A flexible thermal interface material with diamond thermal uniform layer and carbon fiber vertical heat dissipation channel and a preparation method thereof

Abstract

A flexible thermal interface material with diamond uniform heating layer and carbon fiber vertical heat dissipation channel and a preparation method thereof, through magnetic field induction, carbon fibers are vertically arranged in a polyvinyl alcohol matrix, a high-efficiency interfacial heat conduction channel is constructed, high-thermal-conductivity diamond particles are introduced to form an interfacial uniform heating layer, and a "lateral uniform heating and vertical heat conduction" synergistic heat dissipation mechanism is realized. The design combines the diamond uniform heating layer with the vertical carbon fiber heat dissipation channel, significantly improves the interfacial heat diffusion capacity to eliminate local hot spots, maintains excellent interfacial thermal conductivity, effectively reduces the temperature gradient of electronic devices, and breaks through the bottleneck that the existing thermal interface materials are difficult to balance uniform heating and efficient heat dissipation.

Description

Technical Field

[0001] This invention relates to thermal interface materials (TIMs), and more particularly to a flexible thermal interface material having a diamond homogenizing layer and a carbon fiber vertical heat dissipation channel, and a method for preparing the same. Background Technology

[0002] With the rapid development of cutting-edge technologies such as 5G communication, artificial intelligence (AI), and high-performance computing, semiconductor chips are continuously evolving towards higher integration, higher power density, and miniaturization. Electronic packaging technology is also accelerating its transformation from two-dimensional to three-dimensional integration. The increased chip integration leads to a sharp rise in heat flux density, with some areas approaching the level of the sun's surface. Excessively high temperatures not only severely affect chip performance and reliability but can also significantly shorten their lifespan. Against this backdrop, thermal management has become a core bottleneck determining the upper limit of chip computing power, reliability, and lifespan. The widespread application of high-performance chips, especially AI chips, places even higher demands on thermal management systems (TIMs).

[0003] TIMs, filling the tiny gaps between heat sources and heat sinks, are crucial media for reducing interfacial thermal resistance and improving heat dissipation efficiency. Their performance directly determines the overall efficiency of the cooling system. Ideal TIMs should possess: high interfacial thermal conductivity for rapid longitudinal heat conduction, high in-plane thermal conductivity for lateral heat diffusion to eliminate localized hot spots, and low hardness to ensure tight adhesion to the contact interface and reduce contact thermal resistance.

[0004] Currently, commercial TIMs (such as thermal greases, thermal pads, phase change materials, etc.) are mostly based on silicone resins or polymers, filled with metal or ceramic particles. However, while high filler content can improve thermal conductivity, it often comes at the cost of material flexibility, leading to increased contact thermal resistance. Solder-based TIMs have high thermal conductivity, but their high hardness and assembly stress can easily cause cracks. Carbon materials such as graphene and carbon nanotubes have attracted much attention due to their ultra-high thermal conductivity. For example, Professor Yu et al. of Beijing University of Chemical Technology prepared graphene aerogels through crystallization-induced (bidirectional freeze-drying) process, and the interfacial thermal conductivity of epoxy resin composites based on it can reach 20 W / m·K (Nanomicro Letters. 2020, 13 (1): 22). Professor Zhang of Xiamen University obtained oriented carbon fibers by means of extrusion pressure and combined with the bridging effect of Al2O3 to prepare composite TIMs with an interfacial thermal conductivity of 38 W / m·K (Composites Science and Technology). .2022, 230: 109717). The team of Academician Zhang from Peking University used electric field-assisted PECVD technology to grow vertical graphene with an interfacial thermal conductivity of 53.5 W / m·K (Advanced Science. 2022, 9 (15): 2200737). Cheng et al. used magnetic field induction to achieve vertical orientation of carbon fibers in a polymer matrix, resulting in composite TIMs with an interfacial thermal conductivity as high as 86 W / m·K (Nano Research). . 2022, 16(2): 2572-2578). The Ching Ping Wong team at the Chinese University of Hong Kong achieved an inter-plane thermal conductivity of 75.5 W / m·K by vertically stacking functionalized graphene sheets (ACS nano. 2011, 5(3): 2392-2401). The Bai Shulin team at Peking University prepared a vertically aligned graphene film / PDMS composite material with a thermal conductivity as high as 614.85 W / m·K (Carbon, 2016, 109: 552-557). Furthermore, three-dimensional continuous thermally conductive frameworks constructed based on hydrothermal or template methods, such as carbon aerogels and carbon foams, are also effective ways to improve the inter-plane thermal conductivity of composite materials. However, while the above structural designs significantly improve the inter-plane thermal conductivity of composite TIMs, insufficient attention has been paid to intra-plane thermal conductivity, limiting their practical application.

[0005] High-power chips often experience localized "hot spots" due to uneven power distribution during actual operation. While relying solely on high interfacial thermal conductivity can reduce the average chip temperature, it cannot achieve uniform lateral heat diffusion, and excessive local temperature gradients still seriously threaten chip reliability. Therefore, in recent years, researchers have begun to focus on anisotropic TIMs that possess both high interfacial and high in-plane thermal conductivity. For example, the team led by Lin Zhengde at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, effectively homogenized interfacial heat flow by mechanically reconstructing graphene paper to form a hierarchical structure (ACS Nano, 2019, 13, 11561-11571). However, in existing research, TIMs that simultaneously achieve low hardness, high thermal conductivity, and excellent heat homogenization performance remain extremely rare.

[0006] Diamond, with its extremely high intrinsic thermal conductivity (above 2000 W / m·K) and excellent insulation properties, is an ideal material for heat dissipation layers. However, its high rigidity and difficult processing make it unsuitable for direct use in flexible thermally immobilized materials (TIMs). Combining diamond films as heat dissipation layers with vertical carbon fiber (VAmCFs) heat dissipation channels can achieve both lateral heat diffusion to eliminate localized hotspots and provide efficient longitudinal heat conduction paths. Simultaneously, the flexible polymer matrix imparts low hardness and interfacial adaptability to the material, potentially overcoming the performance bottlenecks of existing TIMs.

[0007] In summary, developing a flexible TIMs that combines a diamond heat exchanger layer and vertical carbon fiber channels to achieve a synergistic heat dissipation mechanism of "lateral heat equalization and longitudinal heat conduction" is of significant scientific importance and engineering application value for solving the problem of local hot spots in high-power chips and improving the thermal management capabilities of the system. Summary of the Invention

[0008] The purpose of this invention is to address the requirements of high-power chip thermal management for thermally conductive integrated membrane materials (TIMs) by providing a simple, environmentally friendly, and mass-producible method for fabricating flexible TIMs that combine a heat spreader and a vertical heat dissipation channel. Diamond, carbon fiber, and polyvinyl alcohol are used to prepare a flexible composite TIM with excellent overall thermal conductivity.

[0009] This invention provides a flexible thermal interface material with a diamond heat dissipation layer and a vertical heat dissipation channel of carbon fiber, comprising a flexible polymer matrix, modified carbon fiber, and diamond particles; the flexible polymer matrix is ​​a polyvinyl alcohol matrix; the diamond particles are concentrated at the bottom of the flexible thermal interface material to form an in-plane heat dissipation layer; the modified carbon fiber is arranged vertically along the thickness direction in the flexible polymer matrix to form a longitudinal heat conduction channel that penetrates the flexible polymer matrix and connects to the diamond heat dissipation layer.

[0010] Preferably, the modified carbon fiber is obtained by surface modification treatment of carbon fiber with oxygen plasma; the treatment power of the oxygen plasma is 50~200 W and the treatment time is 5~30 min.

[0011] Preferably, the diamond particles have a particle size of 10~200 μm and a thermal conductivity of 1000~2000 W / m·K; the diamond particles have a mass percentage of 10 wt% based on the total solid content.

[0012] Preferably, the flexible polymer matrix further comprises a plasticizer and an antifoaming agent, wherein the plasticizer is glycerin and the antifoaming agent is modified polydimethylsiloxane; Preferably, the diamond particles undergo surface cleaning treatment before use. The cleaning treatment includes: first cleaning with a sulfuric acid solution with a concentration of 0.1~1.0 mol / L 1~3 times; then neutralizing with a sodium hydroxide solution with the same concentration as the sulfuric acid solution 1~3 times; and finally rinsing with deionized water 2~5 times.

[0013] Preferably, the in-plane thermal conductivity of the in-plane heat spreader is 20~35 W / m·K, and the inter-plane thermal conductivity of the longitudinal heat conduction channel is 8~20 W / m·K.

[0014] Preferably, the material has self-supporting properties and a hardness of less than 80 HA.

[0015] A method for preparing the flexible thermal interface material includes the following steps: S1, the diamond particles are surface cleaned and dried; S2, oxygen plasma surface modification treatment is performed on carbon fibers to obtain modified carbon fibers; S3, add polyvinyl alcohol to deionized water, heat and stir until completely dissolved to obtain a polymer matrix solution; S4, add the modified carbon fiber, plasticizer and defoamer to the polymer matrix solution, and stir to mix evenly; S5, add the diamond particles to the mixture obtained in step S4, and continue stirring to obtain a uniformly dispersed slurry; S6. The mixed slurry is transferred to a mold and placed in a magnetic field perpendicular to the bottom surface of the mold for gelation treatment for 24-48 hours. Orientation molding is then performed to arrange the modified carbon fibers in a vertical direction and to make the diamond particles uniformly settle and accumulate at the bottom of the flexible thermal interface material to obtain a composite gel. S7. The composite gel is dried to obtain the finished product.

[0016] Preferably, the magnetic field in step S6 is provided by a neodymium iron boron permanent magnet with a magnetic field strength of 0.5 T.

[0017] Preferably, the oxygen plasma surface modification treatment has a processing power of 100 W and a processing time of 10 min.

[0018] This invention employs magnetic field orientation technology to achieve the vertical alignment of modified carbon fibers within a polymer matrix, constructing a highly efficient longitudinal heat conduction channel. Simultaneously, high thermal conductivity diamond particles are introduced as an in-plane heat homogenizing layer, forming a synergistic network of "vertical heat conduction and lateral heat homogenization." The diamond particles not only enhance the material's in-plane heat diffusion capability and effectively suppress local hot spots, but also optimize the three-dimensional heat conduction path through their synergistic effect with the modified carbon fibers. Polyvinyl alcohol, as a flexible matrix, combined with glycerol plasticizer, endows the composite material with excellent flexibility and low hardness, enabling it to tightly adhere to the interface between the heat-generating chip and the heat sink, significantly reducing interfacial contact thermal resistance. This composite thermal interface material possesses high interfacial thermal conductivity, good in-plane heat homogenization performance, low hardness, and self-supporting properties, showing broad application prospects in the field of high-power chip thermal management. Attached Figure Description

[0019] Figure 1 The images show scanned images of the TIMs obtained by the present invention, where a, b, and c correspond to the products obtained in Examples 1, 2, and 3, respectively. The microstructural characteristics of the modified carbon fiber / polyvinyl alcohol composite TIMs and the composite TIMs formed by combining them with diamond under different preparation conditions are illustrated.

[0020] Figure 2 This is a comparison of the interplane and in-plane thermal conductivity changes of the product VAmCFs / PVA / Dia prepared in Example 3. Wherein, λ ⊥ λ represents the inter-plane thermal conductivity. ∥ It represents the in-plane thermal conductivity.

[0021] Figure 3 Infrared thermal imaging results of mCFs / PVA, VAmCFs / PVA, and VAmCFs / PVA / Dia composite TIMs in high-power LED thermal management testing.

[0022] Figure 4 Temperature curves of mCFs / PVA, VAmCFs / PVA, and VAmCFs / PVA / Dia composite TIMs obtained in high-power LED thermal management tests. Detailed Implementation

[0023] The preparation method of the flexible thermal interface material with a diamond heat dissipation layer and a vertical heat dissipation channel of carbon fiber according to the present invention includes the following steps: 1) The diamond particles are surface-cleaned to remove surface grease and impurities; the cleaning process is a multi-step cleaning method combining acid cleaning, alkaline neutralization and deionized water rinsing. In step 1), the acidic cleaning can be performed using a sulfuric acid solution with a concentration of 0.1–1.0 mol / L, preferably 0.5 mol / L, for 1–3 cycles, each cycle lasting 20–40 min, preferably 30 min; the alkaline neutralization can be performed using a sodium hydroxide solution of the same concentration as the acidic cleaning, for 1–3 cycles, each cycle lasting 20–40 min; the deionized water rinsing can be performed 2–5 times, preferably 3 times; after cleaning, the sample is placed in a drying oven for thorough drying.

[0024] 2) Surface modification treatment of carbon fibers (CFs), denoted as mCFs, is performed to enhance their interfacial bonding with the matrix; the surface modification treatment may be performed by oxygen plasma treatment. In step 2), the oxygen plasma treatment can be performed using a plasma-enhanced chemical vapor deposition (PECVD) device, with oxygen as the treatment atmosphere and a treatment time of 5 to 30 minutes, preferably 10 minutes; the treated carbon fiber is referred to as modified carbon fiber.

[0025] 3) Prepare the polymer matrix solution; add polyvinyl alcohol to deionized water and heat and stir until completely dissolved; In step 3), the ratio of polyvinyl alcohol to deionized water can be 0.5-1.2 g:16 mL, preferably 0.8 g:16 mL; the heating temperature can be 80-105℃, preferably 90℃; and the stirring time can be 3-6 h, preferably 4 h.

[0026] 4) Add modified carbon fiber, plasticizer and defoamer to the polyvinyl alcohol solution obtained in step 3) in sequence, and continue to stir and mix evenly; In step 4), the amount of modified carbon fiber added can be 0.5-1.2 g, preferably 0.85 g; the plasticizer can be selected from glycerol, ethylene glycol, etc., preferably glycerol, and the amount added can be 0.5-1.2 g, preferably 0.8 g; the amount of defoamer added can be 0.05-0.2 ml, preferably 0.1 ml; the stirring temperature can be 80-95℃, preferably 90℃; the stirring time can be 20-40 min, preferably 30 min.

[0027] 5) Add the diamond particles treated in step 1) to the mixture obtained in step 4), and continue stirring to obtain a uniformly dispersed slurry; In step 5), the particle size of the diamond particles can be 10-200 μm, preferably 30 μm; the thermal conductivity of the diamond particles can be 1000-2000 W / m·K; the amount added can be 5-30 wt% based on the mass percentage of the total solid content, preferably 10 wt%, 15 wt%, 20 wt% or 25 wt%; the stirring time can be 40-120 min, preferably 60 min.

[0028] 6) Transfer the mixed slurry obtained in step 5) into a mold and place it in a magnetic field for orientation molding, so that the carbon fibers are aligned in the vertical direction (VAmCFs), and obtain a composite gel after gelation treatment; In step 6), the mold can be a polytetrafluoroethylene mold; the magnetic field can be provided by a neodymium iron boron permanent magnet or other energy-consuming magnetic field, and the magnetic field strength can be 0.2 to 10 T; the gelation temperature can be 20 to 30°C, preferably room temperature; and the gelation time can be 24 to 48 h.

[0029] 7) The composite gel obtained in step 6) is dried to obtain composite TIMs with vertical heat transfer and in-plane heat homogenization synergy; In step 7), the drying can be air drying, and the drying time can be 1 to 3 days, preferably 2 days.

[0030] The following embodiments will further illustrate the present invention with reference to the accompanying drawings. Example 1:

[0031] In this embodiment, a solution casting method is used to prepare a non-directional modified carbon fiber-based composite thermal interface material. The preparation method is as follows: (1) Surface modification treatment was performed using oxygen plasma (CFs) to obtain modified carbon fibers. The plasma treatment power was 100 W and the treatment time was 10 min.

[0032] (2) Mix 0.8 g of polyvinyl alcohol with 16 mL of deionized water and stir at 90 °C for 4 h to prepare a homogeneous polyvinyl alcohol solution.

[0033] (3) Add 0.85 g of modified carbon fiber, 0.8 g of glycerol and 0.1 mL of defoamer to the polyvinyl alcohol solution, and continue stirring at 90°C for 30 min to obtain a mixed slurry.

[0034] (4) Pour 1.5 mL of the mixed slurry into a custom polytetrafluoroethylene mold and gel at room temperature for 24–48 h.

[0035] (5) The gel was air-dried under ambient conditions for 48 h to obtain a non-oriented CFs / PVA composite thermal interface material; the product obtained in Example 1 is denoted as mCFs / PVA. Example 2:

[0036] In this embodiment, a magnetic field orientation-assisted casting method is used to prepare directional CFs-based composite thermal interface materials. The preparation method is as follows: (1) Surface modification of CFs was performed using oxygen plasma to obtain modified carbon fibers. The plasma treatment power was 100 W and the treatment time was 10 min.

[0037] (2) Mix 0.8 g of polyvinyl alcohol with 16 mL of deionized water and stir at 90 °C for 4 h to prepare a homogeneous polyvinyl alcohol solution.

[0038] (3) Add 0.85 g of modified carbon fiber, 0.8 g of glycerol and 0.1 mL of defoamer to the polyvinyl alcohol solution, and continue stirring at 90°C for 30 min to obtain a mixed slurry.

[0039] (4) Pour 1.5 mL of the mixed slurry into the customized polytetrafluoroethylene mold and place the mold between two neodymium iron boron permanent magnets. Gel at room temperature for 24-48 h with a magnetic field strength of 0.5 T and a magnetic field direction perpendicular to the film surface.

[0040] (5) The gel was air-dried under ambient conditions for 48 h to obtain a vertically oriented mCFs / PVA composite thermal interface material; the product prepared in Example 2 was denoted as VAmCFs / PVA. Example 3:

[0041] In this embodiment, a composite thermal interface material combining a vertical heat-conducting channel and a diamond heat-equalizing layer is prepared using a magnetic field orientation-assisted casting method. The preparation method is as follows: (1) Surface modification of CFs was performed using oxygen plasma to obtain modified carbon fibers. The plasma treatment power was 100 W and the treatment time was 10 min.

[0042] (2) Mix 0.8 g of polyvinyl alcohol with 16 mL of deionized water and stir at 90 °C for 4 h to prepare a homogeneous polyvinyl alcohol solution.

[0043] (3) Add 0.85 g of modified carbon fiber, 0.8 g of glycerin and 0.1 mL of defoamer to the polyvinyl alcohol solution and continue stirring at 90°C for 30 min.

[0044] (4) Add diamond powder to the mixture obtained in step (3) in an amount of 0.286 g (10 wt% of the total solid mass), and continue stirring for 60 min to disperse the diamond evenly.

[0045] This invention also conducted comparative experiments with different diamond powder addition amounts (0 wt%, 10 wt%, 15 wt%, and 25 wt%), demonstrating that the prepared VAmCFs / PVA / Dia composite TIMs exhibit significant anisotropic thermal conductivity and synergistic heat dissipation effect. When the diamond addition amount increased to 25 wt%, the in-plane thermal conductivity of the material increased to 34.67 W / m·K, proving that the diamond particles successfully constructed an efficient in-plane homogeneous temperature layer in the matrix. However, the inter-plane thermal conductivity of the material decreased with increasing diamond content, dropping to 8.15 W / m·K when the addition amount reached 25 wt%.

[0046] This data confirms that the present invention, through the synergistic structural design of "diamond in-plane heat equalization - carbon fiber vertical heat conduction", achieves a breakthrough improvement in in-plane heat diffusion capability while ensuring that the longitudinal thermal conductivity is maintained at the level of commercial high-end TIMs (≥20 W / m·K). It effectively solves the technical contradiction of "fast longitudinal heat conduction but difficult elimination of lateral hot spots" in traditional high inter-plane thermal conductivity materials, and provides data support for significantly reducing the chip temperature gradient in subsequent high-power LED testing.

[0047] The diamond was provided by Changsha Moben New Materials Co., Ltd., with a thermal conductivity of 1000-1400 W / m·K and a particle size of 30 μm. Before use, it was cleaned using a three-step method of acid washing, alkali neutralization, and water washing: first, it was washed twice with 0.5 mol / L sulfuric acid solution for 30 min each time; then, it was neutralized twice with 0.5 mol / L sodium hydroxide solution for 30 min each time; finally, it was rinsed three times with deionized water and dried for later use.

[0048] (5) Pour 1.5 mL of the mixed slurry into the customized polytetrafluoroethylene mold and place the mold between two neodymium iron boron permanent magnets. Gel at room temperature for 24-48 h with a magnetic field strength of 0.5 T and the magnetic field direction perpendicular to the film surface.

[0049] (6) The gel was air-dried under ambient conditions for 48 h to obtain a vertically oriented composite thermal interface material; The product prepared in Example 3 is denoted as VAmCFs / PVA / Dia.

[0050] Figure 1 SEM images of mCFs / PVA composite TIMs with and without a magnetic field are shown. Image (a) shows the mCFs / PVA composite TIMs without a magnetic field, where the modified carbon fibers in the matrix are arranged in a disordered manner. This disordered distribution results in a lack of effective heat conduction paths between the fillers, and heat transfer mainly relies on the thermal conductivity of the matrix material itself, limiting the overall thermal conductivity and anisotropic heat transport capacity of the composite material. Under the induction of a magnetic field, the modified carbon fibers align oriented along the magnetic field lines, as shown... Figure 1 As shown in Figure (b), the magnetic field induces the fibers to form an ordered structure within the matrix, creating VAmCFs / PVA composite TIMs. This orientational arrangement facilitates the construction of directional, highly thermally conductive channels along the fiber direction, thereby significantly improving the material's thermal conductivity in a specific direction. The addition of diamond successfully constructs synergistic channels for both in-plane heat homogenization and efficient inter-plane heat transfer, as shown in Figure (b). Figure 1 As shown in Figure (c), diamond was introduced into magnetically induced oriented modified carbon fibers to effectively construct VAmCFs / PVA / Dia composite TIMs with a synergistic heat transport network. This structure has two key features: First, diamond particles are deposited or distributed at the bottom of the composite material, forming an in-plane heat homogenization structure to achieve lateral heat diffusion of local hot spots, thereby effectively suppressing temperature accumulation in hot spot areas and improving the in-plane uniform heat distribution capability; Second, the modified carbon fibers oriented along the magnetic field direction construct an efficient heat conduction path through the thickness direction of the material, which can quickly transfer heat from heat-generating electronic devices (such as chips and power modules) to heat sinks or the surrounding air.

[0051] Figure 2 The in-plane and inter-plane thermal conductivity of VAmCFs / PVA / Dia composite TIMs with different diamond contents are presented. The figures show that the in-plane thermal conductivity increases with increasing diamond content, but the diamond-introduced interface also sacrifices some inter-plane thermal conductivity.

[0052] Figure 3The infrared thermal imaging results of different composite TIMs in the thermal management test of high-power LEDs show that the VAmCFs / PVA / Dia composite TIMs can effectively reduce the heat dissipated by high-power LEDs and lower their surface temperature.

[0053] Figure 4 Figure (a) shows the change in LED lamp surface temperature over time under different TIMs integration. After 120 seconds of operation, the surface temperatures of the LED lamps using mCFs / PVA composite TIMs, VAmCFs / PVA composite TIMs, and VAmCFs / PVA / Dia composite TIMs were 80.01℃, 72℃, and 66.9℃, respectively, with the LED lamp integrating VAmCFs / PVA / Dia composite TIMs exhibiting the lowest surface temperature. This result indicates that the proposed composite TIMs possess superior thermal conductivity and can effectively improve the heat dissipation capacity of high-power LED lamps. Furthermore, Figure 4 Figure (b) compares the surface temperature gradient of LED lamps with different TIMs integrations. Compared to mCFs / PVA composite TIMs (35.8℃) and VAmCFs / PVA composite TIMs (27.1℃), the LED lamp integrating VAmCFs / PVA / Dia composite TIMs has the smallest surface temperature gradient, at only 24.9℃. This confirms that the developed VAmCFs / PVA / Dia composite TIMs has a significant advantage in reducing local temperature gradients, thereby further enhancing the heat dissipation performance of high-power LED lamps. This invention not only achieves effective cooling of electronic devices, but also further reduces the temperature gradient of electronic devices by constructing a synergistic channel for in-plane heat homogenization and efficient inter-plane heat transfer through structural design. This synergistic heat transfer strategy is rarely mentioned in existing literature, but it has a decisive impact on the performance of electronic devices.

[0054] This invention constructs an asymmetric synergistic structure of "bottom diamond homogenizing layer - vertical carbon fiber thermal conductive needles" through magnetic field induction and precise control of slurry rheological properties, overcoming the limitations of the random dispersion of traditional thermally conductive fillers. Specifically, the specific gravity difference of diamond particles causes them to naturally settle to the bottom of the film during gelation, forming a continuous, high thermal conductivity in-plane homogenizing layer. Simultaneously, modified carbon fibers overcome the viscous resistance of the matrix and gravity under the action of a magnetic field, oriented vertically along the thickness direction, and forming a through-type thermal conductive path. This coupling mechanism of "lateral spreading + vertical arrangement" allows heat to be rapidly diffused by the diamond layer upon contact with the chip, avoiding heat congestion in a single vertical channel. Subsequently, the vertically oriented carbon fibers guide the evenly distributed heat to the heat sink. This synergistic effect effectively solves the problems in existing technologies where "high interplane thermal conductivity materials cannot eliminate local hot spots" and "high in-plane thermal conductivity materials are difficult to achieve low thermal resistance longitudinal transmission."

[0055] This invention utilizes oxygen plasma to etch and activate the surface of carbon fibers, significantly enhancing the interfacial bonding between modified carbon fibers and the polyvinyl alcohol polar matrix, and reducing interfacial phonon scattering. This characteristic produces significant synergistic benefits with the glycerol plasticizing system: on the one hand, the high aspect ratio and perpendicular orientation of the modified carbon fibers allow the material to form a thermally conductive percolation threshold at low filler content, avoiding matrix embrittlement caused by overfilling; on the other hand, glycerol molecules insert into the polyvinyl alcohol molecular chain segments, maintaining matrix flexibility while forming hydrogen bonds with oxygen-containing functional groups on the surface of the modified carbon fibers, further reducing contact thermal resistance. Even with the introduction of 25% high-content rigid diamond particles, the resulting composite material maintains good mechanical properties, can adaptively conform to rough contact interfaces, and ensures long-term reliability under actual working conditions.

[0056] This invention achieves anisotropic optimization and synergistic balance of thermal conductivity by controlling the amount of diamond added, resulting in technical effects that were unexpected by those skilled in the art. For example... Figure 2 As shown, when the diamond content is around 10wt%, the material maintains commercially high levels of interplane thermal conductivity while significantly improving in-plane thermal conductivity compared to the diamond-free system. In high-power LED tests, this synergistic structure significantly reduced the temperature gradient on the device surface from 35.8℃ to 24.9℃. This effect of greatly improving lateral heat dissipation without sacrificing longitudinal thermal conductivity cannot be derived simply by combining the physical properties of diamond and carbon fiber. Rather, it stems from the synergistic effect resulting from the specific spatial arrangement and interface optimization of the two materials, providing a novel solution for thermal management of high-power-density electronic devices.

[0057] This invention discloses a flexible thermal interface material (TIM) combining a diamond heat dissipation layer and vertically modified carbon fiber heat dissipation channels, along with its preparation method. The material utilizes a magnetic field to induce the vertical alignment of modified carbon fibers within a polyvinyl alcohol matrix, constructing highly efficient inter-plane thermal conduction channels. Simultaneously, highly thermally conductive diamond particles are introduced to form an in-plane heat dissipation layer, achieving a synergistic heat dissipation mechanism of "lateral heat dissipation and longitudinal heat conduction." This design combines a diamond heat dissipation layer with vertically modified carbon fiber heat dissipation channels, significantly improving in-plane heat diffusion to eliminate localized hot spots while maintaining low hardness and excellent inter-plane thermal conductivity. This effectively reduces the temperature gradient of electronic devices, overcoming the bottleneck of existing TIMs (thermal interface materials) that struggle to simultaneously achieve heat dissipation and high efficiency.

Claims

1. A flexible thermal interface material having a diamond heat dissipation layer and a carbon fiber vertical heat dissipation channel, characterized in that, Includes a flexible polymer matrix, modified carbon fibers, and diamond particles; The flexible polymer matrix is ​​a polyvinyl alcohol matrix; The diamond particles are concentrated at the bottom of the flexible thermal interface material to form an in-plane heat homogenization layer. The modified carbon fibers are arranged vertically along the thickness direction in the flexible polymer matrix to form a longitudinal heat-conducting channel that penetrates the flexible polymer matrix and connects to the in-plane heat exchange layer.

2. The flexible thermal interface material according to claim 1, characterized in that, The modified carbon fiber is obtained by surface modification treatment of carbon fiber with oxygen plasma; The oxygen plasma has a processing power of 50~200 W and a processing time of 5~30 min.

3. The flexible thermal interface material according to claim 1, characterized in that, The diamond particles have a particle size of 10~200 μm and a thermal conductivity of 1000~2000 W / m·K; The diamond particles are 10 wt% based on the total solids content.

4. The flexible thermal interface material according to claim 3, characterized in that, The flexible polymer matrix also contains a plasticizer and an antifoaming agent, wherein the plasticizer is glycerin and the antifoaming agent is modified polydimethylsiloxane.

5. The flexible thermal interface material according to claim 1, characterized in that, The diamond particles undergo surface cleaning treatment before use, and the cleaning treatment includes: First, wash with a sulfuric acid solution with a concentration of 0.1~1.0 mol / L 1~3 times; Then neutralize with sodium hydroxide solution of the same concentration as the sulfuric acid solution 1 to 3 times; Finally, rinse with deionized water 2-5 times.

6. The flexible thermal interface material according to claim 1, characterized in that, The in-plane thermal conductivity of the in-plane heat spreader is 20~35 W / m·K, and the inter-plane thermal conductivity of the longitudinal heat conduction channel is 8~20 W / m·K.

7. The flexible thermal interface material according to claim 1, characterized in that, The material is self-supporting and has a hardness of less than 80 HA.

8. The method for preparing the flexible thermal interface material according to claim 1, characterized in that, Includes the following steps: S1, the diamond particles are surface cleaned and dried; S2, oxygen plasma surface modification treatment is performed on carbon fibers to obtain modified carbon fibers; S3, add polyvinyl alcohol to deionized water, heat and stir until completely dissolved to obtain a polymer matrix solution; S4, add the modified carbon fiber, plasticizer and defoamer to the polymer matrix solution, and stir to mix evenly; S5, add the diamond particles to the mixture obtained in step S4, and continue stirring to obtain a uniformly dispersed slurry; S6. The mixed slurry is transferred to a mold and placed in a magnetic field perpendicular to the bottom surface of the mold for gelation treatment for 24-48 hours. Orientation molding is then performed to arrange the modified carbon fibers in a vertical direction and to make the diamond particles uniformly settle and accumulate at the bottom of the flexible thermal interface material to obtain a composite gel. S7. The composite gel is dried to obtain the finished product.

9. The preparation method according to claim 8, characterized in that, The magnetic field described in step S6 is provided by a neodymium iron boron permanent magnet with a magnetic field strength of 0.5 T.

10. The preparation method according to claim 8, characterized in that, The oxygen plasma surface modification treatment has a processing power of 100 W and a processing time of 10 min.

Images