A flexible thermal interface material and its preparation method and application

Abstract

The application discloses a flexible thermal interface material and a preparation method and application thereof, and relates to the technical field of thermal interface materials, and specifically discloses a flexible thermal interface material which comprises a first metal layer, a composite material layer and a second metal layer which are sequentially stacked; the composite material layer comprises a metal nano array, a graphene material and a polymer; the metal nano array is formed by a metal nano column array, the graphene material is distributed in the metal nano array, and a three-dimensional network structure is formed between the graphene material and the metal nano array; the three-dimensional network structure has pores; and the pores are filled with the polymer. The thermal interface material in the application is composed of the metal nano array, the graphene material and the polymer, and the thermal interface material has excellent properties such as high thermal conductivity, high flexibility, thermal cycle reliability, oxidation resistance and corrosion resistance, and can be widely applied to planar or curved surfaces in electronic devices, heat dissipaters or mechanical devices, so that high-efficiency heat transfer channels are established, and good heat conduction effects are achieved.

Description

Technical Field

[0001] This invention belongs to the field of materials, specifically relating to a flexible thermal interface material, its preparation method, and its application. Background Technology

[0002] Thermal interface materials (TIMs), also known as thermally conductive interface materials, fill the gaps between working devices and heat dissipation devices, reducing contact thermal resistance and improving heat dissipation performance. An ideal TIM should have a low bonding layer thickness (BLT), high thermal conductivity to minimize thermal resistance, and good mechanical properties, such as high flexibility and compliance to adapt to flexible curved surfaces, and the ability to withstand thermal stress caused by the difference in thermal expansion between the two connecting materials. However, traditional TIMs, such as solder, grease, gel, and epoxy resin, cannot simultaneously meet the critical requirements of high thermal conductivity and good mechanical properties. Polymer-based TIMs have high flexibility but very low thermal conductivity, often requiring the embedding of high thermal conductivity additives such as metal nanoparticles and graphite into the polymer matrix. However, the interfacial thermal resistance between the additives and the polymer is high, and the thermal conductivity still cannot meet the current heat transfer requirements of electronic and mechanical components. Metal-based thermal interface materials (TIMs) have a thermal conductivity an order of magnitude higher than polymer-based TIMs, exhibiting excellent heat transfer performance. However, they suffer from drawbacks such as high melting point, high welding temperature, and very poor mechanical compliance, making them unsuitable for the curved surfaces of flexible devices. Therefore, existing thermal interface materials cannot meet the increasingly sophisticated requirements of electronic and mechanical components for high thermal conductivity and flexible thermal interface materials. Summary of the Invention

[0003] In order to overcome the problems existing in the prior art, one of the objectives of the present invention is to provide a flexible thermal interface material.

[0004] The second objective of this invention is to provide a method for preparing a flexible thermal interface material.

[0005] The third objective of this invention is to provide an application of a flexible thermal interface material in electronic components, heat sinks, or mechanical devices.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a flexible thermal interface material, comprising a first metal layer, a composite material layer, and a second metal layer stacked sequentially; the composite material layer comprises a metal nanoarray, graphene material, and a polymer; the metal nanoarray is formed by an array of metal nanopillars, and graphene material is distributed in the metal nanoarray, forming a three-dimensional network structure between the graphene material and the metal nanoarray; the three-dimensional network structure has pores; and the pores are filled with a polymer.

[0008] This invention employs a metal nanoarray as its basic framework to achieve high thermal conductivity in the vertical direction. Graphene material is grown on the surface of the metal nanoarray, forming a protective layer that encapsulates the metal nanoarray and connects adjacent metal nanopillars, enhancing lateral thermal conductivity and protecting the metal nanoarray structure from corrosion and oxidation. Furthermore, polymer infiltration fills the pores. Through the synergistic effect of the metal nanoarray, graphene material, and polymer, the thermal interface material achieves highly efficient thermal conduction, and simultaneously possesses advantages such as ultra-low thermal resistance, high flexibility, and oxidation and corrosion resistance.

[0009] Preferably, one end of the metal nanopillar is connected to the first metal layer, and the other end of the metal nanopillar is connected to the second metal layer.

[0010] Preferably, the thickness of the thermal interface material is 20 μm to 800 μm; more preferably, the thickness of the thermal interface material is 20 μm to 400 μm; even more preferably, the thickness of the thermal interface material is 20 μm to 200 μm; even more preferably, the thickness of the thermal interface material is 20 μm to 100 μm; more preferably, the thickness of the thermal interface material is 20 μm to 40 μm. The overall thickness of the thermal interface material of the present invention is adjustable, enabling ultra-high performance heat transfer with very low thickness.

[0011] Preferably, the thickness of the first metal layer is 100 nm to 10 μm. The first metal layer can serve to support and prevent the penetration of impurity solder, thus protecting the thermal interface material.

[0012] Preferably, the thickness of the second metal layer is 100 nm to 10 μm.

[0013] Preferably, the diameter of the metal nanopillars is 30–1000 nm. If the diameter of the metal nanopillars is too small, they are prone to breakage during processing; if they are too large, their density will decrease, thus reducing thermal conductivity. A higher density of metal nanopillars (i.e., the mass percentage of metal nanopillars in the composite material layer; for metal nanopillars of the same thickness, a higher mass percentage indicates a higher density) is more beneficial to improving the thermal conductivity of the thermal interface material. This invention can improve the thermal conductivity of the thermal interface by increasing the density of metal nanopillars. When the mass percentage of metal nanopillars reaches 60%, the thermal conductivity can reach over 200 W / m·K.

[0014] Preferably, the thickness of the composite material layer is 10–800 μm.

[0015] Preferably, the metal materials in the first metal layer, the second metal layer, and the metal nanoarray are all the same.

[0016] Preferably, the metallic material is selected from at least one of gold, silver, copper, aluminum, nickel, and tin.

[0017] Preferably, the polymer is selected from at least one of polydimethylsiloxane and polymethyl methacrylate. After the metal nanoarrays in the composite material layer are grown and connected by graphene material, some micropores still exist. These pores can affect the heat transfer performance of the resulting thermal interface material. Filling these pores with low-viscosity polymers such as PDMS and PMMA can further improve the heat transfer performance of the thermal interface material.

[0018] Preferably, the angle between the metal nanopillar and the first metal layer / second metal layer is 80-90°; more preferably, the angle between the metal nanopillar and the first metal layer / second metal layer is 85-90°; even more preferably, the angle between the metal nanopillar and the first metal layer / second metal layer is 88-90°; more preferably, the angle between the metal nanopillar and the first metal layer / second metal layer is 90°.

[0019] Preferably, the graphene material is a sheet-like material. The sheet-like graphene materials are interconnected laterally, achieving the effects of improving lateral thermal conductivity and preventing corrosion and oxidation of the metal nanoarray. Furthermore, the graphene sheets have a dense structure with uniform thickness and composition, allowing them to adhere tightly to the metal nanoarray to form a uniform network structure.

[0020] This invention designs a self-made fixture to protect the metal seed layer-metal nanoarray structure from damage. The film growth time is preferably 3-5 hours, which can be flexibly adjusted according to material requirements.

[0021] Preferably, the material of the connecting layer is selected from at least one of tin, silver, copper, tin-lead alloy, copper-zinc alloy, and silver-copper alloy.

[0022] Preferably, the thermal interface material includes a bonding layer located on the first metal layer and / or the second metal layer.

[0023] Preferably, the thickness of the connecting layer is 3–5 μm. The function of the connecting layer is to enable the thermal interface material to have good bonding performance with other substrates. Repeated experiments have determined that a connecting layer of 3–5 μm thickness is sufficient to tightly bond the thermal interface material with other rough substrates. The thickness of the connecting layer is significantly reduced compared to existing technologies, further reducing interfacial contact thermal resistance. To maintain solderability and reduce the contact thermal resistance between the metal nanoarray and the first metal layer / second metal layer, this invention electroplats an ultrathin connecting layer on the first metal layer and / or the second metal layer, thereby minimizing contact thermal resistance.

[0024] The thermal interface material in this invention can be applied to the surfaces of various materials, such as polymer materials, ceramic materials, and metal materials.

[0025] The second aspect of the present invention provides a method for preparing the flexible thermal interface material provided in the first aspect of the present invention, comprising the following steps:

[0026] S1: Prepare a metal nanoarray on the second metal layer, then deposit graphene material in the metal nanoarray, and then fill it with polymer to obtain a composite material layer;

[0027] S2: Electroplating a first metal layer onto the composite material layer to obtain the flexible thermal interface material.

[0028] Preferably, the step of depositing graphene material in the metal nanoarray employs plasma-enhanced chemical vapor deposition to grow graphene material in the metal nanoarray.

[0029] Preferably, the step of depositing graphene material in the metal nanoarray specifically involves: using methane and argon as reactant gases, depositing graphene material in the metal nanoarray at a radio frequency power of 55-70 W under conditions of a temperature of 480-520°C, a total pressure of 0.8-1 Torr, and a methane partial pressure of 40-50 mTorr. Gas flow pressure affects the deposition rate and effect; low gas flow pressure enhances gas diffusion, resulting in good deposition but a low deposition rate. Considering all factors, this invention uses the gas pressure within the aforementioned range, which allows for faster deposition of high-quality graphene sheets. This invention uses radio frequency plasma to improve the deposition rate, but high plasma power increases the inhomogeneity of the graphene sheets. After optimization, this invention found that a radio frequency power between 55 W and 70 W allows for faster deposition of uniform graphene sheets.

[0030] Preferably, the step of preparing the metal nanoarray on the second metal layer specifically involves: firstly forming a second metal layer on the surface of a nanoporous template by sputtering, then forming a metal nanoarray on the second metal layer by electrodeposition, and finally removing the nanoporous template to obtain the metal nanoarray.

[0031] Preferably, the step of preparing the metal nanoarray on the second metal layer specifically involves: preparing the metal nanoarray on the second metal layer by electrodeposition using a nanoporous template, and then removing the nanoporous template to obtain the metal nanoarray; more preferably, the step of preparing the metal nanoarray on the second metal layer specifically involves: placing both the second metal layer and the nanoporous template in an electrolyte, applying an electric current to allow the metal in the electrolyte to deposit and grow in the nanoporous template, thereby forming a metal nanoarray on the second metal layer, and then removing the nanoporous template by wet etching to obtain the metal nanoarray.

[0032] Preferably, the metal ions in the electrolyte are the same as the metal materials in the metal nanoarray.

[0033] Preferably, the template removal step involves removing the template using a wet etching method. More preferably, the template removal step involves placing a nanoporous template containing a metal nanoarray in a solution to corrode and dissolve the nanoporous template, retaining the metal nanoarray, and then removing the solution using a critical point drying method.

[0034] Preferably, the nanoporous template is a nanoporous anodic aluminum oxide template.

[0035] Preferably, the pore size of the nanoporous template is 10 μm to 500 μm, and the pore size can be adjusted according to the diameter of the required metal nanopillars.

[0036] Metal nanoarrays can be fabricated on various substrates using nanoporous templates. The substrate must be conductive. If the substrate is a metallic material (in this case, the substrate serves as the second metal layer), vertical metal nanoarrays can be directly fabricated on the substrate using a nanoporous template. If the substrate is a dielectric, semiconductor, or non-conductive substrate such as ceramic, an adhesive layer (e.g., a chromium layer with a thickness of 10 nm to 20 nm) and a second metal layer need to be electroplated on the substrate first. Then, the metal nanoarray is fabricated on the second metal layer using a nanoporous template. The density and length of the metal nanoarray can be controlled by the pore density and thickness of the nanoporous template. Therefore, by adjusting the pore density and thickness of the nanoporous template, metal nanoarrays of different densities and lengths can be fabricated. After sputtering the second metal layer onto the nanoporous template, electroplating is performed in an electrolyte. The metal deposits and grows on the second metal layer. Applying current to the metal electrolyte promotes the growth of the metal nanoarray. The length of the metal nanopillars can also be controlled by controlling the current and the electroplating time. After the metal nanoarray is grown by electroplating, it is separated from the nanoporous template by wet etching and critical point drying. That is, the nanoporous template containing the metal nanoarray is placed in a solution to etch and dissolve the nanoporous template, retaining the metal nanoarray, and then the solution is removed by critical point drying to avoid nanowire aggregation and maintain the vertical array arrangement.

[0037] Preferably, the step of filling the polymer is to spin-coat the polymer solution or immerse the polymer in the polymer solution, so that the polymer is impregnated into the pores of the three-dimensional network structure.

[0038] The third aspect of the present invention provides the application of the flexible thermal interface material provided in the first aspect of the present invention in electronic components, heat sinks or mechanical devices.

[0039] The beneficial effects of this invention are as follows: The thermal interface material of this invention combines metal nanoarrays, graphene materials, and polymers, giving it excellent properties such as high thermal conductivity, high flexibility, reliable thermal cycling, and resistance to oxidation and corrosion. It can be widely used in planar or curved surfaces of electronic devices, heat sinks, or mechanical components to establish efficient heat transfer channels and achieve good heat conduction. Furthermore, graphene materials can significantly improve the oxidation and corrosion resistance of the thermal interface material; the metal nanopillars will not oxidize or corrode even after one year of storage, and it also improves the lateral thermal conductivity of the thermal interface material.

[0040] The thermal interface material of this invention exhibits high flexibility, enabling it to adapt not only to flat device surfaces but also to rough, uneven, or curved device surfaces. Furthermore, the thermal interface material of this invention possesses an ultra-low thermal resistance of approximately 0.24 mm. 2 • K / W, low elasticity and low shear modulus of about 1 MPa. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the thermal interface material in Example 2.

[0042] Figure 2 The diagram shows the heat transfer model of the graphene-copper nanowire with the best least squares fit.

[0043] Figure 3 The thermal resistance test diagram is shown for the thermal interface material in Example 1.

[0044] Figure 4 The graph shows the Young's modulus test result of the thermal interface material in Example 1.

[0045] Figure 5 The images show the XRD patterns of copper nanowires and graphene-copper nanowires from Example 1.

[0046] Figure 6 The image shows the water contact angle test results for the copper nanowires and graphene-copper nanowires in Example 1.

[0047] Figure 7 This is a thermal stability test diagram of the thermal interface material in Example 1. Detailed Implementation

[0048] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0049] Example 1

[0050] Reference Figure 1 As shown in the schematic diagram of the thermal interface, the flexible, high thermal conductivity, corrosion-resistant, and efficient thermal interface material in this example includes a first tin layer, a first copper layer (also known as a copper cap), a composite material layer, a second copper layer (also known as a copper base), and a second tin layer, stacked sequentially. The composite material layer includes a copper nanowire array (also known as copper nanowires), a low-viscosity polymer, and graphene material. The graphene material is dispersed in the copper nanowire array, forming a three-dimensional network structure with pores filled with the low-viscosity polymer. The copper nanowires are arranged perpendicularly to the first copper layer.

[0051] The thickness of the first tin layer is 5 μm, the thickness of the first copper layer is 8 μm, the thickness of the composite material layer is 20 μm, the thickness of the second copper layer is 2 μm, and the thickness of the second tin layer is 5 μm. The diameter of the copper nanowire is 140 nm, and the mass percentage of the copper nanowire is 20% based on the total mass percentage of the composite material layer being 100%.

[0052] The low-viscosity polymer is PMMA.

[0053] Graphene materials are in sheet form.

[0054] The flexible, highly thermally conductive, corrosion-resistant, and enhanced thermal interface material in this example was prepared using the following method, with the specific steps as follows:

[0055] 1. Fabrication of vertically aligned copper nanowire arrays

[0056] First, a second copper layer (approximately 2 μm thick) was sputtered onto a porous anodic alumina (AAO) template (pore size 140 nm, pore spacing 450 nm, thickness 50 μm), forming the seed layer and support layer for the electroplated copper nanowire array. To control the nanowire growth direction, a sample support was placed on one side of the copper substrate to block the copper, ensuring that copper was deposited only on the AAO side, i.e., the copper nanowires grew along the exposed pores of the AAO. Subsequently, a square wave current was applied in a copper electrolyte (purchased from Sigma-Aldrich) to promote the growth of the copper nanowire array. A 0.15 A current was applied for 3 seconds, followed by a 0 A current applied for 1 second (4 seconds per cycle), with 1600 cycles. The duration of the square wave current determined the length of the copper nanowire array; in this example, the length of the copper nanowire array was approximately 20 μm. Then, the independent copper nanowire array / second copper layer was separated from the AAO by wet etching and critical point drying. Specifically, the AAO template was dissolved in a 1 mol / L KOH solution to release the copper nanowire array / second copper layer, while the solution was removed by critical point drying to avoid nanowire aggregation caused by liquid surface tension, thus obtaining the copper nanowire array / second copper layer structure, i.e., copper nanowires.

[0057] 2. Graphene growth on copper nanowire arrays using plasma-enhanced chemical vapor deposition.

[0058] The copper nanowire array / second copper layer structure was clamped in a fixture and placed in a reaction chamber. Argon gas was introduced for protection and the temperature was raised to approximately 500°C, held for 20 minutes. Then, the argon gas supply was stopped, and methane gas was introduced instead, creating a methane-argon mixture (CH4 / Ar = 1:19, 50 sccm) with a total gas pressure of 0.9 Torr and a methane partial pressure of 45 mTor. The gas was then activated using 60W radio frequency power to generate plasma in the reaction chamber. Ionized electrons, ions, and free radicals formed in the plasma and reacted with the methane gas. After maintaining this for 4 hours, the reaction was complete. The power was then cut off, the methane gas supply was shut off, and argon gas was introduced again until the reaction chamber cooled to room temperature. The resulting graphene-coated copper nanowire array, i.e., graphene-copper nanowires, was then removed.

[0059] During graphene synthesis, due to the size effect, the melting point of the copper nanowire array is lower than that of the second copper layer. Therefore, the temperature of the chemical vapor deposition process needs to be optimized. In this example, plasma-assisted deposition was used to lower the graphene synthesis temperature to 500℃. If the synthesis temperature is too high, the copper nanowire array melts, failing to maintain its unique structure. If the synthesis temperature is too low, graphene structures cannot form on the surface of the copper nanowire array. In the initial stage of synthesis, CH4 molecules directly contact the copper nanowire array. Under the combined action of high temperature and plasma, the CH bonds break, generating various carbon fragments (CHx), and a large amount of carbon is adsorbed on the surface of the copper nanowires. After the dehydrogenation of methane molecules, the carbon on the surface of the copper nanowires aggregates, forming new C-C bonds and clusters, initiating graphene nucleation. As the number of graphene nuclei on the copper surface increases, subsequently generated carbon atoms or clusters continuously attach to the nucleation sites, causing the graphene nuclei to gradually grow until they "stitch" together, ultimately connecting to form a continuous graphene film. However, as the deposition process proceeds, the copper nanowire array-graphene structure becomes thicker, the gaps between adjacent nanostructures become narrower, and the surface of the copper nanowires is covered by a thin graphene film, making further deposition of CH4 molecules difficult. Lower pressure results in a longer mean free path for the reactant molecules. To increase gas diffusion and allow gas molecules to sink further, a lower pressure is needed; however, higher pressure is beneficial for increasing the deposition rate. Considering the effects of pressure, this example uses a total pressure of 0.9 Torr, equivalent to a methane partial pressure of 45 mTorr. Furthermore, although radio frequency plasma is beneficial for the deposition rate, high plasma power leads to more molecular collisions, thus amplifying the inhomogeneity of the graphene coating. This example uses 60 W of radio frequency power for 4 hours to synthesize graphene, resulting in a fast deposition rate and good uniformity after forming. By optimizing parameters such as deposition temperature, deposition gas pressure, and deposition radio frequency power, graphene with suitable shape and thickness, and uniformity, can be synthesized in copper nanowire arrays at a higher rate and lower temperature.

[0060] 3. Spin-coating penetrating low-viscosity polymer

[0061] Low-viscosity polymers (25–35 mPa·s), such as PMMA, are spin-coated onto the surface of a graphene-coated copper nanowire array. This allows the low-viscosity polymer to penetrate into the pores within the nanoarray and graphene network, filling the pores and thus creating a composite material layer.

[0062] 4. Electroplating the first copper layer

[0063] After spin-coating the polymer, the top surface of the composite material layer was planed using a chemical mechanical polishing process until the copper nanostructure was exposed, at which point polishing was stopped. Subsequently, copper electroplating was performed again, in which copper was deposited only on the top of the composite material layer, forming a continuous layer of about 8 μm thick, resulting in the first copper layer, or copper cap.

[0064] 5. Electroplated thin tin layer

[0065] A first tin layer and a second tin layer are electroplated on the surfaces of the first copper layer and the second copper layer, respectively. The thickness of the first tin layer and the second tin layer is 5μm, thus obtaining the flexible, high thermal conductivity, anti-corrosion and enhanced thermal interface material in this example.

[0066] This example demonstrates how electroplated tin layers can diffuse and bond with other substrates. Through repeated experiments, it was determined that a 3-5 μm thick tin layer is sufficient to bond two relatively rough surfaces. The electroplated tin layer thickness is much lower than that of traditional solder wire (≥20 μm), reducing thermal resistance. The flexible metal nanoarray can adapt well to the main surface protrusions, and the liquid tin only needs to fill the remaining tiny gaps, significantly reducing the tin layer thickness required for bonding the TIM to the substrate.

[0067] Example 2

[0068] This example provides a method for using a flexible, highly thermally conductive, corrosion-resistant, and enhanced thermal interface material. The specific steps are as follows:

[0069] First, the thermal interface material from Example 1 is sandwiched between two substrates. A slight pressure is applied, and the mixture is heated to the melting point of tin (~240°C). The tin in the first and second tin layers melts within a few seconds. The molten tin can flow and conforms to the surface roughness of the matching substrates. After cooling, it can firmly bond the two substrates and the thermal interface material from Example 1 together. In this example, the substrate is a ceramic material.

[0070] Furthermore, the thermal interface material in Example 1 can be applied to the surface of a metal material or a polymer material according to the usage method in Example 2.

[0071] Performance testing:

[0072] The thermal conductivity of the thermal interface materials in Example 1 was tested respectively. The best least squares fit heat transfer model diagram of graphene-copper nanowires is shown in the figure below. Figure 2 As shown, the thermal conductivity of the thermal interface material in Example 1 was measured to be 128±19 W / m·K. Therefore, the thermal interface material in Example 1 has excellent thermal conductivity.

[0073] The thermal resistance of the copper cap, copper cap / graphene-copper nanowire, graphene-copper nanowire, copper-based / graphene-copper nanowire, copper-based, and the thermal interface material of Example 1 were tested respectively. Specific test results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the thermal resistance of the thermal interface material in Example 1 is 0.24 mm. 2 ·K / W, with ultra-low thermal resistance, its thermal resistance is lower than that of lead-tin alloy solder (approximately 5mm). 2The K / W ratio is one order of magnitude smaller than that of thermal grease (thermal resistance 10–200 mm). 2 ·K / W), thermally conductive gel (thermal resistance 15~100mm) 2 • K / W) and thermal pads (thermal resistance 100-300 mm) 2 The thermal resistance is several orders of magnitude lower (·K / W).

[0074] Indentation and scratch experiments were performed on copper nanowires, graphene-copper nanowires, and the thermal interface material in Example 1. Young's modulus was measured using the Oliver-Pharr model. The test results are as follows: Figure 4 ,Depend on Figure 4 It is evident that the thermal interface material in Example 1 exhibits high flexibility, with a low elastic modulus and shear modulus of approximately 1 MPa. The thickness of the thermal interface material in Example 1 is less than 40 μm; its small thickness and softness meet the requirements for flexible device bending surface applications.

[0075] The graphene-coated copper nanowire array in Example 1 prevents copper from oxidizing in air, exhibiting excellent antioxidant and corrosion-resistant properties. After the copper nanowires from step (1) of Example 1 and the graphene-copper nanowires from step (2) of Example 1 were placed for six months, XRD was used to detect the presence of oxides. Specific test results are as follows: Figure 5 As shown, by Figure 5 It can be seen that only copper nanowire structures exhibit oxides such as CuO and Cu2O, while no oxides appear in graphene-copper nanowires. This indicates that introducing graphene into the copper nanowire array for coating can improve the antioxidant properties of the copper nanowire array and obtain a composite material layer with superior antioxidant properties.

[0076] Water droplets were placed on the surfaces of the copper nanowires in step (1) of Example 1 and the graphene-copper nanowires in step (2) of Example 1, respectively, and the water contact angle was measured. The specific test results are as follows: Figure 6 As shown, by Figure 6 It can be seen that the water contact angle on the surface of the copper nanowire array is 0°, while the water contact angle on the surface of the graphene-copper nanowire is 135.7°. This indicates that after coating the copper nanowire array with graphite, the water wetting behavior changes from superhydrophilic with a contact angle of 0° to hydrophobic with a contact angle of 135.7°, and the graphene layer is firmly bonded to the metal nanowire array.

[0077] The thermal stability of the thermal interface material in Example 1 was tested using the following method: Thermal cycling tests were performed on the thermal interface material and the thermal paste (commercially available Vetroo INC, used as a control). One thermal cycle consisted of raising the temperature from -55°C to 125°C for 2 minutes, holding for 30 seconds, then lowering the temperature from 125°C to -55°C for 2 minutes, holding for 30 seconds. A total of 1000 thermal cycles were tested. Specific test results are as follows: Figure 7 As shown, by Figure 7 It can be seen that the thermal interface material in Example 1 still has thermal cycling stability over a wide temperature range after more than 1,000 thermal cycles, and has high reliability. Moreover, compared with thermal grease, the top surface temperature of the thermal interface material increases faster, and the maximum temperature is about 7°C higher than that of thermal grease.

[0078] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A flexible thermal interface material, characterized in that: The device comprises a first metal layer, a composite material layer, and a second metal layer stacked sequentially. The composite material layer includes a metal nanoarray, graphene material, and a polymer. The metal nanoarray is composed of an array of metal nanopillars, in which graphene material is distributed, forming a three-dimensional network structure between the graphene material and the metal nanoarray. The three-dimensional network structure has pores, and the pores are filled with polymer. The graphene material is a sheet-like material; the sheet-like graphene materials are connected to each other laterally; Graphene material is grown on the surface of the metal nanopillar array, and the graphene material coats the metal nanopillar array to form a protective layer and connects adjacent metal nanopillar materials. The polymer is selected from at least one of polydimethylsiloxane and polymethyl methacrylate.

2. The flexible thermal interface material according to claim 1, characterized in that: One end of the metal nanopillar is connected to the first metal layer, and the other end of the metal nanopillar is connected to the second metal layer.

3. The flexible thermal interface material according to claim 1, characterized in that: The thickness of the first metal layer and the second metal layer is 100 nm to 10 µm; and / or, the diameter of the metal nanopillars is 30 to 1000 nm; and / or, the thickness of the composite material layer is 10 to 800 µm.

4. The flexible thermal interface material according to claim 1, characterized in that: The metal materials in the first metal layer, the second metal layer, and the metal nanoarray are all the same.

5. The flexible thermal interface material according to claim 1, characterized in that: The metallic material is selected from at least one of gold, silver, copper, aluminum, nickel, and tin.

6. The flexible thermal interface material according to claim 1, characterized in that: The angle between the metal nanopillar and the first metal layer / second metal layer is 80~90°.

7. The flexible thermal interface material according to claim 1, characterized in that: The thermal interface material includes a bonding layer located on a first metal layer and / or a second metal layer.

8. The method for preparing the flexible thermal interface material according to any one of claims 1 to 7, characterized in that: Includes the following steps: S1: Prepare a metal nanoarray on the second metal layer, then deposit graphene material in the metal nanoarray, and then fill it with polymer to obtain a composite material layer; S2: Electroplating a first metal layer onto the composite material layer to obtain the flexible thermal interface material.

9. The method for preparing the flexible thermal interface material according to claim 8, characterized in that: The specific steps for depositing graphene material in the metal nanoarray are as follows: using methane and argon as reaction gases, under conditions of a temperature of 480~520℃, a total pressure of 0.8~1 Torr, and a methane partial pressure of 40~50 mTorr, graphene material is deposited in the metal nanoarray with a radio frequency power of 55~70W.

10. The application of the flexible thermal interface material according to any one of claims 1 to 7 in electronic components, heat sinks or mechanical devices.

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