A graphene-reinforced aluminum matrix composite for high power semiconductor devices

Abstract

The application discloses a graphene reinforced aluminum matrix composite for high-power semiconductor devices, and relates to the technical field of metal matrix composites. The graphene reinforced aluminum matrix composite for high-power semiconductor devices realizes the synergistic optimization of heat dissipation performance and packaging reliability through functional partition design and precise preparation process. The composite material comprises an aluminum alloy matrix and a graphene heat dissipation film layer coated on the heat dissipation functional area of the aluminum alloy matrix, and the welding connection area is bare pure aluminum. The preparation process comprises the following steps of base activation pretreatment, welding area shielding, graphene slurry coating, hierarchical solidification and pressure densification, welding area post-treatment and the like. The vehicle-mounted camera rear cover prepared by the application is covered with a graphene film layer, a bottom plate and heat dissipation fins, and the side wall end face is a pure aluminum welding area, and the wet heat aging performance is excellent. The heat dissipation efficiency of the composite material exceeds that of pure copper, and the problem of heat accumulation of high-power semiconductor devices is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composites, and in particular to a graphene-reinforced aluminum matrix composite for high-power semiconductor devices. Background Technology

[0002] With the rapid development of the automotive industry towards intelligence and connectivity, the performance requirements of advanced driver assistance systems (ADAS) and autonomous driving technologies are increasing for automotive cameras. To meet the demands of high-pixel acquisition and high-speed data processing, the operating power of the CMOS image sensor and processing chip within the automotive camera module has significantly increased, leading to a sharp rise in heat flux density. If heat cannot be dissipated in time, it will directly result in increased image noise, equipment aging, and even system failure. As a core heat dissipation material, the rear cover of the automotive camera directly determines the stability and lifespan of the device. Currently, traditional die-cast aluminum alloy materials are limited by their intrinsic thermal conductivity, making it difficult to meet the heat dissipation requirements of next-generation high-power semiconductor devices. Therefore, developing a new lightweight composite material with higher thermal conductivity has become a pressing technical challenge for the industry.

[0003] To improve the thermal conductivity of aluminum-based materials, existing technologies have attempted to utilize the high thermal conductivity of graphene to reinforce the aluminum matrix. For example, Chinese invention patent CN108085524B discloses a method for preparing graphene-reinforced aluminum-based composite materials. This method mainly involves mixing graphene with aluminum powder through a high-energy ball milling process, followed by cold pressing and hot extrusion. The aim is to disperse graphene through mechanical force and increase the material density through plastic deformation, thereby preparing composite rods or profiles with certain thermal conductivity.

[0004] However, the aforementioned existing technologies still have significant drawbacks when applied to complex heat dissipation materials such as automotive camera back covers. First, the high-energy ball milling process involves intense mechanical stirring, which easily disrupts the complete two-dimensional lattice structure of graphene, resulting in impaired intrinsic thermal conductivity and limiting the improvement in the overall thermal conductivity of the composite material. Second, the method does not effectively control the interface between graphene and the aluminum matrix. Direct contact between aluminum and carbon at high temperatures easily leads to interfacial reactions, generating brittle and easily hydrolyzed aluminum carbide phases. This not only increases interfacial thermal resistance but also reduces the corrosion resistance and reliability of the material in the humid and hot environment of an automotive vehicle. Finally, although the hot extrusion process used in this patent can improve density, it causes graphene to align along the extrusion direction, resulting in significant anisotropy in the material, i.e., poor radial thermal conductivity. This fails to meet the heat dissipation requirements of the camera back cover, which needs to diffuse heat in three dimensions. Furthermore, the extrusion process is difficult to directly form the complex structure of the camera back cover shell. Summary of the Invention

[0005] The purpose of this invention is to overcome at least the defects of existing aluminum-based carbon material composite processes, such as easy damage to graphene, the formation of brittle aluminum carbide through interfacial reactions, and poor airtightness of traditional die casting, and to provide a graphene-reinforced aluminum-based composite material for high-power semiconductor devices.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a preparation process for graphene-reinforced aluminum-based composite materials for high-power semiconductor devices, comprising the following steps:

[0007] Step 1: Aluminum alloy substrate forming and surface activation pretreatment

[0008] Select 1-series pure aluminum, 3-series aluminum-manganese alloy or 6-series aluminum-magnesium-silicon alloy with excellent thermal conductivity as raw materials, and form them into the designed aluminum alloy matrix (such as camera back cover) through die casting, extrusion or CNC machining.

[0009] To enhance the adhesion of subsequent coatings, the substrate undergoes surface activation treatment:

[0010] Grinding process: using vibration or magnetic force to grind away the surface lubricating layer and oxide layer;

[0011] Cleaning: Alkaline washing removes oil and acid washing removes rust, removing surface oil and natural oxide film;

[0012] Hole Formation / Roughening: Through anodic oxidation or chemical etching processes, micro-nano porous structures or rough surfaces with pore sizes of 50nm-500nm are constructed on the surface of the aluminum alloy substrate to provide anchor points for the mechanical interlocking of the graphene film.

[0013] Step 2: Shielding and protecting the welding functional area (or removing it during secondary processing).

[0014] Based on the product design, determine the welding area used for sealing connection with mating parts (such as the front cover).

[0015] High-temperature resistant masking tape or specialized physical tooling fixtures are used to tightly cover the welded joint area of ​​the aluminum alloy substrate, establishing an uncoated area (or a CNC removal process is used to remove the graphene coating from the surface). This step aims to ensure that the welded area does not become contaminated with carbon materials during subsequent coating processes, preserving the intrinsic weldability of the aluminum alloy.

[0016] Step 3: Construction of a high thermal conductivity graphene heat dissipation film

[0017] A high-solids-content modified graphene slurry was prepared and applied to the surface (non-masked area) of the aluminum alloy substrate after step 2 treatment:

[0018] Slurry preparation: Few-layer graphene nanosheets (solid content 5wt%-20wt%), polymer film-forming binder and dispersant are mixed in a solvent and dispersed by high-speed shearing or sand milling to prepare a uniform and stable thermally conductive slurry;

[0019] Coating deposition: Using automatic spraying, electrophoretic deposition or spin coating processes, the slurry is evenly covered on the heat dissipation functional area of ​​the aluminum alloy substrate (such as the base plate plane and the surface of the heat dissipation fins) to form a wet film layer.

[0020] Step 4: Film curing and directional densification treatment

[0021] The coated substrate is subjected to heat and pressure treatment to achieve film curing and high orientation alignment of graphene:

[0022] Graded heat treatment: First, dry at low temperature of 100℃-150℃ to remove solvent; then, under the protection of an inert atmosphere, heat up to 250℃-400℃ for high-temperature annealing to cause carbonization or cross-linking reaction of the binder and enhance the cohesion of the film layer.

[0023] Pressure densification: During or after heat treatment, a pressure of 20-100 MPa is applied to the film layer using rolling, isostatic pressing, or molding processes. The pressure forces the graphene sheets to align parallel to the substrate surface, eliminating internal voids and significantly improving in-plane thermal conductivity.

[0024] Step 5: Exposure and post-treatment of the welded area

[0025] Remove the masking material applied to the weld joint area in step 2 to expose the clean aluminum alloy surface (or use a CNC removal process to remove the graphene coating on the surface).

[0026] Laser cleaning: Pulsed laser cleaning is performed on the exposed welded joint area to thoroughly remove any trace amounts of adhesive or oxide spots that may remain, ensuring that the area has a metallic luster and good wettability.

[0027] Ultrasonic and spray cleaning: ensures product cleanliness requirements and removes oil and dust.

[0028] Final inspection: The adhesion of the graphene film and the cleanliness of the welding area were checked to obtain a composite material with a pure aluminum welding area.

[0029] This invention provides a graphene-reinforced aluminum-based composite material (rear cover, front cover, or other products requiring enhanced heat dissipation) for high-power automotive cameras, prepared by the above-described process:

[0030] 1. Product structure characteristics:

[0031] The rear cover of the vehicle-mounted camera is an integrated component with a heterogeneous surface and clearly defined functional zones:

[0032] Heat dissipation functional area: Covers the back cover base plate and the surface of the heat dissipation fins. This area is covered with a graphene heat dissipation film layer with a thickness of 1μm-50μm, which appears black or dark gray. It is responsible for rapidly diffusing the chip's heat along the in-plane direction to the fins and radiating it away.

[0033] Welded connection area: Located on the end face or flange edge of the rear cover side wall, with a width of 1mm-5mm. This area is not coated with graphene, directly exposing the aluminum alloy substrate (with a silvery-white metallic luster), and is specifically used for laser welding or friction stir welding with the front cover.

[0034] 2. Microstructure and interface characteristics:

[0035] Membrane structure: The graphene heat dissipation membrane is composed of highly oriented stacked layers of graphene nanosheets with a dense structure and an in-plane thermal conductivity ≥1000W / (m·K), thus constructing a highly efficient heat conduction highway.

[0036] Interface bonding: The graphene film is not simply attached, but partially embedded in the micropores or oxide layer on the substrate surface, forming a synergistic combination of "embedded" mechanical interlocking and chemical bonding, with a bonding strength ≥10MPa, which can withstand the thermal shock of the vehicle environment without peeling off.

[0037] Characteristics of the welding zone: No carbon residue remains in the welding zone, ensuring the purity of the weld pool and preventing brittle aluminum carbide formation. The formation of the phase results in excellent weld airtightness, meeting the IP69K waterproof rating requirements.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] The benefits of this application are significant, primarily achieving a breakthrough improvement in heat dissipation performance. By constructing a heat dissipation film layer composed of highly oriented stacked multilayer graphene nanosheets in the heat dissipation functional area of ​​the aluminum alloy substrate, the complete two-dimensional lattice structure of graphene is effectively preserved, with an in-plane thermal conductivity ≥1000W / (m・K). This creates a highly efficient heat conduction channel, which, compared to traditional die-cast aluminum alloys and pure copper materials, can more quickly diffuse the heat generated by high-power semiconductor devices (such as CMOS image sensors and processing chips in automotive cameras) along the in-plane direction to the outer shell and heat sink fins for radiation dissipation. This significantly reduces the chip's equilibrium junction temperature, effectively solving the heat dissipation problem caused by the sharp increase in heat flux density of next-generation high-power devices, ensuring the stability of device operation, and extending its service life. Simultaneously, the oriented graphene film layer avoids the anisotropy problem caused by the random orientation of graphene in traditional bulk composite processes, meeting the three-dimensional heat dissipation requirements of complex heat dissipation structures. The heat dissipation effect far exceeds that of traditional composite materials prepared by processes such as high-energy ball milling and hot extrusion.

[0040] Secondly, this application effectively solves the problems of interfacial bonding and insufficient durability between graphene and aluminum substrates. By performing activation treatments such as anodizing or chemical etching on the surface of the aluminum alloy substrate, a micro-nano porous structure with a pore size of 50nm-500nm is constructed, allowing the graphene heat dissipation film layer to be partially embedded in the micropores or oxide layer on the substrate surface, forming a synergistic combination of mechanical interlocking and chemical bonding, with a bonding strength ≥10MPa. This interface design not only significantly improves the adhesion between the film layer and the substrate, enabling it to withstand harsh conditions such as thermal shock and humid heat cycling in the automotive environment, showing no surface changes or peeling after 1000 hours of dual 85 aging test, but also avoids direct contact between aluminum and carbon at high temperatures, preventing the formation of brittle and easily hydrolyzed aluminum carbide phases from the root. This reduces interfacial thermal resistance and improves the corrosion resistance and long-term reliability of the material, solving the pain point of traditional composite materials being prone to failure in the humid heat environment of automotive applications.

[0041] Furthermore, this application ingeniously solves the industry challenge of simultaneously meeting the requirements of high thermal conductivity composite materials and encapsulation sealing. By shielding and protecting the welding connection area during the preparation process, an exposed pure aluminum welding area is ultimately formed. This area is free of graphene residue, ensuring that the welding process is an aluminum-aluminum homogeneous fusion weld, thus guaranteeing the purity of the weld pool. The weld seam after welding has a dense structure, and its airtightness meets the IP69K waterproof rating requirements. Moreover, the conductivity at the weld seam is consistent with that of the aluminum alloy substrate. This completely solves the defects such as weld porosity, cracking, and leakage caused by graphene covering the welding area in existing technologies, providing a reliable guarantee for the encapsulation and sealing of high-power semiconductor devices, and is especially suitable for components requiring strict sealing, such as the rear cover of automotive cameras. Attached Figure Description

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0043] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0045] I. Raw Material Preparation

[0046] Unless otherwise specified, the raw materials used in the following examples and comparative examples are as follows:

[0047] Aluminum alloy matrix raw material: Grade 6063-T6 aluminum-magnesium-silicon alloy or 3003 aluminum-manganese alloy, which is CNC machined into semi-finished products for vehicle camera back covers.

[0048] High thermal conductivity graphene nanosheets (GNPs): prepared by physical exfoliation, with an average sheet diameter of 15-25 μm, a thickness of <2 nm (<5 layers), low defect density (ID / IG<0.1), and a theoretical in-plane intrinsic thermal conductivity of >2000 W / (m·K).

[0049] Film-forming binder: Polyimide (PI) precursor solution (15% solids content) or modified epoxy resin.

[0050] Dispersants and solvents: N-methylpyrrolidone (NMP), ethanol, BYK-161 dispersant.

[0051]

Example 1

[0052] This embodiment provides a graphene-reinforced aluminum-based composite back cover for a high-power automotive camera and its manufacturing process.

[0053] 1. Matrix forming and pretreatment:

[0054] The camera back cover substrate was made from 6063 aluminum alloy bars through cold forging and CNC precision machining. After degreasing by alkaline washing, it was anodized in a 15% phosphoric acid electrolyte (voltage 20V, time 30min) to construct an alumina porous layer with a pore size of approximately 200-300nm on the substrate surface. It was then cleaned and dried for later use.

[0055] 2. Welding area shielding protection:

[0056] High-temperature resistant polyimide tape was used to precisely cover the approximately 3mm wide annular area (i.e. the designed welding connection area) around the edge of the back cover to ensure tight coverage.

[0057] 3. Preparation of graphene heat dissipation film (spraying method):

[0058] (1) Slurry preparation: 20g graphene nanosheets, 100g PI precursor solution and 2g dispersant were added to 500ml NMP solvent and circulated for 30 minutes using a high pressure homogenizer to prepare a graphene thermal conductive slurry with high solid content and uniform dispersion.

[0059] (2) Coating: Using automatic spraying equipment, the slurry is evenly sprayed onto the surface of the masked aluminum alloy substrate (base plate and fin area), the wet film thickness is controlled, and a pre-made film layer is formed through multiple spraying-flash drying cycles.

[0060] 4. Curing and densification treatment:

[0061] (1) Step curing: Place the sprayed workpiece in an oven and perform thermal imidization treatment according to the procedure of 100℃ / 30min+200℃ / 60min+300℃ / 60min to completely cure the PI resin and form a skeleton with graphene.

[0062] (2) Pressure densification: The cured workpiece is placed in an isostatic press and subjected to a pressure of 80 MPa at 150°C for 15 minutes. This step forces the graphene sheets to be aligned along the substrate surface and embedded in the micropores of the substrate surface, eliminating internal voids and ultimately forming a dense graphene heat dissipation film with a thickness of about 25 μm.

[0063] 5. Removal of Masking and Post-Welding Processing: Remove the high-temperature resistant tape from the welding area to expose the underlying aluminum alloy substrate. Use a nanosecond pulsed laser cleaning machine to scan and clean this area, removing trace amounts of penetrated adhesive and oxide spots, revealing a clean, metallic aluminum luster, thus obtaining the final product.

[0064]

Example 2

[0065] This embodiment aims to prepare a product with a thicker film layer to meet extreme heat dissipation requirements, using a blade coating process.

[0066] 1. Substrate and pretreatment: 3003 aluminum alloy substrate is selected, and the surface is roughened by chemical etching.

[0067] 2. Welding area shielding: Custom-made stainless steel tooling fixtures are used to hold and shield the welding edges.

[0068] 3. Preparation of graphene heat dissipation film (scalpel coating method): Prepare a high-viscosity graphene slurry (graphene solid content increased to 15wt%). Apply the slurry to the planar area of ​​the substrate using a precision doctor blade, and use the shear force of the doctor blade to induce the initial orientation of the graphene.

[0069] 4. Curing and densification:

[0070] The heat treatment process was the same as in Example 1. During the densification stage, a hot rolling process (roller temperature 200℃, linear pressure 50kN / m) was used to roll the film layer to further improve its density. The final film thickness was 40μm.

[0071] 5. Post-processing: Remove the tooling and perform plasma cleaning and activation on the welding area.

[0072] Comparative Example 1

[0073] The traditional process of hot-pressing and sintering a mixture of aluminum powder and graphene powder is adopted (referencing the bulk composite material in the original technical solution). Preparation: 1 wt% graphene and aluminum powder are ball-milled and mixed, hot-pressed into a blank, and then machined into the shape of a back cover. Features: Graphene is dispersed inside the aluminum matrix, forming a complete composite with no pure aluminum welding areas on the surface.

[0074] Comparative Example 2

[0075] The same spraying and curing process as in Example 1 was used, but the welding area was not shielded, resulting in the graphene film covering the entire back cover surface (including the edge welding area).

[0076] II. Performance Testing and Result Analysis

[0077] Samples were taken from the camera back covers prepared in the above embodiments and comparative examples, or the finished products were used directly for testing.

[0078] In-plane thermal conductivity: The thermal conductivity of the graphene film was directly measured using the laser scintillation method (LFA467) (example) or the overall thermal conductivity of the composite material (comparative example).

[0079] Welding seal (IP69K): The rear cover is laser welded to the aluminum alloy front cover. After welding, high-pressure water spray and immersion air tightness tests (0.5MPa compressed air) are performed.

[0080] Adhesion strength: The adhesion between the film and the substrate was tested using the cross-cut adhesion test and the pull-off test.

[0081] Heat dissipation test (junction temperature reduction): The back cover was installed on the simulated heat source (50W heat-generating chip) and operated for 1 hour in a natural convection environment. The stable temperature of the chip was recorded.

[0082] Table 1: Performance test results of each group of samples

[0083] In-plane thermal conductivity of film / material (W / m·K) 1,250 1,420 398 210 1,250 Chip equilibrium junction temperature (°C) 62.5 58.4 68.2 75.1 62.8 Membrane adhesion Level 0 (12MPa) Level 0 (14MPa) N / A N / A Level 0 (11 MPa) Welding airtightness (IP69K) Pass (no leakage) Pass (no leakage) qualified qualified Failure (weld cracking / leakage) Resistance to damp heat aging (double 85, 1000h) No change on the surface No change on the surface Severe oxidation and discoloration Minor pitting Cracks at the weld

[0084] Principle Analysis: In traditional bulk composite materials (Comparative Example 1), graphene is encapsulated by an aluminum matrix with random orientation, resulting in severe phonon scattering and limiting the improvement of thermal conductivity. This invention, however, utilizes surface film formation and densification processes to achieve highly oriented and tightly stacked graphene nanosheets, constructing high-speed heat conduction channels similar to highly oriented pyrolytic graphite (HOPG). This allows for extremely efficient and rapid heat dissipation from the chip along the back cover plane to the heat sink fins. Measured chip junction temperatures are 5-10°C lower than those using a pure copper heat sink, demonstrating exceptional heat dissipation performance.

[0085] Welding reliability:

[0086] Examples 1 and 2, by reserving a pure aluminum welding zone, show that the welding process is essentially an aluminum-aluminum homogeneous fusion welding, resulting in a dense weld structure and perfect airtightness that passes the IP69K test.

[0087] In contrast, in Comparative Example 2, due to the lack of shielding, the graphene film at the weld joint underwent a carbonization reaction under the high temperature of the laser, generating brittle aluminum carbide. This process generates a large amount of gas (CO / CO2), leading to severe porosity and cracking in the weld, which fails to meet sealing requirements.

[0088] Bonding strength and durability:

[0089] Thanks to the micro-nanoporous structure on the substrate surface and the densification pressure treatment, the film layer in this embodiment forms a "mechanical interlock" structure with the substrate, achieving a bonding force of level 0 (ISO standard). No peeling or performance degradation was observed after the double 85 aging test, proving the automotive-grade reliability of this process.

[0090] In summary, this invention successfully solves the problem of the incompatibility between heat dissipation (surpassing the performance of pure copper) and encapsulation sealing (pure aluminum welding quality) of high-power devices by constructing a structure of "ultra-high thermal conductivity graphene film + pure aluminum welding window" on the surface of an aluminum substrate.

Claims

1. A graphene-reinforced aluminum-based composite material for high-power semiconductor devices, characterized in that, The composite material includes an aluminum alloy matrix and a graphene heat dissipation film layer coated on the surface of the aluminum alloy matrix; The aluminum alloy substrate is a one-piece molded structure, and its surface is divided into a heat dissipation functional area and a welding connection area; the graphene heat dissipation film layer covers the heat dissipation functional area and is tightly connected to the aluminum alloy substrate through an interface bonding layer. The welding connection area is located at the edge or joint of the composite material. This area is not covered with a graphene heat dissipation film layer, and the exposed material is aluminum, which is used to achieve direct welding with the pure aluminum of the mating parts.

2. The graphene-reinforced aluminum-based composite material for high-power semiconductor devices according to claim 1, characterized in that, The thickness of the graphene heat dissipation film layer is 1μm-50μm, and it is composed of multiple layers of graphene nanosheets arranged in an oriented manner and stacked, with an in-plane thermal conductivity ≥1000W / (m·K); the material of the aluminum alloy substrate is one of 1-series pure aluminum, 3-series aluminum-manganese alloy or 6-series aluminum-magnesium-silicon alloy.

3. The graphene-reinforced aluminum-based composite material for high-power semiconductor devices according to claim 1, characterized in that, The interface bonding layer is a micro-nano-scale rough structure or a chemical conversion film layer. The graphene heat dissipation film layer is partially embedded in the micropores or oxide layer on the surface of the aluminum alloy substrate, forming a synergistic combination of mechanical interlocking and chemical bonding, with a bonding strength ≥10MPa.

4. A preparation process for the graphene-reinforced aluminum-based composite material according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Substrate forming and pretreatment. The aluminum alloy raw material is processed into an aluminum alloy substrate of the designed shape, and the substrate surface is cleaned and activated. Step 2: Welding area shielding and protection. The pre-set welding connection area of ​​the aluminum alloy substrate is physically shielded or protected with a film to establish the uncoated area. Step 3: Preparation of graphene heat dissipation film layer. Modified graphene slurry is applied to the surface of the aluminum alloy substrate after step 2, and a wet film layer is formed by coating deposition process. Step 4: Curing and densification treatment. The substrate with the wet film layer is heat-treated and cured, and pressure is applied to densify and orient the graphene film layer. Step 5: Remove the shielding material from the welded joint area to expose the clean aluminum surface, resulting in a composite material with a pure aluminum welded area.

5. The preparation process of a graphene-reinforced aluminum-based composite material for high-power semiconductor devices according to claim 4, characterized in that, The coating deposition process described in step 3 is selected from one of the following methods: spraying, electrophoretic deposition, spin coating, or blade coating. The modified graphene slurry comprises graphene nanosheets, dispersant, film-forming binder and solvent, wherein the solid content of the graphene nanosheets is 5wt%-20wt%.

6. The preparation process of a graphene-reinforced aluminum-based composite material for high-power semiconductor devices according to claim 4, characterized in that, The activation process described in step 1 includes anodic oxidation or chemical etching of the aluminum alloy substrate to construct a porous structure with a pore size of 50nm-500nm on the aluminum alloy surface, thereby enhancing the adhesion of the graphene film.

7. The preparation process of a graphene-reinforced aluminum-based composite material for high-power semiconductor devices according to claim 4, characterized in that, Step 4, the curing and densification process, specifically includes: First, dry at a low temperature of 100℃-150℃ to remove the solvent; then, under a protective atmosphere or vacuum, heat to 250℃-400℃ for high-temperature annealing to carbonize or crosslink the binder. Simultaneously or subsequently, a pressure of 20-100 MPa is applied to the film layer using rolling or isostatic pressing processes to improve the density of the graphene film layer and its adhesion to the substrate.

8. The preparation process of a graphene-reinforced aluminum-based composite material for high-power semiconductor devices according to claim 4, characterized in that, Step 5 is followed by step 6: laser cleaning or plasma cleaning of the exposed weld joint area to remove the surface oxide film and residual organic matter, ensuring the wettability of the pure aluminum weld interface.

9. A vehicle-mounted camera rear cover, characterized in that, The back cover is made of the graphene-reinforced aluminum-based composite material according to any one of claims 1-3, or is prepared by the preparation process according to any one of claims 4-8; The rear cover includes a base plate, heat dissipation fins, and a sidewall surrounding the base plate. The graphene heat dissipation film layer continuously covers the outer surface of the base plate and the surface of the heat dissipation fins; The end face of the sidewall is the welding connection area, which has an exposed aluminum metallic luster and is used for laser welding or friction stir welding to seal with the front cover of the camera.

10. The vehicle-mounted camera rear cover according to claim 9, characterized in that, The width of the welded connection area is 1mm-5mm. There is no graphene residue in this area. The airtightness of the weld after welding meets the IP69K waterproof rating requirement, and the conductivity of the weld is consistent with that of the aluminum alloy substrate.

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