Diamond-metal composite material with six surfaces coated with metal as well as processing method and application of diamond-metal composite material

Abstract

The invention discloses a diamond-metal composite material with six surfaces coated with metal as well as a processing method and application of the diamond-metal composite material. The diamond-metal composite material with the six surfaces coated with the metal is a composite material formed by sintering a hexahedral metal shell and at least one diamond-metal composite layer arranged in the metal shell. The diamond-metal composite layer comprises a metal net and diamond particles, the surfaces of the diamond particles are coated with coatings, the diamond particles are arranged in grids of the metal net, and gaps between the grids and the diamond particles are filled with metal powder; metal atoms in the metal net penetrate through the coating to diffuse towards the surface of the diamond, and a mixed transition area is formed. The structural composition of the diamond-metal composite material is adjusted, and the surface of the diamond-metal composite material is coated with metal to form the diamond-metal composite material with six surfaces coated with metal, so that the diamond in the composite material is prevented from being exposed, and the problem that the surface of the diamond is difficult to machine and gold is difficult to plate is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal composite materials and their processing, and specifically relates to a diamond-metal composite material with six-sided metal coating, its processing method and application. Background Art

[0002] With the continuous miniaturization, integration and high performance of modern electronic devices (including computing, 5G / 6G, batteries and power electronic devices), the power density is continuously increasing, resulting in a sharp rise in the heat generation of devices. Subsequently, there is a decline in performance and device failure. Efficient heat dissipation is becoming an important issue in electronic products. To alleviate this problem, integrating advanced thermal management materials on electronic devices can significantly improve their heat dissipation capacity.

[0003] Traditional Invar and Kovar alloys have low thermal conductivity; although tungsten copper and molybdenum copper alloys have low thermal expansion coefficients, they have low thermal conductivity and high density; while metal matrix composites can combine the good thermal conductivity of metals with the low expansion coefficient of reinforcements, and the material properties are adjustable, which is a commonly used thermal management material. Diamond is the material with the highest thermal conductivity in nature (1200 - 2000 W·m-1·K-1), and has a low thermal expansion coefficient (1x10-6 K-1), which is an ideal material for the reinforcement phase. Moreover, the current artificial synthesis technology of diamond is quite mature, and the manufacturing cost is relatively low compared with other high thermal conductivity carbon materials; aluminum, copper and silver have good electrical and thermal conductivity, and relatively low density, which are commonly used matrix materials. Among them, the thermal conductivity of Cu is slightly lower than that of Ag but better than that of Al, and the thermal expansion coefficient is the lowest among the three, and the price is also moderate. Therefore, diamond / copper composite materials are gradually becoming the high thermal conductivity metal matrix composite materials with the widest research scope and the most prominent achievements in the world.

[0004] Diamond has high hardness, and neither reacts with copper nor has good wettability, making it difficult to ensure the forming quality of diamond / copper composites. Its preparation process has become an important factor affecting the performance of diamond / copper composites. Currently, most preparation processes of diamond / copper composites rely on temperature and pressure to form the composites. Among them, the preparation methods widely used in industry include hot pressing sintering method, infiltration method, and spark plasma sintering method. Hot pressing sintering is a common powder metallurgy process. When using this method to prepare diamond / copper composites, usually, the mixed powder of diamond and copper is put into a mold and then heated and pressed simultaneously in a vacuum hot pressing furnace to form. The hot pressing sintering method is simple to operate and does not require high equipment requirements. However, the bonding between the diamond and copper phases is not strong, and the thermal conductivity is not high, making it difficult to meet the current requirements for high-power devices. Infiltration can be divided into pressureless infiltration (PLI) and pressure infiltration (PI). Using the principle that the melting point of the metal matrix is lower than that of the reinforcing particles, under the action of pressure or capillary action, the copper melt is infiltrated into the gaps between diamond particles to obtain bulk composites. The pressureless infiltration method has a simple process, is easy to operate, is relatively easy to implement, and the shape of the prepared composite material is convenient to control. However, the pressureless infiltration method has extremely high requirements for the wettability of the interface between diamond and copper. The transition layer between diamond and copper must be uniform and complete. Moreover, the pressureless infiltration method does not apply external pressure and only relies on the capillary force of the green body to drive the infiltration of the copper melt, resulting in a long infiltration time and unsatisfactory results. Pressure infiltration is to apply external force during the infiltration process, which can promote the infiltration of the copper liquid. The diamond composites prepared by pressure infiltration require short time, high efficiency, high density, and a wider application range. However, pressure infiltration is a relatively complex process. The preparation of the reinforcement preform, the melting of the matrix, the flow of gas during infiltration, and the solidification of the matrix all have a great impact on the performance of the sample. Using this method requires high requirements for the design of the graphite mold, the control of sintering parameters, and the selection of sintering equipment. Spark plasma sintering (SPS) is a new material preparation method developed in recent years, which can rapidly densify powder particles at a temperature below the melting point. Its main process is to apply pulsed current to the powder particles and apply a certain pressure, and the plasma generated instantaneously by spark discharge uniformly heats the particles, thereby activating the particle surface and achieving ultra-rapid densification sintering, with the advantages of fast sintering speed, rapid heating and cooling, low sintering temperature, directly sintering into a dense body, energy saving and environmental protection, etc. However, the mechanism of spark plasma sintering is still not fully understood at present, and it is also impossible to quantitatively determine the entire sintering process of the actual composite material. Therefore, it is difficult to precisely control the composition of the two-phase interface and the size of the interface products. Coupled with the relatively low sintering temperature and pressure, it is also difficult to produce the phenomenon of diamond bonding and connection. Therefore, the thermal conductivity of the materials prepared by this method is rarely higher than 700 W / (m·K). Moreover, the temperature and pressure of spark plasma sintering are relatively small, making it difficult to meet the tight bonding between diamond and copper. Therefore, the thermal conductivity of the obtained composite material is not high.

[0005] In addition, there are other methods for preparing diamond-copper composites in the prior art. For example, for the diamond-copper composites prepared by the hot pressing method, although a certain particle grading is carried out, due to the inability to control the distribution of diamonds, the volume fraction of diamonds in the finally prepared composite material is still low, and the porosity is high, resulting in a limited adjustable range of the thermal expansion coefficient and thermal conductivity. Moreover, the surface finish of the composite material is poor and it is impossible to achieve complete densification. On this basis, the diamond-copper composite material prepared by the pressure infiltration method can obtain a relatively dense material. However, driven by the fluidity of the copper liquid, the diamond particles will move during the preparation process, making it impossible to guarantee the uniformity and consistency of the composite material, and the repeatability cannot be guaranteed.

[0006] Patent CN110453126B discloses a diamond / metal-based composite heat-conducting material and a preparation method thereof. The steps are as follows: laying a metal foil at the bottom of a mold, placing a metal mesh with a mesh specification consistent with the diamond powder specification of the first diamond layer, and filling the diamond powder of the first diamond layer; continuing to lay a metal foil, placing a metal mesh with a mesh specification consistent with the diamond powder specification of the second diamond layer, and filling the diamond powder of the second diamond layer; repeating the above steps and stacking them reciprocally to the required number of layers to obtain a diamond / metal-based layered composite; sintering the diamond / metal-based layered composite by the vacuum hot pressing method to prepare the diamond / metal composite heat-conducting material. This method uses a metal foil intermediate layer to fill the remaining voids between diamond particles. However, it is difficult to select the thickness of the metal foil, and it is necessary to conduct multiple tests to obtain a suitable thickness of the metal foil. Moreover, with the change of the diamond particle size, the thickness of the metal foil needs to be readjusted; there is a risk of peeling between the layers of the diamond powder layer, and the brittleness of the composite material is large.

[0007] Since the electrode potential difference between diamond and other metals is relatively large, the time required for copper plating on the surface of the diamond / copper composite material is long, and the prepared copper plating layer has poor density and unevenness. Summary of the Invention

[0008] In order to overcome the deficiencies of the prior art, the purpose of this application is to provide a diamond-metal composite material with six-sided metal coating. By adjusting the structural composition of the diamond-metal composite material and coating the metal on its surface to form a diamond-metal composite material with six-sided full-metal coating, the exposure of diamonds in the composite material is avoided, the problems of difficult processing and difficult gold plating on the diamond surface are solved, and thus the cost of heat sink products (such as diamond copper) is reduced. At the same time, the surface performance and thermal conductivity of the composite material are improved.

[0009] To solve the above problems, the technical solutions adopted in this application are as follows: An embodiment of the present application provides a diamond-metal composite material with six-sided metal coating, which is a composite material sintered from a hexahedral metal shell and at least one layer of diamond-metal composite layer placed in the metal shell; the diamond-metal composite layer includes a metal mesh and diamond particles coated with a coating, and the diamond particles are arranged in the grids of the metal mesh, and metal powder consistent with the material of the metal mesh is filled in the gaps between the grids and the diamond particles; metal atoms in the metal mesh diffuse through the coating to the surface of the diamond to form a mixed transition zone.

[0010] As a further preferred solution, the grid in the embodiment of the present application is a regular hexahedron structure or a honeycomb structure of a regular octahedron, the wall thickness of the grid is 10-20 μm, and the edge length L of the grid is 10-20 μm larger than the particle size D of a single diamond particle.

[0011] As a further preferred solution, the diamond in the embodiment of the present application is one or more of artificial high-temperature high-pressure diamond, artificial CVD diamond or natural diamond, and the particle size of the diamond particles is 100-1000 μm.

[0012] As a further preferred solution, the mixed transition zone in the embodiment of the present application is a ternary phase formed by metal-coating material-C, such as a ternary phase formed by Cu-coating material-C, Al-coating material-C; the thickness of the ternary phase is 1-2 μm.

[0013] As a further preferred solution, the coating in the embodiment of the present application is a coating formed by one of the materials Ti, Cr, W, V, Zr or a composite coating formed by two or more materials; the thickness of the coating is 0.1-0.5 μm.

[0014] As a further preferred solution, the metal shell in the embodiment of the present application is an aluminum foil shell, and the materials of the metal mesh and the metal powder are both aluminum; there is an alumina nanolayer with a thickness of 3-8 nm at the bonding interface between the aluminum foil shell and the diamond.

[0015] As a further preferred solution, the metal shell in the embodiment of the present application is a copper foil shell, the metal mesh is a copper mesh, and the metal powder used to fill the voids is pure copper powder or mixed copper powder mixed with active ingredients; the particle size of the copper powder is 0.5-5 μm.

[0016] The embodiment of the present application also provides a processing method for a diamond-metal composite material with six-sided metal coating, including the following steps, Manufacture a hexahedral metal box body: stamp and fold a metal sheet into a hexahedral metal box body with an upper cover and an opening, and place it in a mold; Select a metal mesh: Use a metal mesh with uniform meshes, and the size of the metal mesh is the same as the inner bottom surface size of the hexahedral metal box body; Lay the metal mesh in the above-mentioned hexahedral metal box body; Arrange diamond particles: Use an arranging machine to arrange diamond particles coated with a coating on each mesh of the metal mesh; Void filling: Place the hexahedral metal box body and the mold with arranged diamond particles on a vibrating table, and spray metal powder onto the metal mesh in a vibrating mode until the metal powder fills the voids of the metal mesh and reaches the same height as the metal mesh; Multi-layer stacking: After the void filling step, place a metal mesh in the hexahedral metal box body, and perform the steps of arranging diamond particles and void filling until the metal mesh is flush with the height of the hexahedral metal box body. Cover the upper cover at the opening, and integrate the upper cover with the metal box body to obtain a preform; Sintering and forming: Place the above-mentioned preform in a sintering furnace for sintering to obtain a sintered composite material.

[0017] As a further preferred solution, in the processing method described in the embodiment of the present application, when making the hexahedral metal box body, first punch out the developed pattern of the hexahedron, and reserve creases at the edges; Fold along the edges to form a hexahedral box, and use a metal adhesive to connect at the edge joints.

[0018] As a further preferred solution, in the processing method described in the embodiment of the present application, when making the hexahedral metal box body, use laser cutting or wire cutting to cut into the developed pattern of the hexahedron, and pre-engrave creases at the edges; After folding along the edges, locally weld at the edge joints to combine adjacent edges.

[0019] As a further preferred solution, in the processing method described in the embodiment of the present application, the mesh of the metal mesh is a regular hexahedron structure or a honeycomb structure of a regular octahedron, and the edge length L of the mesh is 10-20 μm larger than the particle size D of a single diamond particle.

[0020] As a further preferred solution, in the processing method described in the embodiment of the present application, the vibrating table is a mechanical vibrating table, the vibration frequency is 2-10 Hz, the vibration time is 5-20 min, and the amplitude is 0.1-0.5 mm.

[0021] As a further preferred solution, in the processing method described in the embodiment of the present application, when filling voids, an electrostatic spraying technology is used to apply an electric field to make the metal powder fill the grid gaps directionally, and the electric field voltage is 5-10 kV.

[0022] As a further preferred solution, in the embodiment of the present application, the metal shell is a copper foil shell, the metal mesh is a copper mesh, and the metal powder used to fill the voids is pure copper powder or mixed copper powder mixed with active ingredients; the particle size of the copper powder is 0.5 - 5 μm.

[0023] As a further preferred solution, in the processing method described in the embodiment of the present application, the active ingredient is one or a mixture of two or more of nano - Al2O3, nano - SiC, nano - TiC, nano - Y2O3, and nano - graphene, and the dosage of the active ingredient accounts for 0.1 - 1.0 wt% of the weight of the copper powder.

[0024] As a further preferred solution, in the processing method described in the embodiment of the present application, the sintering and forming is carried out by vacuum hot - press sintering, the vacuum degree in the furnace is < 10 Pa, the hot - press pressure is 20 - 40 MPa, the sintering temperature is 850 - 920 °C, and the time is 55 - 65 min.

[0025] As a further preferred solution, in the processing method described in the embodiment of the present application, the sintering and forming is carried out by segmented sintering, including Pre - sintering: Pulse - current - assisted sintering is adopted, the sintering temperature is 820 - 850 °C, the pressure is 20 - 30 MPa, the time is 10 - 20 min, a pulse current of 100 - 1000 A is superimposed, and the frequency is 1 - 10 Hz; Final sintering: Hot - press sintering combined with hydrogen - atmosphere control is adopted, the sintering temperature is 880 - 900 °C, the pressure is 30 - 40 MPa, the sintering time is 30 - 60 min; the oxygen content in the H2 atmosphere is ≤ 10 ppm.

[0026] As a further preferred solution, in the embodiment of the present application, the metal shell is an aluminum foil shell, the metal mesh is an aluminum mesh, and the metal powder used to fill the voids is aluminum powder; the particle size of the aluminum powder is 0.5 - 5 μm.

[0027] In the solution with an aluminum foil shell, for pre - sintering in sintering and forming: Pulse - current - assisted sintering is adopted, the sintering temperature is 520 - 550 °C, the pressure is 30 - 40 MPa, the time is 10 - 20 min, and a pulse current of 500 - 30000 A is superimposed; Final sintering: Hot - press sintering combined with hydrogen - atmosphere control is adopted, the sintering temperature is 600 - 650 °C, the pressure is 30 - 40 MPa, the sintering time is 30 - 60 min; the oxygen content in the H2 atmosphere is ≤ 10 ppm.

[0028] As a further preferred solution, the processing method described in the embodiment of the present application further includes a step of surface polishing treatment for the sintered and formed composite material.

[0029] Application of the diamond-metal composite material with six-sided metal coating in manufacturing a heat dissipation substrate for electronic devices.

[0030] An embodiment of the present application further provides a heat dissipation substrate for electronic devices, which includes a composite material sintered from a hexahedral metal shell and at least one layer of diamond-metal composite layer disposed in the metal shell; the diamond-metal composite layer includes a metal mesh and diamond particles coated with a coating on the surface, the diamond particles are arranged in the meshes of the metal mesh, and metal powder is filled in the voids between the meshes and the diamond particles; metal atoms in the metal mesh diffuse towards the diamond surface through the coating to form a mixed transition zone.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The diamond-metal composite material with six-sided metal coating described in the embodiment of the present application adopts a six-sided coating structure. After sintering, the metal box body forms a dense outer layer, which improves the bending strength of the composite material, provides electromagnetic shielding and antioxidant protection at the same time; and is combined with the inner layer as a whole through subsequent sintering. The six-sided coating design prevents the penetration of oxidation and corrosion media.

[0032] 2. In the diamond-metal composite material with six-sided metal coating described in the embodiment of the present application, the diamond-metal composite layer includes a metal mesh and diamond particles coated with a coating on the surface. During sintering, the diamond forms a three-dimensional interpenetrating structure, and the metal mesh and metal powder are filled to construct a continuous heat conduction path, effectively improving the overall thermal conductivity of the composite material and making it suitable for heat dissipation substrates of high-power electronic devices.

[0033] 3. In the diamond-metal composite material with six-sided metal coating described in the embodiment of the present application, the volume fractions of the metal mesh skeleton and the diamond particles are adjustable. By regulating the aperture of the metal mesh, the thermal expansion coefficient of the composite material can be nearly matched with electronic components such as semiconductor chips; the coating on the diamond surface enhances the interfacial bonding strength through chemical bonding, avoiding interfacial peeling during high-temperature service.

[0034] 4. In the processing method of the diamond-metal composite material with six-sided metal coating described in the embodiments of the present application, metal atoms in the diamond-metal composite layer diffuse to the diamond surface through the coating to form a mixed transition zone, alleviating the problem of poor wettability between diamond and metal and reducing the interfacial thermal resistance; metal powder is filled in the voids between the grid and diamond particles. On the one hand, the metal powder and the metal mesh jointly support the diamond particles, avoiding interface cracking caused by local stress concentration; on the other hand, the metal powder fills the local micron-level voids, reducing the interfacial thermal resistance and increasing the thermal conductivity. During the sintering process, due to the large specific surface area and high activity of the metal powder, it preferentially melts and penetrates into the micropores of the diamond surface coating, promoting the diffusion of metal atoms to the diamond surface, forming a mixed transition zone, and enhancing the interfacial bonding strength. It solves the performance bottleneck caused by the interface discontinuity of traditional diamond / metal composite materials and provides a new direction for high-density electronic packaging.

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0037] Figure 1 It is a physical diagram of the diamond-copper composite material with six-sided copper coating described in the embodiments of the present application after surface grinding, showing the diamond-copper layer.

[0038] Figure 2 It is an X-ray diagram of the single-layer arrangement of diamonds in the diamond-metal composite material with six-sided metal coating described in the embodiments of the present application.

[0039] Figure 3 It is an X-ray diagram of the double-layer arrangement of diamonds in the diamond-metal composite material with six-sided metal coating described in the embodiments of the present application.

[0040] Figure 4 It is a schematic flow chart of the processing method of the diamond-metal composite material with six-sided metal coating described in the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0042] In this application, the term "comprising" and other equivalent descriptive methods involved in the specification and claims are intended to cover non-exclusive inclusion, that is, it includes both the content clearly described in the specification and claims, and can also include steps or units inherent in the product, method, or structure but not described in the specification and claims.

[0043] The embodiments of this application provide a diamond-metal composite material with six-sided metal coating, which is a composite material sintered from a hexahedral metal shell and at least one layer of diamond-metal composite layer placed in the metal shell. The hexahedral metal shell is used to form a six-sided coating structure on the surface of the diamond-metal composite layer, forming a dense shell to block the penetration of oxygen and water vapor. The wettability between the metal and the diamond is poor, relying on high-cost coatings and having a high interfacial thermal resistance. The metal shell and the internal metal mesh synergistically diffuse during sintering, which can effectively reduce the interfacial thermal resistance. Due to the large difference in the coefficient of thermal expansion (CTE) between the metal / diamond of traditional materials, thermal stress cracking is likely to occur. In the embodiments of this application, the diamond-metal composite layer includes a metal mesh and diamond particles coated with a coating on the surface. The diamond particles are arranged in the grids of the metal mesh, and the voids between the grids and the diamond particles are filled with metal powder. Through this scheme combining the metal mesh framework and metal powder filling, the adjustment of the coefficient of thermal expansion can be realized, making it nearly match the coefficient of thermal expansion of electronic components such as semiconductor chips. The metal shell and metal powder filling reduce the sintering temperature to avoid diamond graphitization, reduce energy consumption, and improve the yield. In the embodiments of this application, during the sintering process, metal atoms in the metal mesh will diffuse through the coating to the surface of the diamond, forming a mixed transition zone. The thermal conductivity of traditional materials is significantly anisotropic and difficult to meet the requirements of directional heat dissipation. In the embodiments of this application, the metal shell and the internal metal mesh-metal powder form a three-dimensional interpenetrating structure, which can effectively improve the thermal conductivity and isotropy of the composite material.

[0044] Further, the grid described in some embodiments of the present application is a regular hexahedral structure, and the regular hexahedral grid forms a homogeneous metal skeleton in the three directions of X / Y / Z. The regular arrangement of the wire diameter of the metal mesh and the length of the mesh edge can reduce the isotropic deviation of thermal conductivity; the 90° intersection structure of the regular hexahedral grid forms a four-way support when bent (such as bending test), which is conducive to improving the efficiency of stress dispersion; the right-angled edges of the regular hexahedral grid can also guide the molten metal powder to flow along the edge direction during sintering, and can preferentially wrap the surface of the diamond particles; in addition, the regular porosity of the regular hexahedral structure allows the metal powder to be fully densified at a lower temperature to avoid local unmelted areas. When the diamond particles are embedded in the grid through a vibration arrangement machine, a gap needs to be reserved to compensate for the particle size tolerance and arrangement mechanical error to avoid the particles from getting stuck or scratching the surface of the metal mesh; at the same time, the gap can also provide a flow channel for the metal powder. During the vibration process, the metal powder can penetrate into the micro-gap between the particles and the grid wall, increase the interface contact area, and form a "diamond-metal powder-metal mesh" three-phase cross-linked structure. Due to the limited flow of the metal melt and incomplete interface bonding, the reserved gap allows the metal powder to fully wrap the diamond particles during sintering and melting, and the metal atoms diffuse along the coating on the surface of the particles to form a transition layer, providing interface integrity. The thermal expansion mismatch between diamond and metal will generate stress at the interface; the gap can absorb the stress generated at the interface due to the thermal expansion mismatch between diamond and metal through plastic deformation of the metal powder, avoiding stress concentration and microcracks. In addition, the metal powder and the metal mesh have different shrinkage rates during sintering, and the gap provides deformation buffer space, stabilizes the shrinkage rate, and avoids delamination or warping. Therefore, in the embodiment of the present application, the space size of each grid is slightly larger than the particle size of the placed diamond particles. Specifically, through precise calculation, when the edge length L of the grid is 10~20μm larger than the particle size D of a single diamond particle (L=D+10~20μm), it can effectively balance the particle positioning accuracy, interface bonding strength and process tolerance. In the present application, the wall thickness of the grid is 10~20μm. In addition to the above-mentioned regular hexahedron structure, in other embodiments, the grid is a regular octahedron honeycomb structure. When subjected to multi-directional loads, the stress distribution is uniform and has higher compressive strength than the regular hexahedron structure. When under pressure, the energy is absorbed by the buckling of the wall panels, and the energy absorption efficiency is higher than that of the regular hexahedron structure. However, compared with the regular hexahedron structure, it is more difficult to manufacture and the cost is relatively high. In the embodiments of the present application, the metal shell, metal mesh and metal powder are made of the same material, and the specific material can be copper or aluminum.

[0045] Based on the above solutions, the diamond used in the embodiments of the present application is one or more of artificial high-temperature high-pressure diamond, artificial CVD diamond, or natural diamond. The size of diamond particles will affect the thermal conductivity, mechanical properties, and the ease of processing of the material. In terms of performance, larger-sized diamond particles form more direct heat conduction paths in the composite material because larger particles are more likely to come into contact with each other, thereby enhancing the thermal conductivity. On the other hand, larger particles will result in more interfaces, leading to poor bonding at the diamond-copper interface, which will instead increase the interfacial thermal resistance and reduce the overall thermal conductivity. Smaller particles can be packed more tightly, but require more interface treatment; otherwise, pores are easily formed, affecting the thermal conductivity and mechanical strength. In terms of processing, larger particles are more easily dispersed during mixing and forming, but higher pressure is required to ensure bonding between particles; while smaller particles are prone to agglomeration. In terms of mechanical properties, larger particles can serve as reinforcing phases to increase the hardness of the composite material, but large particles are likely to be the starting points of cracks, resulting in a decrease in the toughness of the material; smaller particles can be more evenly distributed, improving the overall strength and toughness of the material. Therefore, in some embodiments of the present application, considering the thermal conductivity, mechanical properties, and the ease of processing, the particle size of the diamond particles used is 100 - 1000 μm. The preferred particle size of the diamond is 200 - 500 μm.

[0046] Furthermore, in the embodiments of the present application, the coating on the diamond surface is a coating formed by one of the materials Ti, Cr, W, V, Zr or a composite coating formed by two or more materials, and the thickness of the coating is 0.1 - 0.5 μm. For example, in some embodiments, Ti is used as the target, and a dense layer is formed on the diamond surface by magnetron sputtering, and a TiC phase is generated at the interface, with a thickness of about 100 nm. In other embodiments, the Ti and Cr targets are sputtered simultaneously to achieve an atomic-level mixed coating to improve the interfacial shear strength. In still other embodiments, a composite layer of multiple materials can be used. For example, a Cr layer (0.2 - 0.3 μm) is first formed on the diamond particle surface by magnetron sputtering, and then a W layer (0.1 - 0.2 μm) is formed on the surface of the Cr layer. In some embodiments, it can be set as a Ti-Zr-Cu gradient coating, that is, the bottom layer is a 0.1 - 0.2 μm Ti layer, which reacts with the diamond at the interface to generate TiC to enhance the bonding; the middle layer is a 0.1 - 0.2 μm Zr layer, and the high melting point of the middle layer is used to achieve the transition of the thermal expansion coefficient; the surface layer is a 0.2 - 0.3 μm Cu layer to optimize the wettability of the diamond surface. In addition to the above several implementation methods, it can also be Ti / V alternating deposition, with each layer having a thickness of 20 - 50 nm and the total thickness of the coating being 0.5 μm.

[0047] In some embodiments, the metal housing is a copper foil housing, the metal mesh is a copper mesh, and the material of the metal powder used to fill the voids is copper. In these embodiments, after sintering of the diamond-metal composite material coated with metal on six sides, the surface of the copper foil housing is a nanocrystalline copper layer with a grain size of 50-100 nm. The nanocrystalline copper has high hardness, and the surface wear resistance is improved, avoiding scratches and deformation during processing and service. Moreover, the surface roughness of the nanocrystalline is small. When used as a heat sink material, the interfacial thermal resistance can be reduced. The copper inside the diamond-copper composite material coated with copper on six sides is a coarse-grained copper matrix with a grain size of 5-10 μm. The coarse-grained copper has high thermal conductivity and a higher fracture elongation rate than nanocrystalline copper, which can avoid brittle cracking. Figure 1 This is a physical picture of the diamond-copper layer exposed after polishing the surface of the diamond-copper composite material coated with copper on six sides described in the embodiments of the present application. It can be seen from the figure that the diamond particles are arranged neatly and uniformly.

[0048] In some other embodiments, the metal housing is an aluminum foil housing, and the materials of the metal mesh and the metal powder are both aluminum; diamond serves as the main heat conduction channel and forms a three-dimensional interpenetrating network with the aluminum matrix, which can effectively improve the overall thermal conductivity of the composite material. There is an aluminum oxide nanolayer with a thickness of 3-8 nm at the bonding interface between the aluminum foil housing and the diamond. The 3-8 nm aluminum oxide can inhibit the excessive generation of harmful Al4C3 phase and reduce phonon scattering through an atomically flat interface.

[0049] Furthermore, in the embodiments of the present application, after completely polishing the surface of the diamond-metal composite material coated with metal on six sides with single-layer copper mesh arranged diamond particles and double-layer copper mesh arranged diamond particles sintered, X-rays are used to observe the internal structure. Figure 2 X-ray diagram of single-layer arrangement of diamond particles. Figure 3 This is the X-ray diagram of double-layer arrangement of diamond particles; it can be seen from the figure that through the cross arrangement of diamond particles in the double-layer structure, a denser heat conduction network is formed, further reducing the interfacial thermal resistance. Through testing, it is found that the multi-layer arrangement of diamond can not only achieve directional heat dissipation for local hot spots through the distribution of diamond with different particle sizes or densities, avoiding the performance attenuation caused by heat flow concentration in the single-layer structure; but also achieve hierarchical adaptation of the overall coefficient of thermal expansion (CTE) by adjusting the volume fraction of diamond and copper matrix, thereby reducing the interfacial stress generated by temperature changes and avoiding material cracking. Therefore, preferably, in the embodiments of the present application, the diamond-metal composite layer adopts the method of stacking multi-layer metal meshes to fill diamond particles.

[0050] The embodiments of the present application also provide a processing method for a diamond-metal composite material coated with metal on six sides, including the following steps: Manufacturing a hexahedral metal box body: Stamping and folding a metal sheet into a hexahedral metal box body with an upper cover and an opening, and placing it in a mold; Select a metal mesh: Use a metal mesh with uniform meshes, and the size of the metal mesh is the same as the inner bottom surface size of the hexahedral metal box body; lay the metal mesh in the above-mentioned hexahedral metal box body; Arrange diamond particles: Use an arranging machine to arrange diamond particles coated with a coating on each mesh of the metal mesh; Void filling: Place the hexahedral metal box body and the mold with arranged diamond particles on a vibrating table, and spray metal powder of the same material as the metal mesh on the metal mesh in the vibration mode until the metal powder fills the voids of the metal mesh and reaches the same height as the metal mesh; Multi-layer stacking: After the void filling step, place a metal mesh in the hexahedral metal box body, and repeat the steps of arranging diamond particles and void filling until the metal mesh is flush with the height of the hexahedral metal box body, cover the upper cover at the opening, and integrate the upper cover with the metal box body to obtain a preform; Sintering and forming: Place the above-mentioned preform in a sintering furnace for sintering to obtain a sintered composite material.

[0051] In the processing method described in the embodiment of the present application, when making the hexahedral metal box body, first punch out the unfolded pattern of the hexahedron, and reserve creases at the edges; fold along the edges to form a hexahedral box, and connect at the edge joints with a metal adhesive (such as nano-silver glue); the shrinkage rate of the metal adhesive after curing is small, which can avoid size deviation caused by thermal deformation. As another implementation manner, when making the hexahedral metal box body, use laser cutting or wire cutting to cut into the unfolded pattern of the hexahedron, and pre-engrave creases at the edges; fold along the edges and locally weld at the edge joints to combine adjacent edges.

[0052] In the embodiment of the present application, the meshes of the metal mesh are of regular hexahedron structure or regular octahedron honeycomb structure. In order to avoid mesh collapse and maintain the warpage amount after sintering during the subsequent sintering process, and at the same time shorten the heat conduction path of the metal matrix to maximize the diamond-metal interface; in the present application, the wall thickness of the mesh is 10-20 μm. Since the metal matrix has a shrinkage rate at high temperatures, reserved space is used to offset the stress concentration caused by shrinkage and avoid diamond extrusion and crushing. Therefore, it is necessary to control the voids between the mesh and the diamond particles. In the embodiment of the present application, the edge length L of the mesh is 10-20 μm larger than the particle size D of a single diamond particle; the 10-20 μm gap provides a diffusion space for the metal coating on the diamond surface, which is beneficial to the formation of the interface layer to improve the shear force of the material.

[0053] In this application, the vibrating table used for vibration is a mechanical vibrating table. Through mechanical vibration, dense filling of metal powder and stable arrangement of diamond particles are achieved, while avoiding structural damage caused by excessive vibration. In specific embodiments, adjusting the vibration frequency can control the movement mode of the particles. Controlling the vibration frequency to 5 - 15 Hz can promote the slow sliding of metal powder particles, avoiding the collision between diamond and metal mesh and the deviation of diamond particles. Further, the vibration frequency can be adjusted in two steps. For example, a low-frequency vibration of 5 - 10 Hz is adopted in the initial stage to adapt to the initial loose filling stage. When the porosity is relatively high, a higher frequency of 10 - 15 Hz is used to make up for it. Adjusting the amplitude determines the filling impact energy. A smaller amplitude can eliminate pores and adapt to fine grids, making the surface metal powder more uniform. An excessive amplitude will cause splashing loss of metal powder. Therefore, in the embodiments of this application, the amplitude is controlled to 0.1 - 0.5 mm. Controlling the vibration time is mainly to balance the effect and filling effect. In the embodiments of this application, the vibration time is controlled to 5 - 15 min.

[0054] Further, in some embodiments of this application, when filling voids, an electrostatic spraying technique is used to apply an electric field to make the copper powder fill the grid gaps directionally. The electric field voltage is 5 - 10 kV. Through the 5 - 10 kV high-voltage electric field, the charged metal powder moves directionally along the electric field lines and accurately fills the gaps between diamond particles, solving the "shadow effect" of traditional vibration filling. The metal powder preferentially deposits at the grid corners with high electric field intensity, forming an interlocking skeleton and improving the compressive strength.

[0055] In the solution using a copper foil casing, the metal powder used in some embodiments is pure copper powder, and the particle size of the copper powder is 0.5 - 5 μm. The ultra-fine particle size copper powder has a large specific surface area and a high sintering driving force, which can reduce the densification temperature. In some other embodiments, a mixed copper powder with mixed active components is used. The purpose of adding the active components is to promote the diffusion and combination of copper particles, reduce the sintering temperature, reduce the porosity, make the copper powder compatible with the copper matrix, and avoid the formation of brittle phases due to interfacial reactions at high temperatures. Therefore, the active components are selected from but not limited to one or more mixtures of nano-Al2O3, nano-SiC, nano-TiC, nano-Y2O3, and nano-graphene. Hard particles such as nano-Al2O3 and nano-SiC (particle size ≤ 50 nm) are embedded in the gaps of the copper powder. By hindering grain boundary migration (Zener pinning), it forces copper atoms to rapidly diffuse along the particle surface, effectively reducing the sintering temperature; the graphene sheets form a three-dimensional conductive network, enhancing the local current density and triggering the Joule heat effect in pulsed current sintering, which can accelerate the molten combination on the surface of copper particles; Y2O3 preferentially adsorbs oxygen impurities, inhibits the formation of Cu-O brittle phases, and at the same time reacts with the Ti coating on the diamond surface to form a Y-Ti-O transition layer, which can effectively improve the interfacial shear strength; the thermal expansion coefficient of TiC is between that of copper and diamond, which can buffer thermal stress and avoid cracking at the interface of the composite material. For example, in some embodiments, the active component is nano-Al2O3, and the dosage accounts for 0.1 - 1.0 wt% of the weight of the copper powder. In some other preferred embodiments, a two-component composite of nano-Al2O3 and nano-graphene is used, where the dosages of nano-Al2O3 and nano-graphene respectively account for 0.2 - 0.3 wt% and 0.1 - 0.2 wt% of the weight of the copper powder.

[0056] In some embodiments, in the solution of using a copper foil to make a metal casing, the sintering and forming is carried out by vacuum hot pressing sintering. The vacuum degree in the furnace is < 10 Pa, the hot pressing pressure is 20 - 40 MPa, the sintering temperature is 850 - 920 °C, and the time is 55 - 65 min. In this solution, at a relatively low vacuum degree, the oxidation of copper powder to form Cu2O can be avoided, ensuring the cleanliness of the diamond - Ti coating interface and reducing the interfacial thermal resistance; at the same time, the gas escape rate is accelerated under vacuum, the growth rate of the sintering neck of copper powder is increased, and the densification time is shortened. Isotropic pressure is transmitted through a graphite mold to make the copper powder plastically flow to fill the gaps of the diamond, reduce the porosity, and improve the thermal conductivity.

[0057] In some other embodiments, in the solution of using a copper foil to make a metal casing, the sintering and forming is carried out by segmented sintering, including, Pre-sintering: Pulse current assisted sintering is used, the sintering temperature is 820 - 850 °C, the pressure is 20 - 30 MPa, the time is 10 - 20 min, a 100 - 1000 A pulse current is superimposed, and the frequency is 1 - 10 Hz; Final sintering: Adopt hot-press sintering combined with hydrogen atmosphere control, the sintering temperature is 880 - 900 °C, the pressure is 30 - 40 MPa, and the sintering time is 30 - 60 min; the oxygen content in the H2 atmosphere ≤ 10 ppm.

[0058] The metal shell described in the embodiment of the present application is an aluminum foil shell, the metal mesh is an aluminum mesh, and the metal powder used to fill the voids is aluminum powder; the particle size of the aluminum powder is 0.5 - 5 μm.

[0059] In the above scheme using an aluminum foil shell, pre-sintering for sintering forming: Adopt pulse current-assisted sintering, the sintering temperature is 520 - 550 °C, the pressure is 20 - 30 MPa, the time is 10 - 20 min, and a pulse current of 500 - 3000 A is superimposed; Final sintering: Adopt hot-press sintering combined with hydrogen atmosphere control, the sintering temperature is 600 - 650 °C, the pressure is 30 - 40 MPa, and the sintering time is 30 - 60 min; the oxygen content in the H2 atmosphere ≤ 10 ppm.

[0060] In addition to the above two sintering methods, in some other embodiments of the present application, sintering methods such as spark plasma sintering (SPS) and high-temperature and high-pressure sintering (HTHP) can also be adopted.

[0061] Application of the diamond-metal composite material with six-sided metal coating described in the embodiment of the present application in manufacturing a heat dissipation substrate for electronic devices. For example, it is used on various servers for IGBT heat dissipation, chip heat dissipation, etc. It can also be applied to technical fields with requirements for high thermal conductivity and high-strength materials. For example, in the field of high heat flux density electronic device processing, it can be used for liquid cooling of AI servers, GPU clusters, and cloud computing and big data centers, as well as manufacturing devices such as 5G / 6G base station GaN radio frequency chips and electric vehicle SiC inverter modules; in the field of high-energy laser systems, it is used to manufacture fiber laser pump couplers and solid laser crystal heat sinks; in the field of nuclear energy and fusion devices, it is used to manufacture divertor targets and plasma first walls of nuclear fusion reactors; in the field of special power and energy equipment, it is used to manufacture IGBT modules of electromagnetic catapult systems and contacts of high-voltage DC circuit breakers; in the field of aerospace, it is used for the beam spot area of the electron beam focusing system and the periphery of the metal 3D printing laser melt pool; in the field of quantum and superconductivity, it is used to manufacture superconducting quantum bit microwave resonators and room-temperature superconducting power line joints.

[0062] The embodiment of the present application also provides a heat dissipation substrate for an electronic device, which comprises a composite plate sintered by a hexahedral metal shell and at least one diamond-metal composite layer placed in the metal shell; the diamond-metal composite layer comprises a metal mesh and diamond particles with a coating on the surface, the diamond particles are arranged in the meshes of the metal mesh, and metal powder is filled in the gaps between the meshes and the diamond particles; metal atoms in the metal mesh diffuse through the coating to the surface of the diamond to form a mixed transition zone.

[0063] The following are some embodiments listed in the present application, and the present application will be further described through the following embodiments.

[0064] Embodiment 1

[0065] This embodiment provides a diamond-copper composite material with copper coated on six sides, which is a composite material sintered by a hexahedral copper foil shell and at least one diamond-copper composite layer placed in the copper foil shell; the diamond-copper composite layer comprises a copper mesh and diamond particles with a coating on the surface, the diamond particles are arranged in the meshes of the copper mesh, and copper powder is filled in the gaps between the meshes and the diamond particles; Cu atoms in the copper mesh diffuse through the coating to the surface of the diamond to form a mixed transition zone.

[0066] As Figure 4 shown, the processing process of the diamond / copper composite material with copper coated on six sides specifically comprises the following steps: (1) Punch out the shape of the unfolded diagram of a hexahedron on a copper foil with a thickness of 250 μm, and reserve creases at the edges; bond the edges of the copper foil with the shape of the unfolded diagram with a metal bonding adhesive to form a copper foil box body with an upper cover and an open upper surface; place the copper foil box body with an open upper surface into a graphite mold; (2) Adopt a copper mesh with a regular hexahedron mesh for placing diamond particles, the wall thickness of the mesh is 15 μm, the edge length of the regular hexahedron is 15 μm larger than the particle size of the placed diamond particles, the plane size of the copper mesh is the same as the inner bottom surface of the copper foil box body, and then place the copper mesh into the copper foil box body; (3) Use an arrangement machine to arrange artificial CVD diamond particles with a 0.5 μm Ti coating on the surface in each mesh of the copper mesh, and the particle size of the diamond particles is 300 μm; (4) The copper foil box body arranged with diamond and the graphite mold are placed on a mechanical vibration table. The vibration frequency of the vibration table is turned on to be 10 Hz, the vibration time is 10 min, and the amplitude is controlled to be 0.2 mm; the copper powder is a mixed copper powder mixed with nano-Al2O3. Among them, the dosage of nano-Al2O3 accounts for 0.5 wt% of the weight of the copper powder, and the particle size of the copper powder is 3 μm; the electrostatic spraying technology is used to apply an electric field to make the copper powder directionally fill the grid gaps on the copper mesh until the mixed copper powder fills the entire height of the copper mesh, and the electric field voltage is 5 kV; (5) Place the second layer of copper mesh and repeat the above steps (3) and (4); (6) After four layers are stacked, the copper mesh is flush with the height of the copper foil box body, and then the copper foil on the upper surface is covered and bonded to obtain a preform; (7) The obtained preform is subjected to vacuum hot pressing and sintering. The vacuum degree in the furnace is 1 Pa, the hot pressing pressure is 35 MPa, the sintering temperature is 900 °C, and the time is 60 min; a sintered blank formed composite material is obtained; (8) The sintered composite material is polished on the surface to obtain a diamond-copper composite material with copper covered on six sides.

[0067] The performance of the diamond / copper composite material with copper covered on six sides described in Example 1 is detected. The standards, detection items, and performance results for the detection are shown in Table 1.

[0068] Use SEM to observe the microstructure of the cross-section of the composite material, statistically calculate the area ratio of diamond particles through an image analysis software (ImageJ), and calculate the volume by combining the particle size distribution to determine the diamond volume fraction.

[0069] The method for measuring the density is as follows: After the cross-section of the specimen is ground and polished, observe the pore distribution under a microscope, and calculate the area ratio of pores through the grid counting method; after the sample is cut, inlaid, polished, and corroded with 4% nitric acid alcohol, take a cross-sectional image and calculate the area ratio of pores with software (ImageJ); the density D = 1 - the area ratio of pores.

[0070] Table 1: Performance test results of Example 1

[0071] On the basis of the above Example 1, further, without changing the diamond particle size, explore the influence of the gap size between the grid and the diamond particle size on the performance of the diamond / copper composite material with copper covered on six sides. Use the difference between the grid edge length and the diamond particle size as the investigation condition, and other conditions are the same as those in Example 1. The specific comparison results are shown in Table 2.

[0072] Table 2: Influence of the gap size between the grid and the diamond particle size on the performance of the composite material

[0073] The results in Table 2 show that as the particle size difference increases (the voids increase), the thermal conductivity first increases and then decreases. The interfacial bonding between diamond and copper matrix is improved, the interfacial thermal resistance is reduced, and the heat conduction efficiency is enhanced. However, when the particle size difference exceeds 15 μm, the increase in voids leads to an increase in interfacial defects and enhanced phonon scattering, resulting in a decrease in thermal conductivity. As the particle size difference increases, the filling efficiency of diamond particles decreases, the porosity increases, and the volume fraction of diamond continuously decreases. The relative density first increases and then decreases with the increase of the particle size difference. During the sintering process with a small particle size difference, the pores are more fully filled with copper. However, the increase in voids will lead to difficulties in sintering densification and a decrease in relative density. As the particle size difference increases, the coefficient of thermal expansion shows an upward trend, which is significantly related to the fact that the increase in voids weakens the bonding of the copper-diamond interface and the thermal expansion of the copper matrix dominates. Therefore, according to the performance results in Table 2, in the embodiments of the present application, the edge length L of the control grid is 10 - 20 μm larger than the particle size D of a single diamond particle, and a diamond / copper composite material with six-sided copper coating and performance meeting the application requirements is obtained. Preferably, when the edge length L of the control grid is 10 - 15 μm larger than the particle size D of a single diamond particle, the thermal conductivity, relative density, and coefficient of thermal expansion all show excellent performance.

[0074] On the basis of the above Embodiment 1, the influence of the particle size of diamond particles on the performance of the diamond / copper composite material with six-sided copper coating was further explored. Diamond particles with different particle sizes were selected, and other conditions were the same as those in Embodiment 1. The specific comparison results are shown in Table 3.

[0075] Table 3: Influence of Diamond Particle Size on the Performance of Diamond / Copper Composite Material with Six-Sided Copper Coating

[0076] Table 3 shows the changes in the thermal conductivity, diamond volume fraction, relative density, and coefficient of thermal expansion of the diamond / copper composite material with six-sided copper coating under different diamond particle sizes. The data in Table 3 show that when the diamond particle size increases to 250 μm, the thermal conductivity reaches the peak value (890 W·m -1 ·K -1 ), but when the particle size further increases to 300 μm, the thermal conductivity slightly decreases; this may be related to the fact that larger particles reduce the number of interfaces, resulting in a decrease in interfacial thermal resistance. Both the diamond volume fraction and the relative density increase significantly with the increase of the particle size. Diamond particles with appropriate particle sizes not only occupy more volume themselves but also promote the densification sintering of the composite material and reduce the porosity. The coefficient of thermal expansion is negatively correlated with the diamond particle size. When the particle size increases from 100 μm to 300 μm, the coefficient of thermal expansion decreases from 7.1 ppm·K -1 to 6.0 ppm·K -1, which indicates that larger diamond particles have a stronger constraining effect on the thermal expansion of the copper matrix, effectively restricting the macroscopic thermal expansion of the composite material. Preferably, in the embodiments of the present application, when the particle size of the diamond particles is in the range of 200-250 μm, comprehensive optimization of the thermal conductivity, density and coefficient of thermal expansion can be achieved.

[0077] On the basis of the above-mentioned Embodiment 1, the influence of vibration conditions on the properties of the diamond / copper composite material with copper-coated on six sides was further explored. Different vibration conditions were selected, and other conditions were the same as those in Embodiment 1. The specific comparison results are shown in Table 4.

[0078] Table 4: Influence of vibration conditions on the properties of diamond / copper composite material with copper-coated on six sides

[0079] Table 4 shows the changes in the thermal conductivity, diamond volume fraction, density and coefficient of thermal expansion of the composite material under different vibration frequencies and vibration times. According to the data in Table 4, an increase in the vibration frequency is beneficial to improving the thermal conductivity, diamond volume fraction and density, while significantly reducing the coefficient of thermal expansion. When the vibration frequency continues to increase, although the thermal conductivity can still be improved, it may have an adverse effect on the diamond volume fraction and density, and the effect of reducing the coefficient of thermal expansion weakens. Therefore, in the present application, the vibration frequency is controlled to be 2-10 Hz. Under low-frequency vibration, appropriately extending the vibration time can further improve the material properties; however, excessive vibration should be avoided to prevent introducing new defects or causing uneven particle distribution.

[0080] On the basis of the above-mentioned Embodiment 1, the influence of the vacuum sintering temperature on the properties of the diamond / copper composite material with copper-coated on six sides was further explored. The vacuum sintering temperature was selected, and other conditions were the same as those in Embodiment 1. The specific comparison results are shown in Table 5.

[0081] Table 5: Influence of vacuum sintering temperature on the properties of diamond / copper composite material with copper-coated on six sides

[0082] The data in Table 5 show that when the vacuum sintering temperature is 900 °C, the thermal conductivity reaches the peak value (868 W·m -1 ·K -1 ). Subsequently, when the temperature rises to 920 °C and 950 °C, the thermal conductivity drops to 815 W·m -1 ·K -1 and 743 W·m -1 ·K -1This indicates that the optimal sintering temperature range is 850 - 900 °C. Regarding the influence on the diamond volume fraction, the volume fraction drops to 60.3% at a sintering temperature of 950 °C, which may be related to the loss of diamond particles due to the diamond - copper interface reaction at high temperatures. The density reaches its peak (99.5%) at a sintering temperature of 900 °C, but slightly decreases to 98.6% at 950 °C, indicating that over - sintering may cause deterioration of the microstructure. The influence of the sintering temperature on the coefficient of thermal expansion shows that as the sintering temperature increases, the coefficient of thermal expansion first decreases and then increases. In the embodiments of the present application, by controlling the sintering temperature within the range of 850 - 920 °C, comprehensive optimization of the thermal conductivity, density, and coefficient of thermal expansion can be achieved. Preferably, controlling the vacuum sintering temperature at 850 - 900 °C can balance the thermal conductivity, density, and coefficient of thermal expansion.

[0083] On the basis of the above - mentioned Example 1, the influence of the hot - pressing pressure on the properties of the diamond / copper composite material with copper - coated six - sides during vacuum sintering was further explored. Different hot - pressing pressures were selected while other conditions were the same as those in Example 1. The specific comparison results are shown in Table 6.

[0084] Table 6: Influence of Hot - Pressing Pressure on the Properties of Diamond / Copper Composite Material with Copper - Coated Six - Sides

[0085] The data in Table 6 show that the thermal conductivity, diamond volume fraction, and density all reach their peaks at 25 MPa, and the coefficient of thermal expansion reaches its lowest value of 6.0 ppm·K at 25 MPa. -1 The significant influence of the hot - pressing pressure on the properties of the diamond / copper composite material with copper - coated six - sides is mainly reflected in three aspects: interface bonding, particle crushing, and densification behavior. By controlling the hot - pressing pressure within the range of 20 - 30 MPa, comprehensive optimization of the thermal conductivity, density, and coefficient of thermal expansion can be achieved. Preferably, when the hot - pressing pressure is selected within the range of 20 - 30 MPa, the balance of the thermal conductivity, density, and coefficient of thermal expansion is excellent.

[0086] On the basis of the above - mentioned Example 1, the influence of the copper powder composition on the properties of the diamond / copper composite material with copper - coated six - sides during vacuum sintering was further explored. Different copper powder compositions were selected while other conditions were the same as those in Example 1. The specific comparison results are shown in Table 7.

[0087] Table 7: Influence of Copper Powder Composition on the Properties of Diamond / Copper Composite Material with Copper - Coated Six - Sides

[0088] Table 7 shows that, compared with pure copper powder, the thermal conductivity, diamond volume fraction, and density of the composite materials added with Al2O3 or Al2O3 + graphene are significantly improved, while the coefficient of thermal expansion is significantly reduced. It can be seen that Al2O3 and graphene as reinforcement phases can significantly improve the thermal conductivity and diamond volume fraction of the composite materials. In the embodiments of the present application, by adding appropriate amounts of reinforcement phases such as Al2O3 and graphene, the thermal conductivity, diamond volume fraction, and density of the composite materials can be significantly improved, while the coefficient of thermal expansion is reduced. Among them, the composition of copper powder + 0.2wt% Al2O3 + 0.2wt% graphene exhibits the best comprehensive performance and is an ideal choice for preparing high-performance six-sided copper-clad diamond / copper composite materials.

[0089] Example 2

[0090] This embodiment provides a six-sided copper-clad diamond / copper composite material, which is a composite material sintered from a hexahedral metal shell and at least one layer of diamond-copper composite layer placed in the metal shell; the diamond-copper composite layer includes a copper mesh and diamond particles coated with a coating on the surface, the diamond particles are arranged in the meshes of the copper mesh, and copper powder is filled in the gaps between the meshes and the diamond particles; Cu atoms in the copper mesh diffuse through the coating to the surface of the diamond to form a mixed transition zone.

[0091] The processing technology of the six-sided copper-clad diamond / copper composite material specifically includes the following steps: (1) Stamp out the shape of the unfolded diagram of a hexahedron on a copper foil with a thickness of 350 μm, and reserve creases at the edges; bond the edges of the copper foil with the shape of the unfolded diagram with a metal adhesive to form a copper foil box body with an upper cover and an open upper surface; place the copper foil box body with an open upper surface into a graphite mold; (2) Use a copper mesh with a regular hexahedron mesh to place diamond particles, the mesh wall thickness is 20 μm, the edge length of the regular hexahedron is 20 μm larger than the particle size of the placed diamond particles, the plane size of the copper mesh is the same as the inner bottom surface of the copper foil box body, and then place the copper mesh into the copper foil box body; (3) Use an arrangement machine to arrange artificial CVD diamond particles with a Ti and Cr composite coating on the surface in each mesh of the copper mesh, the coating thickness is 0.3 μm, and the particle size of the diamond particles is 500 μm; (4) The metal box body arranged with diamond and the graphite mold are placed on a mechanical vibration table. The vibration frequency of the vibration table is turned on to be 5 Hz, the vibration time is 15 min, and the amplitude is controlled to be 0.5 mm; the copper powder is a mixed copper powder mixed with nano-Al2O3. Among them, the dosage of nano-Al2O3 accounts for 1.0 wt% of the weight of the copper powder, and the particle size of the copper powder is 3 μm; the electrostatic spraying technology is used to apply an electric field to make the copper powder directionally fill the grid gaps of the copper mesh until the mixed copper powder fills the entire height of the copper mesh, and the electric field voltage is 5 kV; (5) Place the second layer of copper mesh and repeat the above steps (3) and (4); (6) After three layers are stacked, the copper mesh is flush with the height of the metal box body, and then the copper foil on the upper surface is covered and bonded to obtain a preform; (7) The obtained preform is subjected to a sintering method, including, Pre-sintering: Pulse current-assisted sintering is adopted, the sintering temperature is 820 °C, the pressure is 25 MPa, the time is 15 min, and a 500 A pulse current is superimposed, and the frequency is 5 Hz; Final sintering: Hot pressing sintering combined with hydrogen atmosphere control is adopted, the sintering temperature is 900 °C, the pressure is 35 MPa, and the sintering time is 50 min; the oxygen content in the H2 atmosphere ≤ 10 ppm; (8) The sintered composite material is polished on the surface to obtain a diamond / copper composite material with copper-coated on six sides.

[0092] The performance of the diamond / copper composite material with copper-coated on six sides described in Example 2 is detected. The standards, detection items, and performance results for the detection are shown in Table 1.

[0093] Table 8: Performance detection results of Example 2

[0094] On the basis of the above Example 2, the influence of the pre-sintering and final sintering temperatures on the performance of the diamond / copper composite material with copper-coated on six sides is further explored. Different pre-sintering and final sintering temperatures are selected, and other conditions are the same as those in Example 2. The specific comparison results are shown in Table 9.

[0095] Table 9: Influence of pre-sintering and final sintering temperatures on the performance of the diamond / copper composite material with copper-coated on six sides

[0096] The results in Table 9 show that the final sintering temperature is the key factor determining the material properties, while the pre-sintering temperature has a synergistic effect on the final properties by influencing the initial microstructure. In the embodiments of the present application, by optimizing the sintering temperature regime (pre-sintering at 820°C + final sintering at 900°C), the best balance among the thermal conductivity, diamond volume fraction, and coefficient of thermal expansion can be achieved. A final sintering temperature higher than 900°C may lead to diamond graphitization and interface deterioration, and performance compensation needs to be carried out through process optimization (such as atmosphere protection and post-treatment).

[0097] Comparative Example 1

[0098] This embodiment provides a diamond / copper composite material with copper-coated on six sides. The difference from Example 1 is that in step (4), instead of using vibration to fill copper powder, copper foils with a thickness of 15 μm are placed between each layer of copper mesh.

[0099] According to the detection method of Example 1, the performance of the diamond / copper composite material with copper-coated on six sides in this Comparative Example 1 was detected. The results are shown in Table 10.

[0100] Table 10: Performance detection results of Comparative Example 1

[0101] Example 3

[0102] This embodiment provides a diamond-aluminum composite material with aluminum-coated on six sides, which is a composite material sintered from a hexahedral aluminum foil shell and at least one layer of diamond-aluminum composite layer placed in the aluminum foil shell; the diamond-aluminum composite layer includes an aluminum mesh and diamond particles coated with a coating, the diamond particles are arranged in the meshes of the aluminum mesh, and aluminum powder is filled in the gaps between the meshes and the diamond particles; Cu atoms in the aluminum mesh diffuse through the coating to the surface of the diamond to form a mixed transition zone.

[0103] The processing technology of the diamond-aluminum composite material with aluminum-coated on six sides specifically includes the following steps: (1) Punch out the developed shape of a hexahedron on an aluminum foil with a thickness of 250 μm, and reserve creases at the edges; bond the edges of the aluminum foil with the developed shape using a metal adhesive to form an aluminum foil box body with an upper cover and an open upper surface; place the aluminum foil box body with an open upper surface into a graphite mold; (2) Use an aluminum mesh with a regular hexahedron mesh for placing diamond particles, the mesh wall thickness is 15 μm, the edge length of the regular hexahedron is 15 μm larger than the particle size of the placed diamond particles, the plane size of the aluminum mesh is the same as the inner bottom surface of the aluminum foil box body, and then place the aluminum mesh into the aluminum foil box body; (3) Use an arrangement machine to arrange artificial CVD diamond particles with a 0.5-μm Ti coating on the surface in each grid of the aluminum mesh. The particle size of the diamond particles is 300 μm. (4) Place the aluminum foil box body with arranged diamonds and the graphite mold on a mechanical vibrating table. Turn on the vibrating table with a vibration frequency of 10 Hz, a vibration time of 10 min, and an amplitude controlled at 0.2 mm. Apply an electric field using electrostatic spraying technology to direct the filling of aluminum powder into the grid gaps of the aluminum mesh until the mixed aluminum powder fills the entire height of the aluminum mesh. The electric field voltage is 5 kV. (5) Place the second layer of aluminum mesh and repeat steps (3) and (4) above. (6) After three layers are stacked, the aluminum mesh is flush with the height of the aluminum foil box body. Then cover and bond the aluminum foil on the upper surface to obtain a preform. (7) Subject the obtained preform to vacuum hot pressing sintering. Use segmented sintering, including: Pre-sintering: Use pulse current-assisted sintering. The sintering temperature is 520 °C, the pressure is 20 MPa, the time is 10 min, and a 500-A pulse current is superimposed. Final sintering: Use hot pressing sintering combined with hydrogen atmosphere control. The sintering temperature is 600 °C, the pressure is 30 MPa, and the sintering time is 60 min. The oxygen content in the H2 atmosphere ≤ 10 ppm. Obtain a sintered blank-shaped composite material. (8) Polish the surface of the sintered composite material to obtain a diamond-aluminum composite material with aluminum-coated six sides.

[0104] Detect the performance of the diamond-aluminum composite material with aluminum-coated six sides described in Example 3. The standards, detection items, and performance results for the detection are shown in Table 11.

[0105] Use SEM to observe the microstructure of the cross-section of the composite material. Statistically calculate the area ratio of diamond particles through an image analysis software (ImageJ), and calculate the volume by combining the particle size distribution to determine the diamond volume fraction.

[0106] The method for measuring the density is as follows: After grinding and polishing the cross-section of the specimen, observe the pore distribution under a microscope and calculate the area ratio of pores through the grid counting method; after cutting, embedding, and polishing the sample, corrode it with 4% nitric acid alcohol, take a cross-section image, and calculate the area ratio of pores with software (ImageJ); the density D = 1 - the area ratio of pores.

[0107] Table 11: Performance test results of Example 3

[0108] Example 4

[0109] This embodiment provides a diamond-aluminum composite material with aluminum coating on six sides, which is a composite material sintered from a hexahedral aluminum foil shell and at least one layer of diamond-aluminum composite layer placed in the aluminum foil shell; the diamond-aluminum composite layer includes an aluminum mesh and diamond particles coated with a coating on the surface, the diamond particles are arranged in the meshes of the aluminum mesh, and aluminum powder is filled in the gaps between the meshes and the diamond particles; Cu atoms in the aluminum mesh diffuse through the coating to the surface of the diamond to form a mixed transition zone.

[0110] The processing technology of the diamond-aluminum composite material with aluminum coating on six sides specifically includes the following steps: (1) Stamp out the shape of the unfolded drawing of a hexahedron on an aluminum foil with a thickness of 250 μm, and reserve creases at the edges; bond the edges of the aluminum foil with the shape of the unfolded drawing with a metal bonding adhesive to form an aluminum foil box body with an upper cover and an open upper surface; place the aluminum foil box body with an open upper surface into a graphite mold; (2) Use an aluminum mesh with a regular hexahedron mesh to place diamond particles, the wall thickness of the mesh is 10 μm, the edge length of the regular hexahedron is 20 μm larger than the particle size of the placed diamond particles, the plane size of the aluminum mesh is the same as the inner bottom surface of the aluminum foil box body, and then place the aluminum mesh into the aluminum foil box body; (3) Use an arrangement machine to arrange artificial CVD diamond particles with a 0.5 μm Cr coating on the surface in each mesh of the aluminum mesh, and the particle size of the diamond particles is 300 μm; (4) Place the aluminum foil box body with arranged diamonds and the graphite mold on a mechanical vibration table, turn on the vibration table with a vibration frequency of 5 Hz, a vibration time of 20 min, and an amplitude controlled at 0.5 mm; use electrostatic spraying technology to apply an electric field to direct the filling of aluminum powder into the mesh gaps of the aluminum mesh until the mixed aluminum powder fills the entire height of the aluminum mesh, and the electric field voltage is 10 kV; (5) Place the second layer of aluminum mesh and repeat the above steps (3) and (4); (6) After four layers are stacked, the aluminum mesh is flush with the height of the aluminum foil box body, and then cover and bond the aluminum foil on the upper surface to obtain a preform; (7) Perform vacuum hot pressing sintering on the preform, using segmented sintering, including, Pre-sintering: Use pulse current-assisted sintering, the sintering temperature is 550 °C, the pressure is 25 MPa, the time is 15 min, and an 800 A pulse current is superimposed; Final sintering: Use hot pressing sintering combined with hydrogen atmosphere control, the sintering temperature is 650 °C, the pressure is 35 MPa, the sintering time is 40 min; the oxygen content in the H2 atmosphere ≤ 10 ppm; obtain a sintered and formed composite material; (8) Polish the surface of the sintered composite material to obtain a diamond-aluminum composite material with aluminum coating on six sides.

[0111] The performance of the diamond-aluminum composite material with aluminum coating on six sides described in Example 4 was detected. The standards, detection items and performance results for the detection are shown in Table 12.

[0112] The SEM was used to observe the microstructure of the cross-section of the composite material. The area ratio of diamond particles was statistically analyzed by an image analysis software (ImageJ), and the diamond volume fraction was determined by combining the particle size distribution calculation volume.

[0113] The method for measuring the density is as follows: After the cross-section of the specimen is ground and polished, the pore distribution is observed under a microscope, and the area ratio of pores is calculated by the grid counting method; after the sample is cut, inlaid, polished and corroded with 4% nitric acid alcohol, the cross-section image is taken, and the area ratio of pores is calculated by software (ImageJ); the density D = 1 - the area ratio of pores.

[0114] Table 12: Performance detection results of Example 4

[0115] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention cannot be limited thereby. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the protection scope required by the present invention.

Claims

1. A diamond-metal composite material with six-sided metal coating, characterized in that, It is a composite material sintered from a hexahedral metal shell and at least one diamond-metal composite layer placed in the metal shell; the diamond-metal composite layer includes a metal mesh and diamond particles coated with a coating, the diamond particles are arranged in the meshes of the metal mesh, and the voids between the meshes and the diamond particles are filled with metal powder; metal atoms in the metal mesh diffuse through the coating to the diamond surface to form a mixed transition zone.

2. The diamond-metal composite material with six-sided metal coating according to claim 1, characterized in that, The mesh is a regular hexahedron structure or a honeycomb structure of a regular octahedron, the wall thickness of the mesh is 10-20 μm, and the edge length L of the mesh is 10-20 μm larger than the particle size D of a single diamond particle.

3. The diamond-metal composite material with six-sided metal coating according to claim 2, characterized in that, The diamond is one or more of artificial high-temperature high-pressure diamond, artificial CVD diamond or natural diamond, and the particle size of the diamond particles is 100-1000 μm.

4. The diamond-metal composite material with six-sided metal coating according to claim 1, characterized in that, The mixed transition zone is a ternary phase formed by metal-coating material-C, and its thickness is 1-2 μm.

5. The diamond-metal composite material with six-sided metal coating according to claim 1, characterized in that, The coating is a coating formed by one of the materials Ti, Cr, W, V, Zr or a composite coating formed by two or more materials; the thickness of the coating is 0.1-0.5 μm.

6. The diamond-metal composite material with six-sided metal coating according to any one of claims 1-5, characterized in that, The metal shell is an aluminum foil shell, and the materials of the metal mesh and the metal powder are both aluminum; there is an aluminum oxide nano-layer with a thickness of 3-8 nm at the bonding interface between the aluminum foil shell and the diamond.

7. The diamond-metal composite material with six-sided metal coating according to any one of claims 1-5, characterized in that, The metal shell is a copper foil shell, and the materials of the metal mesh and the metal powder are both copper; the surface of the copper foil shell is a nanocrystalline copper layer with a grain size of 50-100 nm; the inside is a coarse-grained copper matrix with a grain size of 5-10 μm.

8. A processing method of a diamond-metal composite material with six-sided metal coating as described in any one of claims 1-7, characterized in that, It includes the following steps Manufacture a hexahedral metal box body: Stamp and fold a metal sheet into a hexahedral metal box body with an upper cover and an opening, and place it in a mold; Select a metal mesh: Adopt a metal mesh with uniform meshes, and the size of the metal mesh is the same as the inner bottom surface size of the hexahedral metal box body; lay the metal mesh in the above-mentioned hexahedral metal box body; Arrange diamond particles: Use an arranging machine to arrange diamond particles coated with a coating in each mesh of the metal mesh; Void filling: Place the hexahedral metal box body with arranged diamond particles and the mold on a vibrating table, and spray metal powder of the same material as the metal mesh on the metal mesh in a vibrating mode until the metal powder fills the voids of the metal mesh and reaches the same height as the metal mesh; Multi-layer stacking: After the void filling step, place a metal mesh in the hexahedral metal box body, repeat the steps of arranging diamond particles and void filling until the metal mesh is flush with the height of the hexahedral metal box body, cover the upper cover at the opening, and integrate the upper cover with the metal box body to obtain a preform; Sintering and forming: Place the above-mentioned preform in a sintering furnace for sintering to obtain a sintered composite material.

9. The processing method according to claim 8, characterized in that, When manufacturing the hexahedral metal box body, first cut out the unfolded pattern of the hexahedron, and reserve creases at the edges; fold along the edges to form a hexahedral box, and connect the edges with a metal adhesive.

10. According to the processing method described in claim 8, when manufacturing a hexahedral metal box body, it is laser cut or wire cut into the unfolded graph of a hexahedron, and creases are pre-etched at the edges; after folding along the edges, local welding is performed at the edge joints to combine adjacent edges.

11. The processing method according to claim 10, wherein, The mesh of the metal mesh is a regular hexahedron structure or a regular octahedron honeycomb structure, and the edge length L of the mesh is 10 - 20 μm larger than the particle size D of a single diamond particle.

12. The processing method according to claim 8, characterized in that, The vibrating table is a mechanical vibrating table, with a vibration frequency of 2 - 10 Hz, a vibration time of 5 - 20 min, and an amplitude of 0.2 - 0.5 mm.

13. The processing method according to claim 12, wherein, When filling the voids, an electrostatic spraying technique is used to apply an electric field to direct the metal powder to fill the mesh gaps, and the electric field voltage is 5 - 10 kV.

14. The processing method according to claim 8, wherein, The metal shell is a copper foil shell, the metal mesh is a copper mesh, and the metal powder used to fill the voids is pure copper powder or a mixed copper powder mixed with active ingredients; the particle size of the copper powder is 0.5 - 5 μm.

15. The processing method according to claim 14, wherein The active ingredient is one or a mixture of two or more of nano - Al2O3, nano - SiC, nano - TiC, nano - Y2O3, and nano - graphene, and the dosage of the active ingredient accounts for 0.1 - 1.0 wt% of the weight of the copper powder.

16. The processing method according to claim 14, characterized in that, The sintering and forming is carried out by vacuum hot - pressing sintering, the vacuum degree in the furnace is < 10 Pa, the hot - pressing pressure is 20 - 40 MPa, the sintering temperature is 850 - 920 °C, and the time is 55 - 65 min.

17. The processing method according to claim 14, characterized in that, The sintering and forming adopts step - by - step sintering, including, Pre - sintering: Pulse - current - assisted sintering is adopted, the sintering temperature is 820 - 850 °C, the pressure is 20 - 30 MPa, the time is 10 - 20 min, a 100 - 1000 A pulse current is superimposed, and the frequency is 1 - 10 Hz; Final sintering: Hot - pressing sintering combined with hydrogen atmosphere control is adopted, the sintering temperature is 880 - 900 °C, the pressure is 30 - 40 MPa, the sintering time is 30 - 60 min; the oxygen content in the H2 atmosphere is ≤ 10 ppm.

18. The processing method according to claim 8, characterized in that, The metal shell is an aluminum foil shell, the metal mesh is an aluminum mesh, and the metal powder used to fill the voids is aluminum powder; the particle size of the aluminum powder is 0.5 - 5 μm.

19. The processing method according to claim 18, wherein The sintering and forming adopts step - by - step sintering, including, Pre - sintering: Pulse - current - assisted sintering is adopted, the sintering temperature is 520 - 550 °C, the pressure is 20 - 30 MPa, the time is 10 - 20 min, and a 500 - 3000 A pulse current is superimposed; Final sintering: Hot - pressing sintering combined with hydrogen atmosphere control is adopted, the sintering temperature is 600 - 650 °C, the pressure is 30 - 40 MPa, the sintering time is 30 - 60 min; the oxygen content in the H2 atmosphere is ≤ 10 ppm.

20. The processing method according to claim 8, wherein, It also includes the step of surface polishing treatment for the sintered and formed composite material.

21. Application of the diamond - metal composite material with six - sided metal coating as described in any one of claims 1 - 7 in manufacturing an electronic device heat dissipation component.

22. A heat dissipation substrate for an electronic device, characterized in that, A composite plate is included, which is sintered by a hexahedral metal outer shell and at least one diamond-metal composite layer disposed in the metal outer shell; the diamond-metal composite layer includes a metal mesh and diamond particles with a coating on the surface, the diamond particles are arranged in the meshes of the metal mesh, and metal powder is filled in the gaps between the meshes and the diamond particles; metal atoms in the metal mesh diffuse through the coating to the diamond surface to form a mixed transition zone.

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