Composite graphene thermal interface material and preparation method thereof

Abstract

The invention provides a composite graphene thermal interface material and a preparation method thereof, and relates to the technical field of heat-conducting composite materials. The material comprises a graphene heat conductor oriented in the thickness direction, a metal contact layer is arranged on the upper end face and / or the lower end face of the graphene heat conductor, the graphene heat conductor is composed of a graphene film and a polymer adhesive, and the raw material of the metal contact layer is room-temperature liquid metal or low-melting-point metal. According to the invention, high-flux heat conduction is realized through the vertically oriented graphene heat conductor, and the interface contact thermal resistance between a chip and a radiator is effectively reduced by using the metal contact layer on the surface layer, so that extremely low thermal resistance is integrally realized, and the heat dissipation requirement of a high-end electronic device is met.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive composite materials technology, and more specifically, to a composite graphene thermal interface material and its preparation method. Background Technology

[0002] With the rapid development of technologies such as artificial intelligence and high-performance computing, the computing power requirements of electronic chips continue to rise, and their power density and heat flux density have reached unprecedented levels. Against this backdrop, efficient heat dissipation has become a crucial aspect of ensuring stable chip performance and extending device lifespan. Thermal interface materials, filled between the chip's heat source and the heat sink (such as heat sink fins, vapor chambers, etc.), are used to eliminate interfacial air and fill microscopic imperfections, thereby significantly reducing contact thermal resistance and playing an indispensable role in the heat dissipation system.

[0003] Ideal thermally conductive materials require both extremely high intrinsic thermal conductivity and excellent interfacial adaptability. Graphene, as a two-dimensional material with ultra-high thermal conductivity (theoretical value approximately 5300 W / (m·K)), has become a research focus for next-generation high-performance thermal interface materials. By assembling graphene into macroscopic films and further utilizing a "laminarization-cutting" process (e.g., first combining and curing the graphene film with a polymer adhesive, then cutting it along a direction perpendicular to the film surface), graphene thermally conductive bulk materials with vertical orientation structures can be constructed. Such structures can utilize the high in-plane thermal conductivity of graphene to achieve efficient heat conduction along the material thickness direction. Chinese patent literature (such as CN118952821A, CN119910954A, etc.) has reported on such methods and the thermal interface materials obtained.

[0004] However, in-depth research by the inventors revealed a significant limitation in the aforementioned prior art, restricting its ultimate heat dissipation performance in practical applications: graphene is essentially a high-modulus hard material. When a vertically oriented heat-conducting layer composed of graphene comes into contact with a hard chip or metal heat sink surface, the actual contact area is much smaller than the apparent area due to the microscopic roughness of both surfaces. This limited contact results in high interfacial thermal resistance, causing heat to encounter bottlenecks at two key interfaces: the flow from the chip to the graphene heat conductor and the flow from the graphene heat conductor to the heat sink. Although the thermal conductivity of the bulk phase of the material has been optimized through the vertically oriented structure, the high interfacial thermal resistance makes it difficult for the overall heat dissipation efficiency to meet the stringent requirements of current high-end chips for extremely low thermal resistance.

[0005] Therefore, there is an urgent need in this field for a new type of composite graphene thermal interface material that not only has high thermal conductivity due to its vertically oriented structure, but also effectively overcomes the core problem of excessively high contact thermal resistance between graphene and metal interfaces. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a composite graphene thermal interface material and its preparation method. By utilizing the metal contact layer disposed on the surface of the graphene thermal conductor, the contact thermal resistance between the material and the chip and the heat sink can be significantly reduced, and the vertical orientation structure of the graphene can ensure efficient heat conduction, thereby achieving extremely low overall thermal resistance.

[0007] This invention provides a composite graphene thermal interface material, comprising a graphene thermal conductor oriented along the thickness direction, wherein the upper and / or lower end surfaces of the graphene thermal conductor are provided with a metal contact layer, the graphene thermal conductor is composed of a graphene film and a polymer adhesive, and the raw material of the metal contact layer is a room temperature liquid metal or a low melting point metal.

[0008] In one possible implementation, the thickness of the metal contact layer is 5-200 μm, and the room temperature liquid metal is selected from at least one of gallium, gallium indium tin alloy, and gallium indium alloy, and the low melting point metal is selected from at least one of indium, tin bismuth alloy, indium tin alloy, or indium bismuth tin alloy.

[0009] The second objective of this invention is to provide a method for preparing a composite graphene thermal interface material, the method specifically comprising the following steps: Step S1: Graphene thermal conductor is prepared using graphene film and polymer adhesive as raw materials; Step S2: Perform plasma treatment on the graphene heat conductor; Step S3: Using a liquid coating method or a physical vapor deposition method, a metal contact layer is formed on the upper and / or lower surfaces of the plasma-treated graphene thermal conductor.

[0010] In one possible implementation, the specific process of step S1 is as follows: Step S11: Impregnate the graphene film in an uncured polymer adhesive, and stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. Step S12: After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor oriented along the thickness direction.

[0011] In one possible implementation, in step S11, the density of each graphene film is 0.1-0.3 g / cm³. 3 The thickness is 0.1-0.3 mm; and the polymer adhesive is selected from one of epoxy resin, phenolic resin, acrylic resin, polyurethane, silicone rubber and organosilicon.

[0012] In one possible implementation, in step S11, before the impregnation process, the graphene film is pre-drilled. The pre-drilling method is selected from laser drilling, mechanical drilling and punching drilling, and the parameters of the holes obtained by the pre-drilling process are as follows: the diameter of the holes is 0.05-0.3 mm, the hole spacing is 0.1-5 mm, and the hole array is arranged in a regular geometric pattern.

[0013] In one possible implementation, the graphene film undergoes a surface treatment after pre-drilling and before impregnation, and the surface treatment includes a weak surface oxidation treatment and a silane coupling agent modification treatment performed sequentially.

[0014] In one possible implementation, the specific steps of the surface weak oxidation treatment are as follows: the graphene film that has been pre-drilled is immersed in a hydrogen peroxide solution with a mass fraction of 10-50% for immersion treatment, the immersion treatment temperature is 60-80℃, the immersion treatment vacuum degree is <-0.09MPa, and the immersion treatment time is 5-12h.

[0015] In one possible implementation, the silane coupling agent used in the silane coupling agent modification treatment is selected from at least one of aminosilane, mercaptosilane, epoxysilane, vinylsilane, methacryloxysilane, and alkylsilane, and has a mass fraction of 0.5-5%wt.

[0016] In one possible implementation, the parameters for the impregnation treatment in step S11 are as follows: vacuum degree < -0.1MPa, time 1-5h.

[0017] In one possible implementation, the curing parameters in step S12 are as follows: temperature 140-160℃, time 3-6h.

[0018] In one possible implementation, the parameters for plasma treatment in step S2 are as follows: the gas environment is at least one of oxygen, nitrogen and argon, the power is 100-1000W, and the time is 30-600s.

[0019] In one possible implementation, the specific steps of the liquid coating method in step S3 are as follows: when the raw material of the metal contact layer is room temperature liquid metal, the metal contact layer is directly coated on the upper and / or lower end surfaces of the graphene heat conductor after plasma treatment; when the raw material of the metal contact layer is low melting point metal, the graphene heat conductor is placed on a heating stage and heated to a temperature higher than the melting point of the low melting point metal, the solid low melting point metal is placed on the upper and / or lower end surfaces of the heated graphene heat conductor, and after the solid low melting point metal melts into a liquid state, it is uniformly scraped and kept in a heated state, and finally the metal contact layer is obtained after natural cooling treatment; The specific steps of the physical vapor deposition method are as follows: a graphene thermal conductor is placed in a cavity, a high-purity metal contact layer raw material is used as the evaporation source, a vacuum is drawn until the cavity pressure is lower than 5×10-3 Pa, the temperature is increased to evaporate the raw material of the metal contact layer, and then the material is deposited on the upper and / or lower end surfaces of the graphene thermal conductor.

[0020] Compared with the prior art, the present invention has the following advantages: 1. This invention creatively combines a vertically oriented graphene thermal conductor with a metal contact layer. The former utilizes the excellent in-plane thermal conductivity of graphene to construct a highly efficient heat conduction path throughout the material's thickness; the latter utilizes the fluidity and plastic deformation capability of metal to perfectly fill the microscopic gaps between the metal and the chip / heat sink. The synergistic effect of both significantly reduces the critical interfacial contact thermal resistance while ensuring high bulk thermal conductivity, thus achieving a breakthrough optimization of overall thermal resistance.

[0021] 2. This invention employs a series of pretreatment processes for graphene films, including pre-drilling, surface weak oxidation, and silane coupling agent treatment, fundamentally enhancing the interfacial bonding force between graphene and polymer adhesives. This not only effectively prevents the risk of delamination of the composite layer during processing and use but also ensures the integrity and mechanical strength of the vertical thermally conductive structure, thereby endowing the material with excellent structural stability and long-term reliability.

[0022] 3. This invention provides a single / double-sided metal layer structure, and can select room temperature liquid metal or phase change metal as the contact layer, giving the material a high degree of application flexibility. Whether it is a precision interface requiring instant liquid filling or a packaging scenario requiring easy storage and transportation, solid-state installation, and remelting, this invention can provide a suitable solution to meet the heat dissipation needs of various electronic devices from consumer electronics to high-power servers. Attached Figure Description

[0023] Figure 1 A photograph of a physical object with a liquid metal layer on its surface; Figure 2 To and Figure 1 In contrast, here is a picture of an actual object without a liquid metal layer on its surface. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the present invention.

[0025] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0027] A specific embodiment of the present invention provides a composite graphene thermal interface material, including a graphene thermal conductor oriented along the thickness direction, and a metal contact layer provided on the upper end surface and / or lower end surface of the graphene thermal conductor. The graphene thermal conductor is composed of a graphene film and a polymer adhesive, and the raw material of the metal contact layer is a room temperature liquid metal or a low melting point metal.

[0028] This invention achieves a synergistic effect of high-efficiency bulk thermal conductivity and low interfacial contact thermal resistance through a composite structure of vertically oriented graphene thermal conductors and a metal contact layer. The vertically oriented graphene layer constructs a highly efficient thermal conduction pathway throughout its thickness; while the surface metal contact layer, utilizing its fluidity and plasticity, adaptively fills the microscopic gaps between the metal and the chip / heat sink under pressure or heat, significantly increasing the actual contact area. This design fundamentally solves the bottleneck of interfacial thermal resistance caused by the excessive hardness and poor wettability of traditional graphene materials, thereby significantly improving overall heat dissipation performance.

[0029] Specifically, in practical applications, the metal contact layer + vertical graphene thermal conductor + metal contact layer is used when the thermal interface material needs to be in contact with both the heat source and the heat dissipation source at the same time, such as chip heat dissipation in electronic devices and servers. The structure of the metal contact layer + vertical graphene thermal conductor only needs to be in contact with the heat source (in the case of no heat dissipation source), such as in the casing of electronic devices to transfer heat to the air, and in some cases where a heat dissipation source cannot be installed, such as circuit boards.

[0030] Furthermore, the thickness of the metal contact layer is 5-200 μm, and the room-temperature liquid metal is selected from at least one of gallium, gallium-indium-tin alloy, and gallium-indium alloy, while the low-melting-point metal is selected from at least one of indium, tin-bismuth alloy, indium-tin alloy, or indium-bismuth-tin alloy. This invention precisely designs and selects the thickness and material composition of the metal contact layer. The 5-200 μm thickness range ensures that the functional layer can form a continuous and complete interface without excessively increasing the thermal resistance and cost of the material. The selected room-temperature liquid metal (such as gallium and its alloys) has excellent fluidity and wetting properties, enabling it to adaptively fill microscopic gaps at room temperature; while the low-melting-point metal (such as indium and its alloys) combines the mechanical strength of a solid state with the ability to transform into a liquid state for interface filling at operating temperatures. This precise thickness control, combined with a specific material system, ensures that the metal contact layer can perform stable and efficient interface bridging and thermal conductivity functions in different application scenarios.

[0031] This specific embodiment also provides a method for preparing a composite graphene thermal interface material, the preparation method specifically including the following steps: Step S1: Graphene thermal conductor is prepared using graphene film and polymer adhesive as raw materials; Step S2: Perform plasma treatment on the graphene heat conductor; Step S3: Using a liquid coating method or a physical vapor deposition method, a metal contact layer is formed on the upper and / or lower surfaces of the plasma-treated graphene thermal conductor.

[0032] This preparation method, through the synergistic application of three core processes, ensures that the final product possesses both excellent bulk thermal conductivity and extremely low interfacial thermal resistance. First, a vertically oriented graphene thermal conductor, fabricated using a specific process, establishes an efficient heat conduction pathway along the thickness direction. The crucial plasma treatment step effectively activates the graphene surface, significantly improving its wettability and adhesion to subsequent metal layers. Finally, a metal contact layer is formed using liquid coating or physical vapor deposition, creating a dense, uniform, and firmly bonded functional interface with the activated surface. The entire process flow is precisely designed, particularly the seamless integration of the plasma treatment and metal layer formation processes, fundamentally solving the interfacial thermal resistance problem caused by poor wettability between graphene and metal, thus ensuring the reliability and stability of the product's performance.

[0033] Furthermore, the specific process of step S1 is as follows: Step S11: Impregnate the graphene film in an uncured polymer adhesive, and stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. Step S12: After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor oriented along the thickness direction.

[0034] Furthermore, in step S11, the density of each graphene film is 0.1-0.3 g / cm³. 3 The thickness is 0.1-0.3 mm; and the polymeric adhesive is selected from one of epoxy resin, phenolic resin, acrylic resin, polyurethane, silicone rubber, and silicone rubber. This invention precisely optimizes key raw material parameters. The selected low-density, specific-thickness graphene film ensures excellent intrinsic thermal conductivity while also possessing good flexibility and adhesive wettability, laying the foundation for constructing a defect-free vertically oriented structure. The selected series of polymeric adhesives provides broad process adaptability, allowing for flexible selection based on the requirements of flexibility, temperature resistance, and adhesion for different application scenarios, thereby synergistically ensuring the structural stability and excellent thermal conductivity of the graphene thermal conductor.

[0035] Furthermore, in step S11, before the impregnation treatment, the graphene film undergoes a pre-drilling process. The pre-drilling method is selected from laser drilling, mechanical drilling, and stamping drilling, and the parameters of the holes obtained are as follows: hole diameter is 0.05-0.3 mm, hole spacing is 0.1-5 mm, and the hole array is arranged in a regular geometric pattern. This pre-drilling step creates a regular array of through-holes on the graphene film, providing longitudinal penetration channels for the polymer adhesive. This not only significantly increases the amount of adhesive impregnated but also forms penetrating "mechanical anchoring points" within the composite material, thereby effectively enhancing interlayer bonding, preventing the graphene sheets from separating during processing and use, and significantly improving the structural integrity and mechanical reliability of the graphene thermal conductor.

[0036] In practice, regular geometric arrangements can be square arrays, hexagonal arrays, or other regular geometric arrays.

[0037] Furthermore, after pre-drilling, the graphene film undergoes surface treatment before impregnation, which includes sequential weak oxidation and silane coupling agent modification. Through this synergistic process of "weak oxidation-silane coupling," interfacial chemical modification of the graphene film is achieved.

[0038] Furthermore, the specific steps of the surface weak oxidation treatment are as follows: the graphene film that has undergone pre-drilling treatment is immersed in a hydrogen peroxide solution with a mass fraction of 10-50% for immersion treatment, the immersion treatment temperature is 60-80℃, the vacuum degree of immersion treatment is <-0.09MPa, and the immersion treatment time is 5-12h.

[0039] Furthermore, the silane coupling agent used in the silane coupling agent modification treatment is selected from at least one of aminosilane, mercaptosilane, epoxysilane, vinylsilane, methacryloxysilane, and alkylsilane, and has a mass fraction of 0.5-5%wt.

[0040] Weak oxidation introduces active functional groups on the graphene surface, laying the foundation for subsequent reactions; the silane coupling agent acts as a "molecular bridge," bonding one end to the functional groups on the graphene surface and reacting with the polymer adhesive at the other end, thereby establishing a strong chemical bond between the two and fundamentally solving the core problem of weak interfacial bonding.

[0041] Furthermore, in step S11, the parameters for the impregnation treatment are as follows: vacuum degree < -0.1MPa, time is 1-5h.

[0042] Furthermore, in step S12, the curing parameters are as follows: temperature is 140-160℃, and time is 3-6h.

[0043] Furthermore, in step S2, the parameters for plasma treatment are as follows: the gas environment is at least one of oxygen, nitrogen, and argon; the power is 100-1000W; and the time is 30-600s. As a key interface activation step before the formation of the metal contact layer, plasma treatment efficiently cleans the surface of the graphene thermal conductor through the bombardment and action of high-energy particles, and introduces polar functional groups to significantly increase its surface energy. This treatment significantly enhances the wettability and chemical affinity of the graphene surface for subsequent metal materials, providing a crucial guarantee for the formation of a uniform, dense, and firmly bonded metal contact layer.

[0044] Furthermore, in step S3, the specific steps of the liquid coating method are as follows: when the raw material of the metal contact layer is room temperature liquid metal, the metal contact layer is directly coated on the upper and / or lower end surfaces of the graphene heat conductor after plasma treatment; when the raw material of the metal contact layer is low melting point metal, the graphene heat conductor is placed on a heating stage and heated to a temperature higher than the melting point of the low melting point metal, the solid low melting point metal is placed on the upper and / or lower end surfaces of the heated graphene heat conductor, and after the solid low melting point metal melts into a liquid state, it is uniformly scraped and kept in a heated state, and finally the metal contact layer is obtained after natural cooling treatment; The specific steps of the physical vapor deposition method are as follows: A graphene thermal conductor is placed in the cavity; a high-purity metal contact layer raw material is used as the deposition source; and a vacuum is drawn until the cavity pressure is below 5 × 10⁻⁶. -3 Pa, after the temperature is increased to evaporate the raw material of the metal contact layer, it is deposited on the upper and / or lower end surfaces of the graphene heat conductor.

[0045] The following is a further explanation based on specific embodiments.

[0046] Example 1 This embodiment provides a composite graphene thermal interface material, including a graphene thermal conductor oriented along the thickness direction, and a metal contact layer provided on the upper end face of the graphene thermal conductor. The graphene thermal conductor is composed of a graphene film and a polymer adhesive, and the raw material of the metal contact layer is indium, with a thickness of 20 μm.

[0047] The composite graphene thermal interface material in this embodiment was prepared through the following steps: S1. Impregnate the graphene film in an uncured polymer adhesive. The impregnation parameters are as follows: vacuum degree < -0.1 MPa, time 1 h. Stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. The density of each graphene film is 0.2 g / cm³. 3 The thickness is 0.1mm; and the polymer adhesive is epoxy resin; S2. After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor with a thickness of 0.3 mm and orientation along the thickness direction. The curing parameters are as follows: temperature is 140℃ and time is 3h. S3. The graphene heat conductor is subjected to plasma treatment. The parameters of the plasma treatment are as follows: the gas environment is oxygen and nitrogen, the power is 100W, and the time is 40s. S4. Place the plasma-treated graphene heat conductor in the cavity of the vacuum evaporation equipment. Place high-purity indium (99.99% purity) in the evaporation boat as the evaporation source. Evacuate the cavity until the pressure is below 5 × 10⁻⁶. -3 Pa, then apply current to the evaporation boat and slowly heat it to evaporate indium. Monitor the deposition thickness with a quartz crystal film thickness gauge. When the deposition thickness reaches 20 μm, stop the evaporation to form a uniform metallic indium contact layer on the upper surface of the graphene heat conductor.

[0048] The composite graphene thermal interface material prepared in this embodiment has a thermal resistance of 0.51 K·cm² / W at 80 °C and a thermal resistance of 0.043 K·cm² / W at 160 °C.

[0049] Example 2 This embodiment provides a composite graphene thermal interface material, including a graphene thermal conductor oriented along the thickness direction, and a metal contact layer provided on the upper and lower end surfaces of the graphene thermal conductor. The graphene thermal conductor is composed of a graphene film and a polymer adhesive. The thickness of the metal contact layer is 5 μm. The raw material of the metal contact layer is a tin-bismuth alloy, and the mass percentage ratio of tin to bismuth is 1:1.

[0050] The composite graphene thermal interface material in this embodiment was prepared through the following steps: S1. Impregnate the graphene film in an uncured polymer adhesive. The impregnation parameters are as follows: vacuum degree < -0.1 MPa, time 2 h. Stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. The density of each graphene film is 0.1 g / cm³. 3 The thickness is 0.2mm; and the polymer adhesive is silicone. S2. After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor with a thickness of 0.3 mm and orientation along the thickness direction. The curing parameters are as follows: temperature 160℃, time 3h. S3. The graphene heat conductor is subjected to plasma treatment. The parameters of the plasma treatment are as follows: the gas environment is oxygen, the power is 500W, and the time is 200s. S4. Place the plasma-treated graphene heat conductor in the cavity of the vacuum evaporation equipment. Place high-purity tin and high-purity bismuth (99.99% purity) in the evaporation boat as the evaporation source. Evacuate the cavity until the pressure is below 5 × 10⁻⁶. -3 Pa, then apply current to the evaporation boat, slowly heat to evaporate tin and bismuth, monitor with a quartz crystal film thickness gauge, stop evaporation when the deposition thickness reaches 5 μm, forming a uniform metal contact layer on the upper surface of the graphene heat conductor; repeat the above steps to form a uniform metal contact layer on the lower surface of the graphene heat conductor.

[0051] The composite graphene thermal interface material prepared in this embodiment has a thermal resistance of 0.37 K·cm² / W at 80 °C and a thermal resistance of 0.086 K·cm² / W at 160 °C.

[0052] Example 3 This embodiment provides a composite graphene thermal interface material, including a graphene thermal conductor oriented along the thickness direction, and a metal contact layer provided on the lower end face of the graphene thermal conductor. The graphene thermal conductor is composed of a graphene film and a polymer adhesive. The thickness of the metal contact layer is 20 μm, and the raw material of the metal contact layer is a gallium indium tin alloy (Ga: 68.5%, In: 21.5%, Sn: 10%).

[0053] The composite graphene thermal interface material in this embodiment was prepared through the following steps: S1. Impregnate the graphene film in an uncured polymer adhesive. The impregnation parameters are as follows: vacuum degree < -0.1 MPa, time 5 h. Stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. The density of each graphene film is 0.3 g / cm³. 3 The thickness is 0.3mm; and the polymer adhesive is acrylic resin; S2. After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor with a thickness of 0.3 mm and orientation along the thickness direction. The curing parameters are as follows: temperature 160℃, time 3h. S3. The graphene heat conductor is subjected to plasma treatment. The parameters of the plasma treatment are as follows: the gas environment is nitrogen and argon, the power is 1000W, and the time is 30s. S4. Using a scraping method, a room-temperature liquid gallium indium tin alloy (Ga: 68.5%, In: 21.5%, Sn: 10%) is coated onto the lower end face of the plasma-treated graphene heat conductor, with the alloy coating thickness controlled to be 20 μm.

[0054] The composite graphene thermal interface material prepared in this embodiment has a thermal resistance of 0.042 K·cm² / W.

[0055] Example 4 This embodiment provides a composite graphene thermal interface material, including a graphene thermal conductor oriented along the thickness direction, and a metal contact layer provided on the upper and lower end surfaces of the graphene thermal conductor. The graphene thermal conductor is composed of a graphene film and a polymer adhesive. The thickness of the metal contact layer is 120 μm, and the raw material of the metal contact layer is indium.

[0056] The composite graphene thermal interface material in this embodiment was prepared through the following steps: S1. Impregnate the graphene film in an uncured polymer adhesive. The impregnation parameters are as follows: vacuum degree < -0.1 MPa, time 2.5 h. Stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. The density of each graphene film is 0.2 g / cm³. 3 The thickness is 0.2mm; and the polymer adhesive is phenolic resin; S2. After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor with a thickness of 0.3 mm and orientation along the thickness direction. The curing parameters are as follows: temperature 145℃, time 4h. S3. The graphene heat conductor is subjected to plasma treatment. The parameters of the plasma treatment are as follows: the gas environment is oxygen and argon, the power is 600W, and the time is 250s. S4. Place the graphene heat conductor on a hot plate and heat it to 170°C (higher than the melting point of indium, 156°C). Place solid pure indium on the upper surface of the heated graphene heat conductor. After it melts into a liquid state, use a scraper to spread it evenly at a constant speed to form a uniform liquid indium layer. Keep it heated for about 10 seconds to allow it to spread fully. Then remove the heat source and allow it to cool naturally in the air to room temperature to solidify and form a metal contact layer. By controlling the scraping parameters, the thickness of the metal contact layer is made to be 120μm. Repeat the above steps to form a uniform metal contact layer on the lower surface of the graphene heat conductor.

[0057] The composite graphene thermal interface material prepared in this embodiment has a thermal resistance of 0.46 K·cm² / W at 80 °C and a thermal resistance of 0.051 K·cm² / W at 160 °C.

[0058] Example 5 This embodiment provides a composite graphene thermal interface material, including a graphene thermal conductor oriented along the thickness direction, and a metal contact layer provided on the upper surface of the graphene thermal conductor. The graphene thermal conductor is composed of a graphene film and a polymer adhesive. The thickness of the metal contact layer is 20 μm, and the raw material of the metal contact layer is indium.

[0059] The composite graphene thermal interface material in this embodiment was prepared through the following steps: S1. Impregnate the graphene film in an uncured polymer adhesive. The impregnation parameters are as follows: vacuum degree < -0.1 MPa, time 4 h. Stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. The density of each graphene film is 0.15 g / cm³. 3 The thickness is 0.15mm; and the polymer adhesive is polyurethane. S2. After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor with a thickness of 0.3 mm and orientation along the thickness direction. The curing parameters are as follows: temperature 150℃, time 4h. S3. The graphene heat conductor is subjected to plasma treatment. The parameters of the plasma treatment are as follows: the gas environment is nitrogen, the power is 800W, and the time is 60s. S4. Place the graphene heat conductor on a hot plate and heat it to 170°C (higher than the melting point of indium, 156°C). Place solid pure indium on the upper surface of the heated graphene heat conductor. After it melts into a liquid state, use a scraper to scrape it at a uniform speed to form a uniform liquid indium layer. Keep it heated for about 10 seconds to allow it to spread fully. Then remove the heat source and let it cool naturally in the air to room temperature to solidify and form a metal contact layer. By controlling the scraping parameters, the thickness of the metal contact layer is 20μm.

[0060] The composite graphene thermal interface material prepared in this embodiment has a thermal resistance of 0.32 K·cm² / W at 80 °C and a thermal resistance of 0.044 K·cm² / W at 160 °C.

[0061] Comparative Example 1 This comparative example provides a composite graphene thermal interface material. The only difference from Example 1 is that this comparative example undergoes pre-drilling treatment before impregnation during the preparation process. The specific steps are as follows: S1. Pre-drilling process: Laser drilling is used, and the parameters of the holes obtained by the pre-drilling process are as follows: the diameter of the hole is 0.05mm, the hole spacing is 0.5mm, and the hole array is arranged in a regular geometric pattern. S2. The pre-perforated graphene film is immersed in an uncured polymer adhesive for impregnation. The impregnation parameters are as follows: vacuum degree < -0.1MPa, time 1h. Multiple impregnated graphene films are stacked to a predetermined thickness to obtain a laminate. The density of each graphene film is 0.2g / cm³. 3 The thickness is 0.1mm; and the polymer adhesive is epoxy resin; S3. After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor with a thickness of 0.3 mm and orientation along the thickness direction. The curing parameters are as follows: temperature 140℃, time 3h. S4. The graphene heat conductor is subjected to plasma treatment. The parameters of the plasma treatment are as follows: the gas environment is oxygen and nitrogen, the power is 100W, and the time is 40s. S5. Place the plasma-treated graphene heat conductor in the cavity of the vacuum evaporation equipment. Place high-purity indium (99.99% purity) in the evaporation boat as the evaporation source. Evacuate the cavity until the pressure is below 5 × 10⁻⁶. -3 Pa, then apply current to the evaporation boat and slowly heat it to evaporate indium. Monitor the deposition thickness with a quartz crystal film thickness gauge. When the deposition thickness reaches 20 μm, stop the evaporation to form a uniform metallic indium contact layer on the upper surface of the graphene heat conductor.

[0062] The composite graphene thermal interface material prepared in this comparative example has a thermal resistance of 0.47 K·cm² / W at 80 °C and a thermal resistance of 0.039 K·cm² / W at 160 °C.

[0063] Comparative Example 2 This comparative example provides a composite graphene thermal interface material. The only difference from Comparative Example 1 is that the specific operation of the pre-drilling treatment in this comparative example is as follows: S1. Pre-drilling treatment: Mechanical drilling is used, and the parameters of the holes obtained by the pre-drilling treatment are as follows: the diameter of the holes is 0.3mm, the spacing between holes is 0.1mm, the hole array is arranged in a regular geometric pattern, and the others are the same as those in Comparative Example 1, so they will not be repeated here.

[0064] The composite graphene thermal interface material prepared in this comparative example has a thermal resistance of 0.58 K·cm² / W at 80 °C and 0.047 K·cm² / W at 160 °C.

[0065] Comparative Example 3 This comparative example provides a composite graphene thermal interface material. The only difference from Comparative Example 1 is that the specific operation of the pre-drilling treatment in this comparative example is as follows: S1. The punching method is adopted, and the parameters of the holes obtained by pre-punching are as follows: the diameter of the holes is 0.05mm, the hole spacing is 5mm, the hole array is arranged in a regular geometric pattern, and the others are the same as those in Comparative Example 1, which will not be repeated here.

[0066] The composite graphene thermal interface material prepared in this comparative example has a thermal resistance of 0.52 K·cm² / W at 80 °C and a thermal resistance of 0.041 K·cm² / W at 160 °C.

[0067] Comparative Example 4 This comparative example provides a composite graphene thermal interface material. The only difference between this comparative example and Comparative Example 1 is that, in the preparation process of this comparative example, before the impregnation treatment, after the pre-drilling treatment, it also undergoes surface weak oxidation treatment and silane coupling agent modification treatment. The specific steps are as follows: S1. Pre-drilling process: Laser drilling is used, and the parameters of the holes obtained by the pre-drilling process are as follows: the diameter of the hole is 0.05mm, the hole spacing is 0.5mm, and the hole array is arranged in a regular geometric pattern. S2. Surface weak oxidation treatment: The pre-drilled graphene film is immersed in a 10% hydrogen peroxide solution for immersion treatment. The immersion treatment temperature is 60℃, the vacuum degree of immersion treatment is <-0.09MPa, and the immersion treatment time is 5h. S3. Silane coupling agent modification treatment: The silane coupling agent used is aminosilane, and the mass fraction is 0.5%wt.

[0068] S4. The graphene film modified with silane coupling agent is immersed in an uncured polymer adhesive for impregnation. The impregnation parameters are as follows: vacuum degree < -0.1MPa, time 1h. Multiple impregnated graphene films are stacked to a predetermined thickness to obtain a laminate. The density of each graphene film is 0.2g / cm³. 3 The thickness is 0.1mm; and the polymer adhesive is epoxy resin; S5. After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor with a thickness of 0.3 mm and orientation along the thickness direction. The curing parameters are as follows: temperature 140℃, time 3h. S6. The graphene heat conductor is subjected to plasma treatment. The parameters of the plasma treatment are as follows: the gas environment is oxygen and nitrogen, the power is 100W, and the time is 40s. S7. Place the plasma-treated graphene heat conductor in the cavity of the vacuum evaporation equipment. Place high-purity indium (99.99% purity) in the evaporation boat as the evaporation source. Evacuate the cavity until the pressure is below 5 × 10⁻⁶. -3 Pa, then apply current to the evaporation boat and slowly heat it to evaporate indium. Monitor the deposition thickness with a quartz crystal film thickness gauge. When the deposition thickness reaches 20 μm, stop the evaporation to form a uniform metallic indium contact layer on the upper surface of the graphene heat conductor.

[0069] The composite graphene thermal interface material prepared in this comparative example has a thermal resistance of 0.46 K·cm² / W at 80 °C and a thermal resistance of 0.031 K·cm² / W at 160 °C.

[0070] Comparative Example 5 This comparative example provides a composite graphene thermal interface material, which differs from Comparative Example 4 only in the parameters of the surface weak oxidation treatment and silane coupling agent modification treatment, as detailed below: S2. Surface weak oxidation treatment: The pre-drilled graphene film is immersed in a 50% hydrogen peroxide solution for immersion treatment. The immersion treatment temperature is 80℃, the vacuum degree of immersion treatment is <-0.09MPa, and the immersion treatment time is 12h. S3. Silane coupling agent modification treatment: The silane coupling agent used is mercaptosilane with a mass fraction of 5%wt.

[0071] Comparative Example 6 This comparative example provides a composite graphene thermal interface material, which differs from Comparative Example 4 only in the parameters of the surface weak oxidation treatment and silane coupling agent modification treatment, as detailed below: S2. Surface weak oxidation treatment: The pre-drilled graphene film is immersed in a 25% hydrogen peroxide solution for immersion treatment. The immersion treatment temperature is 70℃, the vacuum degree of immersion treatment is <-0.09MPa, and the immersion treatment time is 8h. S3. Silane coupling agent modification treatment: The silane coupling agent used is methacryloxysilane, and the mass fraction is 2.5%wt.

[0072] Comparative Example 7 This comparative example provides a composite graphene thermal interface material. The only difference from Example 1 is that this comparative example uses a solid-state bonding method to prepare a metal contact layer on the surface of a graphene thermal conductor. The specific steps are as follows: S4. Select a pure indium foil with a thickness of 20μm as the metal contact layer, align it with the graphene heat conductor after plasma treatment at room temperature, place it in a press mold, apply a pressure of 30 MPa and hold the pressure for 5 minutes, use the pressure to make the indium foil plastically deform, and achieve mechanical interlocking and cold welding with the surface of the graphene heat conductor.

[0073] The results above demonstrate that this invention creatively combines a vertically oriented graphene thermal conductor with a metal contact layer. The former utilizes graphene's excellent in-plane thermal conductivity to construct a highly efficient heat conduction path throughout the material's thickness; the latter utilizes the fluidity and plastic deformation capabilities of metal to perfectly fill the microscopic gaps between the metal and the chip / heat sink. The synergistic effect of both significantly reduces the critical interfacial contact thermal resistance while ensuring high bulk thermal conductivity, thus achieving a breakthrough optimization of overall thermal resistance.

[0074] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A composite graphene thermal interface material, characterized in that, The invention includes a graphene thermal conductor oriented along its thickness direction, wherein the upper and / or lower surfaces of the graphene thermal conductor are provided with a metal contact layer, the graphene thermal conductor is composed of a graphene film and a polymer adhesive, and the raw material of the metal contact layer is a room temperature liquid metal or a low melting point metal.

2. The composite graphene thermal interface material as described in claim 1, characterized in that, The thickness of the metal contact layer is 5-200 μm, and the room temperature liquid metal is selected from at least one of gallium, gallium indium tin alloy and gallium indium alloy, and the low melting point metal is selected from at least one of indium, tin bismuth alloy, indium tin alloy or indium bismuth tin alloy.

3. A method for preparing a composite graphene thermal interface material as described in any one of claims 1-2, characterized in that, The preparation method specifically includes the following steps: Step S1: Graphene thermal conductor is prepared using graphene film and polymer adhesive as raw materials; Step S2: Perform plasma treatment on the graphene heat conductor; Step S3: Using a liquid coating method or a physical vapor deposition method, a metal contact layer is formed on the upper and / or lower surfaces of the plasma-treated graphene thermal conductor.

4. The preparation method according to claim 3, characterized in that, The specific process of step S1 is as follows: Step S11: Impregnate the graphene film in an uncured polymer adhesive, and stack multiple impregnated graphene films to a predetermined thickness to obtain a laminate. Step S12: After curing, the laminate is cut along the thickness direction to obtain a graphene thermal conductor oriented along the thickness direction.

5. The preparation method according to claim 4, characterized in that, In step S11, the density of each graphene film is 0.1-0.3 g / cm³. 3 The thickness is 0.1-0.3 mm; and the polymer adhesive is selected from one of epoxy resin, phenolic resin, acrylic resin, polyurethane, silicone rubber and organosilicon.

6. The preparation method according to claim 5, characterized in that, In step S11, before the impregnation process, the graphene film is pre-drilled. The pre-drilling method is selected from one of laser drilling, mechanical drilling and punching drilling. The parameters of the holes obtained by the pre-drilling process are as follows: the diameter of the holes is 0.05-0.3mm, the hole spacing is 0.1-5mm, and the hole array is arranged in a regular geometric pattern.

7. The preparation method according to claim 6, characterized in that, After the graphene film undergoes pre-perforation treatment, it also undergoes surface treatment before impregnation treatment, and the surface treatment includes a weak surface oxidation treatment and a silane coupling agent modification treatment performed sequentially. The specific steps of the surface weak oxidation treatment are as follows: the graphene film that has been pre-drilled is immersed in a hydrogen peroxide solution with a mass fraction of 10-50% for immersion treatment. The immersion treatment temperature is 60-80℃, the vacuum degree of immersion treatment is <-0.09MPa, and the immersion treatment time is 5-12h. The silane coupling agent used in the silane coupling agent modification treatment is selected from at least one of aminosilane, mercaptosilane, epoxysilane, vinylsilane, methacryloxysilane, and alkylsilane, and has a mass fraction of 0.5-5%wt.

8. The preparation method according to claim 4, characterized in that, In step S11, the parameters for the impregnation treatment are as follows: vacuum degree < -0.1MPa, time is 1-5h; In step S12, the curing parameters are as follows: temperature is 140-160℃, and time is 3-6h.

9. The preparation method according to claim 3, characterized in that, in step S2, the parameters of the plasma treatment are as follows: the gas environment is at least one of oxygen, nitrogen and argon, the power is 100-1000W, and the time is 30-600s.

10. The preparation method according to claim 3, characterized in that, In step S3, the specific steps of the liquid coating method are as follows: When the raw material of the metal contact layer is room temperature liquid metal, room temperature liquid metal is directly coated on the upper and / or lower end surfaces of the graphene heat conductor after plasma treatment to obtain the metal contact layer; when the raw material of the metal contact layer is low melting point metal, the graphene heat conductor is placed on a heating stage and heated to a temperature higher than the melting point of the low melting point metal. The solid low melting point metal is placed on the upper and / or lower end surfaces of the heated graphene heat conductor. After the solid low melting point metal melts into a liquid state, it is uniformly scraped and kept in a heated state. Finally, after natural cooling treatment, the metal contact layer is obtained. The specific steps of the physical vapor deposition method are as follows: A graphene thermal conductor is placed in the cavity; a high-purity metal contact layer raw material is used as the deposition source; and a vacuum is drawn until the cavity pressure is below 5 × 10⁻⁶. -3 Pa, after the temperature is increased to evaporate the raw material of the metal contact layer, it is deposited on the upper and / or lower end surfaces of the graphene heat conductor.

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