic preparation process. The process has strong compatibility and does not require significant adjustments to the existing process. By accurately controlling the weight ratio of microcapsules, the reversible bonding effect in the phase change bonding area can be ensured to meet the equipment repair requirements, while not affecting the bonding reliability of the non-phase change bonding area.

[0024] Optionally, the carbon fiber mesh layer is prepared by electrospinning, with a fiber diameter of 10-50 μm and a mesh spacing of 100-200 μm. The shape of a single mesh includes one or more of triangles, hexagons, squares, and rhombuses. The graphene film and the carbon fiber mesh layer are alternately stacked along the thickness direction of the thermal conductive layer to a predetermined number of layers to form a layered structure with intervals, thus obtaining the thermal conductive layer.

[0025] By adopting the above technical solution, the preparation details of the carbon fiber mesh layer and the stacking method of the thermal conductive layer were clarified. The electrospinning method can stably control the size and shape of the mesh, and the alternating stacking process ensures the uniformity of the thermal conductive layer structure. The vertical thermal conductive channels formed by the carbon fiber mesh run through the entire thermal conductive layer, effectively improving the interlayer thermal conductivity. At the same time, the preparation process of the thermal conductive channels is simplified, and the production cost is reduced by 18% compared with the traditional through-hole processing technology.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. The thermally conductive layer adopts a structure with graphene film and carbon fiber mesh layer interspersed. The carbon fiber mesh naturally forms vertical thermal conduction channels, eliminating the need for laser drilling and filler filling steps, reducing production costs by 18% and improving interlayer thermal conductivity by 12%. The gradient porosity design of the adhesive layer balances adhesion and thermal resistance, reducing the adhesive layer thickness to 1-6μm, reducing thermal resistance by 20%, and increasing the thermal conductivity to 150W / (m・K), meeting the heat dissipation requirements of highly integrated electronic devices. 2. The adhesive layer is set with a phase change adhesive area, and reversible bonding is achieved through the photothermal response phase change of paraffin carbon nanotube microcapsules. During repair, local near-infrared irradiation can quickly debond the gasket. The adhesive retention rate is >90% after the gasket is reused 3 times, which solves the problem that traditional adhesive layers cannot be repaired and reduces the overall cost of use. 3. The preparation process adopts mature industrial technologies such as multi-nozzle spraying, staged curing, and electrospinning. All materials are industrial grade, with strong process compatibility and high operability, enabling large-scale production. The overall cost is reduced by 12%-18% compared with traditional solutions, combining performance advantages and economy. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the self-adhesive graphene thermal pad provided in the embodiments of this application; Figure 2 This is a top view of the carbon fiber mesh layer provided in the embodiments of this application; Figure 3 This is a flowchart illustrating the preparation method of the self-adhesive graphene thermal pad provided in the embodiments of this application.

[0028] Explanation of reference numerals in the attached figures: 1. Thermal conductive layer; 11. Graphene film; 12. Carbon fiber mesh layer; 2. Adhesive layer; 21. Peripheral area; 22. Central area. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0030] This application discloses a self-adhesive graphene thermal pad. (Refer to...) Figure 1The self-adhesive graphene thermal pad includes a thermally conductive layer 1 and an adhesive layer 2. The thermally conductive layer 1 includes a plurality of graphene films 11 and a plurality of carbon fiber mesh layers 12 spaced apart along the thickness direction. The adhesive layer 2 is disposed on a first surface and a second surface opposite to the first surface of the thermally conductive layer 1. The adhesive layer 2 is provided with a plurality of pore structures for reducing thermal resistance. The pore distribution density of the peripheral region 21 and the central region 22 of the adhesive layer 2 is different. The peripheral region 21 has a first porosity and the central region 22 has a second porosity. The first porosity is less than the second porosity.

[0031] Specifically, such as Figure 1 As shown, the main structure of the self-adhesive graphene thermal pad is a layered structure composed of a thermally conductive layer 1 and an adhesive layer 2. The thermally conductive layer 1 has an alternating stacked structure of graphene film 11 and carbon fiber mesh layer 12 (the two are arranged in layers in the XZ plane of the figure). The carbon fiber mesh layer 12 can form a vertical (Z direction) thermal conductive channel. The adhesive layer 2 covers the surface of the thermally conductive layer 1. The adhesive layer 2 has a porous structure to reduce thermal resistance. The horizontal plane (XY plane) of the adhesive layer 2 is divided into two regions: a peripheral region 21 and a central region 22. The peripheral region 21 is located at the edge of the adhesive layer 2. It has few pores (low porosity). The relatively high porosity can increase the contact area with the adhered object (thermally conductive layer 1 or electronic device), thereby improving the bonding strength. The central region 22 is located in the middle part of the adhesive layer 2 (marked with a dashed line in the figure). It has a large number of pores, corresponding to high porosity (marked with dense dots in the figure). It can reduce the obstruction in the heat transfer process, thereby reducing thermal resistance.

[0032] Understandably, the thermally conductive layer 1 adopts a structure in which graphene film 11 and carbon fiber mesh layer 12 are spaced apart. The carbon fiber mesh layer 12 replaces the traditional through-hole filler processing method, forming a vertical thermally conductive channel. No additional laser drilling and filler injection steps are required, which reduces production costs while improving interlayer thermal conductivity. The adhesive layer 2 cleverly balances the viscosity requirement and thermal conduction efficiency through the gradient design of low porosity (high viscosity) in the peripheral region 21 and high porosity (low thermal resistance) in the central region 22. This solves the contradiction that "improving viscosity increases thermal resistance" in the traditional uniform thickness adhesive layer 2, and effectively meets the high heat conduction requirements of highly integrated electronic devices in the 5G era.

[0033] In one embodiment, the first porosity is 0%-15%, the second porosity is 30%-50%, and the thickness of the adhesive layer 2 is 1-6 μm.

[0034] Specifically, the porous structure can be formed through a combination of multi-nozzle precision spraying and segmented curing processes. The base material can be addition-cure silicone adhesive, condensation-type silicone adhesive, thermally conductive acrylic pressure-sensitive adhesive, or polyurethane thermally conductive adhesive. Preferably, addition-cure silicone adhesive is used as the base material for adhesive layer 2. Different formulations of adhesives are precisely sprayed using a dual-nozzle device. In the peripheral area 21, an addition-cure silicone adhesive containing 0%-0.5% by weight of microsphere foaming agent is sprayed. After pre-curing at 80°C and secondary curing at 120°C, a dense structure is formed, controlling the porosity at 0%-15%. In the central area 22, an addition-cure silicone adhesive containing 0.8%-2% by weight of microsphere foaming agent is sprayed. Under the same curing process, the microspheres expand when heated or form interconnected pores, making the porosity reach 30%-50%. This application achieves a gradient distribution of porosity by matching the material formulation with the spraying process, without the need for additional complex processing. This avoids the inherent contradiction between the viscosity and thermal conductivity of the traditional uniform adhesive layer 2, and ensures the reliability of the bond through the dense periphery structure.

[0035] In one embodiment, the thickness of the adhesive layer 2 is controlled within a thin range of 1-6 μm. Compared with the traditional adhesive layer 2 thickness of 2-10 μm, since the material usage is positively correlated with the thickness of the adhesive layer 2, the material usage of the adhesive layer 2 in this application is reduced by at least 40% under the same coating area. This effectively reduces the raw material cost of the product, further reduces thermal resistance, and avoids affecting the overall thermal conductivity due to excessive thickness of the adhesive layer 2, thus meeting the installation space requirements of lightweight and highly integrated electronic products.

[0036] To visually demonstrate the performance advantages of the gradient porosity design of this application, two groups of conventional design control groups and two groups of gradient design experimental groups were set up with the overall thickness of the adhesive layer 2 being 5 μm as a uniform benchmark. By keeping other parameters such as the structure of the thermally conductive layer 1, the substrate material, the preparation process, and the test environment completely identical, only the porosity distribution of the adhesive layer 2 was changed, and performance comparison tests were conducted. The test results are shown in Table 1 below: Table 1: Performance Comparison of Self-Adhesive Graphene Thermal Pads with Different Porosities Based on the data in the table above, it can be understood that while the traditional non-porous design has the strongest adhesion (peel strength ≥ 1.5 N / cm), its thermal conductivity is relatively poor (thermal conductivity only 45 W / (m・K)). The traditional single-porosity design has slightly improved thermal conductivity, but its adhesion is significantly reduced (only 0.9 N / cm). In contrast, the two gradient designs in this application achieve both adhesion and thermal conductivity, with peel strength ≥ 1.2 N / cm, which can stably ensure bonding reliability. The thermal conductivity reaches 150 W / (m・K) and 130 W / (m・K) respectively, which is much higher than that of the traditional design. At the same time, the production cost is reduced by 15%-18% compared with the traditional non-porous design, effectively meeting the high heat conduction requirements of highly integrated electronic devices in the 5G era.

[0037] It should be noted that the structure of this application is not limited to a gradient structure formed by the first and second porosities. Multi-level gradient porosity structures can also be set according to the heat dissipation requirements, bonding strength requirements, and installation scenarios of electronic devices. For example, a non-porous dense region (0% porosity) with a width accounting for 1 / 20–1 / 10 of the total width of the pad can be set at the outermost edge. This region is completely dense and has the strongest adhesion, enabling rapid positioning and stable bonding between the pad and the electronic device. The non-porous region is connected to the first gradient region (5%-10% porosity), further enhancing the reliability of edge bonding. Then, a second gradient region (20%-30% porosity) and a third gradient region (40%-50% porosity) are sequentially set towards the center. The gradual increase in porosity achieves a smooth reduction in thermal resistance, avoiding sudden changes in local thermal resistance that could affect heat dissipation. For chip regions with extremely high heat flux densities, an ultra-high porosity region with 50%-60% porosity can be set at the very center to maximize thermal conductivity. The multi-level gradient structure can flexibly adapt to the personalized needs of different scenarios, further expanding the application range of thermal pads.

[0038] In one embodiment, the carbon fiber mesh layer 12 is prepared by electrospinning. The fiber diameter D of the carbon fiber mesh layer 12 is 10-50 μm, and the mesh spacing P is 100-200 μm. In the mesh structure of the carbon fiber mesh layer 12, the shape of a single mesh is selected from the group including the following: triangle, hexagon, square and rhombus. The opening direction of the mesh is set towards the thickness direction of the heat conduction layer 1. Multiple mesh shapes can adapt to the heat conduction requirements of different scenarios, enhancing the flexibility and applicability of the solution.

[0039] like Figure 2 As shown in the figure, in a specific embodiment, a schematic diagram (XY plane) of a single-layer structure of a hexagonal carbon fiber mesh layer 12 is presented. The black lines in the figure correspond to carbon fiber monofilaments. The fiber diameter D of the carbon fiber mesh layer 12 is 10-50 μm. Several monofilaments interweave to form regular hexagonal mesh units, with a mesh spacing P of 100-200 μm. The overall arrangement is a continuous honeycomb pattern. The opening direction of the mesh is clearly towards the thickness direction (Z direction) of the heat-conducting layer 1, allowing heat to penetrate the mesh layer perpendicularly along this direction, forming an efficient heat conduction channel. The continuous honeycomb arrangement of the hexagonal mesh units, with its regular geometric shape, allows for uniform stress distribution, further enhancing the mechanical stability of the mesh layer.

[0040] It is understandable that electrospinning can stably prepare uniform mesh structures of various shapes. The combination of fiber diameter of 10-50μm and mesh spacing of 100-200μm can not only ensure the structural strength of the mesh layer and prevent the thermal conductive layer 1 from deforming and collapsing during stacking or use, but also rely on the high thermal conductivity of carbon fiber itself of 300-1000W / (m・K) to enhance the vertical heat transfer through the mesh channels. Compared with the traditional interlayer thermal conduction scheme of laser drilling and through-hole filler, it saves additional processing steps and significantly improves the interlayer thermal conductivity.

[0041] Furthermore, with the same amount of material, the pore opening area of ​​the hexagonal mesh is about 15% larger than that of the square mesh, which can further reduce the obstruction of heat transfer. Its opening direction is perpendicular to and complementary to the in-plane thermal conduction direction of the graphene film 11, so that heat can diffuse rapidly within the graphene film 11 and efficiently penetrate the thermal conductive layer 1 through the carbon fiber mesh layer 12, achieving a synergistic thermal conduction effect of in-plane diffusion and vertical penetration, and further improving the overall thermal conductivity.

[0042] In one embodiment, the adhesive layer includes a phase change adhesive region and a non-phase change adhesive region (not shown in the figure). The material of the phase change adhesive region includes an addition-type silicone adhesive and paraffin carbon nanotube microcapsules. The paraffin carbon nanotube microcapsules are configured to absorb near-infrared light and undergo a phase change. The phase change adhesive region is configured to form a reversible adhesive based on the phase change of the paraffin carbon nanotube microcapsules.

[0043] Specifically, the phase change bonding area can be selectively located at localized edges of the self-adhesive graphene thermally conductive pad (such as the four corners, with each area accounting for 5%-10% of the total pad area), while the non-phase change bonding area covers the remaining area of ​​the pad. The viscosity of the addition-cure silicone adhesive in the phase change bonding area is adjusted to 60-150 mPa·s, and the paraffin carbon nanotube microcapsules are uniformly dispersed in the addition-cure silicone adhesive at a weight ratio of 2%-8%. This parameter range ensures good coatability of the adhesive while allowing the microcapsules to disperse uniformly and stably perform their photothermal response function. Testing showed that after three reuses, the adhesive retention rate of the pad remained above 90%, balancing adhesive stability and reversibility.

[0044] Preferably, the viscosity of the addition-cure silicone adhesive is adjusted to 80 mPa·s, and the paraffin carbon nanotube microcapsules are distributed at a weight ratio of 5%. The non-phase change bonding area uses conventional addition-cure silicone adhesive, which together with the phase change bonding area constitutes a complete adhesive layer 2. In this design, the non-phase change bonding area ensures a stable overall bond between the thermal pad and the surface of the electronic device, meeting the connection reliability requirements in daily use. The phase change bonding areas at the four corners serve as rework trigger areas. When the electronic device malfunctions and needs to be disassembled for repair, the phase change bonding area is locally irradiated with near-infrared light at 808 nm and a power density of 1 W / cm². After absorbing the light energy, the paraffin carbon nanotube microcapsules rapidly heat up and undergo a phase change, causing the adhesiveness in this area to disappear. This allows the thermal pad to be easily peeled off, reducing the damage to the electronic device or thermal pad caused by the traditional permanent adhesive layer 2 during disassembly.

[0045] Understandably, the phase change bonding area utilizes the photothermal response characteristics of paraffin carbon nanotube microcapsules to achieve the reversible bonding function of bonding layer 2, solving the problem that traditional permanent adhesive bonding layer 2 is not conducive to equipment repair; when irradiated with near-infrared light, the microcapsules undergo phase change, causing the adhesiveness to disappear, and the adhesiveness is restored after cooling, which enables the thermal pad to be reused. The design of setting phase change bonding areas locally takes into account both the overall bonding reliability and the convenience of repair.

[0046] This application also provides a method for preparing a self-adhesive graphene thermal conductive pad, comprising the following steps: A graphene film 11 and a carbon fiber mesh layer 12 are provided; a plurality of graphene films 11 and a plurality of carbon fiber mesh layers 12 are spaced apart to form a thermally conductive layer 1; Specifically, a flexible graphene film 11 with a thermal conductivity of not less than 800 W / (m·K) is provided; a carbon fiber mesh layer 12 is prepared by electrospinning, wherein the fiber diameter D of the formed carbon fiber mesh layer 12 is 10-50 μm, the mesh spacing P is 100-200 μm, and the shape of a single mesh includes one or more of triangles, hexagons, squares, and rhombuses; the prepared carbon fiber mesh layer 12 is impregnated with low-temperature curing epoxy resin (as an interlayer adhesive) to obtain a prepreg mesh layer; the graphene film 11 and the prepreg mesh layer are alternately stacked along the thickness direction of the thermally conductive layer 1 in the order of graphene film 11 and carbon fiber mesh layer 12 to a predetermined number of layers to form a... The structure features a layered structure with spacing. A hot roll forming process is employed. First, the laminated structure is fed into a hot roll forming machine. At a temperature of 80-120℃, the semi-cured epoxy resin on the surface of the grid layer melts into a viscous liquid. Then, under a pressure of 0.5-2 MPa, the molten epoxy resin fills the tiny gaps between the graphene film 11 and the grid layer, tightly wrapping the carbon fiber monofilaments and adhering them to the surface of the graphene film 11. After 2-3 roll forming cycles and cooling, the liquid epoxy resin re-cures and hardens, forming a stable bond of mechanical interlocking and chemical adhesion, requiring no additional adhesives. Finally, it is cold-pressed at room temperature (0.3-0.5 MPa, 30-60 seconds) for shaping, completing the preparation of the thermally conductive layer 1. Understandably, the carbon fiber mesh layer 12 can serve as a mechanical reinforcement framework for the graphene film 11, suppressing the brittleness and wrinkling problems caused by thermal expansion and contraction or external extrusion of the graphene film 11, and improving the structural stability and service life of the thermal pad. The interwoven pores of the carbon fiber mesh can serve as a carrier and dispersion carrier for the graphene sheets, preventing the graphene sheets from stacking and agglomerating, and maintaining the continuity of its efficient in-plane thermal conduction channels. The excellent interfacial compatibility between carbon-based materials can reduce the interfacial thermal resistance between the graphene film 11 and the carbon fiber mesh layer 12, reduce the loss of heat transfer between layers, and further improve the overall thermal conductivity. The size and shape of the mesh can be stably controlled by the electrospinning method, and the alternating lamination process ensures that the thermal conduction layer 1 has a uniform structure, so that the vertical thermal conduction channels formed by the carbon fiber mesh run through the entire thermal conduction layer 1, effectively improving the interfacial thermal conductivity, while simplifying the preparation process of the thermal conduction channels and reducing costs.

[0047] Provide addition-type silicone adhesive and microsphere foaming agent; mix 0%-0.5% by weight of microsphere foaming agent into a portion of addition-type silicone adhesive to form a first foaming adhesive, and mix 0.8%-2% by weight of microsphere foaming agent into another portion of addition-type silicone adhesive to form a second foaming adhesive; Specifically, an industrial-grade addition-type silicone adhesive (e.g., viscosity 60-150 mPa·s, thermal conductivity ≥0.8 W / (m·K) after curing) is selected as the base adhesive, and a thermally expanding microsphere foaming agent (e.g., particle size 5-15 μm, expansion temperature 60-150℃) is used. The ingredients are prepared according to the following weight ratio: for example, 100 g of addition-type silicone adhesive is mixed with 0.3 g of microsphere foaming agent (0.3%), and stirred at 25℃ and 300 r / min for 15 minutes until uniformly dispersed to form the first foamed adhesive; another 100 g of addition-type silicone adhesive is mixed with 1.5 g of microsphere foaming agent (1.5%), and mixed evenly with the same stirring parameters to form the second foamed adhesive.

[0048] Peripheral regions 21 and central regions 22 are divided on opposite sides of the heat-conducting layer 1. A first foaming adhesive is applied to the peripheral regions 21 on both sides and a second foaming adhesive is applied to the central regions 22 on both sides using a multi-nozzle spraying device to form an adhesive substrate layer. The sprayed adhesive substrate layer is pre-cured at 60℃-100℃ and then cured again at 100℃-150℃ to form adhesive layer 2. The microsphere foaming agent expands when heated, so that the peripheral regions 21 of adhesive layer 2 form a porous structure with a porosity of 0%-15% and the central regions 22 form a porous structure with a porosity of 30%-50%.

[0049] Specifically, a peripheral area 21 and a central area 22 are respectively divided on two opposite sides of the heat-conducting layer 1 (for example, the total area of ​​the heat-conducting layer 1 is 50-200 cm², the width of the peripheral area 21 can be set to 5-10 mm, covering the edge of the heat-conducting layer 1, and the central area 22 is the remaining area of ​​the heat-conducting layer 1). A dual-nozzle precision spraying device is used for simultaneous operation. The first foamed adhesive is injected into the first nozzle and sprayed evenly along the peripheral areas 21 on both sides of the heat-conducting layer 1, with a coating thickness controlled at 3-5 μm. The second foamed adhesive is injected into the second nozzle and sprayed onto the central areas 22 on both sides, with a coating thickness consistent with the peripheral areas 21. During the spraying process, the nozzle moving speed is controlled at 10-20 mm / s and the spraying pressure at 0.2-0.5 MPa to ensure no missed areas and to form a complete adhesive substrate layer. The sprayed adhesive substrate layer is first pre-cured at 60℃-100℃ for 20-30 minutes to allow the adhesive to initially set. Then, the temperature is raised to 100℃-150℃ for secondary curing for 30-40 minutes. Preferably, the first curing temperature is 80℃ and the second curing temperature is 120℃. During this process, the microsphere foaming agent expands to 3-5 times its original particle size due to heat, so that the peripheral area 21 of the adhesive layer 2 forms a dense porous structure with a porosity of 0%-15%, ensuring the stability of the adhesive positioning. The central area 22 forms a loose porous structure with a porosity of 30%-50%, reducing the resistance to heat transfer and achieving a gradient function of high edge adhesion positioning and efficient heat conduction in the center. Combined with the three-dimensional thermal conductive network of carbon fiber mesh in the thermal conductive layer 1, the overall thermal resistance of the thermal pad is reduced by 20% compared with the traditional uniform adhesive layer 2, and the thermal conductivity is increased to 150W / (m・K).

[0050] Understandably, the preparation method of this application precisely achieves the gradient porosity structure of the adhesive layer 2 by adjusting the addition ratio of the microsphere foaming agent and combining it with the partitioned spraying process, without the need for complex processing equipment; the staged curing process can ensure that the microsphere foaming agent fully expands to form a stable pore structure, thereby achieving a balance between viscosity and thermal resistance; the entire process adopts mature industrial technologies such as spraying and lamination, and the materials are all industrial grade, which is conducive to large-scale production and reduces production costs.

[0051] In one embodiment, the preparation method further includes the steps of: providing paraffin carbon nanotube microcapsules; mixing 2%-8% by weight of paraffin carbon nanotube microcapsules into a partially addition-cured silicone adhesive to obtain a phase change adhesive; and coating the phase change adhesive onto a predetermined phase change bonding area of ​​the adhesive substrate layer so that the obtained adhesive layer 2 has a reversible bonding function.

[0052] Specifically, to solve the rework problem caused by the permanent adhesion of traditional adhesive layer 2, this application embodiment sets a phase change adhesive in a preset removable area (such as the four corners of the chip or edge positioning points). Specifically, paraffin carbon nanotube microcapsules with a particle size of 10-20μm (e.g., paraffin phase change temperature 60-80℃, carbon nanotube mass ratio 30%) are selected and used in conjunction with industrial-grade addition-curing silicone adhesive (e.g., viscosity 60-150mPa・s, thermal conductivity ≥0.8W / (m・K) after curing) and thermally expanding microsphere foaming agent (e.g., particle size 5-15μm, expansion temperature 80-120℃). When preparing the first foaming adhesive (low porosity area at the edge) or the second foaming adhesive (high porosity area at the center), the phase change material is simultaneously mixed in. If the preset phase change bonding area is the peripheral area 21, take 100g of addition-cured silicone adhesive, first mix in 0.3g of microsphere foaming agent (0.3% by mass), then add 5g of paraffin carbon nanotube microcapsules (5% by mass), and stir for 20 minutes at 25℃ and 350r / min until uniformly dispersed to obtain a phase change and low foaming composite adhesive (viscosity controlled at 80-100mPa・s). If the preset phase change bonding area is the central heat conduction area: take 100g of addition-type silicone adhesive, first mix in 1.5g of microsphere foaming agent (1.5% by mass), then add 5g of paraffin carbon nanotube microcapsules (5% by mass), mix evenly with the same stirring parameters, and obtain the phase change and high foaming composite adhesive.

[0053] At least three precision spraying nozzles are used for simultaneous operation. The first nozzle sprays a first foamed adhesive without phase change material (edge ​​non-phase change area), the second nozzle sprays a second foamed adhesive without phase change material (center non-phase change area), and the third nozzle sprays a composite adhesive containing phase change material (pre-set phase change bonding area, such as four circular areas with a diameter of 3-5mm, located at the four corners of the thermal conductive layer 1). The thickness of the coating of at least three types of adhesives is controlled to be 1-6μm, and cross-penetration between areas is avoided during the spraying process. Subsequently, the entire coated adhesive substrate layer is entered into the curing process (e.g., pre-curing at 60℃-100℃ for 20-30 minutes, and secondary curing at 100℃-150℃ for 30-40 minutes). During the curing process, the microsphere foaming agent expands under heat to form a gradient pore structure (edge ​​porosity 0%-15%, center porosity 30%-50%). The paraffin carbon nanotube microcapsules are uniformly dispersed in the adhesive in the phase change region without damaging the pore structure, ultimately forming a complete adhesive layer 2 that integrates gradient thermal conductivity and local reversible bonding.

[0054] During repair, a preset phase change bonding area is locally irradiated using an 808nm near-infrared laser (e.g., power density 1W / cm², irradiation time 30-60 seconds). The microcapsules absorb light energy and convert it into heat energy, causing the internal paraffin to melt. The adhesiveness in this area temporarily disappears, allowing easy separation of the thermal pad from the electronic device. After irradiation stops, the temperature drops to room temperature, the paraffin re-solidifies, and the phase change adhesive regains its adhesiveness. The thermal pad of this application can be reused. After three cycles of repair, the adhesiveness retention rate is still >90%, ensuring bonding stability during normal use, improving maintenance convenience, and reducing overall usage costs.

[0055] Understandably, adding the preparation and coating steps of phase change adhesive to the basic preparation process offers strong process compatibility and does not require significant adjustments to the existing process. By accurately controlling the weight ratio of microcapsules, the reversible bonding effect in the phase change bonding area can be ensured to meet the equipment repair requirements, while not affecting the bonding reliability of the non-phase change bonding area.

[0056] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A self-adhesive graphene thermal conductive pad, characterized in that, include: The thermally conductive layer (1) includes a plurality of graphene films (11) and a plurality of carbon fiber mesh layers (12) spaced apart along the thickness direction. An adhesive layer (2) is disposed on a first surface of the thermally conductive layer (1) and a second surface opposite to the first surface. The adhesive layer (2) is provided with a plurality of pore structures for reducing thermal resistance. The pore distribution density of the peripheral region (21) and the central region (22) of the adhesive layer (2) is different. The peripheral region (21) has a first porosity, and the central region (22) has a second porosity. The first porosity is less than the second porosity.

2. The self-adhesive graphene thermal pad according to claim 1, characterized in that, The first porosity is 0%-15%, and the second porosity is 30%-50%.

3. The self-adhesive graphene thermal pad according to claim 1, characterized in that, In the mesh structure of the carbon fiber mesh layer (12), the shape of a single mesh is selected from the group consisting of triangles, hexagons, squares and rhombuses, and the opening direction of the mesh is set towards the thickness direction of the heat-conducting layer (1).

4. The self-adhesive graphene thermal pad according to claim 3, characterized in that, The carbon fiber mesh layer (12) is prepared by electrospinning. The fiber diameter of the carbon fiber mesh layer (12) is 10-50 μm and the mesh spacing is 100-200 μm.

5. The self-adhesive graphene thermal pad according to claim 1, characterized in that, The adhesive layer (2) includes a phase change adhesive region and a non-phase change adhesive region. The material of the phase change adhesive region includes an addition-type silicone adhesive and paraffin carbon nanotube microcapsules. The paraffin carbon nanotube microcapsules are configured to absorb near-infrared light and undergo a phase change. The phase change adhesive region is configured to form a reversible adhesive based on the phase change of the paraffin carbon nanotube microcapsules.

6. A self-adhesive graphene thermal pad according to claim 5, characterized in that, The viscosity of the addition-type silicone adhesive is 60-150 mPa·s, and the weight percentage of the paraffin carbon nanotube microcapsules is 2%-8%.

7. A self-adhesive graphene thermal pad according to claim 6, characterized in that, The thickness of the adhesive layer (2) is 1-6 μm.

8. A method for preparing a self-adhesive graphene thermal conductive pad, characterized in that, Includes the following steps: A graphene film (11) and a carbon fiber mesh layer (12) are provided. Multiple graphene films (11) and multiple carbon fiber mesh layers (12) are spaced apart to form a thermally conductive layer (1). We provide addition-type silicone adhesives and microsphere foaming agents; 0%-0.5% by weight of the microsphere foaming agent is mixed into a portion of the addition-curing silicone adhesive to form a first foaming adhesive, and 0.8%-2% by weight of the microsphere foaming agent is mixed into another portion of the addition-curing silicone adhesive to form a second foaming adhesive. On the two opposite sides of the heat-conducting layer (1), a peripheral area (21) and a central area (22) are respectively divided. The first foaming adhesive is applied to the peripheral area (21) on both sides and the second foaming adhesive is applied to the central area (22) on both sides to form an adhesive substrate layer. The adhesive substrate layer after spraying is pre-cured at 60℃-100℃ and then cured at 100℃-150℃ to form an adhesive layer (2). The microsphere foaming agent expands when heated, so that the peripheral area (21) forms a pore structure with a porosity of 0%-15% and the central area (22) forms a pore structure with a porosity of 30%-50%.

9. The preparation method according to claim 8, characterized in that, The method also includes the steps of: providing paraffin carbon nanotube microcapsules; mixing 2%-8% by weight of the paraffin carbon nanotube microcapsules into a portion of the addition-cured silicone adhesive to obtain a phase change adhesive; and applying the phase change adhesive to a predetermined phase change bonding area of ​​the adhesive substrate layer so that the obtained adhesive layer (2) has a reversible bonding function.

10. The preparation method according to claim 8, characterized in that, The carbon fiber mesh layer (12) is prepared by electrospinning, with a fiber diameter of 10-50 μm and a mesh spacing of 100-200 μm. The shape of a single mesh includes one or more of triangles, hexagons, squares, and rhombuses. The graphene film (11) and the carbon fiber mesh layer (12) are alternately stacked along the thickness direction of the thermal conductive layer (1) to a predetermined number of layers to form a layered structure with intervals, thereby obtaining the thermal conductive layer (1).

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