Method for producing copper heat dissipation material by electrolytic copper powder injection molding

Abstract

The application provides a method for preparing copper heat dissipation material by electrolytic copper powder injection molding, and relates to the technical field of powder metallurgy. The method comprises the following steps: obtaining electrolytic copper powder subjected to grinding and crushing treatment; performing high-temperature and high-speed closed kneading on the electrolytic copper powder, alloy powder and wax-based binder to obtain high-purity feedstock; then performing injection molding on the high-purity feedstock to obtain a green part; then performing solvent degreasing and heating degreasing on the green part to obtain a sample after thermal degreasing; then sequentially performing normal-pressure sintering in a hydrogen atmosphere, solid solution aging treatment and pressure sintering on the sample after thermal degreasing; and finally performing annealing stress relief treatment to obtain the copper heat dissipation material. The electrolytic copper powder has high purity, large specific surface area, high sintering activity, excellent electric conductivity and thermal conductivity, and the material has high strength and excellent ductility through solid solution aging treatment, so that the preparation of high-thermal-conductivity large-size complex structure copper heat dissipation material is realized, the preparation process is stable, the price is low, and the method is more suitable for mass production and use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder metallurgy, and particularly to a method for preparing copper heat dissipation material by electrolytic copper powder injection molding. BACKGROUND

[0002] Copper is widely used in modern national economic construction and people's daily life. In high-energy physics, superconducting technology, low-temperature engineering and other cutting-edge technologies, copper is also indispensable. Copper has excellent performance: high electrical conductivity, high corrosion resistance, good processing deformation ability, high mechanical properties and good plasticity.

[0003] Electrolytic copper powder has high purity, developed dendritic morphology, easy forming, high sintering strength, and excellent electrical and thermal conductivity, and is widely used in diamond tools, carbon brushes, friction plates and other fields. However, the loose bulk density of electrolytic copper powder is relatively small, which greatly increases the difficulty of application by downstream customers, because the smaller loose bulk density means a larger volume at a certain mass, which greatly limits the wide application of electrolytic copper powder.

[0004] The advantage of powder injection molding is that it can integrally form complex metal parts in large quantities, and the density and organization of each part of the product are uniform and excellent in performance. Therefore, how to take advantage of the high sintering activity of electrolytic copper and the excellent sintering performance of the part puts higher requirements on existing technical personnel.

[0005] Chinese patent CN118926519A discloses a kind of nano-porous copper heat dissipation material based on composite copper mesh and surface modification and its preparation method. The method adopts copper salt mixture compaction to form loose structure, lays multiple layers of copper mesh with different mesh numbers to form composite gradient copper mesh, and then presses into tablets. After chemical etching, the nano-porous copper heat dissipation material is obtained. Obviously, the structure of the heat dissipation material is complex, the preparation process is long, the production cost is high, and the efficiency is low.

[0006] Chinese patent CN114131018A discloses a preparation method of pressure net copper nano-pile-up bed heat dissipation material. The method needs to use four kinds of mixed particles, and the arrangement mode and copper mesh structure setting increase the cost. The cold pressing method and vacuum sintering make the prepared heat dissipation material a porous structure material, which has poor electrical conductivity and uneven thermal conductivity performance. Chinese patent CN113458396A discloses a preparation method of copper-based metal honeycomb heat dissipation material. Similarly, the structure of the heat dissipation material is set to improve the heat dissipation performance. However, it needs to be sintered in an oxygen atmosphere furnace to remove the binder carbon residue and oxidize the carbon, which reduces the heat debinding efficiency of the heat dissipation material. If the removal is excessive, the heat dissipation material will be oxidized, and the heat dissipation performance will be poor.

[0007] Chinese patent CN111455373A discloses a preparation method of high-thermal-conductivity high-temperature-resistant composite copper alloy heat dissipation material. The method needs to be prepared through raw material selection, powder mixing and pre-preparation, surface cladding, and mechanical processing. However, the addition of hard particles in the raw material selection increases the strength and hardness of the prepared heat dissipation material, but reduces the plasticity. Therefore, thermal stress in the mechanical processing process may cause cracks or fractures in the material. SUMMARY

[0008] To solve the problems of low utilization rate, complex structure, difficult preparation, and high production cost of the heat dissipation material in the prior art, if alloy particles are added to improve the thermal conductivity and electrical conductivity, there will be technical problems such as the inability to simultaneously improve the performance of both, the mismatch of strong plasticity, the inability to prepare complex-shaped copper parts, and the difficulty in operation. The present application provides a method for preparing copper heat dissipation material by injection molding of electrolytic copper powder, which can solve the above problems. The technical solution is as follows:

[0009] A method for preparing copper heat dissipation material by injection molding of electrolytic copper powder, which comprises the following steps:

[0010] S1, powder grinding and crushing treatment of electrolytic copper powder: weigh the electrolytic copper powder, crush the electrolytic copper powder particles by a superfine mechanical impact grinding mill, and obtain the powder ground and crushed electrolytic copper powder;

[0011] S2, powder compounding: high-temperature and high-speed compounding of the powder ground and crushed electrolytic copper powder, alloy powder, and wax-based binder to obtain high-purity feedstock;

[0012] S3, injection molding: injection molding of the high-purity feedstock to obtain a green part with no defects, no deformation, and uniform composition; then catalytic and thermal debinding of the green part to obtain a sample after thermal debinding;

[0013] S4, normal pressure sintering + aging treatment + hot isostatic pressing sintering: sequentially performing hydrogen atmosphere normal pressure sintering + aging treatment + pressurized sintering under nitrogen atmosphere on the sample after thermal debinding to obtain a sintered copper heat dissipation material;

[0014] S5, annealing: stress relief annealing of the sintered copper heat dissipation material to finally obtain a copper heat dissipation material with high strength, high thermal conductivity, and excellent ductility.

[0015] Optionally, the particle size D50 of the electrolytic copper powder in S1 is 15-20 µm.

[0016] Optionally, the experimental parameters of the superfine mechanical impact grinding mill in S1 are: inlet air volume 200-300 m 3 / h, mill speed 2500-3000 r / min, grading impeller speed 1500-2500 r / min, feed rate 100-200 g / min, after high-speed powder treatment for 2-4 h, screen out 10-15 μm powder, alloy powder is ZrCuAlNi, add 1.5-3.0% by mass.

[0017] Optionally, in S2, the mass fraction of microcrystalline wax in the wax-based binder is 50-70%, the mass fraction of polyethylene is 15-25%, the mass fraction of polypropylene is 10-15%, the mass fraction of ethylene-vinyl acetate copolymer is 10-15%, and the mass fraction of vinyl bis-stearamide is 5-10%; the compounding atmosphere selects argon or nitrogen as the protective atmosphere.

[0018] Optionally, in S2, the temperature of high-temperature and high-speed compounding is 150-170℃, the speed of the compounding machine is 25-40 rpm, and the compounding time is 1-2 h.

[0019] Optionally, in S3, the injection temperature is 150-170℃, the injection pressure is 40-80 bar, the injection speed is 40-60 mm / s, and the mold temperature is 50-75℃; the main component of the binder removed by solvent debinding is microcrystalline wax; the heating rate is 1℃ / min when heating from room temperature to 500℃ for thermal debinding, and the holding time is 30 min at 250℃, 380℃, and 550℃, respectively.

[0020] Optionally, in S3, trichloroethylene is selected for solvent debinding, and the main component of the binder, microcrystalline wax, is removed by solvent debinding at 40-55℃ for 15-30 h.

[0021] Optionally, after thermal debinding in S3, the debinding rate of the sample is 6.0-7.8%, and the density is 4.55-5.10 g / cm 3 .

[0022] Optionally, in the step of S4, the flow rate of the hydrogen gas is ≥3 m 3 / min, the sintering temperature is 1065-1075℃, and the holding time is 3-5 h; during the aging treatment, the aging temperature is 110-140℃, the aging time is 30-50 h, and during the pressure sintering, the sintering is carried out in a nitrogen atmosphere at a pressure of 5-15 bar and a temperature of 1000-1050℃ for 2-4 h.

[0023] Optionally, in S5, the annealing treatment is carried out at 500-650℃ for 45-80 min, and then the sample is cooled in a hydrogen atmosphere.

[0024] Optionally, the S5 copper heat dissipation material has a density of 98.2-99.5%, a hardness of 105-146 HV, a tensile strength of 288.6-325.2 MPa, an elongation of 25.5-34.2%, a thermal conductivity of 352-367 W / (m·K), and an electrical conductivity of 78.8-85.6% IACS.

[0025] The above technical solution has at least the following advantages compared with the existing technology:

[0026] The above-mentioned solution proposes a method for preparing copper heat dissipation materials by injection molding of electrolytic copper powder, which can solve the problems of low utilization rate, complex structure and difficulty in preparation, and high production cost of heat dissipation materials in the prior art. If alloy particles are added to improve thermal conductivity and electrical conductivity, there will be technical problems such as the inability to improve the two properties in a synergistic way, the mismatch between strong plasticity and strong plasticity, the inability to prepare copper parts with complex shapes, and the high difficulty of operation.

[0027] The preparation method of this invention prevents the high activity and easy oxidation of copper, realizes the sintering activation of electrolytic copper powder and the liquid phase sintering of low melting copper-nickel powder, and achieves high shape preservation and high degreasing rate of plastic matrix samples. It also adopts multiple mechanisms to promote sintering densification, such as hydrogen atmosphere sintering and hot isostatic pressing sintering, which can significantly improve sintering densification.

[0028] The grinding and crushing process of this invention enables agglomerated particles to disperse using the impact force generated during collisions. Furthermore, the friction between particles wears away the sharp edges of their surfaces, resulting in smoother and more regular particle surfaces, thus producing spherical or near-spherical particles. Near-spherical particles are more easily coated by binder particles, significantly increasing the powder loading and resulting in a higher density of the sintered product, thereby improving its thermal and electrical conductivity and mechanical properties.

[0029] By selecting a wax-based binder, this invention enables the feedstock to have good flow properties, which can meet the requirements of rapid prototyping of large and complex parts in the subsequent injection process, and can manufacture products with complex shapes and high precision requirements.

[0030] This invention enables the integral molding of complex parts through injection molding with almost no material loss and a utilization rate of up to 98%. It solves the problems of low material utilization, difficult manufacturing of complex structures, and high production costs in heat sink machining, and provides a new approach for the preparation of heat sink devices with high material costs and complex structures.

[0031] The present application can significantly improve the tensile strength and ductility of the copper heat dissipation material by ensuring the full growth of the strength grains and the close combination between the grains, and then forming the strengthening phase in the matrix by solid solution aging treatment. The solid solution aging treatment can refine the grains, reduce the stress concentration at the grain boundary, prevent the brittle fracture of the material under external force, and improve the service life of the product. The residual stress in the heat dissipation product may cause deformation during subsequent processing. The solid solution aging treatment can also eliminate or reduce the residual stress, so that the size of the part is more stable. For some copper alloy products, the solid solution aging treatment can make the impurity elements uniformly distributed, reduce the lattice distortion, and improve the thermal and electrical conductivity of the alloy. This is of great significance in heat dissipation materials, which can improve the electrical performance of electronic components and reduce power loss. The sintered part is basically fully dense, and excellent comprehensive performance is obtained to meet the use requirements of the heat sink.

[0032] The present application can eliminate the residual stress by stress relief annealing of the sintered part, which can make the microstructure of the material more uniform, improve the dimensional stability, prevent the deformation of the workpiece during subsequent use, and finally obtain a copper heat dissipation material with high strength, high thermal conductivity and excellent ductility.

[0033] The copper heat dissipation material prepared by the present application has a density of 98.2% or more, a thermal conductivity of 352 W / (m·K) or more, and an electrical conductivity of 85.6% IACS or more. It has excellent thermal and electrical conductivity, and the copper sample has an elongation of 34.2% and a tensile strength of 325.2 MPa. It has good ductility and tensile properties, and is not prone to fracture and damage. It can meet the performance requirements of high-thermal-conductivity complex-structure copper heat sinks.

[0034] In summary, the method of the present application can realize the preparation of integrated needle-shaped heat dissipation materials by controlling the powder particle size, micro-shaping, atmosphere protection mixing, activation sintering, solid solution aging treatment, pressure sintering and stress relief annealing, which can improve the thermal conductivity, electrical conductivity, strength and plasticity of the copper heat dissipation material. The method is simple, easy to operate, green, low in cost, short in process and high in efficiency, and can meet the preparation of high-thermal-conductivity large-size complex-structure copper heat dissipation materials, which is beneficial to industrial large-scale production and promotion. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any inventive labor.

[0036] Figure 1is a process flow chart of a method for preparing copper heat dissipation material by electrolytic copper powder injection molding according to the present application;

[0037] Figure 2 is a microstructure diagram of the copper heat dissipation material prepared by the method for preparing copper heat dissipation material by electrolytic copper powder injection molding according to the embodiment 1 of the present application;

[0038] Figure 3 is a microstructure diagram of the copper heat dissipation material prepared by the method for preparing copper heat dissipation material by electrolytic copper powder injection molding according to the embodiment 2 of the present application. DETAILED DESCRIPTION

[0039] The technical solutions in the present application will be described below with reference to the drawings.

[0040] In the embodiments of the present application, the words such as "exemplary", "for example", etc. are used to represent an example, illustration or description. Any embodiment or design scheme described as "exemplary" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. In fact, the word "exemplary" is intended to present the concept in a specific manner. In addition, in the embodiments of the present application, the meaning expressed by "and / or" can be both, or can be either one of the two.

[0041] In the embodiments of the present application, "image" and "picture" can be used interchangeably at times. It should be pointed out that when the distinction is not emphasized, the meanings expressed are consistent.

[0042] In the embodiments of the present application, sometimes the subscript such as W1 can be written in the form of non-subscript such as W1. When the distinction is not emphasized, the meanings expressed are consistent.

[0043] In order to make the technical problems, technical solutions and advantages of the present application clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0044] A method for preparing copper heat dissipation material by electrolytic copper powder injection molding, the method for preparing copper heat dissipation material by electrolytic copper powder injection molding comprises the following steps:

[0045] S1, powder grinding and crushing treatment of electrolytic copper powder: electrolytic copper powder is weighed, and electrolytic copper powder particles are crushed by a superfine mechanical impact grinding mill to obtain electrolytic copper powder after powder grinding and crushing;

[0046] S2, powder compounding: the electrolytic copper powder after powder grinding and crushing in S1, alloy powder and wax-based binder are high-temperature and high-speed compounded to obtain high-purity feedstock;

[0047] S3, injection molding: the high-purity feedstock in S2 is injection molded to obtain a green part with no defects, no deformation and uniform composition; then the green part is subjected to catalytic and heating degreasing to obtain a sample after thermal degreasing;

[0048] S4, normal pressure sintering + aging treatment + hot isostatic sintering: the sample after S3 heat removal is sequentially subjected to normal pressure sintering in a hydrogen atmosphere + aging treatment + pressure sintering in a nitrogen atmosphere, to obtain a sintered copper heat dissipation material;

[0049] S5, annealing: the sintered copper heat dissipation material of S4 is subjected to stress relief annealing, to finally obtain a copper heat dissipation material with high strength, high thermal conductivity and excellent ductility.

[0050] In particular, the particle size D50 of the S1 electrolytic copper powder is 15-20 µm.

[0051] In particular, the experimental parameters of the S1 ultra-fine mechanical impact mill are: inlet air volume 200-300 m 3 / h, mill speed 2500-3000 r / min, classification impeller speed 1500-2500 r / min, feeding rate 100-200 g / min, after high-speed powder treatment for 2-4 h, the powder with a particle size of 10-15 µm is screened out, and the alloy powder is ZrCuAlNi, and the mass fraction of the additive is 1.5-3.0%.

[0052] In particular, in S2, the mass fraction of microcrystalline wax in the wax-based binder is 50-70%, the mass fraction of polyethylene is 15-25%, the mass fraction of polypropylene is 10-15%, the mass fraction of ethylene-vinyl acetate copolymer is 10-15%, and the mass fraction of vinyl bis-stearamide is 5-10%; argon or nitrogen is selected as the protective atmosphere for the internal mixing.

[0053] In particular, in S2, the temperature for high-temperature and high-speed internal mixing is 150-170 ℃, the speed of the internal mixer is 25-40 rpm, and the internal mixing time is 1-2 h.

[0054] In particular, in the injection process of S3, the injection temperature is 150-170 ℃, the injection pressure is 40-80 bar, the injection speed is 40-60 mm / s, and the mold temperature is 50-75 ℃; the main component of the solvent debinding binder is microcrystalline wax; the heat debinding is carried out at a heating rate of 1 ℃ / min from room temperature to 500 ℃, and the sample is kept at 250 ℃, 380 ℃ and 550 ℃ for 30 min, respectively.

[0055] In particular, in S3, trichloroethylene is used for solvent debinding, and the main component of the binder, microcrystalline wax, is removed by dissolving and debinding at 40-55 ℃ for 15-30 h.

[0056] In particular, the debinding rate of the sample after S3 heat removal is 6.0-7.8%, and the density is 4.55-5.10 g / cm 3 .

[0057] In particular, in the S4 step of normal pressure sintering, the flow rate of the hydrogen gas is ≥ 3 m 3 / min, the sintering temperature is 1065-1075℃, the holding time is 3-5h; in the aging treatment, the aging temperature is 110-140℃, the aging time is 30-50h; in the pressure sintering, the sintering is carried out in the atmosphere of nitrogen gas, the pressure is 5-15bar, and the temperature is 1000-1050℃, and the holding time is 2-4h.

[0058] In particular, the annealing treatment in S5 is carried out at 500-650℃, and the holding time is 45-80min, and then the furnace is cooled in the hydrogen atmosphere.

[0059] In particular, the density of the copper heat dissipation material in S5 is 98.2-99.5%, the hardness is 105-146HV, the tensile strength is 288.6-325.2MPa, the elongation is 25.5-34.2%, the thermal conductivity is 352-367W / (m·K), and the electrical conductivity is 78.8-85.6%IACS.

[0060] Example 1

[0061] A method for preparing a copper heat dissipation material by electrolytic copper powder injection molding, the method comprising the following steps:

[0062] S1, powder grinding treatment of electrolytic copper powder: 5kg of 500 mesh electrolytic copper powder is subjected to mechanical impact grinding and powder particle crushing, the mill speed of the superfine mechanical impact grinder is set to 2500r / min, the classification impeller speed is 1500r / min, and the feeding rate is 200g / min; after 3h of high-speed powder treatment, 2kg of 10-15µm powder ground electrolytic copper powder is screened out;

[0063] S2, powder compounding: 2kg of the powder ground electrolytic copper powder of S1, 1.5% of ZrCuAlNi alloy powder, and injection molding binder (the mass fraction of microcrystalline wax is 60%, the mass fraction of polyethylene is 15%, the mass fraction of polypropylene is 10%, the mass fraction of ethylene-vinyl acetate copolymer is 10%, and the mass fraction of vinyl bis-stearamide is 5%) are mixed at a volume ratio of 1:1, and then subjected to 60min of compounding at 165℃ and 30r / min in an argon atmosphere to obtain high-purity feedstock.

[0064] Solvent debinding and heat debinding to obtain the sample after heat debinding; during injection, the injection temperature is 160℃, the injection pressure is 60bar, the injection speed is 50mm / s, and the mold temperature is 65℃; the main component of the solvent debinding binder is microcrystalline wax; the heat debinding is heated at a heating rate of 1.5℃ / min from room temperature to 500℃, and is kept at 250℃, 380℃ and 500℃ for 30min respectively; the debinding rate of the sample after heat debinding is 6.8%, and the density is 4.82g / cm 3 ;

[0065] S4, atmospheric sintering + aging treatment + pressure sintering: the sample after S3 heat debinding is sequentially subjected to atmospheric sintering in a hydrogen atmosphere, solid solution aging treatment and pressure sintering, wherein in the atmospheric sintering step, the flow rate of the hydrogen gas is 3.0m 3 / min, the temperature is raised to 500℃ at a rate of 1℃ / min, the temperature is raised to 1070℃ at a rate of 2℃ / min after 500℃, and then kept for 150min; then cooled to room temperature in the furnace, and then subjected to aging treatment, the aging temperature is 120℃, and the aging time is 40h; during pressure sintering, the sample is kept at 1030℃ for 3h in a nitrogen atmosphere under a pressure of 5bar.

[0066] S5, annealing: the copper heat dissipation material after sintering in S4 is subjected to annealing treatment at 550℃, kept for 60min at this temperature, and then cooled in a hydrogen atmosphere to obtain a defect-free and deformation-free heat sink sample.

[0067] As shown in Figure 2 , the shape of the heat sink sample prepared in this embodiment is a needle column high specific surface area heat sink, and the microstructure is as shown in Figure 3 ; in terms of performance, the density is 98.6%, the hardness is 123HV, the tensile strength is 301.6MPa, the elongation is 28.2%, the thermal conductivity is 359W / (m·K), and the electrical conductivity is 82.3%IACS.

[0068] Comparative Example 1 is disclosed in Chinese Patent CN114131018A, which discloses a preparation method of a pressure net copper nano-pile bed heat dissipation material. The method needs to use four kinds of mixed particles, arrangement mode and copper net structure setting, cold pressing method and vacuum sintering, so that the prepared heat dissipation material is a porous structure material. The method can simplify the production process, reduce the difficulty of the preparation process and the requirement for instrument precision; the prepared heat dissipation material can be applied to phase change heat transfer, can have excellent phase change heat transfer performance, and can greatly improve the cooling efficiency of electronic devices.

[0069] From the comparative example 1 and the comparative example 2, it can be seen that simply mixing multiple powders plays a role in dispersion strengthening copper, so that the yield strength of the material is greatly improved, but the electrical conductivity of the material is poor, and the thermal conductivity performance is not uniform. Through the solid solution of the electrolytic powder after treatment and the alloy powder, and the subsequent aging treatment after sintering, the uniformity of the powder particles is maximized, and then the pressure sintering is carried out, so that the sintering is fully dense. In the case of ensuring the excellent thermal and electrical conductivity of copper, the mechanical properties such as strength and hardness of the material are also greatly improved.

[0070] Example 2

[0071] A method for preparing a copper heat dissipation material by electrolytic copper powder injection molding, the method for preparing a copper heat dissipation material by electrolytic copper powder injection molding comprises the following steps:

[0072] S1, powder grinding and crushing treatment of electrolytic copper powder: 5 kg of 500 mesh electrolytic copper powder is treated by mechanical impact grinding and crushing of powder particles, the mill speed of the ultra-fine mechanical impact grinder is set to 2500 r / min, the classification impeller speed is 1500 r / min, and the feeding rate is 200 g / min. After 3 h of high-speed powder treatment, 2 kg of 10-15 µm powder grinding and crushing electrolytic copper powder is screened out;

[0073] S2, powder compounding: 3 kg of powder grinding and crushing electrolytic copper powder, 1.8% of ZrCuAlNi alloy powder and injection molding binder (microcrystalline wax mass fraction 65%, polyethylene mass fraction 15%, polypropylene mass fraction 8%, ethylene-vinyl acetate copolymer mass fraction 8%, and vinyl bis-stearamide mass fraction 4%) are mixed at a volume ratio of 55:45, and are compounded at 160℃ and 25 r / min for 80 min. The compounding atmosphere is selected as argon as the protective atmosphere, and high-purity feedstock is obtained;

[0074] S3, injection molding: a defect-free, deformation-free and composition-uniform heat sink green part is obtained by injection molding of the high-purity feedstock using an injection molding machine and a matched mold; then the heat sink green part is subjected to solvent debinding and heating debinding, and a sample after thermal debinding is obtained; during the injection process, the injection temperature is 165℃, the injection pressure is 65 bar, the injection speed is 55 mm / s, and the mold temperature is 60℃; the main component of the binder removed by solvent debinding is microcrystalline wax; during thermal debinding from room temperature to 500℃, the heating rate is 1℃ / min, and the sample is kept at 200℃, 300℃ and 450℃ for 30 min respectively. The debinding rate of the sample after thermal debinding is 7.0%, and the density is 5.01 g / cm 3 .

[0075] S4, normal pressure sintering + aging treatment + pressure sintering: the sample after S3 heat removal is sequentially subjected to normal pressure sintering in a hydrogen atmosphere, solid solution aging treatment and pressure sintering. In the normal pressure sintering step, the flow rate of the hydrogen gas is 3.5 m 3 / min, the temperature is raised to 500°C at a rate of 1°C / min, the temperature is raised to 1070°C at a rate of 1.5°C / min after 500°C, and then the temperature is kept for 220 min; then the furnace is cooled to room temperature, and then aging treatment is performed, the aging temperature is 130°C, the aging time is 35 h, and in the pressure sintering, the nitrogen atmosphere is used, the pressure is 10 bar, and the temperature is kept for 2 h at 1040°C.

[0076] S5, annealing: the copper heat dissipation material after sintering in S4 is subjected to annealing treatment at 600°C, the temperature is kept for 50 min, and then the sample is cooled in a hydrogen atmosphere to obtain a defect-free and deformation-free heat sink sample.

[0077] The heat sink sample prepared in this embodiment has a needle column shape and a high specific surface area. In terms of performance, the density is 98.4%, the hardness is 121 HV, the tensile strength is 295.9 MPa, the elongation is 26.8%, the thermal conductivity is 356 W / (m·K), and the electrical conductivity is 80.1% IACS.

[0078] Example 3

[0079] A method for preparing a copper heat dissipation material by electrolytic copper powder injection molding, the method comprising the following steps:

[0080] S1, powder grinding and crushing treatment of electrolytic copper powder: 5 kg of 500 mesh electrolytic copper powder is subjected to mechanical impact grinding and crushing of powder particles, the mill speed of the ultra-fine mechanical impact grinder is set to 2000 r / min, the classification impeller speed is 1200 r / min, and the feeding rate is 180 g / min. After high-speed powder treatment for 2.5 h, 2.5 kg of 10-15 µm ground and crushed electrolytic copper powder is screened out;

[0081] S2, powder compounding: 2 kg of ground and crushed electrolytic copper powder in S1, 1.8% of ZrCuAlNi alloy powder and injection molding binder (70% microcrystalline wax, 10% polyethylene, 8% polypropylene, 7% ethylene-vinyl acetate copolymer and 5% vinyl bis-stearamide) are mixed at a volume ratio of 3:2, and then compounded at 155°C and 35 r / min for 60 min. Nitrogen is selected as the protective atmosphere, and high-purity feedstock is obtained.

[0082] S3, injection molding: a defect-free, non-deformed, composition-uniform heat sink green part is obtained by using a high-purity feeding injection molding machine and a matched mold; then the heat sink green part is subjected to solvent debinding and heating debinding to obtain a sample after thermal debinding; during the injection process, the injection temperature is 155°C, the injection pressure is 70 bar, the injection speed is 40 mm / s, and the mold temperature is 55°C; the main component of the binder removed by solvent debinding is microcrystalline wax; the heating debinding is carried out at room temperature to 450°C at a heating rate of 1.5°C / min, and the sample after thermal debinding is heated and kept at 220°C, 310°C and 450°C for 30 min respectively, and the debinding rate of the sample after thermal debinding is 7.2%, and the density is 5.10 g / cm 3 .

[0083] S4, normal pressure sintering + aging treatment + pressure sintering: the sample after thermal debinding in S3 is sequentially subjected to normal pressure sintering in a hydrogen atmosphere, solid solution aging treatment and pressure sintering. In the normal pressure sintering step, the flow rate of the hydrogen gas is 3.8 m 3 / min, the temperature is increased to 500°C at a rate of 2°C / min, and then increased to 1070°C at a rate of 1.5°C / min after 500°C, and then kept for 250 min; then the furnace is cooled to room temperature, and then the aging treatment is carried out, the aging temperature is 115°C, the aging time is 45 h, and the pressure sintering is carried out in a nitrogen atmosphere at a pressure of 12 bar and a temperature of 1050°C for 2.5 h.

[0084] S5, annealing: the copper heat sink material after sintering in S4 is subjected to annealing treatment at 580°C, kept for 75 min at this temperature, and then cooled in a hydrogen atmosphere to obtain a defect-free, non-deformed heat sink sample.

[0085] The shape of the heat sink sample prepared in this embodiment is a needle columnar high specific surface area heat sink. In terms of performance, the density is 99.1%, the hardness is 131 HV, the tensile strength is 315.4 MPa, the elongation is 26.9%, the thermal conductivity is 362 W / (m·K), and the electrical conductivity is 84.6% IACS.

[0086] Example 4

[0087] A method for preparing a copper heat sink material by electrolytic copper powder injection molding, the method for preparing a copper heat sink material by electrolytic copper powder injection molding comprising the following steps:

[0088] S1, powder grinding treatment of electrolytic copper powder: 5 kg of 500 mesh electrolytic copper powder is subjected to mechanical impact grinding and powder breaking, the mill speed of the ultra-fine mechanical impact grinder is set to 2300 r / min, the classification impeller speed is 1300 r / min, and the feeding rate is 150 g / min. After 3 h of high-speed powder treatment, 3 kg of 10-15 µm powder ground and broken electrolytic copper powder is screened out.

[0089] S2, powder compounding: 3 kg of the powder-milled electrolytic copper powder of S1 is mixed with 2.2% of the ZrCuAlNi alloy powder injection molding binder (the mass fraction of microcrystalline wax is 60%, the mass fraction of polyethylene is 21%, the mass fraction of polypropylene is 12%, the mass fraction of ethylene-vinyl acetate copolymer is 6%, and the mass fraction of vinyl bis-stearamide is 1%) at a volume ratio of 58:42, and is compounded at 158°C and 28 r / min for 80 min. Nitrogen is selected as the protective atmosphere during compounding, to obtain a high-purity feedstock;

[0090] S3, injection molding: a defect-free, deformation-free, and composition-uniform heat sink green part is obtained by using an injection molding machine and a matched mold to injection mold the high-purity feedstock; then the heat sink green part is subjected to catalytic debinding and heating debinding, to obtain a sample after thermal debinding; during the injection process, the injection temperature is 158°C, the injection pressure is 65 bar, the injection speed is 35 mm / s, and the mold temperature is 50°C; the main component of the solvent debinding binder is microcrystalline wax; during thermal debinding, the sample is heated at a heating rate of 1.8°C / min from room temperature to 500°C, and is kept at 240°C, 320°C, and 480°C for 30 min, respectively; the debinding rate of the sample after thermal debinding is 6.6%, and the density is 4.73 g / cm 3 .

[0091] S4, normal-pressure sintering + aging treatment + pressure sintering: the sample after thermal debinding of S3 is sequentially subjected to hydrogen atmosphere normal-pressure sintering, solid solution aging treatment, and pressure sintering. In the normal-pressure sintering step, the flow rate of the hydrogen gas is 2.8 m 3 / min, the temperature is increased to 500°C at a rate of 1°C / min, the temperature is increased to 1070°C at a rate of 1.8°C / min after 500°C, and then the temperature is kept at 1070°C for 240 min; then the sample is cooled to room temperature in the furnace, and is subjected to aging treatment at an aging temperature of 110°C for an aging time of 30 h; during pressure sintering, the sample is kept at 1010°C for 2 h under the atmosphere of nitrogen gas at a pressure of 15 bar.

[0092] S5, annealing: the copper heat sink material after sintering of S4 is subjected to annealing treatment at 610°C for 50 min, and then is cooled to room temperature in a hydrogen atmosphere, to obtain a defect-free and deformation-free heat sink sample.

[0093] The heat sink sample prepared in this example has a needle columnar shape and a high specific surface area. In terms of performance, the compactness is 98.2%, the hardness is 105 HV, the tensile strength is 288.6 MPa, the elongation is 25.5%, the thermal conductivity is 352 W / (m·K), and the electrical conductivity is 78.8% IACS.

[0094] Example 5

[0095] A method for preparing a copper heat dissipation material by electrolytic copper powder injection molding, the method comprising the following steps:

[0096] S1, powder grinding treatment of electrolytic copper powder: 5 kg of 500 mesh electrolytic copper powder is ground by mechanical impact milling, the mill speed of the ultra-fine mechanical impact mill is set to 3000 r / min, the classification impeller speed is 1800 r / min, and the feeding rate is 220 g / min. After 3 h of high-speed powder treatment, 3 kg of 10-15 µm ground electrolytic copper powder is screened out;

[0097] S2, powder compounding: 3 kg of ground electrolytic copper powder, 2.5% of ZrCuAlNi alloy powder, and injection molding binder (microcrystalline wax mass fraction 55%, polyethylene mass fraction 15%, polypropylene mass fraction 12%, ethylene-vinyl acetate copolymer mass fraction 12%, and vinyl bis-stearamide mass fraction 6%) are mixed at a volume ratio of 58:42, and are compounded at 163°C and 40 r / min for 60 min in an argon atmosphere to obtain high-purity feedstock;

[0098] S3, injection molding: a defect-free, deformation-free, and composition-uniform heat sink green part is obtained by injection molding of the high-purity feedstock using an injection molding machine and a matched mold; then the heat sink green part is subjected to catalytic and thermal debinding to obtain a sample after thermal debinding; during the injection process, the injection temperature is 163°C, the injection pressure is 70 bar, the injection speed is 60 mm / s, and the mold temperature is 56°C; the main component of the solvent debinding binder is microcrystalline wax; the thermal debinding is performed at a heating rate of 1.2°C / min from room temperature to 500°C, and the sample is kept at 220°C, 350°C, and 500°C for 30 min, respectively; the debinding rate of the sample after thermal debinding is 7.8%, and the density is 5.10 g / cm 3 .

[0099] S4, normal pressure sintering + aging treatment + pressure sintering: the sample after thermal debinding in S3 is sequentially subjected to normal pressure sintering in a hydrogen atmosphere, solid solution aging treatment, and pressure sintering. In the normal pressure sintering step, the flow rate of the hydrogen gas is 4.2 m 3 / min, the temperature is raised to 500°C at a rate of 1°C / min, and then raised to 1075°C at a rate of 1.2°C / min after 500°C, and then kept at 1075°C for 300 min; then the sample is cooled to room temperature in the furnace, and then subjected to aging treatment at an aging temperature of 120°C for 40 h; in the pressure sintering, the sample is kept at 1050°C for 3 h under a nitrogen atmosphere at a pressure of 15 bar.

[0100] S5, annealing: the sintered copper heat sink material of S4 is annealed at 650℃ for 80min, and then cooled in a hydrogen atmosphere to obtain a defect-free and deformation-free heat sink sample.

[0101] The heat sink sample prepared in this embodiment has a needle column shape and a high specific surface area. In terms of performance, the density is 99.5%, the hardness is 146HV, the tensile strength is 325.2MPa, the elongation is 34.2%, the thermal conductivity is 367W / (m·K), and the electrical conductivity is 85.6%IACS.

[0102] Example 6

[0103] A method for preparing a copper heat sink material by electrolytic copper powder injection molding, the method comprising the following steps:

[0104] S1, powder grinding treatment of electrolytic copper powder: 5kg of 500 mesh electrolytic copper powder is ground by mechanical impact milling to break the powder particles. The mill speed of the ultra-fine mechanical impact mill is set to 2200r / min, the classification impeller speed is 1300r / min, and the feed rate is 160g / min. After 3h of high-speed powder treatment, 2.5kg of 10-15µm ground electrolytic copper powder is screened out;

[0105] S2, powder compounding: 2.5kg of ground electrolytic copper powder of S1, 1.5% of ZrCuAlNi alloy powder, and injection molding binder (microcrystalline wax mass fraction 60%, polyethylene mass fraction 18%, polypropylene mass fraction 8%, ethylene-vinyl acetate copolymer mass fraction 8%, and vinyl bis-stearamide mass fraction 6%) are mixed at a volume ratio of 55:45, and then compounded at 155℃ and 30r / min for 60min. Argon is selected as the protective atmosphere. A high-purity feedstock is obtained;

[0106] S3, injection molding: a defect-free, deformation-free, and composition-uniform heat sink green part is obtained by injection molding using a high-purity feedstock and a matched mold. Then, the heat sink green part is subjected to catalytic and thermal debinding to obtain a heat-debindered sample. During injection molding, the injection temperature is 155℃, the injection pressure is 55bar, the injection speed is 40mm / s, and the mold temperature is 50℃. The main component of the solvent debinding binder is microcrystalline wax. During thermal debinding, the sample is heated at a rate of 1.5℃ / min from room temperature to 480℃, and then held at 200℃, 320℃, and 480℃ for 30min, respectively. The debinding rate of the heat-debindered sample is 6.9%, and the density is 4.96g / cm 3 .

[0107] S4. Atmospheric Pressure Sintering + Aging Treatment + Pressure Sintering: The sample after thermal stripping in S3 is sequentially subjected to atmospheric pressure sintering in a hydrogen atmosphere, solution aging treatment, and pressure sintering. In the atmospheric pressure sintering step, the flow rate of the hydrogen gas is 3.5 m / s. 3 The temperature was increased to 500℃ at a rate of 1.5℃ / min, and then increased to 1065℃ at a rate of 2.5℃ / min, followed by holding at that temperature for 180 min. Subsequently, the temperature was cooled to room temperature in the furnace, and then aged at 125℃ for 40 h. During pressure sintering, the temperature was held at 1030℃ for 3 h under a nitrogen atmosphere and a pressure of 8 bar.

[0108] S5. Annealing: The copper heat dissipation material after S4 sintering is annealed at 630℃ and held at this temperature for 80 minutes. Then, it is cooled in the furnace under a hydrogen atmosphere to obtain a heat dissipation sample without defects or deformation.

[0109] The heat sink sample prepared in this embodiment is a needle-shaped high specific surface area heat sink. In terms of performance, the density is 98.8%, the hardness is 126HV, the tensile strength is 295.5MPa, the elongation is 29.3%, the thermal conductivity is 362W / (m·K), and the electrical conductivity is 83.4%IACS.

[0110] The above-mentioned solution proposes a method for preparing copper heat dissipation materials by injection molding of electrolytic copper powder, which can solve the problems of low utilization rate, complex structure and difficulty in preparation, and high production cost of heat dissipation materials in the prior art. If alloy particles are added to improve thermal conductivity and electrical conductivity, there will be technical problems such as the inability to improve the two properties in a synergistic way, the mismatch between strong plasticity and strong plasticity, the inability to prepare copper parts with complex shapes, and the high difficulty of operation.

[0111] The preparation method of this invention prevents the high activity and easy oxidation of copper, realizes the sintering activation of electrolytic copper powder and the liquid phase sintering of low melting copper-nickel powder, and achieves high shape preservation and high degreasing rate of plastic matrix samples. It also adopts multiple mechanisms to promote sintering densification, such as hydrogen atmosphere sintering and hot isostatic pressing sintering, which can significantly improve sintering densification.

[0112] The grinding and crushing process of this invention enables agglomerated particles to disperse using the impact force generated during collisions. Furthermore, the friction between particles wears away the sharp edges of their surfaces, resulting in smoother and more regular particle surfaces, thus producing spherical or near-spherical particles. Near-spherical particles are more easily coated by binder particles, significantly increasing the powder loading and resulting in a higher density of the sintered product, thereby improving its thermal and electrical conductivity and mechanical properties.

[0113] The application can make the feed have good flow performance by selecting the wax-based binder, can meet the rapid prototyping of large-size complex parts in subsequent injection process, and can manufacture products with complex shape and high precision.

[0114] The application can integrally form the complex structure part by injection molding, and the material utilization rate is as high as 98%, solves the problems of low material utilization rate, complex structure and high production cost of the heat sink, and provides a new idea for preparing the heat sink with high material cost and complex structure.

[0115] The application can improve the strength of the grains by sintering under normal pressure, aging treatment and pressure sintering, and the grains are tightly combined, and after the solid solution aging treatment, the alloying elements form a dispersed strengthening phase in the matrix, which can significantly improve the tensile strength and ductility. The solid solution aging can refine the grains, reduce the stress concentration at the grain boundary, prevent brittle fracture of the material under external force, and improve the service life of the product. The heat dissipation product may be deformed due to residual stress in the subsequent processing process. The solid solution aging treatment can also eliminate or reduce residual stress, so that the size of the part is more stable. For some copper alloy products, the solid solution aging treatment can make the impurity elements uniformly distributed, reduce the lattice distortion, and improve the thermal and electrical conductivity of the alloy. This is of great significance in heat dissipation materials, and can make the electrical properties of electronic components better and reduce power loss. The sintered part is basically fully dense, has excellent comprehensive performance, and meets the use requirements of the heat sink.

[0116] The application can eliminate residual stress by stress relief annealing of the sintered part, so that the microstructure of the material is more uniform, the dimensional stability is improved, deformation of the workpiece in subsequent use is prevented, and finally a copper heat dissipation material with high strength, high thermal conductivity and excellent ductility is obtained.

[0117] The copper heat dissipation material prepared by the application has a density of 98.2% or more, a thermal conductivity of 352 W / (m·K) or more, and an electrical conductivity of 85.6% IACS, has excellent thermal and electrical conductivity, a copper sample elongation of 34.2%, a tensile strength of 325.2 MPa, good ductility and tensile properties, and is not easy to break, which can meet the performance requirements of high-thermal-conductivity complex-structure copper heat sinks.

[0118] In summary, the method of the present application realizes the preparation of integrated needle-shaped heat dissipation materials by controlling the powder particle size and micro-shaping, atmosphere protection mixing, activation sintering, solid solution aging treatment, pressure sintering, stress relief annealing and other sintering densification mechanisms, so that the thermal conductivity performance, electrical conductivity performance and strength plasticity of the copper heat dissipation material are synergistically improved; the method is simple and easy to operate, green and environmentally friendly, low in cost, short in process, high in efficiency, meets the preparation of high-thermal-conductivity large-size complex-structure copper heat dissipation materials, and is beneficial to industrial large-scale production and popularization.

[0119] It should be understood that the term "and / or" herein merely describes an association relationship of associated objects, and indicates that there can be three relationships, for example, A and / or B can represent three cases of A alone, A and B together, and B alone, wherein A and B can be singular or plural. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects, but can also represent an "and / or" relationship, which can be understood according to the context before and after.

[0120] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or the like means any combination of the items, including any combination of single item or multiple items. For example, at least one of a, b, or c can represent a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0121] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and the execution order of the processes should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0122] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of producing a copper heat dissipation material by electrolytic copper powder injection molding, characterized by, The method steps of preparing the copper heat dissipation material by the electrolytic copper powder injection molding are as follows: S1, powder grinding and crushing treatment of electrolytic copper powder: electrolytic copper powder is weighed, and electrolytic copper powder particles are crushed by a superfine mechanical impact grinding mill to obtain electrolytic copper powder after powder grinding and crushing; S2, powder compounding: the electrolytic copper powder after powder grinding and crushing in S1, alloy powder and wax-based binder are subjected to high-temperature and high-speed compounding, the temperature of high-temperature and high-speed compounding is 150-170℃, the rotating speed of the compounding machine is 25-40rpm, the compounding time is 1-2h, and high-purity feedstock is obtained; the alloy powder is ZrCuAlNi, and the mass fraction of the alloy powder is 1.5-3.0%; S3, injection molding: the high-purity feedstock in S2 is injection molded to obtain a green part without defects, deformation and uniform composition; then the green part is subjected to catalytic and heating debinding to obtain a sample after thermal debinding; S4, the sample after thermal debinding in S3 is sequentially subjected to normal-pressure sintering in a hydrogen atmosphere + aging treatment + pressure sintering in a nitrogen atmosphere to obtain a sintered copper heat dissipation material; S5, annealing: the sintered copper heat dissipation material in S4 is subjected to stress relief annealing, and finally a copper heat dissipation material with high strength, high thermal conductivity and excellent ductility is obtained.

2. The method of claim 1, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. The particle size D50 of the electrolytic copper powder in S1 is 15-20µm.

3. The method of claim 1, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. The experimental parameters of the S1 ultrafine mechanical impact mill are: inlet air flow 200-300 m 3 / h, mill speed 2500-3000 r / min, classification impeller speed 1500-2500 r / min, feed rate 100-200 g / min, after high-speed powder treatment for 2-4 h, the powder of 10-15 pm is sieved out.

4. The method of claim 1, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. In S2, the mass fraction of microcrystalline wax in the wax-based binder is 50-70%, the mass fraction of polyethylene is 15-25%, the mass fraction of polypropylene is 10-15%, the mass fraction of ethylene-vinyl acetate copolymer is 10-15%, and the mass fraction of vinyl bis-stearamide is 5-10%; argon or nitrogen is selected as the protective atmosphere for compounding.

5. The method of claim 1, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. In S3, the injection temperature is 150-170℃, the injection pressure is 40-80bar, the injection speed is 40-60mm / s, and the mold temperature is 50-75℃; the main component of the binder removed by solvent debinding is microcrystalline wax.

6. The method of claim 4, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. In S3, trichloroethylene is selected for solvent debinding, and the main component of the binder, i.e., microcrystalline wax, is removed by solvent debinding at 40-55℃ for 15-30h.

7. The method of claim 1, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. The defatting rate of the sample after S3 heat removal is 6.0-7.8%, and the density is 4.55-5.10 g / cm 3 .

8. The method of claim 1, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. S4 In the step of normal pressure sintering, the flow rate of the hydrogen gas is ≥ 3 m 3 / min, the sintering temperature is 1065-1075℃, the holding time is 3-5h; in the aging treatment, the aging temperature is 110-140℃, the aging time is 30-50h; in the pressure sintering, the sintering is carried out in the atmosphere of nitrogen gas, under the pressure of 5-15bar, and the temperature is 1000-1050℃, and the holding time is 2-4h.

9. The method of claim 1, wherein the copper heat dissipation material is prepared by electrolytic copper powder injection molding. In S5, the annealing treatment is performed at 500-650℃, and the temperature is kept for 45-80min, and then the furnace is cooled in a hydrogen atmosphere.

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