A film coating method of a heat-conducting graphene heat sink

Abstract

The application discloses a film coating method of heat-conducting graphene heat-dissipating sheet, relates to the technical field of heat-dissipating sheet film coating, and comprises the following steps: S1, preparing a graphene heat-dissipating sheet base; S2, performing plasma treatment on the graphene heat-dissipating sheet base to form a pit-shaped microstructure on the surface of the graphene heat-dissipating sheet base; wherein the plasma treatment comprises plasma cleaning and plasma bombardment; and S3, performing vacuum coating treatment on the surface of the graphene heat-dissipating sheet base after the plasma treatment to obtain a heat-conducting graphene heat-dissipating sheet with an insulating layer. Through the synergistic effect of the plasma cleaning and the plasma bombardment in step S2, the pit-shaped microstructure is formed on the surface of the graphene heat-dissipating sheet base, which is beneficial to the uniform deposition and mechanical embedding of the insulating layer in the vacuum coating in subsequent step S3, so that the adhesion of the insulating layer is enhanced. Therefore, the application solves the technical problem of insufficient film coating adhesion of the heat-conducting graphene heat-dissipating sheet in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fin coating, in particular to a coating method of heat-conducting graphene fin. BACKGROUND

[0002] The graphene fin is a high-orientation heat-conducting fin stacked by multiple layers of graphene, which has good heat transfer performance, excellent flexibility, light weight and other characteristics, and is a new type of high-heat-conducting material.

[0003] In the prior art, most electronic products (such as mobile phones, tablets, etc.) need to be insulated and heat-insulated in circuit design, so the surface of the graphene heat-conducting fin needs to be coated for insulation. However, due to the difference in thermal expansion coefficient between the graphene heat-conducting fin and the coating material, the adhesion of the coating is insufficient, and delamination occurs in high-low temperature cycle and bending performance tests. This delamination is particularly prominent under extreme temperature changes or repeated bending conditions, which seriously restricts the application of graphene heat-conducting fins in electronic devices that require high reliability and long service life (such as wearable devices, foldable screen devices, and automotive electronics). SUMMARY

[0004] The purpose of the present application is to provide a coating method of heat-conducting graphene fin, which solves the technical problem of insufficient adhesion of the coating of the heat-conducting graphene fin in the prior art.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] A coating method of heat-conducting graphene fin, comprising:

[0007] Step S1, preparing a graphene fin substrate;

[0008] Step S2, plasma treating the graphene fin substrate to form a pit-shaped microstructure on the surface of the graphene fin substrate; wherein the plasma treatment includes plasma cleaning and plasma bombardment;

[0009] Step S3, vacuum coating the surface of the graphene fin substrate after plasma treatment to obtain a heat-conducting graphene fin with an insulating layer; wherein the thickness of the insulating layer is 0.5-20 μm.

[0010] Optionally, the step S1 comprises:

[0011] Step S11, selecting few-layer graphene powder as raw material, the number of layers of the few-layer graphene is 5-15 layers;

[0012] Step S12, the few-layer graphene powder is oriented and spread in a forming mold, and pre-compaction is performed by applying a pressure of 10-50 MPa to obtain a pre-compacted body;

[0013] Step S13, the pre-compacted body is subjected to stepwise heating treatment under inert gas protection to obtain a graphitized base;

[0014] Step S14, the graphitized base is subjected to a two-way isostatic pressing treatment, a silicon oil is selected as a pressure medium, a pressure of 100-150 MPa is applied at a temperature of 180-220 ℃, and a pressure maintaining time is greater than or equal to 60 min to form a graphene heat dissipation sheet base with a thickness of 10-100 μm.

[0015] Optionally, the step S13 comprises:

[0016] Step S131, the pre-compacted body is placed in a graphitization furnace, vacuum is extracted to a pressure less than or equal to 10 -3 Pa, and then argon protection gas is introduced, and a flow rate of the argon is controlled to be 5-10 L / min;

[0017] Step S132, the pre-compacted body is heated to 800-1000 ℃ at a heating rate of 5 ℃ / min, and a holding time is 30 min;

[0018] Step S133, the pre-compacted body is continuously heated to 2500-2800 ℃ at a heating rate of 10 ℃ / min, and a holding time is 60-120 min;

[0019] Step S134, after stopping heating, the pre-compacted body is cooled to 800 ℃ at a cooling rate of 20 ℃ / min, and then cooled to room temperature to obtain the graphitized base.

[0020] Optionally, after the step S14, the step S1 further comprises:

[0021] Step S15, a polishing treatment is performed on a surface of the graphene heat dissipation sheet base;

[0022] The step S15 specifically comprises:

[0023] Step S151, the surface of the graphene heat dissipation sheet base is subjected to ultrasonic cleaning by using anhydrous ethanol, and a cleaning time is 10-15 min;

[0024] Step S152, the surface of the graphene heat dissipation sheet base after ultrasonic cleaning is subjected to rough polishing treatment by using a diamond suspension and a polishing disc; wherein a particle size of the diamond abrasive is 1-3 μm, a rotating speed of the polishing disc is 200-300 rpm, a polishing pressure is 0.05-0.1 MPa, and a polishing time is 3-5 min;

[0025] Step S153: Replace the diamond suspension with nano-alumina polishing slurry and perform fine polishing on the surface of the graphene heat sink substrate after rough polishing; wherein, the particle size of the nano-alumina abrasive is 50~100nm, the rotation speed of the polishing disc is 100~150rpm, the polishing pressure is 0.01~0.03MPa, and the polishing time is 8~10min.

[0026] Step S154: The graphene heat sink substrate after fine polishing is ultrasonically cleaned with deionized water, and then dried to obtain the graphene heat sink substrate with a surface roughness Ra less than or equal to 0.5 μm.

[0027] Optionally, step S2 includes:

[0028] Step S21: Place the graphene heat sink substrate in the vacuum chamber of the plasma processing equipment and fix it to the water-cooled cathode stage. The temperature of the water-cooled cathode stage is controlled at 15~25℃.

[0029] Step S22: Evacuate the vacuum chamber until the base pressure is ≤5×10⁻⁶. -2 Pa, and argon gas is introduced as the working gas, with the gas flow rate controlled at 30~50 sccm, maintaining the chamber pressure at 15~25 Pa;

[0030] Step S23: Turn on the radio frequency power supply and apply a plasma with a radio frequency power of 50~80W to perform plasma cleaning on the surface of the graphene heat sink substrate; wherein, the cathode bias voltage is set to -50~-100V and the plasma cleaning time is 3~5min.

[0031] Step S24: Adjust the radio frequency power to 100~200W, and use argon ions to directionally bombard the surface of the plasma-cleaned graphene heat sink substrate to obtain the graphene heat sink substrate with pitted microstructure; wherein, the cathode bias voltage is increased to -300~-600V, the argon flow rate is increased to 50~80sccm, the chamber pressure is maintained at 20~40Pa, and the directional bombardment time is 8~15min.

[0032] Optionally, in step S24, the depth of the pit-like microstructure is 0.8~3μm, the diameter is 2~6μm, and the distribution density is (2~8)×10⁻⁶. 4 pcs / cm 2 .

[0033] Optionally, step S3 includes:

[0034] Step S31, place the graphene heat dissipation sheet substrate after plasma treatment on a rotating heating base in a vacuum reaction chamber, and control the temperature of the rotating heating base at 150-200℃;

[0035] Step S32, vacuumize the vacuum reaction chamber to a pressure of ≤1×10 -3 Pa, and introduce argon carrier gas with a flow rate of 100-200sccm;

[0036] Step S33, pulse introduce trimethylaluminum vapor and oxygen into the vacuum reaction chamber; wherein the pulse flow rate of the trimethylaluminum vapor is 5-10sccm with an on-off ratio of 1:3, the flow rate of the oxygen is 20-40sccm, and the pressure of the reaction chamber is 0.1-0.5Pa;

[0037] Step S34, start a radio frequency power source to excite plasma, set the radio frequency power at 200-400W, set the rotating speed of the base at 10-20rpm, and set the deposition time at 60-180min;

[0038] Step S35, deposit an aluminum oxide insulating layer with a thickness of 0.5-2.0μm on the surface of the graphene heat dissipation sheet substrate to obtain a heat-conductive graphene heat dissipation sheet with an aluminum oxide insulating layer.

[0039] Optionally, after step S35, the method further comprises:

[0040] Step S36, after the deposition is completed, stop introducing the trimethylaluminum vapor, cool down to below 80℃ at a cooling rate of 5℃ / min in an argon atmosphere, and take out the heat-conductive graphene heat dissipation sheet with an aluminum oxide insulating layer.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] The application provides a film coating method of a heat-conducting graphene heat dissipation sheet. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0044] The structures, proportions, sizes, etc. shown in the drawings of the present specification are only used to cooperate with the content disclosed in the present specification, to be understood and read by those skilled in the art, and do not define the limiting conditions for the implementation of the present application, so they do not have technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.

[0045] Figure 1 A flowchart of a film coating method of a heat-conducting graphene heat dissipation sheet is provided. DETAILED DESCRIPTION

[0046] In order to make the purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the following described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0047] In the description of the present application, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there can be a component disposed therebetween.

[0048] The technical solutions of the present application will be further described below in conjunction with the drawings and through specific embodiments.

[0049] The present application provides a film coating method for heat-conducting graphene heat dissipation sheet, as shown in the figure, comprising: Figure 1

[0050] Step S1, a graphene heat dissipation sheet substrate is prepared.

[0051] In an embodiment, step S1 specifically comprises:

[0052] Step S11, select few-layer graphene powder as raw material, the number of layers of few-layer graphene is 5-15 layers; In this embodiment, few-layer graphene refers to a material stacked by 2 to 15 layers of graphene layers, which is a two-dimensional carbon material between single-layer graphene and traditional graphite; The layers are stacked together by van der Waals force, and the honeycomb-like carbon atom lattice structure between the layers remains similar to that of single-layer graphene, but the overall properties change with the increase of the number of layers;

[0053] Step S12, spread the few-layer graphene powder in the forming mold in a directional manner, and apply a pressure of 10-50 MPa for pre-compaction to obtain a pre-compacted body;

[0054] Step S13, under the protection of inert gas, the pre-compacted body is subjected to stepwise heating treatment by a graphitization furnace to obtain a graphitized substrate; In this embodiment, the graphitization furnace is a device known in the art, which will not be described here;

[0055] Step S14, the graphitized substrate is subjected to two-way isostatic pressing treatment by an isostatic pressing treatment device, the pressure medium is selected to be silicone oil, a pressure of 100-150 MPa is applied at a temperature of 180-220℃, the pressure holding time is greater than or equal to 60 min, and a graphene heat dissipation sheet substrate with a thickness of 10-100 μm is formed. The isostatic pressing treatment device is a device known in the art, which will not be described here.

[0056] ​It should be noted that by using few-layer graphene powder as raw material, the overall mechanical strength and forming stability of the material can be improved while maintaining excellent thermal conductivity; then, the powder is pre-pressed by a pressure of 10-50 MPa to make it preliminarily dense, thereby providing a structural basis for the graphitization in step S13 and the isostatic pressing in step S14, so as to effectively improve the thermal conductivity and structural uniformity of the final graphene heat sink substrate. In step S13, the pre-pressed body is subjected to stepwise heating treatment in a graphitization furnace under inert gas protection, which helps the ordered recombination of graphite crystal structure, improves the graphitization degree and crystalline orientation, thereby enhancing the in-plane thermal conductivity of the graphene heat sink and providing a high-performance basis for the composite insulation layer in subsequent step S3.

[0057] Specifically, in step S14, bidirectional isostatic pressing is performed at 180-220℃ and 100-150 MPa using a silicon oil medium, which not only further compacts the graphitized structure, significantly improves the density and flatness of the graphene heat sink substrate, but also improves its micro-porosity and surface defects, which is beneficial to the formation of more uniform pit-like microstructure in the subsequent plasma treatment process in step S2, and improves the adhesion uniformity and interface bonding strength of the insulation layer during vacuum coating in step S3. By adjusting the isostatic pressing parameters, the thickness of the graphene heat sink substrate is controlled to be between 10-100μm, which meets the size design requirements of different electronic device heat dissipation structures, and also takes into account flexibility and strength, providing process flexibility for product diversification applications.

[0058] In an embodiment, step S13 comprises:

[0059] Step S131, the pre-pressed body is placed in a graphitization furnace, vacuumized to a pressure less than or equal to 10 -3 Pa, then argon protection gas is introduced, with a flow rate of 5-10L / min; vacuumization is used to completely remove active gases such as oxygen and water vapor, to prevent carbon material oxidation and ablation at high temperatures; inert gas is used to isolate air, maintaining an oxygen-free environment, and the 5-10L / min argon flow rate ensures stable furnace pressure and timely removal of pyrolysis volatiles.

[0060] Step S132, the pre-pressed body is heated to 800-1000℃ at a heating rate of 5℃ / min, and the holding time is 30min; in this embodiment, a heating rate of 5℃ / min is set to avoid cracking of the body or violent escape of volatiles due to sudden temperature rise; the temperature range of 800-1000℃ is the pyrolysis temperature window of organic matter such as high molecular binder and residual solvent, and 30 minutes of holding time can ensure that the organic matter is fully decomposed and carbonized to form an initial carbon skeleton.

[0061] Step S133, continue heating to 2500-2800℃ at a temperature increasing rate of 10℃ / min, and the holding time is 60-120min; in this embodiment, by setting the temperature increasing rate of 10℃ / min, the preparation efficiency is improved under the premise of ensuring controllable thermal stress; the temperature range of 2500-2800℃ can trigger carbon atom rearrangement, and the amorphous carbon is converted into graphite microcrystal, which significantly reduces the defect density; the holding time is 60-120min, which ensures the full graphitization of the carbon structure and improves the electrical conductivity, thermal conductivity and mechanical strength of the material.

[0062] Step S134, after stopping heating, cool down to 800℃ at a temperature decreasing rate of 20℃ / min, and then cool to room temperature to obtain a graphitized substrate. In this embodiment, by setting the temperature decreasing rate of 20℃ / min, the excessive growth of crystal grains in the high temperature range can be inhibited, and the re-precipitation of impurities caused by slow cooling can be avoided. Natural cooling after 800℃ can prevent thermal stress cracks caused by rapid cooling, effectively reduce the risk of micro-cracks and warping caused by uneven thermal expansion, improve the mechanical stability and flatness of the final substrate, and provide a high-quality basis for the subsequent two-way isostatic pressing process in step S14 and the vacuum coating process in step S3, on the other hand, it saves energy consumption.

[0063] It should be noted that by introducing the staged temperature control strategy, vacuum and argon protective atmosphere control, and slow cooling process in step S13, the following performances can be significantly improved: high graphitization degree, ordered crystal structure, excellent thermal conductivity; high purity, less impurities, which helps to maintain the stability of thermal conductivity and electrical insulation; dense structure and complete surface, which is beneficial to the subsequent isostatic pressing densification treatment and the formation of a stable coating interface. Step S3 significantly enhances the structural uniformity, thermal conductivity and processability of the graphene heat sink substrate, and provides a solid physical foundation for the subsequent construction of the concave microstructure and the composite of the insulating layer,

[0064] After step S14, the step S1 further comprises:

[0065] Step S15, polishing the surface of the graphene heat sink substrate by a polishing device. The polishing device is a device known in the art, which will not be described here.

[0066] In an embodiment, step S15 specifically comprises:

[0067] Step S151, ultrasonic cleaning the surface of the graphene heat sink substrate with anhydrous ethanol, and the cleaning time is 10-15min; in this embodiment, the silicon oil medium on the surface of the graphene heat sink substrate is removed by ultrasonic cleaning with anhydrous ethanol.

[0068] Step S152, using a diamond suspension and a polishing disc to perform rough polishing on the surface of the graphene heat sink substrate after ultrasonic cleaning; wherein the particle size of the diamond abrasive is 1-3 μm, the rotation speed of the polishing disc is 200-300 rpm, the polishing pressure is 0.05-0.1 MPa, and the polishing time is 3-5 min; in this embodiment, by using diamond abrasive with a particle size of 1-3 μm, the surface micro-irregular structure and residual machining marks of the graphene heat sink substrate are efficiently removed, and the surface topography is quickly corrected.

[0069] Step S153, replacing the diamond suspension with a nano-alumina polishing liquid to perform fine polishing on the surface of the graphene heat sink substrate after rough polishing; wherein the particle size of the nano-alumina abrasive is 50-100 nm, the rotation speed of the polishing disc is 100-150 rpm, the polishing pressure is 0.01-0.03 MPa, and the polishing time is 8-10 min; in this embodiment, by using nano-alumina abrasive with a particle size of 50-100 nm, the polishing process is further refined, the surface roughness of the graphene heat sink substrate is significantly reduced, and the graphene heat sink substrate obtains a high-smoothness polished surface. The smooth and clean surface not only ensures the consistency of the microstructure in the subsequent step S2 plasma treatment process, but also significantly improves the interfacial bonding force between the insulating layer and the graphene heat sink substrate during vacuum coating in step S3, avoiding failure problems such as film layer cavities, peeling, and skinning.

[0070] Step S154, using deionized water to ultrasonically clean the graphene heat sink substrate after fine polishing, and then drying to obtain a graphene heat sink substrate with a surface roughness Ra less than or equal to 0.5 μm. In this embodiment, the surface of the graphene heat sink substrate is effectively cleaned by ultrasonic cleaning with deionized water, and the polishing liquid residue (nano-alumina and diamond) is completely removed.

[0071] It should be noted that ultrasonic cleaning with anhydrous ethanol and deionized water before and after polishing can effectively remove dust, particle residues, and chemical impurities on the surface of the substrate, prevent scratches, surface defects, or plating inclusions in the subsequent processing process, and provide a clean base for polishing and plating processes. This step 15 realizes precise control of the surface topography of the graphene heat sink substrate from micro to nanoscale through the systematic cleaning-rough polishing-fine polishing-re-cleaning process, not only significantly reduces the surface roughness to Ra≤0.5 μm, meets the basic surface conditions required for high-quality coating, but also enhances the adhesion of the film layer and the thermal interface conduction performance, and overall improves the stability of the thermal management and the reliability of the process in the heat-insulating composite structure of the present application.

[0072] Step S2, performing plasma treatment on the graphene heat sink substrate to form a pit-shaped microstructure on the surface of the graphene heat sink substrate; wherein the plasma treatment comprises plasma cleaning and plasma bombardment.

[0073] In an embodiment, step S2 specifically comprises:

[0074] Step S21, placing the graphene heat sink substrate in a vacuum chamber of a plasma treatment device and fixing it to a water-cooled cathode stage, the temperature of the water-cooled cathode stage being controlled at 15-25℃; in this embodiment, the plasma treatment device is a device known in the art, which will not be described here. By fixing the graphene substrate to the temperature-controlled water-cooled cathode stage (temperature 15-25℃), the heat generated during the bombardment process can be effectively removed, avoiding damage to the graphene lattice structure or thermal deformation due to local overheating; a stable low-temperature environment also helps to control the controllability and repeatability of the plasma etching process, improving product consistency.

[0075] Step S22, vacuumizing the vacuum chamber to a base pressure ≤5×10 -2 Pa, and introducing argon as the working gas, with a gas flow rate of 30-50 sccm to maintain the chamber pressure at 15-25 Pa. In this embodiment, argon (Ar) is selected as the treatment atmosphere, which has high inertness and moderate ion mass, stable discharge, and no chemical corrosion to graphene materials; argon ions can provide directional kinetic energy in subsequent steps for stable and controllable physical bombardment etching to build a pit-shaped microstructure; argon does not chemically react with graphene, maintaining the intrinsic properties of the material, such as high thermal conductivity and low resistivity. The vacuum pretreatment, argon flow rate and pressure control in step S22 provide the prerequisites for the plasma cleaning in step S23 and the directional bombardment in step S24; it helps to reproduce the plasma treatment process in batch processing, improving the consistency and process yield of the entire graphene heat sink product.

[0076] Step S23, turning on the radio frequency power source and applying a plasma with a radio frequency power of 50-80 W to clean the surface of the graphene heat sink substrate; wherein the cathode bias is set to -50 to -100 V, and the plasma cleaning time is 3-5 min; in this embodiment, the argon plasma cleaning can effectively remove dust, residual polishing particles, organic contaminants and other contaminants on the surface of the substrate, significantly improving the surface cleanliness of the graphene heat sink substrate; plasma cleaning can also activate the local functional groups on the surface of graphene, improve the surface energy and surface chemical activity, and help the adhesion of the subsequent film layer and the etching efficiency of the plasma bombardment; the cleaning process is mild, avoiding damage to the graphitized crystal structure and maintaining high thermal conductivity.

[0077] Step S24, the radio frequency power is adjusted to 100-200 W, the surface of the graphene heat dissipation sheet substrate after the argon ion pair plasma cleaning is directionally bombarded to obtain a graphene heat dissipation sheet substrate with a pit-shaped microstructure; wherein, the cathode bias is raised to -300--600 V, the argon flow is increased to 50-80 sccm, the chamber pressure is maintained at 20-40 Pa, and the directional bombardment time is 8-15 min. In step S24, the depth of the pit-shaped microstructure is 0.8-3 μm, the diameter is 2-6 μm, and the distribution density is (2-8) × 10 4 cm 2 In this embodiment, the pit-shaped microstructure is etched in situ by high-speed argon ion bombardment on the surface of the graphene substrate without introducing additional materials; by controlling the parameters, the depth of the pit-shaped microstructure can be 0.8-3 μm, the diameter can be 2-6 μm, and the distribution density can be (2-8) × 10 4 cm 2 , so that the microstructure has high consistency and repeatability in size and distribution; the microstructure significantly increases the surface roughness and specific surface area per unit area, improves the physical embedding and mechanical engagement ability of the film layer, and effectively suppresses the risk of film layer peeling and cracking caused by interface stress or thermal cycling.

[0078] It should be noted that step S2 uses precision control parameters for plasma two-stage processing to construct a pit-shaped microstructure with a specific depth, size and distribution density on the basis of achieving a high-clean, high-activity surface, which not only significantly improves the adhesion and interface heat conduction efficiency of the insulating layer in subsequent step S3, but also enhances the overall stability and durability of the composite structure.

[0079] In an embodiment, step S3 includes:

[0080] Step S31, the graphene heat dissipation sheet substrate after plasma treatment is placed on a rotating heating base in a vacuum reaction chamber, and the temperature of the rotating heating base is controlled at 150-200℃; in this embodiment, the substrate is heated to the required reaction temperature in advance, which helps the adsorption reaction and film formation uniformity of the trimethylaluminum vapor and active oxygen species; the preheating treatment can remove trace amounts of moisture, solvents and the like that may be left on the surface of the substrate, improve the interface cleanliness, and enhance the adhesion of the film layer; by rotating the base, the uniformity of the film layer deposition can be further improved, and the thickness unevenness caused by local temperature difference or trimethylaluminum vapor concentration difference can be reduced.

[0081] Step S32, the vacuum reaction chamber is evacuated to a pressure ≤1 × 10 -3Pa, argon carrier gas is introduced, the gas flow is 100-200sccm; in this embodiment, the vacuum environment can effectively exclude impurity gas in the reaction cavity, prevent the formation of non-target byproduct or defect film layer; argon as an inert carrier, ensure the stable transportation of trimethylaluminum vapor (trimethylaluminum) in the gas phase, do not participate in the side reaction, establish a stable, clean reaction atmosphere, lay the foundation for the controllable atmosphere of the subsequent pulse atomic layer deposition; further avoid the microstructure formed by the early plasma bombardment from being polluted or oxidized, protect the active surface of the substrate.

[0082] Step S33, pulse into trimethylaluminum vapor and oxygen in the vacuum reaction chamber; wherein the pulse flow of trimethylaluminum vapor is 5-10sccm and the on-off ratio is 1:3, the flow of oxygen is 20-40sccm, and the reaction chamber pressure is 0.1-0.5Pa; in this embodiment, the trimethylaluminum is adsorbed on the graphene surface layer by layer by pulse injection (on-off ratio 1:3), which is helpful for the construction of single molecular layer film; by controlling the flow ratio of trimethylaluminum vapor and oxygen and the reaction chamber pressure, a self-limiting reaction is realized, and the thickness of the aluminum oxide film layer is effectively controlled. The reaction rate of trimethylaluminum and the oxygen species excited by plasma in the subsequent step S34 is fast and efficient, the reaction byproduct is volatile alkane, which is easy to remove, and it is conducive to the formation of dense and pinhole-free insulating film; precise adjustment of reactant flow and on-off rhythm helps to improve the filling and uniform deposition of the film in the microstructure area.

[0083] Step S34, turn on the radio frequency power to excite plasma, the radio frequency power is set to 200-400W, the substrate rotation speed is set to 10-20rpm, and the deposition time is 60-180min; in this embodiment, the oxygen is excited to O + , O2 - highly active oxygen species by plasma excitation, which has a high-efficiency reaction with trimethylaluminum vapor, overcoming the technical problem of low-temperature reaction deficiency in the traditional atomic layer deposition process. By adjusting the radio frequency power, the deposition rate and film density are bidirectionally controlled; by rotating the substrate, the thickness uniformity of the deposited layer on the graphene heat sink substrate is further ensured; effectively compatible with the surface of the microstructure, ensuring continuous coverage of the film layer without breaking.

[0084] Step S35, deposit an aluminum oxide insulating layer with a thickness of 0.5-2.0μm on the surface of the graphene heat sink substrate to obtain a heat-conducting graphene heat sink with an aluminum oxide insulating layer; in this embodiment, the deposited aluminum oxide layer structure is dense and has high thermal stability, not only providing insulation function, but also having certain mechanical protection and heat diffusion effect; the thickness of the film layer is controlled between 0.5-2.0μm, taking into account the insulation effect and heat conduction efficiency, avoiding the increase of thermal resistance caused by too thick insulating layer.

[0085] Step S36, after the deposition is stopped, stop the three methyl aluminum vapor, under the argon atmosphere, the cooling rate is 5℃ / min, and the temperature is below 80℃, and the heat-conducting graphene heat sink with an aluminum oxide insulation layer is taken out. In this embodiment, the slow cooling (5℃ / min) can reduce the thermal stress between the film layer and the substrate, prevent the film layer from cracking or peeling due to rapid cooling; the argon environment continuously protects the film layer and the substrate, prevents the film layer from being hygroscopic, oxidized or pore formed due to residual oxygen or water in the thermal annealing process; the cooling to below 80℃ before taking out of the furnace is conducive to the safety of product operation; and finally the graphene heat sink structure with a uniform and dense aluminum oxide film layer on the surface, high thermal conductivity, strong electrical insulation and excellent adhesion is obtained.

[0086] It should be noted that step S3 successfully deposits a dense, strong interface adhesion and thickness controllable aluminum oxide insulation film layer on the graphene heat sink substrate with a pit microstructure by integrating high vacuum environment, inert gas transport, pulsed atomic layer deposition reaction and plasma excitation mechanism, and realizes the coexistence of high thermal conductivity and high insulation. The process has the advantages of accurate temperature control, clean reaction, excellent film quality and strong structure adaptability.

[0087] Working principle: the film coating method of the heat-conducting graphene heat sink provided by the application, through the synergistic effect of the plasma cleaning and the plasma bombardment of step S2, not only forms a pit-shaped microstructure on the surface of the graphene heat sink substrate, but also significantly improves the roughness and activity of the surface of the substrate, which is conducive to the uniform deposition and mechanical embedding of the insulation layer in the vacuum coating of step S3, thereby enhancing the adhesion of the insulation layer and avoiding the influence of peeling or edge lifting on the long-term operation of the device thermal management performance. The thickness of the insulation layer formed by the vacuum coating of step S3 is 0.5-20μm, which can effectively block current leakage, meet the electrical insulation requirements of high-power electronic components, and at the same time, does not significantly reduce the high thermal conductivity of the graphene material itself, ensuring excellent heat dissipation performance and improving the reliability and safety of the overall device under high temperature and high load. The plasma treatment and vacuum coating used in the application are mature technologies, which have the characteristics of controllable process and strong repeatability, and are suitable for integrated implementation in large-scale production of graphene materials. Therefore, the application solves the technical problem of insufficient film coating adhesion of the heat-conducting graphene heat sink in the prior art.

[0088] The above-described embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for coating a heat conductive graphene heat sink, characterized by, The application relates to a preparation method of a graphene heat dissipation sheet. S1, preparing a graphene heat dissipation sheet substrate; S2, performing plasma treatment on the graphene heat dissipation sheet substrate to form a pit-shaped microstructure on the surface of the graphene heat dissipation sheet substrate; wherein the plasma treatment comprises plasma cleaning and plasma bombardment; S3, performing vacuum coating treatment on the surface of the graphene heat dissipation sheet substrate after the plasma treatment to obtain a heat-conducting graphene heat dissipation sheet with an insulating layer; wherein the thickness of the insulating layer is 0.5-20 mu m, and the insulating layer is an aluminum oxide insulating layer; The step S1 comprises: S11, selecting few-layer graphene powder as raw material, and the number of layers of the few-layer graphene is 5-15 layers; S12, spreading the few-layer graphene powder in a forming mold in a directional manner, and applying a pressure of 10-50 MPa to pre-compact to obtain a pre-pressed compact; S13, performing stepwise heating treatment on the pre-pressed compact under the protection of inert gas to obtain a graphitized substrate; S14, performing two-way isostatic pressing treatment on the graphitized substrate, and selecting silicon oil as the pressure medium; a pressure of 100-150 MPa is applied at a temperature of 180-220 DEG C, and the pressure maintaining time is greater than or equal to 60 min to form a graphene heat dissipation sheet substrate with a thickness of 10-100 mu m; The step S2 comprises: S21, placing the graphene heat dissipation sheet substrate in a vacuum chamber of a plasma treatment device, and fixing the graphene heat dissipation sheet substrate on a water-cooled cathode support table; the temperature of the water-cooled cathode support table is controlled to be 15-25 DEG C; Step S22, vacuum the vacuum chamber to a base pressure ≤ 5 x 10 -2 Pa, and introduce argon as a working gas, with a gas flow controlled to 30-50 sccm, to maintain the chamber pressure at 15-25 Pa; S23, starting a radio frequency power supply, and applying a plasma with a radio frequency power of 50-80 W to perform plasma cleaning on the surface of the graphene heat dissipation sheet substrate; wherein the cathode bias voltage is set to be-50--100 V, and the plasma cleaning time is 3-5 min; S24, adjusting the radio frequency power to 100-200 W, and performing directional bombardment on the surface of the graphene heat dissipation sheet substrate after the plasma cleaning by argon ions to obtain a graphene heat dissipation sheet substrate with a pit-shaped microstructure; wherein the cathode bias voltage is increased to-300--600 V, the argon flow is increased to 50-80 sccm, the chamber pressure is maintained at 20-40 Pa, and the directional bombardment time is 8-15 min.

2. The method of claim 1, wherein the method is characterized by: The step S13 comprises: Step S131, placing the pre-pressed body in a graphitization furnace, vacuumizing to a pressure less than or equal to 10 -3 After the pressure is reduced to 1 Pa, argon protection gas is introduced, and the flow rate of the argon is controlled at 5-10 L / min. S132, heating the pre-pressed compact to 800-1000 DEG C at a heating rate of 5 DEG C / min, and maintaining the temperature for 30 min; S133, continuously heating to 2500-2800 DEG C at a heating rate of 10 DEG C / min, and maintaining the temperature for 60-120 min; S134, after stopping heating, cooling to 800 DEG C at a cooling rate of 20 DEG C / min, and then naturally cooling to room temperature to obtain a graphitized substrate.

3. The method of claim 1, wherein the method is characterized by: After the step S14, the step S1 further comprises: S15, performing polishing treatment on the surface of the graphene heat dissipation sheet substrate; The step S15 specifically comprises: S151, performing ultrasonic cleaning on the surface of the graphene heat dissipation sheet substrate by using anhydrous ethanol, and the cleaning time is 10-15 min; Step S152, using the diamond suspension and the polishing disc to perform rough polishing treatment on the surface of the graphene heat sink substrate after ultrasonic cleaning; wherein the particle size of the diamond abrasive is 1-3 μm, the rotation speed of the polishing disc is 200-300 rpm, the polishing pressure is 0.05-0.1 MPa, and the polishing time is 3-5 min; Step S153, replacing the diamond suspension with a nano-alumina polishing liquid to perform fine polishing treatment on the surface of the graphene heat sink substrate after rough polishing treatment; wherein the particle size of the nano-alumina abrasive is 50-100 nm, the rotation speed of the polishing disc is 100-150 rpm, the polishing pressure is 0.01-0.03 MPa, and the polishing time is 8-10 min; Step S154, using deionized water to perform ultrasonic cleaning on the graphene heat sink substrate after fine polishing treatment, and performing drying treatment after cleaning to obtain a graphene heat sink substrate with a surface roughness Ra less than or equal to 0.5 μm.

4. The method of claim 1, wherein the method is characterized by: In step S24, the depth of the concave microstructure is 0.8-3 μm, the diameter is 2-6 μm, and the distribution density is (2-8)×10 4 cm 2 -2.

5. The method of claim 1, wherein the method is characterized by: The step S3 comprises: Step S31, placing the graphene heat sink substrate after plasma treatment on a rotating heating base in a vacuum reaction chamber, and controlling the temperature of the rotating heating base at 150-200℃; Step S32, vacuumize the vacuum reaction cavity to pressure ≤ 1 × 10 -3 Pa, introduce argon carrier gas, gas flow is 100~200sccm; Step S33, pulsing trimethylaluminum vapor and oxygen into the vacuum reaction chamber; wherein the pulse flow of the trimethylaluminum vapor is 5-10 sccm with an on-off ratio of 1:3, the flow of the oxygen is 20-40 sccm, and the pressure of the reaction chamber is 0.1-0.5 Pa; Step S34, starting a radio frequency power supply to excite plasma, setting the radio frequency power to 200-400 W, setting the rotation speed of the base to 10-20 rpm, and setting the deposition time to 60-180 min; Step S35, depositing an alumina insulating layer with a thickness of 0.5-2.0 μm on the surface of the graphene heat sink substrate to obtain a heat-conductive graphene heat sink with an alumina insulating layer.

6. The method of claim 5, wherein the method is characterized by: After step S35, further comprising: Step S36, stopping the input of trimethylaluminum vapor after deposition, cooling to below 80℃ at a cooling rate of 5℃ / min in an argon atmosphere, and taking out the heat-conductive graphene heat sink with an alumina insulating layer.

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