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

Abstract

The invention belongs to the field of alloy composite materials, and discloses a preparation method of a high-thermal-conductivity copper / diamond composite material, which comprises the following steps: preparing copper alloy powder capable of forming carbide elements including at least one of Cr, Zr, Ti, Y and La; the surfaces of the diamond particles are plated with transition metal layers, and transition metal comprises at least one of Cr, W, Zr and Ti; copper alloy powder and the diamond particles plated with the transition metal layers are mixed, and copper alloy / diamond composite powder is obtained; a three-layer structure is formed through layered powder laying, the upper layer and the lower layer are pure copper or copper alloy layers, and the middle layer is a copper alloy / diamond composite powder layer; and then spark plasma sintering or vacuum sintering is carried out, and the high-thermal-conductivity copper / diamond composite material is obtained. The composite material with a three-layer structure is constructed through a layered powder laying process, the processing performance of the composite material is improved, and meanwhile it is guaranteed that the heat-conducting property, the mechanical property and the surface quality of the composite material are comprehensively balanced.

Description

Technical Field

[0001] This invention belongs to the field of alloy composite materials, and particularly relates to a copper / diamond composite material and its preparation method. Background Technology

[0002] With the rapid development of 5G mobile communication technology, high-performance chips, new energy vehicles, and laser weapon systems, the power density of modern electronic devices is increasing exponentially. Studies show that for every 10-15°C increase in device temperature, its lifespan is shortened by approximately 50%, and most electronic device failures are directly attributed to insufficient heat dissipation. Current mainstream thermal management materials include: Metal-based materials: Although pure copper has good thermal conductivity, its coefficient of thermal expansion is seriously mismatched with that of semiconductor chips, which can easily generate thermal stress and lead to interface delamination.

[0003] Metal matrix composites, such as Mo / Cu and W / Cu, while possessing adjustable coefficients of thermal expansion, suffer from excessively high densities (>9.5 g / cm³). 3 It has poor processing performance and high cost.

[0004] Ceramic composite materials, such as aluminum nitride (AlN) and silicon carbide (SiC), have good insulation properties, but they are brittle, difficult to connect with metal electrodes, and have limited thermal conductivity.

[0005] In contrast, diamond / copper matrix composites have become an important development direction in thermal management materials due to their excellent thermal conductivity, ease of processing, and cost advantages. Introducing diamond into a copper matrix combines high thermal conductivity (theoretically, diamond's thermal conductivity can reach 2000 W / m·K), low density, and an extremely low coefficient of thermal expansion, making it particularly suitable for chip-level, packaging-level, and system-level heat dissipation structures. Furthermore, compared to other thermal management materials, with the decreasing cost of synthetic diamond, the cost of preparing diamond / copper matrix composites is also lower than that of mainstream thermal management materials, making them more promising for industrial production.

[0006] Currently, melt infiltration is commonly used in industry as the mainstream process for large-scale production of copper / diamond composite materials. However, this method faces multiple technical bottlenecks in practical applications. First, melt infiltration relies on pre-fabricated porous diamond frameworks with a certain strength, limiting its application to high-volume-fraction (typically >50%) composite materials. It cannot precisely control the coefficient of thermal expansion to match different semiconductor devices by flexibly reducing the diamond content. Second, the high-temperature melt infiltration process is usually carried out above 1100℃, which means it is difficult to precisely control the thickness of the interfacial reaction layer, easily leading to increased interfacial thermal resistance. Furthermore, the huge residual thermal stress generated during cooling due to thermal expansion mismatch weakens the interfacial bonding strength. In addition, the high volume fraction of diamond results in extremely poor post-processing performance of the material, making it difficult to obtain the surface quality required for high-precision chip mounting, thus severely limiting its further application in the field of high-performance electronic packaging.

[0007] Existing technologies disclose various methods for preparing diamond / copper composites based on solid-state sintering, such as "diamond surface metallization combined with matrix powder alloying followed by conventional cold pressing sintering to obtain the composite material." In addition, studies have employed hot pressing sintering, spark plasma sintering, and hot isostatic pressing to achieve higher thermal conductivity at higher diamond volume fractions. However, these solid-state sintering methods generally suffer from difficulties in densification and numerous porosity and interface defects when dealing with high diamond volume fractions, making it difficult to simultaneously achieve high thermal conductivity and high mechanical properties. Furthermore, due to the cold pressing or pressurized densification process, a large number of diamond particles are distributed to the material surface, making it highly susceptible to direct contact between the cutting tool and the diamond during subsequent precision machining. This results in poor machinability of the diamond / copper composite material and makes it difficult to reduce the surface roughness to a level that meets chip mounting requirements. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a layered high thermal conductivity copper / diamond composite material with high thermal conductivity, good interfacial bonding strength and excellent processing performance, and a method for preparing the same.

[0009] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A method for preparing a high thermal conductivity copper / diamond composite material includes the following steps: (1) Prepare copper alloy powder that can form carbide elements, wherein the elements include at least one of Cr, Zr, Ti, Y, and La; (2) A transition metal layer is deposited on the surface of the diamond particles, wherein the transition metal includes at least one of Cr, W, Zr, and Ti; (3) Mix the copper alloy powder prepared in step (1) with the diamond material coated with the transition metal layer prepared in step (2) to obtain copper alloy / diamond composite powder. A three-layer structure is formed by layering powder, wherein the upper and lower layers are pure copper or copper alloy layers, and the middle layer is a copper alloy / diamond composite powder layer. (4) Perform spark plasma sintering or vacuum sintering on the layered structure of step (3) to obtain a high thermal conductivity copper / diamond composite material.

[0010] In the above preparation method, preferably, in step (1), the composition of the copper alloy powder, by element weight percentage, includes: Cr 0.1-1%, Zr 0.1-0.4%, Ti 0-0.2%, Y 0-0.5%, La 0-0.3%, with the balance being Cu; the particle size of the copper alloy powder is 1-200 μm.

[0011] In the above preparation method, preferably, in step (2), the diamond particles have a particle size of 50-1000 μm and the transition metal coating has a thickness of 0.1-65 μm. More preferably, the diamond particles have a particle size of 600-1000 μm and the transition metal coating has a thickness of 0.1-3 μm.

[0012] In the above preparation method, preferably, in step (2), the method of depositing a transition metal layer on the surface of the diamond particles includes any one of magnetron sputtering, electroplating or electroless plating.

[0013] In the above preparation method, preferably, in step (3), the thickness ratio of the upper layer to the middle layer is 1:3-1:30; and the thickness ratio of the lower layer to the middle layer is 1:3-1:30.

[0014] In the above preparation method, preferably, in step (3), when mixing the materials, diamond coated with the transition metal layer is added at a volume percentage of 30-70 vol %, and a binder is added at a weight percentage of 1-10%, wherein the binder includes one or more of microcrystalline wax, POM, and sodium citrate.

[0015] In the above preparation method, preferably, in step (3), the mixing method is planetary ball milling or V-type mixing; when using planetary ball milling, the ball milling speed is 50-100 rpm, the ball-to-material ratio is 5:1-20:1, and the ball milling time is 2-6 h; when using V-type mixing, the mixing speed is 5-30 rpm, and the mixing time is 3-10 h.

[0016] In the above preparation method, preferably, in step (3), the copper alloy layers in the upper and lower layers include, by element weight percentage, Cr: 0.1-10%; Zr: 0.1-5% and the balance Cu.

[0017] In the above preparation method, preferably, in step (4), the conditions for the discharge plasma sintering are: vacuum degree ≤ 10.-3 Pa, pre-compression is required before sintering. The pre-compression pressure is 10-50 MPa. The sintering temperature is 600-1050 ℃, the heating rate is 50-200 ℃ / min, the sintering pressure is 20-80 MPa, and the holding time is 5-30 min. The vacuum sintering process includes first cold pressing, then heating to 450-550℃ at a heating rate of 0.5-1℃ / min and holding at that temperature for 4-8 hours to remove wax, and finally heating to 800-1000℃ at a heating rate of 2.5-10℃ / min and holding at that temperature for 3-6 hours. The cold pressing pressure is 10-20 t, and the holding time is 0.5-2 min.

[0018] Based on a general inventive concept, the present invention also provides a high thermal conductivity copper / diamond composite material, having a surface roughness ≤3.2μm, a coefficient of thermal expansion ≤8 ppm / K, a room temperature flexural strength ≥200 MPa, a density ≥95%, and a thermal conductivity ≥600 W / m·K.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention constructs a three-layer structure of pure copper (or copper alloy) / diamond composite layer / pure copper (or copper alloy) through a layered powder spreading process. The upper and lower layers are pure copper or copper alloy layers, which can be used as processing buffer layers in subsequent machining processes such as turning, milling, and grinding. The cutting tool mainly contacts the metal layer with better plasticity, avoiding frequent direct contact with high-hardness diamond particles, thereby reducing tool wear and chipping, and improving the processing performance of the composite material. The middle composite layer and the upper and lower metal layers are well matched in terms of thermal expansion coefficient and stiffness, and the overall structure is basically symmetrical about the middle surface. The thermal stress and bending moment generated on the upper and lower sides during sintering and cooling cancel each other out, which is beneficial to reduce plate warping and improve the flatness of the part.

[0020] (2) The present invention constructs a three-layer structure of pure copper (or copper alloy) / diamond composite layer / pure copper (or copper alloy) through a layered powder spreading process. The selection of the layer thickness directly affects the surface roughness and the effective diamond volume fraction of the material. When the upper and lower surface layers are too thin, the diamond particles in the middle layer are easily exposed on the surface due to pressure, resulting in an increase in surface roughness. When the surface layer thickness is controlled within the range defined by the present invention, on the one hand, a lower surface roughness can be obtained, and on the other hand, the overall effective diamond volume fraction will not be excessively reduced, so that the middle composite layer can still form a continuous high thermal conductivity path, thereby achieving a good comprehensive balance between thermal conductivity, mechanical properties and surface quality.

[0021] (3) The present invention adopts a powder metallurgy mixed sintering process, which eliminates the dependence on diamond self-supporting skeleton, which allows the volume fraction of diamond to be flexibly adjusted in a wide range of 30-70 vol%. By adjusting the diamond content, the thermal expansion coefficient of the composite material can be precisely controlled, so that it can perfectly match the thermal expansion requirements of different semiconductor chip materials such as Si, GaAs, and GaN, which significantly broadens the application scenarios of the material.

[0022] (4) This invention constructs multiple interfacial heat conduction channels through a synergistic modification mechanism of matrix alloying and diamond surface coating, thereby improving the interfacial bonding strength of the copper / diamond composite material and thus enhancing its thermal conductivity. During the matrix modification process, the addition of common alloying elements such as Cr, Ti, and Zr, or rare metal elements such as Y and La, can not only enhance the mechanical properties of the matrix through solid solution and precipitation, but also ensure that the copper alloy maintains high electrical and thermal conductivity. In addition, these elements can react in situ with diamond under high temperature conditions to form a stable carbide interfacial layer, thereby enhancing the interfacial bonding. The improved interfacial bonding strength can improve both the mechanical and thermal conductivity of the composite material. During the diamond particle surface modification process, the Cr, W, Zr, and Ti transition metal layers are deposited on the diamond surface by magnetron sputtering, chemical plating, or electroplating, which can effectively avoid direct contact between the diamond and the matrix, thereby achieving intermediate transition layer connection and forming more heat conduction pathways, thus improving the thermal conductivity of the composite material. In addition, the aforementioned elements can also react in situ with diamond during the sintering process, thereby enhancing the interfacial bonding strength and further improving the thermal conductivity of the composite material. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a SEM image of the surface morphology of the high thermal conductivity copper / diamond composite material prepared in Example 1 of this invention. Detailed Implementation

[0025] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0026] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0027] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0028] Example 1: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) Weigh electrolytic copper (purity ≥ 99.99 wt.%), chromium granules (purity ≥ 99.9 wt.%), and zirconium granules (purity ≥ 99.9 wt.%) according to the proportions of Cr 0.1 wt.%, Zr 0.1 wt.%, and the balance Cu. Add the above raw materials to a graphite crucible inside a quartz protective sleeve. Heat to 1250℃ and hold for 20 min in a medium-frequency induction melting furnace under an argon protective atmosphere of 99.99 vol.% purity to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤ 50 ppm. Then, the molten alloy is subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤ 1 × 10⁻⁶ MPa). - 1 MPa, and a small amount of argon gas was added as an inert atmosphere to ensure that the oxygen content during atomization was ≤100 ppm), to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 400 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. Cr with a purity ≥99.9 wt.% was used as the metal target, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 150 W and the substrate temperature is room temperature. Sputtering is carried out continuously for 8 min to form a Cr metal transition layer with a thickness of about 0.1 μm on the diamond surface, thus obtaining diamond particles with a Cr metal transition layer.

[0029] (3) The alloy powder obtained in step (1), the diamond particles with Cr-plated metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of the diamond with Cr-plated metal transition layer is 50 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 5 rpm and the mixing time is 5 h. After mixing, copper alloy / diamond composite powder is obtained.

[0030] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of pure copper powder, and the D of the pure copper powder is... 50 The thickness of the top and bottom layers is 0.1 mm; the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Next, the powder is pre-pressed at a pressure of 30 MPa. Then, the mold is placed in a spark plasma sintering apparatus for sintering. The temperature is first raised to 800 ℃ at a rate of 100 ℃ / min, and then held for sintering for 10 min. The vacuum degree during the sintering process is ≤10. -3 Pa, sintering pressure of 40 MPa, and high thermal conductivity copper / diamond composite material was obtained after sintering.

[0031] The performance of the high thermal conductivity copper / diamond composite material in this embodiment was tested and is shown in Table 1. The microstructure morphology of the intermediate layer material is as follows. Figure 1 As shown. From Figure 1 It can be seen that the intermediate layer consists of a bright copper alloy matrix and dark blocky diamond particles. The diamond particles have an equiaxed polyhedral morphology and are uniformly dispersed in the matrix, with a volume fraction of about 50%. The interface is tightly bonded, and no obvious pores or debonding defects are observed.

[0032] Example 2: A method for preparing a high thermal conductivity copper / diamond composite material includes the following steps: (1) According to the proportions of Cr content 0.1wt.%, Zr content 0.1wt.%, Ti content 0.2%, and the balance being Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), and titanium granules (purity ≥99.9wt.%). Add the above raw materials to a graphite crucible inside a quartz protective sleeve, and heat to 1250℃ and hold for 20 min in a medium-frequency induction melting furnace under an argon protective atmosphere of 99.99 vol.% purity to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. Then, the molten alloy is subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤1×10⁻⁶).-1 MPa, and a small amount of argon gas was added as an inert atmosphere to ensure that the oxygen content during atomization was ≤100 ppm), to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 400 μm were ultrasonically cleaned with acetone and anhydrous ethanol, dried, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. Ti with a purity ≥99.9 wt.% was used as the metal target, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 200 W and the substrate temperature is room temperature. Sputtering is performed continuously for 10 min to form a Ti metal transition layer with a thickness of about 0.1 μm on the diamond surface, resulting in diamond particles with a Ti metal transition layer.

[0033] (3) The alloy powder obtained in step (1), the diamond particles with Ti metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of the diamond with Ti metal transition layer is 50 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 10 rpm and the mixing time is 5 h. After mixing, copper alloy / diamond composite powder is obtained.

[0034] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of pure copper powder, and the D of the pure copper powder is... 50 The thickness of the top and bottom layers is 0.1 mm; the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Next, the powder is pre-pressed at a pressure of 30 MPa. Then, the mold is placed in a spark plasma sintering apparatus for sintering. The temperature is first raised to 800 ℃ at a rate of 100 ℃ / min, and then held for sintering for 10 min. The vacuum degree during the sintering process is ≤10. -3 Pa, sintering pressure of 40 MPa, and high thermal conductivity copper / diamond composite material was obtained after sintering.

[0035] Example 3: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) According to the proportions of Cr content 1%, Zr content 0.4%, Ti content 0.2%, Y content 0.5%, La content 0.3% and the balance Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), titanium granules (purity ≥99.9wt.%), yttrium granules (purity ≥99.9wt.%) and lanthanum granules (purity ≥99.9wt.%). Add the above raw materials into a graphite crucible inside a quartz protective sleeve. Heat to 1250℃ and hold for 20 min in a medium frequency induction melting furnace under an argon protective atmosphere with a purity of 99.99vol.% to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. The molten alloy is then subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤1×10⁻⁶). -1 MPa, and a small amount of argon gas is added as an inert atmosphere to ensure that the oxygen content is ≤100ppm during atomization, to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 400 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. Cr with a purity ≥99.9 wt.% was used as the metal target, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 150 W and the substrate temperature is room temperature. Sputtering is carried out continuously for 8 min to form a Cr metal transition layer with a thickness of about 0.1 μm on the diamond surface, thus obtaining diamond particles with a Cr metal transition layer.

[0036] (3) The alloy powder obtained in step (1), the diamond particles with Cr-plated metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of the diamond with Cr-plated metal transition layer is 50 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 5 rpm and the mixing time is 5 h. After mixing, copper alloy / diamond composite powder is obtained.

[0037] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of pure copper powder, and the D of the pure copper powder is... 50The thickness of the top and bottom layers is 0.1 mm; the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Next, the powder is pre-pressed at a pressure of 30 MPa. Then, the mold is placed in a spark plasma sintering apparatus for sintering. The temperature is first raised to 800 ℃ at a rate of 100 ℃ / min, and then held for sintering for 10 min. The vacuum degree during the sintering process is ≤10. -3 Pa, sintering pressure of 40 MPa, and high thermal conductivity copper / diamond composite material was obtained after sintering.

[0038] Example 4: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) According to the proportions of Cr content 1%, Zr content 0.4%, Ti content 0.2%, Y content 0.5%, La content 0.3% and the balance Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), titanium granules (purity ≥99.9wt.%), yttrium granules (purity ≥99.9wt.%) and lanthanum granules (purity ≥99.9wt.%). Add the above raw materials into a graphite crucible inside a quartz protective sleeve. Heat to 1250℃ and hold for 20 min in a medium frequency induction melting furnace under an argon protective atmosphere with a purity of 99.99vol.% to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. The molten alloy is then subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤1×10⁻⁶). -1 MPa, and a small amount of argon gas is added as an inert atmosphere to ensure that the oxygen content is ≤100ppm during atomization, to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 400 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. Zr with a purity ≥99.9 wt.% was used as the metal target, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 260 W and the substrate temperature is room temperature. Sputtering is carried out continuously for 150 min to form a Zr metal transition layer with a thickness of about 1 μm on the diamond surface, thus obtaining diamond particles coated with a Zr metal transition layer.

[0039] (3) The alloy powder obtained in step (1), the diamond particles with Zr metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of the diamond with Zr metal transition layer is 65 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 10 rpm and the mixing time is 6h. After mixing, copper alloy / diamond composite powder is obtained.

[0040] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of Cu-0.1Cr-0.1Zr powder, and its D 50 The thickness of the top and bottom layers is 1 mm, and the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Next, the powder is pre-pressed at a pressure of 30 MPa. Then, the mold is placed in a discharge plasma sintering (SPCS) apparatus for sintering. The temperature is first raised to 950 ℃ at a rate of 100 ℃ / min, and then held for sintering for 10 min. The vacuum degree during the sintering process is ≤10. -3 Pa, sintering pressure of 50 MPa, and after sintering, a high thermal conductivity copper / diamond composite material is obtained.

[0041] Example 5: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) According to the proportions of Cr content 1%, Zr content 0.4%, Ti content 0.2%, Y content 0.5%, La content 0.3% and the balance Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), titanium granules (purity ≥99.9wt.%), yttrium granules (purity ≥99.9wt.%) and lanthanum granules (purity ≥99.9wt.%). Add the above raw materials into a graphite crucible inside a quartz protective sleeve. Heat to 1250℃ and hold for 20 min in a medium frequency induction melting furnace under an argon protective atmosphere with a purity of 99.99vol.% to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. The molten alloy is then subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤1×10⁻⁶). -1 MPa, and a small amount of argon gas is added as an inert atmosphere to ensure that the oxygen content is ≤100ppm during atomization, to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 800 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. A W metal target with a purity ≥99.9 wt.% was used, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 260 W and the substrate temperature is room temperature. Sputtering is performed continuously for 100 min to form a W metal transition layer with a thickness of about 1 μm on the diamond surface, thus obtaining diamond particles coated with the W metal transition layer.

[0042] (3) The alloy powder obtained in step (1), the diamond particles with W metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed by planetary ball milling. The volume of diamond with W metal transition layer is 65 vol% of the total mixture. During planetary ball milling, the microcrystalline wax is first heated and melted into liquid, and then added into the ball milling jar. The ball milling speed is 100 rpm and the mixing time is 2h. After mixing, copper alloy / diamond composite powder is obtained.

[0043] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of Cu-1Cr-0.4Zr powder, and its D 50 The thickness of the top and bottom layers is 1 mm, and the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Next, the powder is pre-pressed at a pressure of 40 MPa. Then, the mold is placed in a discharge plasma sintering (SPCS) apparatus for sintering. The temperature is first raised to 950 ℃ at a rate of 100 ℃ / min, and then held for sintering for 10 min. The vacuum degree during the sintering process is ≤10. -3 Pa, sintering pressure of 50 MPa, and after sintering, a high thermal conductivity copper / diamond composite material is obtained.

[0044] Example 6: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) According to the proportions of Cr content 1%, Zr content 0.4%, Ti content 0.2%, Y content 0.5%, La content 0.3%, and the balance Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), titanium granules (purity ≥99.9wt.%), yttrium granules (purity ≥99.9wt.%), and lanthanum granules (purity ≥99.9wt.%). Add the above raw materials to a graphite crucible inside a quartz protective sleeve, heat to 1250℃ and hold for 20 min in a medium-frequency induction melting furnace under an argon protective atmosphere of 99.99 vol.% purity to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. Then, the molten alloy is subjected to gas atomization treatment (atomizing gas pressure is 4 ppm). MPa, pre-evacuation of the atomization chamber to ≤1×10 -1 MPa, and a small amount of argon gas is added as an inert atmosphere to ensure that the oxygen content is ≤100ppm during atomization, to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 800 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. A W metal target with a purity ≥99.9 wt.% was used, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 180 W and the substrate temperature is room temperature. Sputtering is carried out continuously for 200 min to form a W metal transition layer with a thickness of about 1 μm on the diamond surface, thus obtaining diamond particles with a W metal transition layer.

[0045] (3) The alloy powder obtained in step (1), the diamond particles with W metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of diamond with W metal transition layer is 50 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 15 rpm and the mixing time is 6h. After mixing, copper alloy / diamond composite powder is obtained.

[0046] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of Cu-1Cr-0.4Zr powder, and its D 50The thickness of the top and bottom layers is 0.1 mm, and the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 0.5 mm. Next, the powder is pre-pressed at a pressure of 40 MPa. Then, the mold is placed in a spark plasma sintering apparatus for sintering. The temperature is first raised to 980 ℃ at a rate of 100 ℃ / min, and then held for sintering for 10 min. The vacuum degree during the sintering process is ≤10. -3 Pa, sintering pressure of 50 MPa, and after sintering, a high thermal conductivity copper / diamond composite material is obtained.

[0047] Example 7: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) According to the proportions of Cr content 1%, Zr content 0.4%, Ti content 0.2%, Y content 0.5%, La content 0.3% and the balance Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), titanium granules (purity ≥99.9wt.%), yttrium granules (purity ≥99.9wt.%) and lanthanum granules (purity ≥99.9wt.%). Add the above raw materials into a graphite crucible inside a quartz protective sleeve. Heat to 1250℃ and hold for 20 min in a medium frequency induction melting furnace under an argon protective atmosphere with a purity of 99.99vol.% to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. The molten alloy is then subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤1×10⁻⁶). -1 MPa, and a small amount of argon gas is added as an inert atmosphere to ensure that the oxygen content is ≤100ppm during atomization, to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 800 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. Cr with a purity ≥99.9 wt.% was used as the metal target, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 180 W and the substrate temperature is room temperature. Sputtering is carried out continuously for 150 min to form a Cr metal transition layer with a thickness of about 1 μm on the diamond surface, thus obtaining diamond particles with a Cr metal transition layer.

[0048] (3) The alloy powder obtained in step (1), the diamond particles with Cr-plated metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of the diamond with Cr-plated metal transition layer is 65 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 25 rpm and the mixing time is 6h. After mixing, copper alloy / diamond composite powder is obtained.

[0049] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of Cu-1Cr-0.4Zr powder, and its D 50 The thickness of the top and bottom layers is 1 mm, and the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Then, the powder is cold-pressed (cold pressing pressure is 20 t, holding time is 2 min), then heated to 500℃ at a heating rate of 0.5 ℃ / min and held for dewaxing for 4 h, and finally heated to 1000℃ at a heating rate of 10 ℃ / min and held for sintering for 6 h. After sintering, a high thermal conductivity copper / diamond composite material is obtained.

[0050] Example 8: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) According to the proportions of Cr content 1%, Zr content 0.4%, Ti content 0.2%, Y content 0.5%, La content 0.3% and the balance Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), titanium granules (purity ≥99.9wt.%), yttrium granules (purity ≥99.9wt.%) and lanthanum granules (purity ≥99.9wt.%). Add the above raw materials into a graphite crucible inside a quartz protective sleeve. Heat to 1250℃ and hold for 20 min in a medium frequency induction melting furnace under an argon protective atmosphere with a purity of 99.99vol.% to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. The molten alloy is then subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤1×10⁻⁶). -1 MPa, and a small amount of argon gas is added as an inert atmosphere to ensure that the oxygen content is ≤100ppm during atomization, to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 800 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. Ti with a purity ≥99.9 wt.% was used as the metal target, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 180 W and the substrate temperature is room temperature. Sputtering is carried out continuously for 150 min to form a Ti metal transition layer with a thickness of about 1 μm on the diamond surface, thus obtaining diamond particles with a Ti metal transition layer.

[0051] (3) The alloy powder obtained in step (1), the diamond particles with Ti metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of the diamond with Ti metal transition layer is 65 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 20 rpm and the mixing time is 6h. After mixing, copper alloy / diamond composite powder is obtained.

[0052] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of Cu-1Cr-0.4Zr powder, and its D 50 The thickness of the top and bottom layers is 0.5 mm, and the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Then, the powder is cold-pressed (cold pressing pressure is 20 t, holding time is 2 min), then heated to 500℃ at a heating rate of 0.5 ℃ / min and held for dewaxing for 4 h, and finally heated to 1000℃ at a heating rate of 10 ℃ / min and held for sintering for 3 h. After sintering, a high thermal conductivity copper / diamond composite material is obtained.

[0053] Example 9: A method for preparing a high thermal conductivity copper / diamond composite material according to the present invention includes the following steps: (1) According to the proportions of Cr content 1%, Zr content 0.4%, Ti content 0.2%, Y content 0.5%, La content 0.3% and the balance Cu, weigh electrolytic copper (purity ≥99.99wt.%), chromium granules (purity ≥99.9wt.%), zirconium granules (purity ≥99.9wt.%), titanium granules (purity ≥99.9wt.%), yttrium granules (purity ≥99.9wt.%) and lanthanum granules (purity ≥99.9wt.%). Add the above raw materials into a graphite crucible inside a quartz protective sleeve. Heat to 1250℃ and hold for 20 min in a medium frequency induction melting furnace under an argon protective atmosphere with a purity of 99.99vol.% to ensure that the alloy composition is fully melted and uniform, and control the oxygen content in the melting chamber to ≤50 ppm. The molten alloy is then subjected to gas atomization treatment (atomizing gas pressure is 4 MPa, and the atomization chamber is pre-evacuated to ≤1×10⁻⁶). -1 MPa, and a small amount of argon gas is added as an inert atmosphere to ensure that the oxygen content is ≤100ppm during atomization, to obtain D 50 The alloy powder is 25 μm in size. (2) Diamond particles with a diameter of 800 μm were ultrasonically cleaned and dried sequentially with acetone and anhydrous ethanol, and then placed on the rotating substrate tray of the magnetron sputtering coating equipment. Cr with a purity ≥99.9 wt.% was used as the metal target, and the background vacuum degree was ≤5×10⁻⁶. -4 After evacuating under Pa conditions, high-purity Ar gas (purity ≥99.999%) is introduced, and the working gas pressure is adjusted to 0.4 Pa. DC magnetron sputtering is used with a sputtering power of 200 W and the substrate temperature is room temperature. Sputtering is carried out continuously for 120 min to form a Cr metal transition layer with a thickness of about 1 μm on the diamond surface, thus obtaining diamond particles with a Cr metal transition layer.

[0054] (3) The alloy powder obtained in step (1), the diamond particles with Cr-plated metal transition layer prepared in step (2) and the microcrystalline wax with a mass fraction of 1% of the total mass of copper alloy powder / diamond are mixed in a V-type manner. The volume of the diamond with Cr-plated metal transition layer is 65 vol% of the total mixture. During the V-type mixing process, the microcrystalline wax is first heated and melted into liquid, and then added into the ball mill jar. The ball milling speed is 15 rpm and the mixing time is 6h. After mixing, copper alloy / diamond composite powder is obtained.

[0055] (4) In a circular graphite mold with a diameter of 30 mm, powder is spread and filled in layers. The upper and lower layers are composed of Cu-0.1Cr-0.4Zr powder, and its D 50The thickness of the top and bottom layers is 0.5 mm, and the middle layer is the copper alloy / diamond composite powder obtained in step (3) with a thickness of 3 mm. Then, the powder is cold-pressed (cold pressing pressure is 20 t, holding time is 2 min), then heated to 500℃ at a heating rate of 0.5 ℃ / min and held for dewaxing for 4 h, and finally heated to 950℃ at a heating rate of 10 ℃ / min and held for sintering for 3 h. After sintering, a high thermal conductivity copper / diamond composite material is obtained.

[0056] Comparative Example 1: The preparation method of the copper / diamond composite material in this comparative example uses the same copper alloy powder, diamond of the same particle size and the same process parameters as in Example 1. The only difference from Example 1 is that the diamond particles are not plated with a Cr metal transition layer in step (2). Other process conditions are exactly the same as in Example 1.

[0057] Comparative Example 2: The preparation method of the copper / diamond composite material in this comparative example uses the same copper alloy powder, diamond with the same particle size and the same process parameters as in Example 1. The only difference from Example 1 is that in step (4), the layered structure is not used for paving. Instead, the composite powder prepared in step (3) is directly pre-pressed and sintered. Other process conditions are exactly the same as in Example 1.

[0058] Comparative Example 3: The preparation method of the copper / diamond composite material in this comparative example uses the same copper alloy powder, diamond of the same particle size and the same process parameters as in Example 1. The only difference from Example 1 is that pure copper powder is used directly without matrix modification in step (1). Other process conditions are exactly the same as in Example 1.

[0059] Comparative Example 4: The preparation method of the copper / diamond composite material in this comparative example uses the same copper alloy powder, diamond with the same particle size, and the same process parameters as in Example 1. The only difference from Example 1 is that the thickness of the upper and lower layers and the middle layer in step (5) is 1 mm.

[0060] The properties of the composite materials prepared in the above embodiments and comparative examples are shown in Table 1, and the test standards for each property are as follows: Bulk density: JB / T 8133.14-2013 Test methods for physicochemical properties of electrocarbon products - Part 14: Bulk density; Thermal conductivity: GB / T22588-2008 Measurement of thermal diffusivity or thermal conductivity by flash method; Bending strength: GB / T232-2010 Metallic materials - Bending test method; Coefficient of thermal expansion: JB / T 8133.18-2017 Test methods for physical and chemical properties of electro-carbon products - Part 18: Coefficient of thermal expansion; Surface roughness: GB / T3505-2009 Geometric Product Specification (GPS) Surface Structure Profile Method Surface Structure Parameters and Values.

[0061] Table 1. Properties of the composite materials prepared in each example and comparative example.

[0062] As shown in Table 1, the density, thermal conductivity, flexural strength, coefficient of thermal expansion, and surface roughness of Example 1 are generally superior to those of Comparative Examples 1-4. Compared with Example 1, Comparative Example 1, which has no Cr coating on the diamond surface, resulted in a significant decrease in the density, thermal conductivity, and strength of the prepared composite material, while its coefficient of thermal expansion increased. Comparative Example 2, which did not use layered powder spreading, had a similar thermal conductivity, but its density decreased and its surface roughness reached approximately 100 μm, indicating that the layered structure of a pure copper surface layer + intermediate composite layer is beneficial for ensuring surface quality. When Comparative Example 3 used a pure copper substrate, its thermal conductivity and strength decreased significantly, while its coefficient of thermal expansion increased significantly, proving that alloying modification of the substrate can improve interface matching and enhance overall performance. Although Comparative Example 4 retained the coating and layered structure, the thickness of each layer was 1 mm, resulting in a decrease in the effective volume fraction of diamond and a weakening of the thermal conductivity pathway, leading to lower thermal conductivity and strength than Example 1.

Claims

1. A method for preparing a high thermal conductivity copper / diamond composite material, characterized in that, Includes the following steps: (1) Prepare copper alloy powder that can form carbide elements, wherein the elements include at least one of Cr, Zr, Ti, Y, and La; (2) A transition metal layer is deposited on the surface of the diamond particles, wherein the transition metal includes at least one of Cr, W, Zr, and Ti; (3) The copper alloy powder prepared in step (1) is mixed with the diamond particles coated with the transition metal layer prepared in step (2) to obtain copper alloy / diamond composite powder. A three-layer structure is formed by layering powder, with the upper and lower layers being pure copper or copper alloy layers, and the middle layer being a copper alloy / diamond composite powder layer. (4) Perform spark plasma sintering or vacuum sintering on the layered structure of step (3) to obtain a high thermal conductivity copper / diamond composite material.

2. The preparation method according to claim 1, characterized in that, In step (1), the composition of the copper alloy powder, by element weight percentage, includes: Cr 0.1-1%, Zr 0.1-0.4%, Ti 0-0.2%, Y 0-0.5%, La 0-0.3%, with the balance being Cu; the particle size of the copper alloy powder is 1-200 μm.

3. The preparation method according to claim 1, characterized in that, In step (2), the diamond particles have a particle size of 50-1000 μm and the transition metal coating has a thickness of 0.1-65 μm.

4. The preparation method according to claim 1, characterized in that, In step (2), the method of depositing a transition metal layer on the surface of the diamond particles includes any one of magnetron sputtering, electroplating or electroless plating.

5. The preparation method according to claim 1, characterized in that, In step (3), the thickness ratio of the upper layer to the middle layer is 1:3-1:30; the thickness ratio of the lower layer to the middle layer is 1:3-1:

30.

6. The preparation method according to claim 1, characterized in that, In step (3), during mixing, diamond particles coated with a transition metal layer are added at a volume percentage of 30-70 vol %, and a binder at a weight percentage of 1-10% is added. The binder includes one or more of microcrystalline wax, POM, and sodium citrate.

7. The preparation method according to claim 1, characterized in that, In step (3), the mixing method is planetary ball milling or V-type mixing; when using planetary ball milling, the milling speed is 50-100 rpm, the ball-to-material ratio is 5:1-20:1, and the milling time is 2-6h; when using V-type mixing, the mixing speed is 5-30 rpm, and the mixing time is 3-10h.

8. The preparation method according to claim 1, characterized in that, In step (3), the copper alloy layers in the upper and lower layers, by element weight percentage, include Cr: 0.1-10%; Zr: 0.1-5% and balance Cu.

9. The preparation method according to claim 1, characterized in that, In step (4), the conditions for the discharge plasma sintering are: vacuum degree ≤ 10. -3 Pa, pre-compression is required before sintering. The pre-compression pressure is 10-50 MPa. The sintering temperature is 600-1050 ℃, the heating rate is 50-200 ℃ / min, the sintering pressure is 20-80 MPa, and the holding time is 5-30 min. The vacuum sintering process includes first cold pressing, then heating to 450-550℃ at a heating rate of 0.5-1℃ / min and holding at that temperature for 4-8 h, and finally heating to 800-1000℃ at a heating rate of 2.5-10℃ / min and holding at that temperature for 3-6 h. The cold pressing pressure is 10-20 t, and the holding time is 0.5-2 min.

10. A high thermal conductivity copper / diamond composite material according to any one of claims 1 to 9, characterized in that, The composite material has a surface roughness ≤3.2μm, a coefficient of thermal expansion ≤8 ppm / K, a room temperature flexural strength ≥200 MPa, a density ≥95%, and a thermal conductivity ≥600 W / m·K.

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