A near-net shape copper / diamond composite material, a preparation method and application thereof

Abstract

The application belongs to the field of copper-based composite materials, and particularly relates to a near-net forming copper / diamond composite material and a preparation method and application thereof. The preparation method comprises the following steps: preparing diamond particles II with a Cr2C3-Cr-Cu composite coating on the surface; mixing the diamond particles II, copper and a binder I to obtain feed A, and mixing a copper alloy and the binder II to obtain feed B; injecting the feed B into a mold cavity to obtain a shell green body, and then injecting the feed A to obtain a copper / diamond composite material green body with a shell-core coating structure; and performing vacuum debinding sintering and hot isostatic pressing sintering on the copper / diamond composite material green body in sequence to obtain the near-net forming copper / diamond composite material. The volume ratio of the binder I in the copper / diamond composite feed A is 30-40 v / v%, and the volume ratio of the binder II in the copper alloy feed B is 40-50 v / v%. The near-net sintering forming can obtain the copper / diamond composite material with excellent performance, and the production efficiency is improved and the cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of copper-based composite materials, specifically relating to a near-net-shape copper / diamond composite material, its preparation method, and its application. Background Technology

[0002] Copper / diamond composites are heterogeneous mixtures with metallic copper and its alloys as the matrix and diamond particles as the reinforcement. They have advantages such as low density, good electrical conductivity, good thermal conductivity, low coefficient of thermal expansion, and dimensional stability, and are widely used in high-power electronic device packaging and other fields. Currently, the main methods for preparing copper / diamond composites include gas pressure infiltration, hot pressing sintering, and high temperature and high pressure methods. All of these rely on applying a certain pressure to force copper and diamond to bond tightly to improve the thermal conductivity of copper / diamond composites. However, copper / diamond composites prepared by these processes have the following disadvantages: (1) They have a single shape and are difficult to make relatively complex parts due to the limitations of molds; (2) They have low efficiency and high manufacturing costs; (3) It is difficult to achieve near-net-shape forming and processing is difficult.

[0003] Metal injection molding (MIM) is a rapidly developing and promising near-net-shape forming technology in the field of powder metallurgy, and is one of the world's most popular metal parts forming technologies. Diamond, with a Mohs hardness of 10, is the hardest naturally occurring substance, making it extremely difficult to process. Current technologies combine MIM with pressureless melting to prepare copper / diamond composites. First, a diamond framework is injected, and then a copper block is placed on the framework for melting. However, for complex parts, molds are needed to prevent deformation during melting, resulting in low production efficiency and high manufacturing costs. Therefore, developing a near-net-shape copper / diamond composite material with high production efficiency, low cost, and excellent performance is crucial. Summary of the Invention

[0004] One of the objectives of this invention is to address the problems of difficult processing, limited shape, and reliance on molds to ensure molding results in copper / diamond composite materials, which lead to low production efficiency and high manufacturing costs in the prior art. This invention provides a near-net-shape copper / diamond composite material, its preparation method, and its application, which simplifies the preparation process, solves the mold limitation problem during the sintering and molding of copper / diamond composite materials, improves production efficiency, and reduces manufacturing costs.

[0005] The second objective of this invention is to provide a near-net-shape copper / diamond composite material prepared by the above method.

[0006] A third objective of this invention is to provide the application of the aforementioned near-net-shape copper / diamond composite material in electronic device packaging.

[0007] Specifically, the preparation method includes the following steps:

[0008] (1) Metallization of diamond particles: The mixture obtained by mixing diamond particles I with Cr-containing powder is subjected to high-temperature vacuum treatment, and then a layer of metallic copper is plated on its surface to obtain diamond particles II with a Cr2C3-Cr-Cu composite coating on the surface.

[0009] (2) Preparation of feed: Diamond particles II are mixed with metallic copper and binder I and then granulated to obtain copper / diamond composite feed A; copper alloy is mixed with binder II and then granulated to obtain copper alloy feed B.

[0010] (3) Injection molding: Inject copper alloy feed B into the mold cavity, and after cooling, obtain the shell blank. Then inject copper / diamond composite feed A into the shell blank to obtain a copper / diamond composite material blank with a shell-core covering structure.

[0011] (4) Near-net-shape sintering: After the copper / diamond composite material green blank with shell-core covering structure is subjected to vacuum degreasing sintering and hot isostatic pressing sintering, a near-net-shape copper / diamond composite material is obtained.

[0012] The volume percentage of binder I in the copper / diamond composite feed A is 30-40 v / v%; the volume percentage of binder II in the copper alloy feed B is 40-50 v / v%.

[0013] In a preferred embodiment, in step (1), the conditions for the high-temperature vacuum treatment include a temperature of 800-900°C, a time of 0.5-1.5h, and a vacuum degree of less than 1Pa; in step (2), the conditions for the mixing include a temperature of 80-120°C and a time of 1-2h; in step (3), the injection temperature of the copper / diamond composite feed A is 120-140°C, and the injection pressure is 80-120MPa; in step (3), the injection temperature of the copper alloy feed B is 100-120°C, and the injection pressure is 60-100MPa. In step (4), the conditions for vacuum degreasing sintering are as follows: the temperature of the first stage is set to 300-350℃ and the time is set to 0.5-1h; the temperature of the second stage is set to 550-600℃ and the time is set to 1-1.5h; and the temperature of the third stage is set to 1000-1050℃ and the time is set to 2-3h. In step (4), the conditions for hot isostatic pressing sintering are as follows: the temperature of the first stage is set to 600-700℃ and the time is set to 1-2h; and the temperature of the second stage is set to 900-980℃ and the time is set to 0.5-1h.

[0014] In a preferred embodiment, in step (1), the Cr-containing powder includes Cr2O3, Cr, NaCl, and CaCl2.

[0015] In a preferred embodiment, the mixture contains 50-60 wt% diamond particles I, 5-10 wt% Cr2O3, 20-30 wt% Cr, 5-10 wt% NaCl, and 5-10 wt% CaCl2.

[0016] In a preferred embodiment, the average particle size of the diamond particles I is 30–300 μm.

[0017] In a preferred embodiment, the thickness of the Cu coating is 200–600 nm.

[0018] In a preferred embodiment, in step (2), the mass ratio of diamond particles I to metallic copper in the copper / diamond composite feed A is 1:(0.4-1.5).

[0019] In a preferred embodiment, the average particle size of the metallic copper is 10–50 μm.

[0020] In a preferred embodiment, in step (2), the copper alloy contains 0.5-1.0 wt% Al, 0.3-0.6 wt% B, 0.1-0.2 wt% Si, 0.1-0.15 wt% Ti, 0.1-0.5 wt% Ni, 0.1-1.5 wt% Cr, and the remainder is Cu.

[0021] In a preferred embodiment, the average grain size of the copper alloy is 5–20 μm.

[0022] In a preferred embodiment, in step (2), adhesives I and II each independently contain 40-50 wt% polyethylene wax, 30-35 wt% microcrystalline wax, 5-15 wt% isotactic polypropylene, 1-3 wt% ethylene-butadiene-styrene block copolymer, and 5-10 wt% thermoplastic polyester elastomer.

[0023] In a preferred embodiment, the number-average molecular weight of the polyethylene wax is 2000–5000 g / mol.

[0024] In a preferred embodiment, the isotactic polypropylene has a number-average molecular weight of 1.0 to 1.5 × 10⁻⁶. 5 g / mol.

[0025] In a preferred embodiment, the number-average molecular weight of the ethylene-butadiene-styrene block copolymer is 0.8 to 1.0 × 10⁻⁶. 5 g / mol.

[0026] In a preferred embodiment, the injection amount of the copper alloy feedstock B is 10-20% of the mold cavity volume; the injection amount of the copper / diamond composite feedstock A is 80-90% of the mold cavity volume.

[0027] In a preferred embodiment, in step (3), the injection rate of the copper / diamond composite feed A is 80-100 g / s, and the mold temperature is 40-60°C; the injection rate of the copper alloy feed B is 60-80 g / s, and the mold temperature is 40-60°C.

[0028] The key to this invention lies in first designing and forming a copper / diamond composite material preform with a shell-core encapsulation structure. Based on this, the adhesive ratio between the copper alloy shell and the copper / diamond core is adjusted to ensure that the shrinkage rate of the shell and core is consistent during near-net-shape sintering, preventing cracks or pores from forming in the shell and core due to sintering stress. The preform can be directly sintered to obtain the product without the need for a mold, simplifying the manufacturing process, improving production efficiency and reducing costs. Furthermore, the copper / diamond composite material obtained by this near-net-shape forming has good thermal conductivity, density, and flexural strength, which can meet the packaging requirements of high-power electronic devices and has good commercial value and application prospects. Attached Figure Description

[0029] Figure 1 This is a process flow diagram for preparing near-net-shape copper / diamond composite materials provided by the present invention.

[0030] Figure 2 This is a SEM image of diamond particles with a Cr2C3-Cr-Cu coating on their surface, as shown in Example 2.

[0031] Figure 3 This is a SEM image of the fracture surface of the near-net-shape copper / diamond composite material prepared in Example 2. Detailed Implementation

[0032] The method for preparing near-net-shape copper / diamond composite material provided by this invention is as follows: Figure 1 As shown, it specifically includes the following steps:

[0033] (1) Metallization of diamond particles: The mixture obtained by mixing diamond particles I with Cr-containing powder is subjected to high-temperature vacuum treatment, and then a layer of metallic copper is plated on its surface to obtain diamond particles II with a Cr2C3-Cr-Cu composite coating on the surface.

[0034] (2) Preparation of feed: Diamond particles II are mixed with metallic copper and binder I and then granulated to obtain copper / diamond composite feed A; copper alloy is mixed with binder II and then granulated to obtain copper alloy feed B.

[0035] (3) Injection molding: Inject copper alloy feed B into the mold cavity, and after cooling, obtain the shell blank. Then inject copper / diamond composite feed A into the shell blank to obtain a copper / diamond composite material blank with a shell-core covering structure.

[0036] (4) Near-net-shape sintering: After the copper / diamond composite material green blank with shell-core covering structure is subjected to vacuum degreasing sintering and hot isostatic pressing sintering, a near-net-shape copper / diamond composite material is obtained.

[0037] The volume percentage of binder I in the copper / diamond composite feed A is 30-40 v / v, such as 30v / v%, 32v / v%, 35v / v%, 38v / v%, 40v / v%, or any value between them. The volume percentage of binder II in the copper alloy feed B is 40-50 v / v, such as 40v / v%, 42v / v%, 45v / v%, 48v / v%, 50v / v%, or any value between them.

[0038] In this invention, in step (1), the conditions for the high-temperature vacuum treatment include a temperature preferably of 800-900℃, such as 800℃, 820℃, 850℃, 880℃, 900℃ or any value between them; a time preferably of 0.5-1.5h, such as; and a vacuum degree preferably less than 1Pa.

[0039] In this invention, in step (1), the Cr-containing powder may include Cr2O3, Cr, NaCl, and CaCl2. The addition of NaCl and CaCl2 at this time allows for more complete contact and reaction between Cr2O3 and Cr and the surface of the diamond particles at high temperatures, which is beneficial for better formation of a Cr2C3-Cr coating on the surface of the diamond particles. Preferably, the mixture may specifically contain diamond particles I, Cr2O3, Cr, NaCl, and CaCl2. More preferably, based on the total mass of the mixture, the content of diamond particles I can be 0.5–1.0 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, or any value therein; the content of Cr2O3 can be 5–10 wt%, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value therein; the content of Cr can be 20–30 wt%, such as 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, or any value therein; the content of NaCl can be 5–10 wt%, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value therein; and the content of CaCl2 can be 5–10 wt%, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value therein. The average particle size of the diamond particles I is preferably 30 to 300 μm, such as 30 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm or any value between them.

[0040] In this invention, in step (1), the method of forming a Cu coating on the surface of diamond particles II with a Cr2C3-Cr coating is not limited, but magnetron sputtering technology is preferred. Specifically, the magnetron sputtering copper plating method is as follows: first, pre-sputtering is performed for 2-5 minutes; then, copper plating is performed for 30-90 minutes, the applied bias voltage is -50-60V, and the power is 100-400W. Before pre-sputtering, the vacuum degree in the coating chamber is maintained at <5*10. -3 The pressure is 0.5-0.9 Pa, then argon gas with a purity of 99.999% and a flow rate of 10-30 sccm is introduced. The preferred thickness of the Cu coating is 200-600 nm, such as 200 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, or any value between them. The presence of the Cu coating can both strengthen the bridging strength between the diamond particles and the metallic copper and enhance the fluidity of the copper alloy shell during sintering, resulting in better density.

[0041] In this invention, in step (2), the mixing conditions include a temperature preferably of 80 to 120°C, such as 80°C, 90°C, 100°C, 110°C, 120°C or any value between them; and a time preferably of 1 to 2 hours, such as 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours or any value between them.

[0042] In this invention, in step (2), the mass ratio of diamond particles I to metallic copper in the copper / diamond composite feed A is preferably 1:(0.4-1.5), such as 1:0.4, 1:0.6, 1:0.8, 1:1.0, 1:1.2, 1:1.5, or any value between them. The average particle size of the metallic copper is preferably 10-50 μm, more preferably 15-25 μm, such as 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, or any value between them. The metallic copper is preferably electrolytic copper powder.

[0043] In this invention, in step (2), the copper alloy preferably contains Al, B, Si, Ti, Ni, and Cr, with the remainder being Cu. Based on the total mass of the copper alloy, the Al content is preferably 0.5–1.0 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, or any value between them; the B content is preferably 0.3–0.6 wt%, such as 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, or any value between them; the Si content is preferably 0.1–0.2 wt%, such as 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.18 wt%, 0.2 wt%, or any value between them; the Ti content is preferably 0.5 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 ...3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, or any value between them; the Si content is preferably 0.1–0.2 wt%, such as 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.18 wt%, 0.2 wt%, or any value between them; the Ti content is preferably 0.5 wt%, such as 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.18 wt%, 0.2 wt The preferred content is 0.1–0.15 wt%, such as 0.1 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, 0.15 wt%, or any value between them; the preferred Ni content is 0.1–0.5 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, or any value between them; the preferred Cr content is 0.1–1.5 wt%, such as 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, or any value between them. Specifically, the copper alloy is preferably prepared using a water-vapor combined atomization technology. The average particle size of the copper alloy is preferably 5–20 μm, more preferably 10–15 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any value between them. In this case, the addition of trace alloying elements such as Al, B, Si, Ti, Ni, and Cr to the copper alloy serves two purposes: firstly, Cu is easily oxidized to CuO2 and CuO during debinding and sintering, and the addition of these trace alloying elements can provide deoxidation protection, which is more conducive to promoting sintering; secondly, they can better form a solid solution with Cu during sintering, lowering the melting point of the copper alloy shell. When heated to a certain temperature, the copper alloy shell becomes a molten liquid phase, while the core is a hard copper / diamond skeleton. Because the binder is removed at high temperatures, leaving pores, the molten copper alloy in the shell penetrates into the core under capillary tension, forming a solid-liquid phase sintering. This ensures that the copper / diamond composite material maintains good shape and size and has high thermal conductivity even without a mold.

[0044] In this invention, in step (2), adhesives I and II each preferably independently contain polyethylene wax, microcrystalline wax, isotactic polypropylene, ethylene-butadiene-styrene block copolymer, and thermoplastic polyester elastomer. Based on the total weight of adhesives I or II, the content of polyethylene wax is preferably 40-50 wt%, such as 40 wt%, 42 wt%, 45 wt%, 48 wt%, 50 wt%, or any value between them; the content of microcrystalline wax is preferably 30-35 wt%, such as 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, or any value between them; the content of polypropylene is preferably 5-15 wt%, such as 5 wt%, 8 wt%, 9 wt%, 10 ... The content of the ethylene-butadiene-styrene block copolymer is preferably 1-3 wt%, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, or any value between them; the content of the thermoplastic polyester elastomer (TPEE) is preferably 5-10 wt%, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value between them. In this case, the binder is more conducive to improving the flowability of the copper / diamond composite feed A during injection molding, allowing the copper / diamond composite feed A, as the core, to bond more tightly with the copper alloy feed B, as the outer shell.

[0045] The number-average molecular weight of the polyethylene wax is preferably 2000–5000 g / mol, such as 2000 g / mol, 3000 g / mol, 4000 g / mol, 5000 g / mol, or any value between them. The number-average molecular weight of the isotactic polypropylene is preferably 1.0–1.5 × 10⁻⁶ g / mol. 5 g / mol, such as 1.0 × 10 5 g / mol, 1.1×10 5 g / mol, 1.2×10 5 g / mol, 1.3×10 5 g / mol, 1.4×10 5 g / mol, 1.5×10 5 g / mol or any value therebetween. The number-average molecular weight of the ethylene-butadiene-styrene block copolymer is preferably 0.8 to 1.0 × 10⁻⁶ g / mol. 5 g / mol, such as 0.8 × 10 5 g / mol, 0.85×10 5 g / mol, 0.9×10 5 g / mol, 0.95×10 5 g / mol, 1.0×10 5 g / mol or any value between them.

[0046] In this invention, in step (3), the injection temperature of the copper / diamond composite feed A is preferably 120–140°C, such as 120°C, 125°C, 130°C, 135°C, 140°C, or any value between them; the injection pressure is preferably 80–120 MPa, such as 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, or any value between them. At this time, the copper / diamond composite feed A has better fluidity when injected into the mold cavity, and is more able to fill the mold cavity completely. The injection temperature of the copper alloy feed B is preferably 100–120°C, such as 100°C, 105°C, 110°C, 115°C, 120°C, or any value between them; the injection pressure is preferably 60–100 MPa, such as 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, or any value between them. The injection amount of the copper alloy feed B is preferably 10-20% of the mold cavity volume, such as 10%, 12%, 15%, 18%, 20% or any value between them; the injection amount of the copper / diamond composite feed A is preferably 80-90% of the mold cavity volume, such as 80%, 82%, 85%, 88%, 90% or any value between them.

[0047] In this invention, in step (3), the injection rate of the copper / diamond composite feed A is preferably 80-100 g / s, such as 80 g / s, 85 g / s, 90 g / s, 95 g / s, 100 g / s, or any value between them; the mold temperature is preferably 40-60℃, such as 40℃, 45℃, 50℃, 55℃, 60℃, or any value between them. The injection rate of the copper alloy feed B is preferably 60-80 g / s, such as 60 g / s, 65 g / s, 70 g / s, 75 g / s, 80 g / s, or any value between them; the mold temperature is preferably 40-60℃, such as 40℃, 45℃, 50℃, 55℃, 60℃, or any value between them.

[0048] In this invention, the conditions and parameters for the vacuum degreasing sintering in step (4) are as follows: the preferred temperature setting for the first stage is 300-350℃, such as 300℃, 310℃, 320℃, 330℃, 340℃, 350℃ or any value between them; the preferred time setting is 0.5-1h, such as 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h or any value between them; the preferred temperature setting for the second stage is 550-600℃, such as 550℃, 560℃, 570℃, 580℃, 5... The preferred temperature setting for the third stage is 90℃, 6000℃, or any value between them, with a preferred time setting of 1 to 1.5 hours, such as 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, or any value between them. The preferred temperature setting for the third stage is 1000 to 1050℃, such as 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃, or any value between them, with a preferred time setting of 2 to 3 hours, such as 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, 3 hours, or any value between them. The conditions and parameters for the hot isostatic pressing sintering are as follows: The preferred temperature setting for the first stage is 600-700℃, such as 600℃, 620℃, 650℃, 680℃, 700℃ or any value between them; the preferred time setting is 1-2h, such as 1h, 1.2h, 1.5h, 1.8h, 2h or any value between them; the preferred temperature setting for the second stage is 900-980℃, such as 900℃, 920℃, 940℃, 960℃, 980℃ or any value between them; the preferred time setting is 0.5-1h, such as 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h or any value between them.

[0049] The present invention will be described in detail below through specific embodiments.

[0050] Example 1

[0051] (1) Metallization of diamond particles: 50wt% diamond particles I (average particle size 100μm), 5wt% Cr2O3 powder, 30wt% Cr powder, 5wt% NaCl and 10wt% CaCl2 were mixed and placed in a tube furnace for high-temperature vacuum treatment at 850℃ for 60min with a vacuum degree of 0.3Pa. After cooling and washing, diamond particles with a Cr2C3-Cr coating on the surface were obtained.

[0052] A layer of metallic copper (approximately 400 nm thick) was deposited on the surface of a Cr2C3-Cr coating using magnetron sputtering technology to obtain diamond particles II containing a Cr2C3-Cr-Cu composite coating. The process involved: copper target purity > 99.99%, and vacuum degree in the coating chamber < 5 × 10⁻⁶. -3After Pa, 99.999% pure argon gas is introduced at a flow rate of 15 sccm and a working pressure of 0.8 Pa; the bias voltage applied for magnetron sputtering copper plating is -55V and the power is 120W; pre-sputtering is performed first for 2 minutes; then copper sputtering is performed for 30 minutes.

[0053] (2) Preparation of feed: Diamond particles II and electrolytic copper powder with an average particle size of 20 μm are mixed evenly at a mass ratio of 4:6 and then mixed with binder I and granulated to obtain copper / diamond composite feed A. Binder I accounts for 35 v / v% of the total volume of feed A. Copper alloy powder with an average particle size of 10 μm is mixed with binder II and then granulated to obtain copper alloy feed B. Binder II accounts for 45 v / v% of the total volume of feed B.

[0054] The copper alloy composition is as follows: 0.8 wt% Al, 0.6 wt% B, 0.1 wt% Si, 0.10 wt% Ti, 0.2 wt% Ni, 0.6 wt% Cr, with the balance being Cu;

[0055] Both adhesives I and II consist of: 40 wt% polyethylene wax (number average molecular weight 3000 g / mol), 35 wt% microcrystalline wax (80# microcrystalline wax), and 12 wt% isotactic polypropylene (number average molecular weight 1.2 × 10⁻⁶). 5 3 wt% ethylene-butadiene-styrene block copolymer (number average molecular weight 1.0 × 10⁻⁶ g / mol) 5 g / mol), 10 wt% thermoplastic polyester elastomer (injection molding grade 1047D);

[0056] The mixing temperature was 100℃, the time was 1.5h, and the mixing mill speed was 80r / min.

[0057] (3) Injection molding: Copper alloy feedstock B is injected into the mold cavity and cooled to obtain the shell blank. When copper alloy feedstock B is injected into the mold cavity, the injection temperature is 100℃, the injection pressure is 80MPa, the injection speed is 80g / s, the injection temperature is 60℃, and the injection amount of copper alloy feedstock B is 15% of the mold cavity volume.

[0058] Copper / diamond composite feed A is injected into the shell preform to obtain a copper-diamond composite preform with a shell-core encapsulation structure. When copper / diamond composite feed A is injected into the shell preform, the injection temperature is 120℃, the injection pressure is 100MPa, the injection speed is 100g / s, the mold temperature is 60℃, and the injection amount of copper / diamond composite feed A is 85% of the mold cavity volume.

[0059] (4) Near-net-shape sintering: The copper / diamond composite material green blank with shell-core covering structure is subjected to vacuum debinding sintering and hot isostatic pressing densification sintering to obtain near-net-shape copper / diamond composite material.

[0060] The conditions and parameters for vacuum debinding and sintering are as follows: first, evacuate to 10... -2 Pa was heated to 300℃ at a rate of 3℃ / min and held for 1 hour, then heated to 600℃ at a rate of 3℃ / min and held for 1 hour, and then heated to 1020℃ at a rate of 5℃ / min and held for 2 hours, and then cooled to room temperature in the furnace.

[0061] The conditions for hot isostatic pressing sintering are as follows: first, evacuate to 0.1 Pa, heat to 600 °C at a rate of 5 °C / min and hold for 1 h, then purge with inert argon gas (purity > 99.99%) to 100 MPa, and then heat to 920 °C at a rate of 1.5 °C / min and hold for 1 h.

[0062] The copper / diamond composite material prepared in this embodiment has a density of 98.9%, a flexural strength of 482 MPa, and a thermal conductivity of 578 W / m·K.

[0063] Example 2

[0064] (1) Metallization of diamond particle surface: 50wt% diamond particles I (average particle size 150μm), 5wt% Cr2O3 powder, 30wt% Cr powder, 5wt% NaCl and 10wt% CaCl2 were mixed and placed in a tube furnace for high temperature vacuum treatment at 820℃ for 60min with a vacuum degree of 0.3Pa. After cooling and washing, diamond particles with Cr2C3-Cr coating on the surface were obtained.

[0065] A layer of metallic copper (approximately 400 nm thick) was deposited on the surface of a Cr2C3-Cr coating using magnetron sputtering technology to obtain diamond particles II containing a Cr2C3-Cr-Cu composite coating. The process parameters were: copper target purity > 99.99%; vacuum degree in the coating chamber < 5 × 10⁻⁶. -3 After Pa, 99.999% pure argon gas is introduced at a flow rate of 15 sccm and a working pressure of 0.8 Pa; the bias voltage applied for magnetron sputtering copper plating is -55V and the power is 120W; pre-sputtering is performed first for 2 minutes; then copper sputtering is performed for 30 minutes.

[0066] (2) Preparation of feed: Diamond particles II and electrolytic copper powder with an average particle size of 20 μm are mixed evenly at a mass ratio of 5:5 and then mixed with binder I and granulated to obtain copper / diamond composite feed A. Binder I accounts for 40 v / v% of the total volume of feed A. Copper alloy powder with an average particle size of 10 μm is mixed with binder II and then granulated to obtain copper alloy feed B. Binder II accounts for 45 v / v% of the total volume of feed B.

[0067] The copper alloy composition is 0.8 wt% Al, 0.6 wt% B, 0.1 wt% Si, 0.10 wt% Ti, 0.2 wt% Ni, 0.6 wt% Cr, with the balance being Cu;

[0068] Both adhesives I and II consist of: 40 wt% polyethylene wax (number average molecular weight 3000 g / mol), 35 wt% microcrystalline wax (80# microcrystalline wax), and 12 wt% random polypropylene (number average molecular weight 1.2 × 10⁻⁶). 5 3 wt% ethylene-butadiene-styrene block copolymer (number average molecular weight 1.0 × 10⁻⁶ g / mol) 5 g / mol), 10 wt% thermoplastic polyester elastomer (injection molding grade 1047D);

[0069] The mixing temperature was 100℃, the time was 1.5h, and the mixing mill speed was 80r / min.

[0070] (3) Injection molding: The copper alloy feedstock B is injected into the mold cavity and cooled to obtain the shell blank. When the copper alloy feedstock B is injected into the mold cavity, the injection temperature is 100℃, the injection pressure is 80MPa, the injection speed is 80g / s, the mold temperature is 60℃, and the injection amount of the copper alloy feedstock B is 20% of the mold cavity volume.

[0071] Copper / diamond composite material feed A is injected into the shell preform to obtain a copper-diamond composite preform with a shell-core encapsulation structure. When the copper / diamond composite feed A is injected into the shell preform, the injection temperature is 120℃, the injection pressure is 120MPa, the injection speed is 100g / s, the mold temperature is 60℃, and the injection amount of copper / diamond composite material feed A is 80% of the mold cavity volume.

[0072] (4) Near-net-shape sintering: The copper-diamond composite material green blank with shell-core encapsulation structure is vacuum debinding sintering and hot isostatic pressing densification sintering to obtain near-net-shape copper / diamond composite material.

[0073] Among them, the vacuum degreasing sintering process: first, vacuum is drawn to 10... -2Pa, first heat to 300℃ at a rate of 3℃ / min and hold for 1 hour, then heat to 600℃ at a rate of 3℃ / min and hold for 1 hour, then heat to 1030℃ at a rate of 5℃ / min and hold for 2 hours, and then cool to room temperature with the furnace;

[0074] The hot isostatic pressing (HIP) sintering process is as follows: first, evacuate to 0.1 Pa, heat to 600 °C at a rate of 5 °C / min and hold for 1 h, then fill with inert argon gas (purity > 99.99%) to 120 MPa, and heat to 930 °C at a rate of 1.5 °C / min and hold for 1 h.

[0075] The copper / diamond composite material prepared in this embodiment has a density of 99.0%, a flexural strength of 453 MPa, and a thermal conductivity of 652 W / m·K.

[0076] like Figure 1 As shown, a uniform Cr2C3-Cr-Cu coating was formed on the surface of the diamond particles. Figure 2 As shown, the diamond is free of defects such as agglomeration and pores, and the diamond is tightly wrapped by copper, indicating a close contact and high bonding strength between the diamond and copper.

[0077] Comparative Examples 1-4

[0078] The reference copper / diamond composite material was prepared according to the method of Example 1, except that feedstocks A and B were prepared according to the volume fraction of the binder in Table 2, while all other conditions were the same.

[0079] Table 2

[0080]

[0081] Comparative Examples 5-6

[0082] The reference copper / diamond composite material was prepared according to the method in Example 1, except that it was sintered and formed according to the conditions in Table 3, while all other conditions were the same.

[0083] Table 3

[0084]

[0085] Comparative Example 7

[0086] A reference copper / diamond composite material was prepared according to the method in Example 1, except that copper alloy feedstock B was not prepared; instead, copper / diamond composite feedstock A was directly injected into the mold cavity to obtain a copper / diamond composite preform. All other conditions were the same. Product test results: The product could not be near-net-shape molded and had a density of 86.9%, a flexural strength of 134 MPa, and a thermal conductivity of 264 W / m·K.

[0087] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a near-net-shape copper / diamond composite material, characterized in that, The preparation method includes the following steps: (1) Metallization of diamond particles: The mixture obtained by mixing diamond particles I with Cr-containing powder is subjected to high-temperature vacuum treatment, and then a layer of metallic copper is plated on its surface to obtain diamond particles II with a Cr2C3-Cr-Cu composite coating on the surface. (2) Preparation of feed: Diamond particles II are mixed with metallic copper and binder I and then granulated to obtain copper / diamond composite feed A; copper alloy is mixed with binder II and then granulated to obtain copper alloy feed B. (3) Injection molding: Inject copper alloy feedstock B into the mold cavity, and after cooling, obtain the shell blank. Then inject copper / diamond composite feedstock A into the shell blank to obtain a copper / diamond composite material blank with a shell-core covering structure. (4) Near-net-shape sintering: The copper / diamond composite material green blank with shell-core covering structure is subjected to vacuum debinding sintering and hot isostatic pressing sintering in sequence to obtain near-net-shape copper / diamond composite material. The volume percentage of binder I in the copper / diamond composite feed A is 30-40 v / v; the volume percentage of binder II in the copper alloy feed B is 40-50 v / v.

2. The method for preparing near-net-shape copper / diamond composite material according to claim 1, characterized in that, In step (1), the conditions for the high-temperature vacuum treatment include a temperature of 800~900℃, a time of 0.5~1.5h, and a vacuum degree of less than 1Pa; In step (2), the mixing conditions include a temperature of 80~120℃ and a time of 1~2h; In step (3), the injection temperature of the copper / diamond composite feed A is 120~140℃ and the injection pressure is 80~120MPa; In step (3), the injection temperature of the copper alloy feed B is 100~120℃ and the injection pressure is 60~100MPa; In step (4), the conditions for vacuum degreasing sintering are as follows: the temperature of the first stage is set to 300~350℃ and the time is set to 0.5~1h; the temperature of the second stage is set to 550~600℃ and the time is set to 1~1.5h; and the temperature of the third stage is set to 1000~1050℃ and the time is set to 2~3h. In step (4), the conditions for hot isostatic pressing sintering are as follows: the temperature of the first stage is set to 600~700℃ and the time is set to 1~2h, and the temperature of the second stage is set to 900~980℃ and the time is set to 0.5~1h.

3. The method for preparing near-net-shape copper / diamond composite material according to claim 1 or 2, characterized in that, In step (1), the Cr-containing powder includes Cr2O3, Cr, NaCl, and CaCl2.

4. The method for preparing near-net-shape copper / diamond composite material according to claim 3, characterized in that, In step (1), the mixture contains 50-60 wt% diamond particles I, 5-10 wt% Cr2O3, 20-30 wt% Cr, 5-10 wt% NaCl, and 5-10 wt% CaCl2.

5. The method for preparing near-net-shape copper / diamond composite material according to claim 3, characterized in that, In step (1), the average particle size of the diamond particles I is 30~300μm.

6. The method for preparing near-net-shape copper / diamond composite material according to claim 3, characterized in that, In step (1), the thickness of the Cu coating is 200~600nm.

7. The method for preparing near-net-shape copper / diamond composite material according to claim 1 or 2, characterized in that, In step (2), the mass ratio of diamond particles I to metallic copper in the copper / diamond composite feed A is 1:(0.4~1.5).

8. The method for preparing near-net-shape copper / diamond composite material according to claim 7, characterized in that, In step (2), the average particle size of the metallic copper is 10~50μm.

9. The method for preparing near-net-shape copper / diamond composite material according to claim 1 or 2, characterized in that, In step (2), the copper alloy contains 0.5~1.0wt% Al, 0.3~0.6wt% B, 0.1~0.2wt% Si, 0.1~0.15wt% Ti, 0.1~0.5wt% Ni, 0.1~1.5wt% Cr, and the remainder is Cu.

10. The method for preparing near-net-shape copper / diamond composite material according to claim 9, characterized in that, In step (2), the average particle size of the copper alloy is 5~20μm.

11. The method for preparing near-net-shape copper / diamond composite material according to claim 1 or 2, characterized in that, In step (2), adhesive I and adhesive II each independently contain 40-50 wt% polyethylene wax, 30-35 wt% microcrystalline wax, 5-15 wt% isotactic polypropylene, 1-3 wt% ethylene-butadiene-styrene block copolymer, and 5-10 wt% thermoplastic polyester elastomer.

12. The method for preparing near-net-shape copper / diamond composite material according to claim 11, characterized in that, In step (2), the number average molecular weight of the polyethylene wax is 2000~5000 g / mol.

13. The method for preparing near-net-shape copper / diamond composite material according to claim 11, characterized in that, In step (2), the number-average molecular weight of the isotactic polypropylene is 1.0~1.5×10⁻⁶. 5 g / mol.

14. The method for preparing near-net-shape copper / diamond composite material according to claim 11, characterized in that, In step (2), the number-average molecular weight of the ethylene-butadiene-styrene block copolymer is 0.8~1.0×10⁻⁶. 5 g / mol.

15. The method for preparing near-net-shape copper / diamond composite material according to claim 1 or 2, characterized in that, In step (3), the injection amount of the copper alloy feed B is 10-20% of the mold cavity volume; the injection amount of the copper / diamond composite feed A is 80-90% of the mold cavity volume.

16. The method for preparing near-net-shape copper / diamond composite material according to claim 15, characterized in that, In step (3), the injection speed of the copper / diamond composite feed A is 80~100g / s, and the mold temperature is 40~60℃; the injection speed of the copper alloy feed B is 60~80g / s, and the mold temperature is 40~60℃.

17. A near-net-shape copper / diamond composite material prepared by the method according to any one of claims 1 to 16.

18. The application of the near-net-shape copper / diamond composite material of claim 17 in electronic device packaging.

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