Preparation method of a coated structure metal-based diamond composite material

Abstract

The present invention discloses a preparation method of a coated structure metal matrix diamond composite material. Metal powder and a binder are kneaded and granulated to obtain a metal powder feedstock; the metal powder feedstock is pressed into a metal powder thin sheet with a thickness of 0.1 to 0.5 mm by a constant temperature hot press; a layer of glue with a unit distribution is prepared on the surface of the metal powder thin sheet by a screen printer, and diamond particles with a coating on the surface are fixed on the glue to obtain a metal matrix diamond composite embryo with a diamond unit distribution; the metal powder thin sheet is used as the upper and lower surface layers, and the metal matrix diamond composite embryo is used as the intermediate layer and stacked in sequence to form an initial embryo; the initial embryo is subjected to degreasing and pre-sintering treatment, and after cooling, a pre-sintered embryo is taken out; the pre-sintered embryo is subjected to high-temperature pressure sintering to obtain a sintered blank; the obtained sintered blank is machined and the surface is polished to obtain a coated structure metal matrix diamond composite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of diamond, and particularly relates to a preparation method of a coated structure metal matrix diamond composite material. Background Art

[0002] With the development of integrated circuit technology, the integration degree of chips is getting higher and higher, and the heat flux density generated during circuit operation increases sharply accordingly. The heat dissipation problem has become a restricting factor for further improvement of chip integration. The thermal conductivity of high-quality single crystal diamond can not only reach 2000 W / mK, but also has a series of advantages such as low dielectric constant and low thermal expansion coefficient, etc., and has important application prospects in the field of electronic packaging materials. The existing processes of metal matrix diamond composites are difficult to ensure the uniformity and stability of the properties of large-size diamond-metal matrix composites.

[0003] At present, the methods for preparing metal matrix diamond composites mainly include powder sintering method and melt infiltration method. The powder sintering method mainly adopts vacuum hot pressing sintering method (VHPS). To ensure that the composite material has a high density and thermal conductivity, the volume fraction of diamond is generally selected as 50-55%. Due to the low volume fraction of diamond, it is difficult to bridge between particles, and the thermal conductivity of the metal matrix diamond composite material prepared by the powder sintering method is generally lower than 500 W / (m·K). The melt infiltration method includes pressure infiltration (gas pressure infiltration and mechanical extrusion infiltration) and pressureless infiltration. Since the molten metal liquid infiltrates into the gaps of the diamond particle packing under the action of protective gas pressure, mechanical extrusion pressure or capillary force, and the aluminum liquid can effectively fill the gaps between diamond particles after seepage, compared with powder metallurgy method, the thermal conductivity of the diamond-Al composite material prepared by the melt infiltration method is higher, but the time required for sample preparation is generally long and the preparation efficiency is very low. The high-pressure infiltration of aluminum liquid will cause the displacement and loosening of the particle packing.

[0004] For the metal matrix diamond composite material to be applied in electronic components, it not only needs to meet the requirements of high thermal conductivity and low thermal expansion, but also needs to meet the requirement of extremely high surface finish to ensure a small thermal resistance (thin welding layer, no defects) and high thermal fatigue life of the welding layer. Since diamond is the hardest material in nature, it is impossible to grind the protrusions on the surface of the composite material with traditional mechanical processing methods. In patent CN102149655A, aluminum alloy liquid is infiltrated into the mold containing a diamond preform through pressure melting infiltration. When the preform is placed, there is a certain gap between the front and back surfaces of the mold groove, so an aluminum alloy layer can be formed on the upper and lower surfaces of the aluminum matrix diamond composite material. By processing the surface of the composite material, the surface roughness of the composite material can be reduced. However, this method requires the preparation of diamond preforms, which is not only complex in process, but also the addition of binders will introduce thermal resistance between diamond particles, making it difficult to form a fast heat transfer channel, restricting the improvement of the thermal conductivity of the composite material and being inconvenient for mass production.

[0005] The difficulties in preparing easily - processable metal - matrix diamond thermal - conductive composites mainly lie in: the processing of high - thermal - conductivity diamond - metal composites is an important factor hindering the industrial application of such composites, and the relatively high processing cost severely restricts the commercialization process of this composite material. With the continuous reduction of the production cost of single - crystal diamond, the size and quality of diamond are continuously increasing, and the manufacturing cost of metal - matrix diamond composites is also continuously decreasing. The only thing that needs to be overcome is the difficult - processing characteristic of diamond composites. Therefore, there is an urgent need in this field to develop a high - thermal - conductivity diamond thermal - conductive composite material with easy processability and high uniform dispersion. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method for a coated - structure metal - matrix diamond composite material, which can ensure the high thermal conductivity, high uniform dispersion of the obtained metal - matrix diamond composite material, and at the same time can ensure the easy processability of six surfaces and has a very high surface finish.

[0007] To achieve the above - mentioned purpose, the following technical solutions are adopted:

[0008] A preparation method for a coated - structure metal - matrix diamond composite material includes the following steps:

[0009] 1) Knead and granulate metal powder and binder to obtain a metal powder feedstock;

[0010] 2) Use a constant - temperature hot press to press the metal powder feedstock into a metal powder thin sheet with a thickness of 0.1 - 0.5 mm;

[0011] 3) Use a screen printer to prepare a layer of glue with unit distribution on the surface of the metal powder thin sheet, fix diamond particles with a coating on the glue to obtain a metal - matrix diamond composite embryo with unit - distributed diamonds; use the metal powder thin sheet as the upper and lower surface layers, and the metal - matrix diamond composite embryo as the middle layer to stack them in sequence to form an initial embryo;

[0012] 4) Debind and pre - sinter the initial embryo, and take it out after cooling to obtain a pre - sintered embryo;

[0013] 5) Perform high - temperature pressure sintering on the pre - sintered embryo to obtain a sintered blank;

[0014] 6) Machine - process the obtained sintered blank and polish its surface to obtain a coated - structure metal - matrix diamond composite material.

[0015] According to the above - mentioned scheme, the metal powder in step 1) is one of copper powder and aluminum powder, with an average particle size of 5 - 30 μm, preferably 10 - 20 μm.

[0016] According to the above - mentioned scheme, the composition of the binder in step 1) is by mass percentage:

[0017] PE wax (average molecular weight 2000 - 5000): 10 - 20%, microcrystalline wax (80# microcrystalline wax): 20 - 35%; Chinese bee wax (acid value 5.0 - 6.0): 10 - 25%, atactic polypropylene (average molecular weight 100,000 - 150,000): 8 - 15%; styrene-butadiene-styrene block copolymer (average molecular weight 80,000 - 100,000): 1 - 3%; homopolyoxymethylene (average molecular weight 30,000 - 50,000): 3 - 10%, TPEE (injection molding grade 1047D): 3 - 10%, stearic acid (molecular weight: 284): 10 - 15%.

[0018] According to the above scheme, in step 1), control the volume ratio of the binder to be 40% - 60%, preferably 45 - 55%; the mixing temperature is 80 - 100 °C, and the time is 3 - 4 h; the rotation speed of the mixer is 80 - 120 r / min. After mixing, use a granulator to make granular feed with a diameter of 0.5 - 1 mm.

[0019] According to the above scheme, in step 2), the metal powder feed is laid flat in a constant temperature hot press mold, the mold temperature is 100 - 140 °C, and the pressure is 30 - 60 Mpa.

[0020] According to the above scheme, in step 3), the diamond particles with a coating on the surface are artificial high-temperature high-pressure diamonds, artificial CVD diamonds or natural diamonds with a surface coating thickness of 0.1 - 0.5 μm; the particle size of the diamond particles is 100 - 500 μm (preferably 100 - 300 μm), and the coating material is one of SiC-Si and TiC-Ti; the coating is prepared on the surface of the diamond particles by ion plating.

[0021] According to the above scheme, the composition of the glue used in screen printing in step 3) is by mass percentage:

[0022] Terpineol 90 - 98%, adipic acid ether plasticizer 0.6 - 1%, hydrogenated castor oil 0.1 - 1%, lecithin 0.2 - 1%, ethyl cellulose 0.1 - 3%.

[0023] According to the above scheme, the degreasing and pre-sintering treatment in step 4) includes the following steps:

[0024] Place the initial embryo in a vacuum sintering furnace with a vacuum degree of 10 -3 Pa, heat it from room temperature (15 - 35 °C) to 450 - 520 °C at a rate of 5 °C / min, and keep it warm for 2 - 4 hours (the purpose of keeping warm is to completely remove the binder and glue), then heat it to the liquidus temperature of the metal powder (600 - 700 °C for aluminum powder, 1050 - 1150 °C for copper powder) at a rate of 3 °C / min, and keep it warm for 1 - 2 hours. After the pre-sintering treatment, the easily processed metal matrix diamond embryo has a certain bonding strength, and the relative density reaches more than 92%.

[0025] According to the above solution, the high-temperature pressure sintering described in step 5) includes the following steps:

[0026] Heat the pre-sintered blank under a vacuum degree of 10 -1 ~10 -2 Pa, an inert atmosphere (argon or helium), or a reducing atmosphere of hydrogen-argon mixture (hydrogen volume fraction is 5%); heat from room temperature at a rate of 10-20 °C / min to a range 50-100 °C below the liquidus temperature of the metal powder (the aluminum powder is heated to 550-600 °C, and the copper powder is heated to 1000-1050 °C); after reaching the highest temperature, apply pressure, the pressure is 30-50 Mpa, keep warm for 30-60 min, and keep the pressure and cool with the furnace to room temperature to obtain a sintered blank.

[0027] According to the above solution, step 6) includes the following steps:

[0028] Use one of the cutting methods of diamond wire saw, laser cutting or water jet to cut out the composite material of the superposition part of diamond and metal matrix, and ensure that the surface shell layer of the obtained composite material is a metal matrix material. After machining and polishing the metal surface shell layer, a coated structure metal matrix diamond composite material with a surface metal shell layer thickness of 0.1-0.3 mm and a roughness Ra lower than 0.4 is obtained.

[0029] In the present invention, first, the metal powder and the binder are mixed, and then the metal powder feedstock is pressed into a metal powder thin sheet with a thickness of 0.1-0.5 mm by a constant temperature press. Then, a layer of glue with a regular pattern is screen-printed on the metal powder thin sheet, and the diamond particles with a surface coating are fixed on the glue. Then, the metal powder thin sheet is used as the upper and lower surfaces, and the metal powder thin sheet containing diamond is used as the intermediate layer, and they are stacked and pre-pressed at a constant temperature. The binder and the glue are removed by vacuum high-temperature purification, and a pre-sintered blank with a certain density is obtained by high-temperature pre-sintering. Finally, after high-temperature pressure sintering, the regular pattern is cut out, and after machining and polishing, a metal matrix diamond composite material with six surfaces having a high smoothness is obtained. The surface of the metal matrix diamond composite material designed by the present invention is a metal with a thickness of 0.1-0.5 mm, the surface metal thickness is adjustable, and it shows excellent machinability; the volume fraction content of the metal matrix diamond in the intermediate layer is 50-70%, and it shows excellent high thermal conductivity. The comprehensive thermal conductivity TC of the metal matrix diamond composite material prepared by the present invention is ≥500 (W / mK), and the surface smoothness Ra is less than 0.4, and it has broad application prospects and practical value in the field of heat dissipation.

[0030] In order to ensure a high thermal conductivity, the present invention uses a metal matrix diamond composite material as the high thermal conductivity intermediate layer, in which the diamond volume fraction is 50-70%, to ensure the same high thermal conductivity in three-dimensional directions.

[0031] Single-layer metal-based diamond composites have high thermal conductivity and low thermal expansion. However, due to the high hardness of diamond particles, the surface processing of single-layer metal-based diamond composites is difficult, and the surface finish Ra > 1. The preparation method adopted in the present invention is to wrap the metal-based diamond composite layer in the middle layer with metal. It can not only ensure the high thermal conductivity of the metal-based diamond composite, but also ensure the machinability of six surfaces and have a very high finish (Ra is less than 0.4).

[0032] To improve the surface finish, the present invention designs that the thickness of the surface metal of the metal-based diamond composite is adjustable, which can not only ensure that diamond particles are not exposed, improve the surface finish and plating property of the metal, but also ensure high overall thermal conductivity and strength.

[0033] To ensure the uniformity of metal powder and the controllable distribution of diamond, the feedstock made by mixing metal powder and binder needs to have good fluidity at high temperature. The metal powder feedstock is pressed into a thin sheet with uniform distribution of metal powder in a constant temperature hot press. After cooling, the metal powder thin sheet has a certain strength. The glue is printed on the metal powder thin sheet by screen printing technology. The diamond particles will firmly adhere to the glue, and there will be no diamond where there is no glue, so as to achieve the controllable distribution of diamond.

[0034] In addition, since diamond is fixed by glue and not embedded in the metal powder, there will be a certain gap between the middle layer and the upper and lower surfaces, which can be used as an exhaust channel. When pre-burning, the binder and glue can be removed completely. The highest pre-burning temperature is set near the melting point temperature of the corresponding metal (the highest temperature of aluminum powder is set at 600 °C - 700 °C, and the highest temperature of copper powder is set at 1050 - 1150 °C). Under the action of capillary force, the molten metal on the surface fills into the middle diamond layer. After pre-burning, a metal-based diamond pre-sintered blank with a relative density higher than 92% is obtained. Control the corresponding heating rate and holding time to avoid defects such as deformation, collapse, and cracks in the blank during the sintering process.

[0035] Finally, through high-temperature pressure sintering below the liquidus temperature of the metal powder (aluminum powder is heated to 550 - 600 °C, copper powder is heated to 1000 - 1050 °C), on the one hand, the metal is extruded into the diamond gap by external force to further improve the relative density of the metal-based diamond composite to complete densification, strengthen the bonding strength between diamond and metal, and improve the thermal conductivity. On the other hand, when under the action of pressure, the grains of the metal matrix deform to play a certain deformation strengthening role, increasing the overall strength of the metal-based diamond composite.

[0036] A metal-based diamond composite with a coating structure. The metal-based diamond composite prepared by the described preparation method is applicable to high thermal conductivity composite heat spreaders or encapsulation heat sinks due to its high thermal conductivity and surface machinability. The beneficial effects of the present invention are as follows:

[0037] 1. The diamond in the metal matrix diamond composite material provided by the present invention is evenly distributed, and the diamond volume fraction (the diamond volume fraction in the composite material of this application can reach 50-70%) is such that the surface of the metal matrix diamond layer is completely wrapped by the metal. Since the thickness of the surface metal layer is adjustable, it has high machinability and can be processed into any shape of the surface metal shell layer. The prepared metal matrix diamond composite material has the advantages of high strength, high thermal conductivity, and high surface finish, and can be used to prepare high-precision parts with high surface finish requirements on multiple surfaces.

[0038] 2. The metal powder feedstock prepared by uniformly mixing metal powder and binder in the present invention can be reused, reducing production costs and greatly saving resources.

[0039] 3. The present invention provides a coated structure metal matrix diamond composite material with high thermal conductivity, good compactness, good uniformity, and easy processing. It has broad application prospects in heat dissipation and the development of electronic components.

[0040] 4. The preparation method of the metal matrix diamond composite material is expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 : Process flow chart of the coated structure metal matrix diamond composite material of the present invention;

[0042] Figure 2 : Metal Cu matrix diamond composite embryo with diamond oriented distribution obtained in step 3 of Example 2;

[0043] Figure 3 : Cross-sectional schematic diagram of the copper-coated metal Cu matrix diamond composite material obtained in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0044] The following examples further illustrate the technical solutions of the present invention, but do not limit the protection scope of the present invention.

[0045] The preparation process flow of the coated structure metal matrix diamond composite material of the present invention is as follows with reference to the attached Figure 1 shown as follows:

[0046] 1) Knead and granulate the metal powder and binder to obtain a metal powder feedstock; the metal powder is one of copper powder and aluminum powder, with an average particle size of 5-30 μm, preferably 10-20 μm; control the volume ratio of the binder to be 40%-60%, preferably 45-55%; the kneading temperature is 80-100 °C, and the time is 3-4 h; the rotation speed of the kneader is 80-120 r / min, and after kneading, it is made into granular feedstock with a diameter of 0.5-1 mm by a granulator.

[0047] Among them, the composition of the binder is by mass percentage: PE wax (average molecular weight 2000 - 5000): 10 - 20%, microcrystalline wax (80# microcrystalline wax): 20 - 35%; Chinese bee wax (acid value 5.0 - 6.0): 10 - 25%, atactic polypropylene (average molecular weight 100,000 - 150,000): 8 - 15%; styrene-butadiene-styrene block copolymer (average molecular weight 80,000 - 100,000): 1 - 3%; homopolyoxymethylene (average molecular weight 30,000 - 50,000): 3 - 10%, TPEE (injection molding grade 1047D): 3 - 10%, stearic acid (molecular weight: 284): 10 - 15%.

[0048] 2) Spread the metal powder feedstock evenly in a constant-temperature hot press mold. The mold temperature is 100 - 140 °C, and the pressure is 30 - 60 Mpa; use the constant-temperature hot press to press the metal powder feedstock into a metal powder thin sheet with a thickness of 0.1 - 0.5 mm;

[0049] 3) Use a screen printer to prepare a layer of glue with a unit distribution on the surface of the metal powder thin sheet, and fix the diamond particles with a coating on the glue to obtain a metal-based diamond composite embryo with a diamond unit distribution; use the metal powder thin sheet as the upper and lower surface layers, and stack the metal-based diamond composite embryo as the middle layer in sequence to make an initial embryo;

[0050] Among them, the diamond particles with a coating on the surface are artificial high-temperature high-pressure diamonds, artificial CVD diamonds or natural diamonds with a surface coating thickness of 0.1 - 0.5 μm; the particle size of the diamond particles is 100 - 500 μm (preferably 100 - 300 μm), and the coating material is one of SiC - Si, TiC - Ti; the coating is prepared on the surface of the diamond particles by ion plating.

[0051] The composition of the glue is by mass percentage:

[0052] Terpineol 90 - 98%, adipic acid ether plasticizer 0.6 - 1%, hydrogenated castor oil 0.1 - 1%, lecithin 0.2 - 1%, ethyl cellulose 0.1 - 3%.

[0053] 4) Subject the initial embryo to degreasing and pre-sintering treatments, and take it out after cooling to obtain a pre-sintered embryo; place the initial embryo in a vacuum of 10 -3In a vacuum sintering furnace at a pressure of Pa, the temperature is raised from room temperature (15 - 35 °C) to 450 - 520 °C at a rate of 5 °C / min, and held for 2 - 4 hours (the purpose of holding is to completely remove the binder and glue). Then, the temperature is raised to the liquidus temperature of the metal powder at a rate of 3 °C / min (for aluminum powder, it is 600 °C - 700 °C; for copper powder, it is 1050 - 1150 °C), held for 1 - 2 hours, and cooled to room temperature while maintaining the pressure to obtain a pre-sintered blank. The metal matrix diamond pre-sintered blank obtained after pre-sintering treatment has a certain bonding strength, and the density reaches more than 92%.

[0054] 5) Heat the pre-sintered blank under a vacuum of 10 -1 ~10 -2 Pa, in an inert atmosphere (argon or helium), or in a reducing atmosphere of hydrogen-argon mixture (hydrogen volume fraction is 5%); raise the temperature from room temperature to a range of 50 - 100 °C below the liquidus temperature of the metal powder at a rate of 10 - 20 °C / min (for aluminum powder, raise the temperature to 550 - 600 °C; for copper powder, raise the temperature to 1000 - 1050 °C); apply pressure after reaching the highest temperature, with the pressure being 30 - 50 Mpa, hold for 30 - 60 min, and cool to room temperature while maintaining the pressure to obtain a sintered blank;

[0055] 6) Cut out the composite material of the superposed part of diamond and metal matrix using one of the cutting methods such as diamond wire saw, laser cutting, or water jet, and ensure that the surface shell layer of the obtained composite material is a metal matrix material. After machining, grinding, and polishing, a coated structure metal matrix diamond composite material with a surface metal shell layer thickness of 0.1 - 0.3 mm and a roughness Ra lower than 0.4 is obtained.

[0056] Example 1

[0057] A method for preparing a coated structure metal Al matrix diamond thermal conductive composite material is as follows:

[0058] 1) Knead pure Al powder (average particle size is 13 μm) with a binder. The volume ratio of the binder to pure Al powder is 52%:48%. The kneading temperature is 100 °C, the rotation speed of the kneader is 90 r / min, the kneading time is 2 h, and after cooling, it is made into 0.5 mm sized particle feed; The composition of the binder by mass percentage: PE wax (average molecular weight 2000 - 5000): 13%, microcrystalline wax (80# microcrystalline wax): 32%; Chinese bee wax (acid value is 5.0 - 6.0): 15%, atactic polypropylene (average molecular weight 100,000 - 150,000): 13%; styrene-butadiene-styrene block copolymer (average molecular weight 80,000 - 100,000): 2%; homopolyoxymethylene (average molecular weight 30,000 - 50,000): 5%, TPEE (injection molding grade 1047D): 7%, stearic acid (molecular weight: 284): 13%.

[0059] 2) Spread the pure Al powder feedstock evenly in the mold of a constant-temperature hot press. The mold temperature is 120 °C and the pressure is 50 Mpa. After demolding and cooling, a metal Al powder thin sheet with a thickness of 0.5 mm is made.

[0060] 3) Use a screen printer to prepare a layer of glue units with equally spaced rectangles on the surface of the metal powder thin sheet, and fix diamond particles with a 0.2-μm-thick SiC-Si coating on the glue to obtain a diamond-oriented distributed metal Al-based diamond composite embryo. Use the metal Al powder thin sheet as the upper and lower surface layers, and the metal Al-based diamond composite embryo as the middle layer, and stack them in sequence to make an initial embryo.

[0061] 4) Carry out pre-sintering treatment on the above-prepared metal Al-based diamond initial embryo. The pre-sintering is carried out in a vacuum sintering furnace with a vacuum degree of 10-3 Pa. Heat from room temperature to 460 °C at a rate of 5 °C / min, keep warm for 4 hours to remove the binder and glue completely, then heat to 650 °C at a rate of 3 °C / min, keep warm for 2 hours, and take out after cooling to obtain a pre-sintered embryo.

[0062] 5) Put the above pre-sintered embryo into the mold of a vacuum hot press furnace for high-temperature pressure sintering. The process conditions of high-temperature pressure sintering are: start heating from room temperature under a vacuum degree of 10-2 Pa, heat to 580 °C at a heating rate of 20 °C / min, then apply pressure, the pressure is 45 Mpa, keep warm for 30 min, and keep the pressure and cool with the furnace to room temperature to obtain a sintered embryo.

[0063] 6) Cut out the metal Al-based diamond composite material with a diamond wire saw, and machine it into a cylinder with a metal outer shell layer thickness of 0.1 mm, and polish it to obtain a high-thermal-conductivity metal Al-based diamond composite material.

[0064] After polishing the six surfaces of the aluminum-based diamond composite material prepared in this example, the surface roughness Ra = 0.15, the thermal conductivity TC = 525 (W / mK), the diamond volume fraction is 56.8%, the flexural strength is 283 Mpa, and the porosity is 4.15%.

[0065] Example 2

[0066] A preparation method of a coated-structured metal Cu-based diamond thermal conductive composite material is as follows:

[0067] 1) Mix the metallic Cu powder (average particle size is 11 μm) with the binder. The volume ratio of the binder to the metallic Cu powder is 55%:45%. The kneading temperature is 110 °C, the rotational speed of the kneader is 90 r / min, the kneading time is 2 h, and after cooling, pellets with a size of 0.5 mm are made for feeding; the binder is by mass percentage: PE wax (average molecular weight 2000 - 5000): 15%, microcrystalline wax (80# microcrystalline wax): 35%; Chinese bee wax (acid value 5.0 - 6.0): 15%, atactic polypropylene (average molecular weight 100,000 - 150,000): 10%; styrene-butadiene-styrene block copolymer (average molecular weight 80,000 - 100,000): 3%; homopolyoxymethylene (average molecular weight 30,000 - 50,000): 5%, TPEE (injection molding grade 1047D): 7%, stearic acid (molecular weight: 284): 10%.

[0068] 2) Spread the metallic Cu powder feed on the mold of a constant temperature hot press. The mold temperature is 120 °C and the pressure is 50 Mpa. After demolding and cooling, a metallic copper powder thin sheet with a thickness of 0.5 mm is made.

[0069] 3) Use a screen printer to prepare a layer of glue with rectangular units arranged at equal intervals on the surface of the metallic powder thin sheet, and fix diamond particles with a 0.3 - μm - thick TiC - Ti coating on the glue to obtain a metallic Cu - based diamond composite embryo with diamond oriented distribution (as shown in the attachment). Use the metallic Cu powder thin sheet as the upper and lower surface layers, and the metallic Cu - based diamond composite embryo as the middle layer and stack them in sequence to make an initial embryo. Figure 2 Shown).

[0070] 4) Carry out pre - sintering treatment on the above - prepared metallic Cu - based diamond initial embryo. The pre - sintering is carried out in a vacuum sintering furnace with a vacuum degree of 10⁻³ Pa. Heat from room temperature to 500 °C at a rate of 5 °C / min, keep warm for 4 hours to remove the binder and glue completely, then heat to 1110 °C at a rate of 3 °C / min, keep warm for 2 hours, and take it out after cooling to obtain a pre - sintered embryo;

[0071] 5) Put the above - mentioned pre - sintered embryo into the mold of a vacuum hot press furnace for high - temperature pressure sintering. The process conditions of high - temperature pressure sintering are: start heating from room temperature under a vacuum degree of 10⁻² Pa, heat to 1030 °C at a heating rate of 20 °C / min, then apply pressure, the pressure is 45 Mpa, keep warm for 30 min, keep the pressure and cool with the furnace to room temperature, and take out the sintered embryo.

[0072] 6) Cut out the metallic Cu - based diamond composite material with a diamond wire saw, and machine it into a cuboid with a thickness of 0.2 mm for the metal outer shell layer, and polish it to obtain a metallic Cu - based diamond composite material coated with copper, and its cross - section is as Figure 3 Shown.

[0073] The surface finish Ra of the metal Cu-based diamond composite material prepared in this embodiment is 0.12 after polishing of six surfaces, the thermal conductivity TC is 575 (W / mK), the diamond volume fraction is 60.2%, the flexural strength is 283 Mpa, and the porosity is 3.15%

[0074] Change the mold temperature and pressure during the preparation of the metal powder thin sheet in step 2 of Example 2, and keep the other conditions the same as those in Example 2. Conduct a comparative test on the prepared metal copper powder thin sheet, and the obtained results are shown in Table 1

[0075] Table 1

[0076] Comparative experiment Mold temperature (°C) Pressure (Mpa) Sample test results 1 60 50 The feedstock has poor fluidity and fails to form a thin sheet 2 120 50 Form a thin sheet with uniform thickness 3 180 50 The feedstock has good fluidity and extrudes uneven thickness from the mold gap 4 120 20 The feedstock has poor fluidity and fails to form a thin sheet 5 120 80 Good fluidity, extrudes uneven thickness from the mold gap

[0077] Change the pre-sintering temperature in step 4 of Example 2, and keep the other conditions the same as those in Example 2. Prepare a metal Cu-based diamond pre-sintered blank for a comparative test, and the obtained results are shown in Table 2

[0078] Table 2

[0079] Comparative experiment Pre-sintering temperature Sample test results 1 1000℃ Relative density is 60%, the sample has no deformation, and the surface has no metallic luster 2 1100℃ Relative density is 92.2%, the sample has no deformation, and the surface layer has metallic luster 3 1200℃ The temperature is too high and the sample is deformed

[0080] Change the high-temperature pressure sintering parameters in step 5 of Example 2, and keep the other conditions the same as those in Example 2. Prepare a metal Cu-based diamond composite material for a comparative test, and the obtained results are shown in Table 3

[0081] Table 3

[0082] Comparative experiment Temperature (°C) Pressure (Mpa) Test results of the obtained samples 1 900 45 Relative density is 93.02%, thermal conductivity is 482 (W / mK) 2 1030 45 Relative density is 96.85%, thermal conductivity is 575 (W / mK) 3 1100 45 Relative density is 90.21%, thermal conductivity is 421 (W / mK) 4 1030 20 Relative density is 94.62%, thermal conductivity is 525 (W / mK) 5 1030 70 Relative density is 89.12%, thermal conductivity is 381 (W / mK)

[0083] It can be seen from the comparison of Tables 1-3 above that inappropriate metal powder thin sheet preparation processes, inappropriate pre-sintering temperatures, too high or too low sintering temperatures during high-temperature pressure sintering, and inappropriate sintering pressure times will all cause defects in the products, thereby affecting the product performance

Claims

1. A preparation method of a coated structure metal matrix diamond composite material, characterized in that It includes the following steps: 1) Knead and granulate the metal powder and the binder to obtain a metal powder feedstock; the metal powder is one of copper powder and aluminum powder, with an average particle size of 5 - 30 μm; 2) Use a constant-temperature hot press to press the metal powder feedstock into a metal powder thin sheet with a thickness of 0.1 - 0.5 mm; the metal powder feedstock is laid flat in the constant-temperature hot press mold, the mold temperature is 100 - 140 °C, and the pressure is 30 - 60 Mpa; 3) Use a screen printer to prepare a layer of glue with a unit distribution on the surface of the metal powder thin sheet, and fix the diamond particles with a coating on the glue to obtain a metal-based diamond composite embryo with a diamond unit distribution; use the metal powder thin sheet as the upper and lower surface layers, and stack the metal-based diamond composite embryo as the middle layer in sequence to make an initial embryo; 4) Degrease and pre-sinter the initial blank, and take it out after cooling to obtain a pre-sintered blank; specifically, place the initial blank in a vacuum sintering furnace with a vacuum degree of 10 -3 Pa, heat it from room temperature to 450 - 520 °C at a rate of 5 °C / min, hold for 2 - 4 hours, and then heat it to the liquidus temperature of the metal powder at a rate of 3 °C / min and hold for 1 - 2 hours; 5) Subject the pre-sintered blank to high-temperature pressure sintering to obtain a sintered blank; specifically, heat the pre-sintered blank under a vacuum of 10 -1 ~10 -2 Pa, in an inert atmosphere or a reducing atmosphere; heat from room temperature at a rate of 10 - 20 °C / min to a range of 50 - 100 °C below the liquidus temperature of the metal powder; apply pressure after reaching the highest temperature, with the pressure being 30 - 50 Mpa, hold for 30 - 60 min, and maintain the pressure while cooling with the furnace to room temperature to obtain a sintered blank; 6) Machine-process the obtained sintered blank and polish the surface to obtain a coated structure metal-based diamond composite material.

2. The preparation method of the coated structure metal matrix diamond composite material according to claim 1, characterized in that In step 1), the composition of the binder is by mass percentage: PE wax: 10 - 20%, microcrystalline wax: 20 - 35%; Chinese bee wax: 10 - 25%, atactic polypropylene: 8 - 15%; styrene-butadiene-styrene block copolymer: 1 - 3%; homopolyoxymethylene: 3 - 10%, TPEE: 3 - 10%, stearic acid: 10 - 15%.

3. The preparation method of the coated structure metal matrix diamond composite material according to claim 1, characterized in that In step 1), control the volume ratio of the binder to be 40% - 60%; the kneading temperature is 80 - 100 °C, and the time is 3 - 4 h; the rotation speed of the kneader is 80 - 120 r / min, and after kneading, use a granulator to make granular feedstock with a diameter of 0.5 - 1 mm.

4. The preparation method of the coated structure metal-based diamond composite material according to claim 1, characterized in that In step 3), the diamond particles with a coating on the surface are artificial high-temperature high-pressure diamonds, artificial CVD diamonds or natural diamonds with a surface coating thickness of 0.1 - 0.5 μm; the particle size of the diamond particles is 100 - 500 μm, and the coating material is one of SiC - Si and TiC - Ti; the coating is prepared on the surface of the diamond particles by an ion plating method.

5. The preparation method of the coated structure metal matrix diamond composite material according to claim 1, characterized in that Step 6) includes the following steps: Use one of the cutting methods of diamond wire sawing, laser cutting or water jet to cut out the composite material of the superposed part of diamond and metal matrix, and ensure that the surface shell layer of the obtained composite material is a metal matrix material. After machining, grinding and polishing, a coated structure metal-based diamond composite material with a surface metal shell layer thickness of 0.1 - 0.3 mm and a roughness Ra lower than 0.4 is obtained.

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