High-strength graphene / metal composite heat dissipation plate with transverse and longitudinal high thermal conductivity and preparation method thereof

Abstract

The invention discloses a high-strength graphene / metal composite heat dissipation plate with high transverse and longitudinal thermal conductivity and a preparation method thereof, and relates to the field of chips, the composite heat dissipation plate is formed by connecting a plurality of multi-layer graphene sheets through metal columns, and the upper surface, the lower surface and the peripheral side surfaces are packaged by metal foils; all the components are connected together through seamless diffusion welding. By embedding the high-strength and high-heat-conductivity metal columns into the multi-layer graphene with high transverse heat conductivity, heat can be quickly transferred in the transverse direction and the longitudinal direction at the same time. And packaging is carried out through the high-strength and high-heat-conduction metal foil, so that the strength of the heat dissipation plate is improved. An innovative graphene / metal seamless diffusion welding process is adopted, through precise optimization of the welding temperature and pressure, the part size and the like, efficient seamless combination of the metal-graphene composite material is achieved, the heat conduction performance and the mechanical strength of the composite material are improved, and the interface thermal resistance is reduced.

Description

Technical Field

[0001] The present invention relates to the field of chips, and in particular to a high-strength graphene / metal composite heat dissipation plate with high thermal conductivity in both transverse and longitudinal directions and a preparation method thereof. Background Art

[0002] With the advancement of technology, heat-generating devices such as chips and chassis have become an indispensable part of life and work, and these devices are moving towards high power and thinness. However, there is a close connection between the performance of the device and the temperature, and too high a temperature can lead to reduced reliability. For example, an increase in chip temperature may cause increased circuit delays or even a short circuit that burns the chip. Therefore, it is particularly urgent to develop new heat dissipation materials that can effectively solve the heat dissipation problem of high-power electronic devices.

[0003] The miniaturization and integration of electronic devices have driven high demands on thermal management modules, especially in extreme environments. These modules are at risk of catastrophic structural failure, highlighting the need for new thermal management materials. Ideal materials need to be lightweight, have high thermal conductivity and special structural stability to adapt to extreme application conditions. Graphene film (GF) is regarded as a promising carbon-based thermal management material due to its inherited excellent thermal conductivity and has been widely used. However, GF has obvious shortcomings in two aspects. First, the lateral thermal conductivity is extremely high, reaching 1200W·m -1 ·K -1 But the longitudinal thermal conductivity is low, generally less than 10W·m -1 ·K -1 , resulting in low comprehensive thermal conductivity; secondly, the existing graphene heat sink is relatively thin, mostly below 0.1mm, and the heat flux is low, resulting in unsatisfactory actual heat dissipation capacity. It still faces challenges when dealing with high heat flux levels in extreme environments, especially in maintaining structural stability and providing strong thermal management performance.

[0004] In order to improve the longitudinal thermal conductivity, there is an invention patent with patent number CN117507504A, entitled "Graphene longitudinal thermal conductor, its preparation method and application". By making the extension direction of the graphene sheet in the graphene thermal conductive layer consistent with the thickness direction of the graphene longitudinal thermal conductor, the mechanical strength is improved by tightly combining the resin layer and the graphene thermal conductive layer. However, this method will cause a sharp decrease in the transverse thermal conductivity, resulting in low comprehensive thermal conductivity. Metals are also used to improve the comprehensive thermal conductivity of graphene-based heat sinks due to their own high strength and good thermal conductivity. There is an invention patent with the patent number CN105624747A, named "A copper / graphene composite multilayer heat dissipation film", which sequentially plates graphene film and copper on a metal substrate, and finally dissolves the metal substrate to obtain a self-supporting copper / graphene composite multilayer heat dissipation film, which improves the longitudinal thermal conductivity to a certain extent. However, the thickness of the copper / graphene composite multilayer heat dissipation film prepared by this method is greatly limited, which can only reach 0.05mm, and the heat dissipation heat flux is low. There are patent numbers CN106079693A, CN105517423A, and CN117336944A, named "A graphene-metal composite sheet and its preparation method", "A high thermal conductivity graphene heat dissipation metal foil", and "A high heat dissipation graphene ceramic copper plate and its preparation method", which connect the graphene layer and the metal layer by bonding, but this method has problems such as interfacial air gaps, low thermal conductivity polymer adhesives, and structural instability under extreme conditions.

[0005] Therefore, technicians in this field are committed to developing a high-strength graphene / metal composite heat sink with high thermal conductivity in both the horizontal and vertical directions to improve the thickness, longitudinal thermal conductivity and comprehensive thermal conductivity of the heat sink to meet the heat dissipation needs of heating equipment. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to develop a heat dissipation material with high thermal conductivity and high strength in both the horizontal and vertical directions.

[0007] To achieve the above-mentioned object, the present invention provides a high-strength graphene / metal composite heat sink with high thermal conductivity in transverse and longitudinal directions, comprising a plurality of multi-layer graphene sheets, metal pillars, an upper surface encapsulation metal foil sheet, a lower surface encapsulation metal foil sheet, and a side encapsulation metal foil frame, wherein the plurality of sheets is one sheet or more;

[0008] The plurality of multilayer graphene sheets are provided with openings, and the metal pillars connect the plurality of multilayer graphene sheets through the openings to form a plurality of multilayer graphene sheets / metal pillar stacks;

[0009] The plurality of multi-layer graphene sheets / metal pillars are stacked and arranged in the side packaging metal foil frame;

[0010] The upper surface encapsulation metal foil and the lower surface encapsulation metal foil are respectively arranged on the upper and lower surfaces of the stacked multi-layer graphene sheets / metal pillars;

[0011] The upper surface packaging metal foil is provided with a groove, and the lower surface packaging metal foil is arranged to be in direct contact with the heating element;

[0012] The materials of the metal pillar, the upper surface packaging metal foil, the lower surface packaging metal foil, and the side packaging metal foil frame are isotropic high thermal conductivity metal materials.

[0013] Furthermore, the high thermal conductivity metal material is one of gold, silver, copper, aluminum, beryllium, magnesium, iron, molybdenum, nickel, platinum, tin, titanium, zinc, tungsten, copper alloy, aluminum alloy, brass, and bronze.

[0014] And a method for preparing a high-strength graphene / metal composite heat dissipation plate with high thermal conductivity in both lateral and longitudinal directions, the method comprising the following steps:

[0015] Step 1: Parts preparation, including the following steps:

[0016] The thickness of the side encapsulation metal foil frame is set to be greater than the total thickness of the multiple multi-layer graphene sheets, and the inner contour size of the side encapsulation metal foil frame is greater than or equal to the size of the multiple multi-layer graphene sheets;

[0017] Setting the size of the upper surface packaging metal foil and the lower surface packaging metal foil to be equal to the outer contour size of the side packaging metal foil frame;

[0018] Step 2, surface treatment, includes the following steps:

[0019] 1) soaking the plurality of multilayer graphene sheets, the metal pillars, the metal pillars, the upper surface encapsulation metal foil, the lower surface encapsulation metal foil, and the side encapsulation metal foil frame in an alkaline degreasing agent solution for 20 minutes, then ultrasonically cleaning for 30 minutes and rapidly drying to perform surface degreasing cleaning treatment;

[0020] 2) the metal column, the upper surface encapsulation metal foil, the lower surface encapsulation metal foil, and the side encapsulation metal foil frame are suspended and soaked in a nitric acid solution for 30 minutes, then soaked in ultrapure water for 10 minutes and sprayed with ultrapure water for 10 minutes, then dehydrated with anhydrous ethanol, and finally soaked in an organic anti-oxidation solution to remove the surface oxide layer;

[0021] 3) preparing a titanium carbide coating on the surface of each of the plurality of multilayer graphene sheets by a magnetron sputtering method, performing surface coating treatment, wherein the thickness of the titanium carbide coating is less than or equal to 0.2 um, to obtain a multilayer graphene sheet having a titanium carbide coating on the surface;

[0022] 4) coating solder on the upper and lower surfaces and four side surfaces of each multilayer graphene sheet having a titanium carbide coating on the surface, the side surfaces and upper and lower bottom surfaces of the metal column, the lower surface of the upper surface encapsulated metal foil, the upper surface of the lower surface encapsulated metal foil, and the inner surface and upper and lower surfaces of the side encapsulated metal foil frame, wherein the solder is a high thermal conductivity metal nanolayer;

[0023] Step 3: According to the designed hole pattern, laser hole processing is performed on the plurality of multilayer graphene sheets by using laser cutting technology, and the accuracy of the laser hole processing is controlled within ±1 um;

[0024] Step 4: Parts assembly, including the following steps:

[0025] On the base of the welding tool, positioning is performed layer by layer from bottom to top in the order of the lower surface packaging metal foil, the side packaging metal foil frame, the multiple multi-layer graphene sheets, the metal column, and the upper surface packaging metal foil using positioning pins;

[0026] A pin hole is provided on the base of the welding tool, and the positioning pin is installed in the pin hole;

[0027] A high temperature resistant and high strength spring is also installed at the bottom of the positioning pin;

[0028] The spacing of the positioning pins in the length and width directions are 0.01 to 0.03 mm larger than the size of the lower surface encapsulation metal foil, the upper surface encapsulation metal foil, and the side encapsulation metal foil frame;

[0029] Step 5, seamless diffusion welding, including the following steps:

[0030] Checking the interface gaps between the lower surface encapsulation metal foil, the side encapsulation metal foil frame, the upper surface encapsulation metal foil and the plurality of multi-layer graphene sheets, and filling the interface gaps with solder;

[0031] The seamless diffusion welding is performed under the conditions of a temperature of 818° C. to 822° C., a pressure of 0.5 to 0.8 MPa and a high vacuum environment.

[0032] Furthermore, the alkaline degreasing agent solution in step 2 is formed by dissolving the alkaline degreasing agent at 35-40°C.

[0033] Furthermore, the nitric acid solution in step 2 is a 1% nitric acid solution.

[0034] Furthermore, the high thermal conductivity metal nanolayer in step 2 is one of the ternary nanometal layers of Ag-Cu-Ti, Al-Cu, Sn-Ag-Cu-Ti, Ni-Cr-P-Cu, and Ti-Zr-Cu-Ni.

[0035] Furthermore, the coating in step 2 is spraying.

[0036] Furthermore, the welding tooling described in step 4 is made of TZM material.

[0037] Furthermore, the positioning pin in step 4 and the base pin hole are clearance-fitted.

[0038] Furthermore, the high vacuum environment in step 5 has an air pressure of less than 0.001 Pa·m 3 / s.

[0039] The technical effects of the present invention are as follows:

[0040] 1) By embedding high-strength, high-thermal-conductivity metal pillars into multi-layer graphene with high lateral thermal conductivity, while maintaining the high lateral thermal conductivity of the multi-layer graphene, the high longitudinal thermal conductivity of the metal pillars is combined, which greatly improves the longitudinal thermal conductivity and significantly improves the comprehensive thermal conductivity of the heat sink, achieving rapid heat transfer in both the lateral and longitudinal directions.

[0041] 2) The strength of the heat sink is improved by encapsulating it with high-strength and high-thermal-conductivity metal foil.

[0042] 3) Adopt innovative graphene / metal seamless diffusion welding process to achieve efficient metal-graphene composite material combination and improve the thermal conductivity and mechanical strength of the composite material. Through precise optimization of welding temperature and pressure, part size, etc., it is achieved that graphene and metal, two materials with large differences in properties, are efficiently and strongly combined without damaging the graphene structure, and the gap between the bonding surfaces is avoided, thereby reducing the interface thermal resistance. Using high-strength and high-thermal-conductivity nanometal layers as welding intermediate fillers, the metal fillers will diffuse to the graphene layer and the metal layer under the promotion of high temperature and high pressure to form structurally stable carbides and metal-based solid solutions, and realize seamless, firm, and low-thermal-resistance connection between multiple sheets of multi-layer graphene, between multiple sheets of graphene and metal pillars, and between multiple sheets of multi-layer graphene / metal pillar stacking structure and the outer metal foil. The welding layer is ultra-thin, the porosity is low, and the welding material has high thermal conductivity, so that the stacking thickness of multiple sheets of multi-layer graphene / metal pillars can reach more than 2-10mm.

[0043] 4) The production process is simple and can be manufactured through processes such as laser cutting and vacuum diffusion welding, which is suitable for large-scale production.

[0044] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1It is an overall exploded view of a preferred embodiment of the present invention;

[0046] Figure 2 It is a diffusion welding process principle diagram of a preferred embodiment of the present invention;

[0047] Figure 3 It is a schematic diagram of a gap processing method according to a preferred embodiment of the present invention;

[0048] Figure 4 It is a schematic diagram of the assembly sequence of parts of a preferred embodiment of the present invention;

[0049] Figure 5 It is a schematic diagram of assembly positioning and welding tooling of a preferred embodiment of the present invention;

[0050] Figure 6 is a transverse thermal conductivity diagram of a preferred embodiment of the present invention;

[0051] Figure 7 is a longitudinal thermal conductivity diagram of a preferred embodiment of the present invention;

[0052] Among them, 1-lower surface encapsulated metal foil, 2-side encapsulated metal foil frame, 3-multilayer graphene sheet, 4-metal column, 5-upper surface encapsulated metal foil, 6-base, 7-spring, 8-pin hole, 9-positioning pin, 10-pressing plate. DETAILED DESCRIPTION

[0053] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the present invention is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0054] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0055] like Figure 1As shown, a high-strength graphene / metal composite heat sink with high thermal conductivity in the horizontal and vertical directions includes multiple multilayer graphene sheets 3, metal pillars 4, upper surface encapsulated metal foil sheets 5, lower surface encapsulated metal foil sheets 1, and side encapsulated metal foil frames 2, and the multiple sheets are 2 or more; the multiple multilayer graphene sheets 3 are provided with openings, and the metal pillars 4 connect the multiple multilayer graphene sheets 3 through the openings to form multiple multilayer graphene sheets 3 / metal pillars 4 stacked; the multiple multilayer graphene sheets 3 / metal pillars 4 are stacked and arranged in the side encapsulated metal foil frame 2, and the upper surface encapsulated metal foil sheets 5 and the lower surface encapsulated metal foil sheets 1 are respectively arranged on the upper and lower surfaces of the multiple multilayer graphene sheets 3 / metal pillars 4 stacked; the upper surface encapsulated metal foil sheets 5 are provided with grooves, and the lower surface encapsulated metal foil sheets 1 are arranged to be in direct contact with the heating element; the materials of the metal pillars 4, the upper surface encapsulated metal foil sheets 5, the lower surface encapsulated metal foil sheets 1, and the side encapsulated metal foil frames 2 are isotropic high thermal conductivity metal materials.

[0056] In some embodiments, the multiple multilayer graphene sheets 3 are two 1mm thick multilayer graphene sheets 3; the metal column 4 is an oxygen-free copper column, which is embedded in the two 1mm thick multilayer graphene sheets 3, the diameter of the oxygen-free copper column is 6mm, and the number is 9; the upper surface encapsulated metal foil 5 is a 0.4mm thick copper foil, which is arranged on the top of the composite heat sink for dissipating heat to the environment. The reason for using thick copper foil on the top is that after the composite heat sink is processed and assembled as a whole, grooves need to be etched on the thick copper foil to enhance the heat exchange area and heat exchange coefficient of the composite heat sink, thereby enhancing the overall heat dissipation performance; the lower surface encapsulated metal foil 1 is a 0.1mm thick copper foil, which is arranged at the bottom of the composite heat sink; the side encapsulated metal foil frame 2 is a 0.3mm thick copper foil, which is arranged on the four sides of the composite heat sink.

[0057] The oxygen-free copper column, copper foil and multi-layer graphene sheet 3 are tightly bonded by diffusion welding technology, and the heat sink obtained thereby has high thermal conductivity and good mechanical strength. The thickness of the copper foil, the thickness and number of multi-layer graphene sheets 3, the hole diameter and the number of oxygen-free copper columns can be adaptively adjusted according to the actual application scenario to the overall thickness, weight, thermal conductivity, heat capacity, volume and other requirements of the heat sink.

[0058] In some embodiments, the metal column 4, the upper surface encapsulated metal foil 5, the lower surface encapsulated metal foil 1, and the side encapsulated metal foil frame 2 can also be made of isotropic high thermal conductivity metal materials such as gold, silver, aluminum, beryllium, magnesium, iron, molybdenum, nickel, platinum, tin, titanium, zinc, tungsten, copper alloy, aluminum alloy, brass, and bronze.

[0059] In some embodiments, the multilayer graphene sheet 3 is prepared by a pressure-induced vacuum molding method. Specifically, by applying appropriate pressure to the graphene raw material under a vacuum environment, the graphene raw material is evenly distributed and tightly stacked to form a lightweight and highly thermally conductive multilayer graphene sheet 3. This method ensures that the multilayer graphene sheet 3 has excellent in-plane thermal conductivity (i.e., the heat conduction capacity along the plane of the plate) while maintaining a relatively low longitudinal thermal conductivity (i.e., the heat conduction capacity perpendicular to the plane of the plate), which is conducive to the effective directional transfer of heat inside the heat sink.

[0060] In some embodiments, the openings of the multilayer graphene sheet 3 are formed by opening processing using high-precision laser cutting technology. Specifically, the opening pattern is pre-designed, and the opening pattern can be of any shape, size, number, and arrangement, which is adjusted specifically according to the weight limit and thermal conductivity requirements. The laser beam is precisely focused on the multilayer graphene sheet 3, and a plurality of openings of the required size and shape are precisely cut out. The accuracy of the laser processing is within ±1um, and the accuracy can be specifically controlled by a combination of one or more of the following methods: selecting a suitable laser type (such as a femtosecond laser), optimizing laser parameters (power, pulse frequency, focus position), accurately controlling the processing path, maintaining a stable processing environment (stable temperature and humidity, shockproof), regularly maintaining equipment, and using advanced CAD / CAM software and a closed-loop feedback system. These openings provide precise positioning points for the subsequent embedding of oxygen-free copper columns.

[0061] In some embodiments, the oxygen-free copper column is made of isotropic high thermal conductivity oxygen-free copper material, and its thermal conductivity is about 398W / mK. This material has excellent thermal conductivity and can quickly transfer heat from the heat source to the surface of the heat sink, effectively reducing the operating temperature of the heat generating device. The size and shape of the oxygen-free copper column match the opening on the multilayer graphene sheet 3 to ensure that it can be smoothly embedded and form a close contact with the multilayer graphene sheet 3.

[0062] In some embodiments, the copper foil of the upper surface encapsulation metal foil 5, the lower surface encapsulation metal foil 1, and the side encapsulation metal foil frame 2 is isotropic, high thermal conductivity oxygen-free copper foil with a thermal conductivity of approximately 398W / mK. The thickness can be adjusted according to the requirements of the actual application to resist impact force, and is usually set in the range of 0.1 to 0.5mm.

[0063] like Figure 2 As shown, a method for preparing a high-strength graphene / metal composite heat sink with high thermal conductivity in both the lateral and longitudinal directions comprises the following steps:

[0064] Step 1: Parts preparation, including the following steps:

[0065] The thickness of the side packaging metal foil frame 2 is set to be greater than the total thickness of the multiple multi-layer graphene sheets 3, and the inner contour of the side packaging metal foil frame 2 is greater than or equal to the size of the multiple multi-layer graphene sheets 3, so that the multiple multi-layer graphene sheets can be wrapped from four sides;

[0066] The dimensions of the upper surface packaging metal foil 5 and the lower surface packaging metal foil 1 are set to be equal to the outer contour dimensions of the side packaging metal foil frame 2 .

[0067] Step 2, surface treatment, includes the following steps:

[0068] 1) soaking a plurality of multilayer graphene sheets 3, metal pillars 4, metal pillars 4, upper surface encapsulation metal foil 5, lower surface encapsulation metal foil 1, and side encapsulation metal foil frame 2 in an alkaline degreasing agent solution for 20 minutes, then ultrasonically cleaning for 30 minutes and rapidly drying to perform surface degreasing cleaning treatment;

[0069] 2) The metal column 4, the upper surface encapsulation metal foil 5, the lower surface encapsulation metal foil 1, and the side encapsulation metal foil frame 2 are suspended and soaked in a nitric acid solution for 30 minutes, then soaked in ultrapure water for 10 minutes and sprayed with ultrapure water for 10 minutes, then dehydrated with anhydrous ethanol, and finally soaked in an organic anti-oxidation solution to remove the surface oxide layer;

[0070] 3) preparing a titanium carbide coating on the surface of each of the plurality of multilayer graphene sheets 3 by a magnetron sputtering method, performing surface coating treatment, wherein the thickness of the titanium carbide coating is less than or equal to 0.2 μm, and obtaining a multilayer graphene sheet 3 having a titanium carbide coating on the surface;

[0071] 4) coating a solder on the upper and lower surfaces of each multilayer graphene sheet 3 having a titanium carbide coating on the surface, wherein the solder is a high thermal conductivity metal nanolayer;

[0072] Step 3: According to the designed hole pattern, laser cutting technology is used to perform laser hole processing on multiple multilayer graphene sheets 3, and the accuracy of the laser hole processing is controlled within ±1um;

[0073] Step 4: Parts assembly, including the following steps:

[0074] On the base 6 of the welding tool, the lower surface encapsulation metal foil sheet 1, the side encapsulation metal foil frame 2, the multiple multi-layer graphene sheets 3, the metal pillar 4, and the upper surface encapsulation metal foil sheet 5 are positioned layer by layer from bottom to top using positioning pins 9;

[0075] A pin hole is provided on the base 6 of the welding tool, and a positioning pin 9 is installed in the pin hole;

[0076] A high temperature resistant, high strength spring 7 is also installed at the bottom of the positioning pin 9;

[0077] The spacing of the positioning pins 9 in the length and width directions is 0.01 to 0.03 mm larger than the size of the lower surface encapsulation metal foil 1, the upper surface encapsulation metal foil 5, and the side encapsulation metal foil frame 2;

[0078] Step 5, diffusion welding, including the following steps:

[0079] Check the interface gaps between the lower surface encapsulation metal foil 1, the side encapsulation metal foil frame 2, the upper surface encapsulation metal foil 5 and the multiple multilayer graphene sheets 3, and fill the interface gaps with solder;

[0080] The welding is performed under the conditions of a temperature of 818°C to 822°C, a pressure of 0.5 to 0.8 MPa and a high vacuum environment.

[0081] In some embodiments, for a composite heat sink with a final size requirement of 100.6*100.6*2.5 mm, the diffusion welding process includes the following steps:

[0082] Step 1: Pre-welding processing of parts:

[0083] Prepare two multilayer graphene sheets 3 with a thickness of 1 mm and a size of 100 mm*100 mm;

[0084] Laser cutting was performed on oxygen-free copper foils with a thickness of 0.4 mm and oxygen-free copper foils with a thickness of 0.1 mm, with the size being accurate to 101.6×101.6 mm, with a 0.5 mm margin on each side reserved to cope with deformation in subsequent processing, and the upper surface encapsulation metal foil sheet 5 and the lower surface encapsulation metal foil sheet 1 were obtained respectively; another oxygen-free copper foil with a thickness of 2.0 mm was processed into a side encapsulation metal foil frame 2 with an outer contour size of 101.6×101.6 mm (by laser cutting) and a wall thickness of 0.8 mm (by milling). The design value of the wall thickness of the side encapsulation metal foil frame 2 is 0.3 mm, and the corresponding material has low strength, low rigidity, and is difficult to process, so it is milled to 0.8 mm to improve strength and rigidity.

[0085] Step 2: Surface treatment and solder coating

[0086] 1) Degreasing and cleaning: Use an alkaline degreasing agent to dissolve at 35-40°C, soak the related parts of the composite heat sink (including multiple multilayer graphene sheets 3, metal pillars 4, upper surface encapsulation metal foil 5, lower surface encapsulation metal foil 1, and side encapsulation metal foil frame 2) for 20 minutes, then perform ultrasonic cleaning for 30 minutes, and finally quickly dry to remove cutting fluid and oil stains.

[0087] 2) Remove the surface oxide layer: The oxygen-free copper parts (including the metal column 4, the upper surface encapsulated metal foil 5, the lower surface encapsulated metal foil 1, and the side encapsulated metal foil frame 2) are immersed in nitric acid. Specifically, a 1% nitric acid solution is prepared and the oxygen-free copper parts are immersed for 30 minutes to remove the surface oxide layer. The oxygen-free copper parts need to be suspended for immersion and completely immersed in the treatment solution. After treatment, soak in ultrapure water for 10 minutes, then spray and clean with ultrapure water for 10 minutes, then use anhydrous ethanol for dehydration, and finally soak the dehydrated oxygen-free copper parts in an organic anti-oxidation solution to prevent secondary oxidation.

[0088] 3) Surface coating treatment: A titanium carbide coating is prepared on the surface of each of the multiple multilayer graphene sheets 3 by a magnetron sputtering method, and a surface coating treatment is performed. The thickness of the titanium carbide coating is less than or equal to 0.2 um to improve the interface heat transfer coefficient of the graphene / metal composite material.

[0089] The heat conduction mechanism of metal and graphene is different. Graphene mainly relies on phonon heat conduction, while metal mainly relies on electron heat conduction, which leads to thermal resistance of interface heat transfer. The above surface treatment of the related parts of the composite heat sink before diffusion welding can reduce the Kapitza-type interface thermal resistance, thereby improving the interface heat transfer coefficient.

[0090] 4) adding solder after the surface coating treatment, coating solder on all welding surfaces, i.e., the upper and lower surfaces and four side surfaces of each multilayer graphene sheet with titanium carbide coating sputtered on the surface, the side surface and upper and lower bottom surfaces of the metal column 4, the lower surface of the upper surface encapsulated metal foil 5, the upper surface of the lower surface encapsulated metal foil 1, and the inner surface and upper and lower surfaces of the side encapsulated metal foil frame 2. The specific coating method is to mix the solder powder and the adhesive (the main component of the adhesive is polyvinyl alcohol) evenly and then spray it on the surface of the welding surface;

[0091] The solder is a high thermal conductivity metal nanolayer, which can be any one of Ag-Cu-Ti, Al-Cu, Sn-Ag-Cu-Ti, Ni-Cr-P-Cu, and Ti-Zr-Cu-Ni ternary nanometal layers. These high-strength, high thermal conductivity nanometal layers are used as welding intermediate fillers. Under high temperature, high pressure, and vacuum conditions, the high thermal conductivity metal nanolayer filler diffuses into the graphene layer (multilayer graphene sheet 3) and the metal layer (metal column 4, upper surface encapsulation metal foil 5, lower surface encapsulation metal foil 1, and side encapsulation metal foil frame 2) to form a structurally stable carbide and metal-based solid solution, thereby achieving a seamless, firm, and low thermal resistance connection between the multilayer graphene sheet 3 and the metal. This connection method effectively eliminates internal pores and ensures the high thermal conductivity and structural stability of the composite heat sink under extreme use conditions.

[0092] Step 3: Opening holes in multiple multi-layer graphene sheets

[0093] According to the designed hole pattern, laser cutting technology is used to perform laser hole opening processing on multiple multilayer graphene sheets 3. The accuracy of the laser hole opening processing is controlled within ±1um, which provides precise positioning points for the subsequent embedding of oxygen-free copper columns. At the same time, it avoids excessive damage to the overall structure of the multilayer graphene sheet 3 and maintains its original high thermal conductivity.

[0094] Step 4: Parts assembly:

[0095] On the base 6 of the welding tool, the lower surface encapsulation metal foil 1, the side encapsulation metal foil frame 2, the multiple multi-layer graphene sheets 3, the metal pillars 4, and the upper surface encapsulation metal foil 5 are positioned layer by layer from bottom to top using positioning pins 9, wherein the positioning pins 9 and the lower surface encapsulation metal foil 1, the positioning pins 9 and the upper surface encapsulation metal foil 5, and the positioning pins 9 and the side encapsulation metal foil frame 2 all maintain a gap of 0.01 to 0.03 mm. The process of positioning layer by layer is as follows: Figure 4 and Figure 5 As shown, the specific steps are as follows:

[0096] 1) Selection of welding tooling: First, use special welding tooling made of TZM material (i.e. titanium zirconium molybdenum alloy, a molybdenum alloy containing about 0.5% titanium (Ti), 0.08% zirconium (Zr), 0.02% carbon and about 99% molybdenum (Mo)). This material has excellent high-temperature performance and mechanical strength, low thermal expansion coefficient and high thermal conductivity, which helps to reduce thermal stress deformation.

[0097] 2) Install the positioning pins 9: There are 8 pin holes 8 on the base 6. First, put the high-temperature resistant and high-strength spring 7 into the pin holes 8, and then insert the positioning pins 9 into the pin holes 8 to achieve positioning. Among them, the spacing between the positioning pins 9 at both ends in the length and width directions is 0.01 to 0.03 mm larger than the size of the lower surface package metal foil 1, the upper surface package metal foil 5, and the side package metal foil frame 2, respectively, so as to maintain a certain gap to achieve accurate positioning while facilitating the placement of parts. Because the gap is too small, it is not easy to place the parts in, and the gap is too large, which will damage the final welding effect, and the positioning pins 9 will not have the effect of positioning. The positioning pins 9 and the pin holes 8 adopt a clearance fit. The clearance fit means that there is a certain gap between the mating parts, so that the positioning pins 9 can be easily inserted into the pin holes 8 without interference. The realization of clearance fit includes three stages: 1) Design stage: On the design drawings, the tolerance range of the mating parts is clearly specified to ensure that a suitable gap is generated during assembly, and the diameter of the positioning pin 9 is slightly smaller than the diameter of the pin hole 8; 2) Manufacturing stage: The size of the parts is controlled through precision machining to ensure that the actual size is within the design tolerance range; 3) Assembly stage: Insert the positioning pin 9 into the pin hole 8, and use the clearance to achieve assembly operability and adjustability. The role of clearance: 1) Easy assembly: Clearance fit makes it easy to insert and remove parts, reducing the difficulties in the assembly process; 2) Thermal expansion compensation: The clearance can compensate for the thermal expansion of parts caused by temperature changes, avoiding jamming or deformation caused by thermal expansion and contraction; 3) Allow adjustment: During the positioning process, the clearance can be used for fine-tuning to ensure the accurate position of the parts; 4) Reduce stress concentration: Appropriate clearance can reduce stress concentration caused by tight fit during assembly and extend the service life of parts.

[0098] 3) On the base 6 of the welding tool, assemble the parts from bottom to top in the order of lower surface encapsulation metal foil 1, side encapsulation metal foil frame 2, multiple multi-layer graphene sheets 3, metal pillars 4, and upper surface encapsulation metal foil 5, and use positioning pins 9 to position each layer.

[0099] Step 5: Diffusion welding:

[0100] 1) Inspection and filling: Before welding, check the gap under a microscope. If the gap is too large, fill it with titanium brazing material to avoid gaps. Use a 10x microscope to check the junction between the lower surface encapsulation metal foil 1, the side encapsulation metal foil frame 2, the upper surface encapsulation metal foil 5 and the multiple multilayer graphene sheets 3. Figure 3 As mentioned above, if a gap exists, a filler containing solder is applied to avoid eutectic corrosion.

[0101] Eutectic corrosion is a corrosion phenomenon that occurs at the interface of materials. It is mainly caused by the eutectic reaction between metal and graphene at high temperature, forming brittle phases or voids. These defects will significantly reduce the interfacial bonding strength, causing the material to easily fall off or crack during use, thereby affecting the mechanical properties and thermal conductivity of the material. By using Ti brazing filler for filling, eutectic corrosion can be effectively avoided and the overall performance and service life of the composite material can be improved: the addition of titanium can prevent the direct eutectic reaction between copper and graphene, forming a stable solid solution under high temperature and high pressure, forming a stable titanium carbide (TiC) phase interface, and avoiding eutectic corrosion. This phase has high strength and high thermal conductivity, can effectively fill the gaps at the interface, ensure seamless connection between graphene and copper, reduce interfacial thermal resistance, improve overall thermal conductivity, and enhance interfacial bonding strength.

[0102] 2) Diffusion welding: Under specific temperature (818℃~822℃), pressure (0.5~0.8MPa) and high vacuum environment (<0.001Pa·m 3 / s) for welding. The temperature is controlled at 818℃~822℃ to ensure good welding quality and avoid separation of graphene layers at high temperature. During pressurized welding, the pressing plate 10 of the welding tool is pressed on the upper surface package metal foil 5, and uniform pressure is applied downward, the spring 7 contracts, and the pins are lowered, so that the layers are in close contact, and finally a high-strength graphene / metal composite heat sink with high thermal conductivity in the horizontal and vertical directions is obtained.

[0103] The welding process is a hot pressing process, which will cause a certain deformation of the material. Graphene is a brittle material. If the gap between the opening of the multilayer graphene sheet 3 and the copper column is too small, the opening of the multilayer graphene sheet 3 will crack during the hot pressing process. If it is too large, a gap will be generated between the fits, which will cause a sharp increase in thermal resistance. In addition, the multilayer graphene sheet 3 is a multi-layer composite structure. Excessive temperature will cause the multilayer graphene sheet 3 to separate from the layers, and the separation between the layers will also cause great thermal resistance. This application reduces the deformation to less than 100 microns by strictly controlling the welding pressure, and at the same time controls the process temperature at 818°C to 822°C. While minimizing the gap as much as possible, it effectively avoids the problem of cracking or separation of the layers of the multilayer graphene sheet 3 during the hot pressing process, thereby reducing thermal resistance.

[0104] The above preparation method ensures close contact and uniform pressure between each layer of material through layer-by-layer positioning and pressurized welding process. By using welding tooling made of TZM material and high temperature resistant and high strength spring 7, smooth connection and pressure distribution between each layer of material during welding are ensured.

[0105] Before the solder is coated, the surface treatment process of the substrate can improve the adhesion and uniformity of the solder layer. At the same time, seamless diffusion welding under high temperature and high pressure can reduce the thickness of the solder layer. The solder and the substrate are fully diffused by heating and pressurizing to form a strong bond, eliminating the gap and air gap between the interfaces, so that the thickness of the final solder layer is extremely thin, less than 100 nanometers. And welding is carried out in a high vacuum environment, and extremely low air pressure is maintained during the welding process to reduce gas inclusions and oxide formation, ensuring that there are very few air gaps in the solder layer, achieving seamless bonding between multiple multi-layer graphene sheets 3, avoiding gaps between bonding surfaces, and thus reducing interface thermal resistance. In addition, the seamless diffusion welding technology is used to firmly connect multiple multi-layer graphene sheets 3 under high temperature and high pressure conditions, which can increase the thickness of the stacked multiple multi-layer graphene / metal pillars 4 to a greater extent.

[0106] Step 6: Post-weld measurement and processing:

[0107] Check the thickness deviation (no more than 0.05mm) and edge deformation (no more than 0.1mm) of the high-strength graphene / metal composite heat sink with high thermal conductivity in the horizontal and vertical directions. Use a special vacuum adsorption fixture, the bottom is supported as a whole, and the parts after welding are processed to prevent local damage. Perform electrochemical brightening treatment on one side of the lower surface package metal foil 1, and package after overall cleaning.

[0108] Step 7: Performance test:

[0109] Check the surface finish of the high-strength graphene / metal composite heat sink with high transverse and longitudinal thermal conductivity, and confirm that there are no bulges, poor wrapping of the oxygen-free copper shell, and local exposure of graphene. Measure the final dimensions and record the thickness of each part and the total thickness. Measure the longitudinal and transverse thermal conductivity of the high-strength graphene / metal composite heat sink with high transverse and longitudinal thermal conductivity.

[0110] The preparation method of the present application can make a high-strength graphene / metal composite heat sink with high thermal conductivity in the lateral and longitudinal directions reach more than 10 mm, which is an order of magnitude higher than the existing graphene-based heat sink (within 200 um), and the thermal conductivity is also significantly improved, which is suitable for large heat flux heat dissipation in extreme environments.

[0111] The resulting composite heat sink has no significant loss in transverse thermal conductivity, but significantly improved longitudinal thermal conductivity, and significantly increased comprehensive thermal conductivity, thereby greatly improving heat dissipation efficiency and meeting the heat dissipation needs of high heat flux heat generation equipment. Figure 6 and Figure 7 In the embodiment, the thickness of the composite heat sink is 2.5 mm, and the lateral thermal conductivity is increased from the original 1200 W·m -1 ·K -1 Reduced to about 1000W·m -1·K -1 , the longitudinal thermal conductivity is reduced from the original <10W·m -1 ·K -1 Increased to about 100W·m -1 ·K -1 Compared with existing graphene-based heat sinks, the lateral thermal conductivity of this patented heat sink is comparable, while the thickness and longitudinal thermal conductivity have been significantly improved by nearly an order of magnitude, greatly improving the heat dissipation efficiency.

[0112] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A high-strength graphene / metal composite heat sink with high thermal conductivity in both lateral and longitudinal directions, characterized in that: It includes multiple multi-layer graphene sheets, metal pillars, upper surface encapsulation metal foil sheets, lower surface encapsulation metal foil sheets, and side encapsulation metal foil frames, wherein the multiple sheets are one or more; The plurality of multilayer graphene sheets are provided with openings, and the metal pillars connect the plurality of multilayer graphene sheets through the openings to form a stack of a plurality of multilayer graphene sheets / metal pillars; The plurality of multi-layer graphene sheets / metal pillars are stacked and arranged in the side packaging metal foil frame; The upper surface encapsulation metal foil and the lower surface encapsulation metal foil are respectively arranged on the upper and lower surfaces of the stacked multi-layer graphene sheets / metal pillars; The upper surface packaging metal foil is provided with a groove, and the lower surface packaging metal foil is arranged to be in direct contact with the heating element; The materials of the metal pillar, the upper surface packaging metal foil, the lower surface packaging metal foil, and the side packaging metal foil frame are isotropic high thermal conductivity metal materials.

2. The high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity according to claim 1, characterized in that: The high thermal conductivity metal material is one of gold, silver, copper, aluminum, beryllium, magnesium, iron, molybdenum, nickel, platinum, tin, titanium, zinc, tungsten, copper alloy, aluminum alloy, brass, and bronze.

3. A method for preparing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity as claimed in claim 1, characterized in that: The method comprises the following steps: Step 1: Parts preparation, including the following steps: The thickness of the side encapsulation metal foil frame is set to be greater than the total thickness of the multiple multi-layer graphene sheets, and the inner contour size of the side encapsulation metal foil frame is greater than or equal to the size of the multiple multi-layer graphene sheets; Setting the size of the upper surface packaging metal foil and the lower surface packaging metal foil to be equal to the outer contour size of the side packaging metal foil frame; Step 2, surface treatment, includes the following steps: 1) soaking the plurality of multilayer graphene sheets, the metal pillars, the metal pillars, the upper surface encapsulation metal foil, the lower surface encapsulation metal foil, and the side encapsulation metal foil frame in an alkaline degreasing agent solution for 20 minutes, then ultrasonically cleaning for 30 minutes and rapidly drying to perform surface degreasing cleaning treatment; 2) the metal column, the upper surface encapsulation metal foil, the lower surface encapsulation metal foil, and the side encapsulation metal foil frame are suspended and soaked in a nitric acid solution for 30 minutes, then soaked in ultrapure water for 10 minutes and sprayed with ultrapure water for 10 minutes, then dehydrated with anhydrous ethanol, and finally soaked in an organic anti-oxidation solution to remove the surface oxide layer; 3) preparing a titanium carbide coating on the surface of each of the plurality of multilayer graphene sheets by a magnetron sputtering method, performing surface coating treatment, wherein the thickness of the titanium carbide coating is less than or equal to 0.2 um, to obtain a multilayer graphene sheet having a titanium carbide coating on the surface; 4) coating solder on the upper and lower surfaces and four side surfaces of each multilayer graphene sheet having a titanium carbide coating on the surface, the side surfaces and upper and lower bottom surfaces of the metal column, the lower surface of the upper surface encapsulated metal foil, the upper surface of the lower surface encapsulated metal foil, and the inner surface and upper and lower surfaces of the side encapsulated metal foil frame, wherein the solder is a high thermal conductivity metal nanolayer; Step 3: According to the designed hole pattern, laser hole processing is performed on the plurality of multilayer graphene sheets by using laser cutting technology, and the accuracy of the laser hole processing is controlled within ±1 um; Step 4: Parts assembly, including the following steps: On the base of the welding tool, positioning is performed layer by layer from bottom to top in the order of the lower surface packaging metal foil, the side packaging metal foil frame, the multiple multi-layer graphene sheets, the metal column, and the upper surface packaging metal foil using positioning pins; A pin hole is provided on the base of the welding tool, and the positioning pin is installed in the pin hole; A high temperature resistant and high strength spring is also installed at the bottom of the positioning pin; The spacing of the positioning pins in the length and width directions is 0.01 to 0.03 mm larger than the size of the lower surface packaging metal foil, the upper surface packaging metal foil, and the side packaging metal foil frame respectively; Step 5, seamless diffusion welding, including the following steps: Checking the interface gaps between the lower surface encapsulation metal foil, the side encapsulation metal foil frame, the upper surface encapsulation metal foil and the plurality of multi-layer graphene sheets, and filling the interface gaps with the solder; The seamless diffusion welding is performed under the conditions of a temperature of 818° C. to 822° C., a pressure of 0.5 to 0.8 MPa and a high vacuum environment.

4. The method for producing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity according to claim 3, characterized in that: The alkaline degreasing agent solution in step 2 is formed by dissolving the alkaline degreasing agent at 35-40°C.

5. The method for producing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity according to claim 3, characterized in that: The nitric acid solution in step 2 is a 1% nitric acid solution.

6. The method for producing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity as claimed in claim 3, characterized in that: The high thermal conductivity metal nanolayer in step 2 is one of the ternary nanometal layers of Ag-Cu-Ti, Al-Cu, Sn-Ag-Cu-Ti, Ni-Cr-P-Cu, and Ti-Zr-Cu-Ni.

7. The method for producing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity according to claim 3, characterized in that: The coating in step 2 is spraying.

8. The method for producing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity as claimed in claim 3, characterized in that: The welding tooling described in step 4 is made of TZM material.

9. The method for producing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity as claimed in claim 3, characterized in that: In step 4, the positioning pin and the base pin hole are clearance-fitted.

10. The method for producing a high-strength graphene / metal composite heat sink with high lateral and longitudinal thermal conductivity according to claim 3, characterized in that: The pressure of the high vacuum environment in step 5 is less than 0.001 Pa·m 3 / s.

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