High-thermal-conductivity diamond / copper composite material and preparation method thereof

Abstract

The application discloses a high-thermal-conductivity diamond / copper composite material and a preparation method thereof. A gradient SiC / C composite layer is first deposited on the surface of diamond particles, in which the content of C increases and the content of silicon decreases from inside to outside, and then a metal composite layer is arranged on the surface of the gradient SiC / C composite layer to obtain diamond particles containing a composite interface layer. Then, the diamond particles containing the composite interface layer are uniformly mixed with copper powder to obtain a mixture, the mixture is placed in a mold and subjected to magnetization treatment, and then the mixture is pressed to form a diamond preform. Finally, the diamond preform is infiltrated with copper liquid. The application fundamentally improves the interface bonding between the diamond and the copper, greatly reduces the interface thermal resistance, and the prepared composite material has super-high thermal conductivity, high strength and adjustable thermal expansion coefficient, and is particularly suitable for high-end electronic packaging and heat dissipation fields.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composites technology, specifically to a diamond / copper composite material with high thermal conductivity and its preparation method. Background Technology

[0002] Diamond / copper composites, possessing both the extremely high thermal conductivity of diamond and the excellent processability and matching coefficients of thermal expansion of copper, have become key materials for heat dissipation in next-generation high-power devices. However, existing preparation techniques, such as powder metallurgy, melt infiltration, and pressure impregnation, generally suffer from the following bottlenecks: First, poor interfacial bonding: the high interfacial energy and extremely poor wettability between diamond and copper result in huge interfacial thermal resistance, becoming a major obstacle to heat transfer; second, limitations of traditional modification methods: existing technologies typically involve coating the diamond surface with a single layer of metal such as W, Mo, Cr, or carbide-forming elements, but the physical properties of a single coating layer and copper, such as the coefficient of thermal expansion, still exhibit abrupt changes, leading to interfacial stress concentration and easy failure under thermal cycling, and both excessively thick and thin carbide layers are detrimental to thermal conductivity; third, insufficient optimization of composite material density and thermal conductivity network: simple mixing makes it difficult to achieve the optimal spatial distribution of diamond particles, failing to construct an efficient continuous thermal conductivity pathway.

[0003] Therefore, developing a preparation method that can achieve strong interfacial bonding, low interfacial thermal resistance, and controllable process is a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the first objective of this invention is to provide a method for preparing a high thermal conductivity diamond / copper composite material. This method first involves synergistic surface modification of diamond particles using a gradient SiC / C composite layer and a metal composite layer, creating a reinforced interface with a smooth transition in composition and properties. Then, a three-dimensional ordered thermally conductive framework is constructed through magnetic field-induced directional alignment. Finally, a two-step pressure-assisted melting process is used to achieve complete densification of the composite material. This invention fundamentally improves the interfacial bonding between diamond and copper by constructing a multi-scale gradient interface and a three-dimensional interpenetrating thermal network, significantly reducing interfacial thermal resistance. The prepared composite material possesses ultra-high thermal conductivity, high strength, and an adjustable coefficient of thermal expansion, making it particularly suitable for high-end electronic packaging and heat dissipation applications.

[0005] The second objective of this invention is to provide a diamond / copper composite material with high thermal conductivity prepared by the above-described preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention discloses a method for preparing a high thermal conductivity diamond / copper composite material. First, a gradient SiC / C composite layer is deposited on the surface of diamond particles. Then, a metal composite layer is set on the surface of the gradient SiC / C composite layer to obtain diamond particles containing a composite interface layer. Next, the diamond particles containing the composite interface layer are mixed evenly with copper powder to obtain a mixture. The mixture is placed in a mold and magnetized. Then, it is pressed and molded to obtain a diamond preform. Finally, copper liquid is melt-infiltrated into the diamond preform to obtain the final product.

[0008] In the gradient SiC / C composite layer, the C content increases and the silicon content decreases from the inside to the outside.

[0009] The metal composite layer consists of a bottom layer and a top layer. The metal in the bottom layer is selected from one of tungsten, molybdenum, titanium, chromium, zirconium, tantalum, and niobium. The metal in the top layer is a composite of one of copper, aluminum, silver, magnesium, and tin and one of nickel, cobalt, and iron.

[0010] The method for preparing diamond / copper composite material provided by this invention first deposits a gradient SiC / C composite layer on the surface of diamond particles. From the inside out, the carbon ratio increases while the silicon ratio decreases, achieving a smooth transition in chemical composition and modulus from diamond to the outer metal layer. Then, a metal composite layer is deposited on top of the gradient SiC / C composite layer. The bottom metal layer forms a good bond with SiC and exhibits good miscibility with the top metal layer. The top metal layer contains copper, aluminum, silver, magnesium, and tin, which can undergo in-situ metallurgical bonding with molten copper, thus constructing a reinforced interface with a smooth transition in composition and properties. Furthermore, the top layer of the metal composite layer also contains magnetic over-plated metal. By magnetizing the mixture, the diamond particles with the composite interface layer are oriented in a specific direction in a magnetic field, constructing a three-dimensional ordered thermally conductive framework. This method fundamentally improves the interfacial bonding between diamond and copper, significantly reducing interfacial thermal resistance. The prepared composite material possesses ultra-high thermal conductivity, high strength, and an adjustable coefficient of thermal expansion, making it particularly suitable for high-end electronic packaging and heat dissipation applications.

[0011] In a preferred embodiment, the diamond particles are single-crystal diamond particles with a room temperature thermal conductivity ≥1800W / m·K.

[0012] In this invention, the diamond used is preferably a high thermal conductivity synthetic single crystal diamond particle.

[0013] In a preferred embodiment, the diamond particles adopt a bimodal or trimodal particle size distribution.

[0014] Experiments have shown that combining magnetic field orientation with particle gradation, with coarse particles forming the main skeleton and oriented along the magnetic field direction to form a continuous heat-conducting backbone, and fine particles filling the gaps between coarse particles, not only increases the packing density but also constructs more interconnected heat-conducting bypasses at the microscopic level, thus forming a three-dimensional interpenetrating heat-conducting network from the micrometer to the millimeter scale, maximizing the efficiency of the heat conduction pathway.

[0015] This invention uses magnetic field orientation to align diamond particles of a specific shape along the direction of heat flow, thus constructing a directional heat conduction channel. If only magnetic field orientation is performed without particle size distribution, the gaps between coarse particles cannot be effectively filled by fine particles, resulting in uneven porosity distribution of the preform. After melting and infiltration, local porosity is easily formed, leading to a decrease in the density of the composite material and discontinuous heat conduction pathways, which in turn reduces the overall thermal conductivity.

[0016] In a further preferred embodiment, when the diamond particles adopt a bimodal particle size distribution, the diamond particles are composed of diamond particles A with a particle size of 100-700 μm and diamond particles B with a particle size of 20-50 μm in a volume ratio of 4-6:1. Experiments have shown that the composite material obtained by adopting the above-mentioned bimodal particle size distribution has the best performance. If the particle size and ratio are unreasonable, for example, if the proportion of coarse particles is too high, the fine particles will not be enough to fill all the gaps, resulting in an increase in the porosity of the preform; conversely, if the proportion of coarse particles is too low, it will be difficult to form an effective continuous skeleton, the magnetic field orientation effect will be weakened, and the thermal conductivity network will be incomplete.

[0017] In a further preferred embodiment, when the diamond particles adopt a three-peak particle size distribution, the diamond particles are composed of diamond particles C with a particle size of 400-700μm, diamond particles D with a particle size of 100-300μm, and diamond particles E with a particle size of 20-50μm in a volume ratio of 3-5:1.5-2.5:1.

[0018] In a preferred embodiment, the process of depositing a gradient SiC / C composite layer on the surface of diamond particles is as follows: diamond particles are placed in a chemical vapor deposition furnace, the temperature is controlled at 650-850℃, the pressure is 1-10 kPa, a mixed gas containing silicon source and carbon source is introduced, and the volume flow rate ratio of carbon source to silicon source in the mixed gas is linearly increased from the initial 1-3:1 to 8-12:1 within 30-120 min, and chemical vapor deposition is performed to grow a gradient SiC / C composite layer in situ on the diamond surface.

[0019] In a preferred embodiment, the thickness of the gradient SiC / C composite layer is 50-200 nm.

[0020] By linearly increasing the carbon source gas flow rate over time and correspondingly decreasing the silicon source gas flow rate, a gradient SiC / C composite layer is grown in situ on the diamond surface through chemical vapor deposition. From the inside to the outside, the proportion of carbon structure increases and the proportion of silicon decreases, achieving a smooth transition in chemical composition and modulus from diamond to the outer metal layer.

[0021] In a preferred embodiment, the bottom layer of the metal composite layer is prepared by physical vapor deposition (PVD), using a bottom metal target, under an argon atmosphere, with the working pressure controlled at 0.1-0.5 Pa and the sputtering power at 1000-5000 W, preferably 1500-2500 W.

[0022] In a preferred embodiment, the top layer of the metal composite layer is prepared by physical vapor deposition, using a top metal target, under an argon atmosphere, with the working pressure controlled at 0.1-0.5 Pa and the sputtering power at 900-5000 W, preferably 900-1500 W.

[0023] In a preferred embodiment, the metal in the top layer is composed of one of copper, aluminum, silver, magnesium, and tin combined with one of nickel, cobalt, and iron in a mass ratio of 50-70:30-50. Experiments have shown that controlling the top layer metal within the above range yields optimal performance, ensuring both in-situ metallurgical bonding with the copper substrate and directional alignment along the magnetic field direction after magnetization treatment.

[0024] During the sputtering process of the top layer, an alloy target composed of two metals in the top layer in a designed ratio is selected for single-target sputtering.

[0025] In a preferred embodiment, the bottom layer metal is selected from tungsten or molybdenum, and the top layer metal is a composite of copper and nickel.

[0026] In a preferred embodiment, the thickness of the bottom layer of the metal composite layer is 100-300 nm, and the thickness of the top layer is 100-300 nm.

[0027] In a preferred embodiment, the copper powder has a particle size of 5-20 μm.

[0028] In a preferred embodiment, the volume fraction of copper powder in the mixture is < 5 vol%, preferably 2~4%.

[0029] In this invention, a small amount of fine copper powder is added to the mixture as a binder phase. During pressing, diamond particles with a composite interface layer on the surface are "spot-welded" together to form a preform skeleton with a certain strength, ensuring that the skeleton does not collapse during subsequent melting and infiltration. By controlling the amount of copper powder within the above-mentioned preferred range, the final composite material has the best performance. If there is too much copper powder, it will occupy too much space, hindering the direct contact of diamond particles and the formation of a heat-conducting network, and may cause component segregation during melting and infiltration due to excessive local copper liquid. If there is too little copper powder, the preform will not be strong enough and will easily deform under melting and infiltration pressure. In addition, although copper powder itself is non-magnetic, its particle size and distribution will affect the fluidity of the mixture and the rotation and arrangement of particles under magnetic field induction.

[0030] In a preferred embodiment, the magnetization process involves placing a mold containing the mixture in a DC magnetic field with a magnetic field strength of 0.5-2T, keeping the magnetic field direction consistent with the preset heat flow direction, and letting it stand for 10-30 minutes.

[0031] Through the above magnetization treatment, the magnetic properties of the coating can be used to orient diamond particles containing the composite interface layer along the direction of the magnetic field.

[0032] In actual operation, after magnetization treatment, the mixture is cold-pressed or warm-pressed to obtain a diamond preform with high porosity and interconnected pores.

[0033] In a preferred embodiment, the process of infiltrating copper liquid is as follows: a pure copper block is placed above a diamond preform and heated under vacuum or a protective atmosphere. The temperature is first raised to 1100-1190°C and a pressure of 5-8 MPa is applied, and the temperature is held for 30-90 minutes. Then the temperature is raised to 1200-1300°C, preferably 1200-1250°C, and a pressure of 10-20 MPa is applied, and the temperature is held for 30-120 minutes.

[0034] In this invention, the copper infiltration liquid adopts a two-step method. First, the temperature is raised to a temperature slightly above the melting point of copper and a low pressure is applied to allow the copper liquid to slowly wet the preform. Then, during the heat preservation stage, the temperature is briefly raised to 1200-1300°C, which is below the critical temperature for the interface reaction to produce harmful phases. By applying a higher pressure, the copper liquid is made to completely fill all pores and promotes the in-situ metallurgical bonding between the top layer metal in the coating on the surface of the preform and the molten copper matrix. The bottom layer diffuses moderately, thereby strengthening the interface, but avoiding the formation of an excessively thick brittle phase. Then, it is slowly cooled to room temperature and demolded.

[0035] In a preferred embodiment, the composite material obtained by infiltrating the diamond preform with copper liquid is subjected to annealing treatment to obtain a diamond / copper composite material. The annealing treatment is carried out under a protective atmosphere, the annealing temperature is 300-600℃, preferably 500-600℃, and the annealing time is 0.5-2h, preferably 1-2h.

[0036] In actual operation, the composite material obtained by infiltrating the diamond preform with copper liquid is first subjected to necessary mechanical processing such as cutting, grinding and polishing, and then annealing is performed to eliminate internal stress.

[0037] The present invention also provides a diamond / copper composite material with high thermal conductivity prepared by the above preparation method.

[0038] In a preferred embodiment, the diamond / copper composite material comprises a copper matrix and diamond particles dispersed in the copper matrix. The surface of the diamond particles is coated with a composite interface layer. The composite interface layer consists of a gradient SiC / C composite layer and a metal composite layer from the inside out. In the gradient SiC / C composite layer, the C content increases and the silicon content decreases from the inside out. The metal composite layer consists of a bottom layer and a top layer. The metal in the bottom layer is selected from one of tungsten, molybdenum, titanium, chromium, zirconium, tantalum, and niobium. The metal in the top layer is a composite of one of copper, aluminum, silver, magnesium, and tin and one of nickel, cobalt, and iron.

[0039] Principles and advantages

[0040] The method for preparing diamond / copper composite material provided by this invention first deposits a gradient SiC / C composite layer on the surface of diamond particles. From the inside out, the carbon ratio increases while the silicon ratio decreases, achieving a smooth transition in chemical composition and modulus from diamond to the outer metal layer. Then, a metal composite layer is deposited on top of the gradient SiC / C composite layer. The bottom metal layer forms a good bond with SiC and has good miscibility with the top metal layer. The top metal layer contains copper, aluminum, silver, magnesium, and tin, which can undergo in-situ metallurgical bonding with molten copper, thus constructing a reinforced interface with a smooth transition in composition and properties. Furthermore, the top layer of the metal composite layer also contains magnetic over-plated metal. By magnetizing the mixture, the diamond particles with the composite interface layer are oriented in a specific direction in a magnetic field, constructing a three-dimensional ordered thermally conductive framework. This method fundamentally improves the interface bonding between diamond and copper, significantly reducing interfacial thermal resistance. The prepared composite material possesses ultra-high thermal conductivity, high strength, and an adjustable coefficient of thermal expansion, making it particularly suitable for high-end electronic packaging and heat dissipation applications.

[0041] Compared with the prior art, the present invention has at least the following advantages:

[0042] 1. It is the first to provide a prefabricated composite interface structure of gradient SiC / C composite layer and metal composite layer, realizing a multi-level smooth transition from diamond to copper matrix in terms of chemical composition, coefficient of thermal expansion and modulus, which greatly reduces the interface thermal resistance and stress, while using the transition metal in the outer layer to achieve magnetization treatment.

[0043] 2. By using particle size distribution and magnetic field orientation, a three-dimensional interpenetrating and orientation-optimized heat conduction network was constructed. Combined with pressure-assisted melting and infiltration, a nearly fully dense structure was ensured, making the heat flow path smoother.

[0044] 3. Combining CVD vapor phase modification to construct a strongly bonded inner layer with PVD coating modification to construct a copper-compatible outer layer leverages the advantages of each method, resulting in strong process controllability.

[0045] 4. The diamond / copper composite material prepared using this process can stably achieve a room temperature thermal conductivity of over 800 W / (m·K), while maintaining a flexural strength of no less than 300 MPa and an adjustable coefficient of thermal expansion (5-8×10). -6 / K), with overall performance far exceeding that of existing conventional process products. Attached Figure Description

[0046] Figure 1 This is a microstructure diagram of diamond particle C in Example 1 of the present invention.

[0047] Figure 2 This is a microstructure diagram of the surface of the diamond / copper composite material provided in Embodiment 1 of the present invention.

[0048] Figure 3 This is a microstructure diagram of the surface of the diamond / copper composite material provided in Embodiment 1 of the present invention. Detailed Implementation

[0049] Example 1

[0050] Diamond particle size distribution: High thermal conductivity synthetic single crystal diamond particles (thermal conductivity 1800 W / (m·K)) are selected and are mixed by volume ratio of diamond particles C with an average particle size of 550 μm, diamond particles D with an average particle size of 200 μm, and diamond particles E with a particle size of 30 μm.

[0051] Deposition of a gradient SiC / C composite layer: Mixed diamond particles were placed in a CVD reaction chamber. Silane (SiH4) and methane (CH4) were introduced as reactant gases, with hydrogen as the carrier gas. The reaction temperature was controlled at 750℃ and the pressure at 5 kPa. Using a mass flow controller, the volumetric flow rate ratio of CH4 to SiH4 was linearly increased from 2:1 to 10:1 over 90 min. After deposition, a gradient SiC / C composite layer with a thickness of approximately 120 nm was obtained on the diamond surface.

[0052] Setting up a metal composite layer: After processing the diamond particles, they were placed in a PVD coating apparatus. First, using a pure tungsten target, a W layer with a thickness of approximately 200 nm was deposited under argon atmosphere, working pressure of 0.3 Pa, sputtering power of 2000 W, and time of 60 min. Then, using a copper-nickel alloy (CuNi) with a mass percentage of 6:4 as the target, a CuNi alloy layer with a thickness of approximately 200 nm was deposited under sputtering power of 1000 W and time of 40 min, thus obtaining diamond particles containing a composite interface layer.

[0053] Mixing and Magnetization Molding: The diamond particles were uniformly mixed with copper powder with a particle size of 10 μm, and the volume ratio of copper powder in the mixture was controlled to be 3 vol%. The mixture was placed into a graphite mold and placed in a DC magnetic field with a magnetic field strength of 1 T, keeping the magnetic field direction vertically upward (preset heat flow direction), and left to stand for 20 min. Subsequently, it was pressed into shape at room temperature with a pressure of 50 MPa to obtain a diamond preform.

[0054] Copper infiltration and annealing: A pure copper block was placed above a diamond preform and heated under a vacuum atmosphere. A two-step infiltration method was used: first, the temperature was raised to 1120℃, a pressure of 6 MPa was applied, and the temperature was held for 45 min; then, the temperature was raised to 1220℃, a pressure of 12 MPa was applied, and the temperature was held for 45 min. Subsequently, it was slowly cooled to room temperature and demolded. After machining the resulting composite material, it was annealed at 550℃ under argon protection for 1.5 h to obtain the final product.

[0055] The diamond / copper composite material prepared in this embodiment has a room temperature thermal conductivity of 816 W / (m·K), a flexural strength of 352 MPa, and a coefficient of thermal expansion of 6.5 × 10⁻⁶. -6 / K.

[0056] Example 2

[0057] This embodiment is basically the same as Embodiment 1, except that:

[0058] The diamond particles are bimodal: they are a mixture of particles A with a diameter of 500 μm and particles B with a diameter of 30 μm in a volume ratio of 5:1.

[0059] CVD deposition parameters: temperature 700℃, pressure 3 kPa, deposition time 60 min, CH4 / SiH4 volumetric flow rate ratio linearly increased from 1.5:1 to 8:1, gradient layer thickness approximately 80 nm.

[0060] Setting a bimetallic layer: After processing the diamond particles, they were placed in a PVD coating equipment. First, using a pure molybdenum target, a molybdenum layer with a thickness of about 150 nm was deposited under argon atmosphere, working pressure of 0.3 Pa, sputtering power of 1800 W, and time of 60 min. Then, using a copper-nickel alloy (CuNi) with a mass percentage of 6:4 as the target, a CuNi alloy layer with a thickness of about 150 nm was deposited under sputtering power of 900 W and time of 35 min, thus obtaining diamond particles containing a composite interface layer.

[0061] The volume ratio of copper powder in the mixture is 2 vol.

[0062] Magnetization treatment: magnetic field strength 1.5 T, stand for 15 min.

[0063] Melting process: First stage 1130℃ / 5 MPa / 40 min, second stage 1230℃ / 13 MPa / 40 min.

[0064] The diamond / copper composite material prepared in this embodiment has a room temperature thermal conductivity of 750 W / (m·K), a flexural strength of 335 MPa, and a coefficient of thermal expansion of 6.8 × 10⁻⁶. -6 / K.

[0065] Example 3

[0066] This embodiment is basically the same as Embodiment 1, except that:

[0067] Three-peak gradation ratio: Particles with diameters of 700 μm, 200 μm, and 30 μm are mixed in a volume ratio of 5:2:1.

[0068] CVD deposition parameters: temperature 800℃, pressure 8 kPa, deposition time 110 min, CH4 / SiH4 volumetric flow rate ratio linearly increased from 2.5:1 to 11:1, gradient layer thickness approximately 180 nm.

[0069] Setting a bimetallic layer: After processing the diamond particles, they were placed in a PVD coating equipment. First, using a pure molybdenum target, a molybdenum layer with a thickness of approximately 250 nm was deposited under argon atmosphere, working pressure of 0.3 Pa, sputtering power of 2000 W, and time of 80 min. Then, using a copper-nickel alloy (CuNi) with a mass percentage of 6:4 as the target, a CuNi alloy layer with a thickness of approximately 250 nm was deposited under sputtering power of 1000 W and time of 50 min, thus obtaining diamond particles containing a composite interface layer.

[0070] The volume ratio of copper powder in the mixture is 4 vol.

[0071] Magnetization treatment: magnetic field strength 0.8 T, stand for 25 min.

[0072] Melting process: First stage 1140℃ / 7 MPa / 50 min, second stage 1240℃ / 14 MPa / 50 min.

[0073] The diamond / copper composite material prepared in this embodiment has a room temperature thermal conductivity of 852 W / (m·K), a flexural strength of 368 MPa, and a coefficient of thermal expansion of 6.2 × 10⁻⁶. -6 / K.

[0074] Comparative Example 1

[0075] This comparative example is basically the same as Example 1, except that the mixture was not magnetized.

[0076] Testing revealed that the diamond particles in the resulting composite material were randomly distributed, failing to form a directional thermally conductive framework. The room temperature thermal conductivity was 721 W / (m·K), and the flexural strength was 305 MPa. This indicates that the lack of magnetic field orientation resulted in an incomplete thermally conductive network and a significant decrease in thermal conductivity.

[0077] Comparative Example 2

[0078] This comparative example is basically the same as Example 1, except that: no interface modification was performed, and unmodified diamond particles were directly mixed with copper powder.

[0079] Testing revealed that due to the extremely poor wettability between diamond and copper during the melting and infiltration process, the interfacial bonding was inadequate, resulting in a composite material with low density, a room temperature thermal conductivity of only 386 W / (m·K), and a flexural strength of 198 MPa. This indicates that without an interfacial modification layer, the interfacial thermal resistance is enormous, leading to performance degradation.

[0080] Comparative Example 3

[0081] This comparative example is basically the same as Example 1, except that only a single W layer with a thickness of 200 nm is deposited on the surface of the diamond particles, and no gradient SiC / C composite layer and CuNi top layer are set.

[0082] Testing revealed that while the W layer showed some bonding with the diamond, its metallurgical bond with the copper matrix was weak, and abrupt changes in the coefficient of thermal expansion occurred at the interface. The room temperature thermal conductivity was 595 W / (m·K), and the flexural strength was 278 MPa. This indicates that the lack of a gradient transition and an outer Cu layer resulted in insufficient interfacial performance.

Claims

1. A method for preparing a diamond / copper composite material with high thermal conductivity, characterized in that: First, a gradient SiC / C composite layer is deposited on the surface of diamond particles. Then, a metal composite layer is set on the surface of the gradient SiC / C composite layer to obtain diamond particles with a composite interface layer. Then, the diamond particles with the composite interface layer are mixed with copper powder to obtain a mixture. The mixture is placed in a mold, and the mixture is oriented by a magnetic field. Then, it is pressed into shape to obtain a diamond preform. Finally, copper liquid is melt-infiltrated into the diamond preform to obtain the final product. In the gradient SiC / C composite layer, the C content increases and the silicon content decreases from the inside to the outside. The metal composite layer consists of a bottom layer and a top layer. The metal in the bottom layer is selected from one of tungsten, molybdenum, titanium, chromium, zirconium, tantalum, and niobium. The metal in the top layer is a composite of one of copper, aluminum, silver, magnesium, and tin and one of nickel, cobalt, and iron. The diamond particles are sized using a bimodal or trimodal particle size distribution.

2. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: The diamond particles are single-crystal diamond particles with a room temperature thermal conductivity ≥1800 W / (m·K).

3. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: When the diamond particles adopt a bimodal particle size distribution, the diamond particles are composed of diamond particles A with a particle size of 100-700μm and diamond particles B with a particle size of 20-50μm in a volume ratio of 4-6:

1. When the diamond particles adopt a three-peak particle size distribution, the diamond particles are composed of diamond particles C with a particle size of 400-700μm, diamond particles D with a particle size of 100-300μm, and diamond particles E with a particle size of 20-50μm in a volume ratio of 3-5:1.5-2.5:

1.

4. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: The process of depositing a gradient SiC / C composite layer on the surface of diamond particles is as follows: diamond particles are placed in a chemical vapor deposition furnace, the temperature is controlled at 650-850℃ and the pressure is 1-10 kPa, a mixed gas containing silicon source and carbon source is introduced, and the volume flow rate ratio of carbon source to silicon source in the mixed gas is linearly increased from the initial 1-3:1 to 8-12:1 within 30-120 min, chemical vapor deposition is performed, and a gradient SiC / C composite layer is grown in situ on the diamond surface. The thickness of the gradient SiC / C composite layer is 50-200 nm.

5. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: The bottom layer of the metal composite layer is prepared by physical vapor deposition, using a bottom metal target, under an argon atmosphere, with the working pressure controlled at 0.1-0.5 Pa and the sputtering power at 1000-5000 W. The top layer of the metal composite layer is prepared by physical vapor deposition, using a top metal target, under an argon atmosphere, with the working pressure controlled at 0.1-0.5 Pa and the sputtering power at 900-5000 W. In the metal composite layer, the thickness of the bottom layer is 100-300 nm, and the thickness of the top layer is 100-300 nm.

6. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: The copper powder has a particle size of 5-20 μm; The volume fraction of copper powder in the mixture is <5 vol.

7. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: The magnetic field orientation process is as follows: the mold containing the mixture is placed in a DC magnetic field with a magnetic field strength of 0.5-2 T, the magnetic field direction is kept consistent with the preset heat flow direction, and it is left to stand for 10-30 minutes.

8. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: The process of melting copper liquid is as follows: a pure copper block is placed above a diamond preform and heated under vacuum or a protective atmosphere. The temperature is first raised to 1100-1190℃ and a pressure of 5-8 MPa is applied. The temperature is held for 30-90 minutes. Then the temperature is raised to 1200-1300℃ and a pressure of 10-20 MPa is applied. The temperature is held for 30-120 minutes.

9. The method for preparing a high thermal conductivity diamond / copper composite material according to claim 1, characterized in that: The composite material obtained by infiltrating copper liquid into the diamond preform is annealed to obtain the diamond / copper composite material. The annealing is carried out under a protective atmosphere, the annealing temperature is 300-600℃, and the annealing time is 0.5-2h.

10. A high thermal conductivity diamond / copper composite material prepared by the preparation method according to any one of claims 1-9, characterized in that: The diamond / copper composite material consists of a copper matrix and diamond particles dispersed in the copper matrix. The surface of the diamond particles is coated with a composite interface layer. The composite interface layer consists of a gradient SiC / C composite layer and a metal composite layer from the inside to the outside. In the gradient SiC / C composite layer, the C content increases and the silicon content decreases from the inside to the outside. In the metal composite layer, the bottom layer is composed of one of tungsten, molybdenum, titanium, chromium, zirconium, tantalum, and niobium, and the top layer is composed of one of copper, aluminum, silver, magnesium, and tin combined with one of nickel, cobalt, and iron.

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