High thermal conductive copper-diamond gradient composite material and preparation method thereof

Abstract

The application belongs to the technical field of copper alloy preparation for electronic, and provides a high-thermal-conductivity copper-diamond gradient composite material and a preparation method thereof.The copper-coated titanium hydride composite powder is obtained by low-temperature sensitization and activation of titanium hydride and chemical plating; the copper-based sintering aid is prepared by mechanical activation to promote low-temperature densification; the micro tungsten powder is infiltrated and adsorbed on the surface of the diamond by using a molten salt medium, and the free tungsten powder is removed in the cleaning process to form a tungsten-rich surface layer; the tungsten-coated diamond, copper powder and the functional powder are prepared into a uniform slurry in a tert-butyl alcohol-ethyl cellulose organic carrier, and a continuous gradient green body with a copper-rich bottom is constructed by centrifugal differential sedimentation; finally, the gradient composite material with a good weldable metal bottom layer and a high-thermal-conductivity working layer is obtained by realizing the collaborative control of degassing, reduction, pre-densification and interface reaction under the condition of spark plasma sintering.

Description

Technical Field

[0001] This invention belongs to the field of electronic copper alloy preparation technology, and relates to a copper-diamond gradient composite material with high thermal conductivity and its preparation method. Background Technology

[0002] Copper / diamond composites, combining the good machinability of copper with the ultra-high thermal conductivity of diamond, are considered highly promising thermal management materials for heat dissipation substrates, heat sinks, and advanced packaging in high-power devices. However, current technologies still face multiple bottlenecks in achieving both high thermal conductivity and manufacturability. First, copper and diamond inherently have poor wettability and weak interfacial bonding, easily forming micropores and microgaps during the composite process, leading to a significant increase in interfacial thermal resistance. While thick coatings or multi-layer plating introduced to improve wetting and bonding can increase interfacial strength, they often introduce additional phonon scattering and thermal resistance, weakening the overall thermal conductivity advantage. Second, under high volume fraction conditions, the interparticle channels of diamond are narrow, hindering the densification and infiltration sintering of the copper matrix. Conventional sintering or infiltration processes require stringent temperature and atmosphere control; even slight deviations can induce diamond surface degradation, uncontrolled thickening of the interfacial reaction layer, or carbon phase transformation, resulting in decreased thermal conductivity and insufficient mechanical reliability. Furthermore, composite powders inevitably form an oxide film in the air, which hinders interparticle diffusion and reduces the efficiency of sintering neck formation, making it difficult to obtain high density and stable interface in the material under relatively mild process windows. Existing reduction or deoxidation methods often rely on external reducing atmospheres or complex pretreatment processes, which increases process costs and uncertainties.

[0003] Furthermore, copper and diamond have significantly different coefficients of thermal expansion. Homogeneous, highly filled composite materials are prone to accumulating residual thermal stress under thermal cycling and service loads, leading to cracking, debonding, or delamination, which affects packaging reliability. While layered or gradient designs can alleviate stress concentration, it remains challenging to stably construct a continuous gradient structure, control the transition of components between layers, and maintain interface cleanliness. Finally, in device packaging applications, if the diamond content on the surface of the composite material is high, it is often difficult to achieve reliable brazing or metallization directly. Additional surface electroplating or metallization treatment is usually required, which not only increases the number of processes and costs but may also introduce new interface defects and thermal resistance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a high thermal conductivity copper-diamond gradient composite material and its preparation method. Addressing issues such as poor wetting at the copper-diamond interface, difficulty in densification due to easy oxidation, and thermal stress cracking, the invention introduces low-temperature sensitization activation and stabilization chemical plating to obtain copper-coated titanium hydride composite powder, achieving in-situ reduction purification and interface activation. Molten salt-assisted tungsten infiltration is used to construct a tungsten-rich surface layer, forming a controllable thin-layer transition during sintering. Combined with centrifugal differential sedimentation and freeze-drying, a continuous gradient green body with a copper-rich bottom is obtained. Finally, densification and reliable bonding are achieved through spark plasma sintering, thus meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a copper-diamond gradient composite material with high thermal conductivity, the method comprising:

[0007] S1, TiH2 powder is dispersed in a sensitizing solution and stirred. The sensitizing solution is an aqueous solution containing stannous chloride and hydrochloric acid. After filtration and rinsing with ice water, it is immediately added to an activation solution and stirred. The activation solution is an aqueous solution containing palladium chloride and hydrochloric acid to obtain a wet activated filter cake. Copper sulfate pentahydrate, disodium EDTA, and 2,2'-bipyridine are dispersed in deionized water, mixed evenly, and then added to the above wet activated filter cake. The mixture is stirred and formaldehyde solution is added dropwise to obtain copper-coated titanium hydride composite powder.

[0008] S2, mix electrolytic copper powder, chromium powder, amorphous boron powder and silicon powder, and ball mill them in a glove box filled with high-purity argon in a carbide ball mill jar to obtain copper-based activating sintering aid;

[0009] S3, sodium chloride, potassium chloride and tungsten powder are ground and mixed to prepare a molten salt medium. Diamond micro powder is added to the molten salt medium and mixed evenly and kept at a constant temperature to obtain tungsten-coated diamond. Tert-butanol, ethyl cellulose and oleic acid are mixed to obtain an organic carrier. Tungsten-coated diamond, electrolytic copper powder, copper-coated titanium hydride composite powder and copper-based activating sintering aid are added to the organic carrier. The mixture is ground to obtain a uniform slurry. The slurry is injected into a mold, centrifuged under a centrifugal force field and freeze-dried to obtain a green body with a bottom copper-rich gradient structure.

[0010] S4. The green blank is placed in a spark plasma sintering furnace and sintered to obtain a copper-diamond gradient composite material with high thermal conductivity.

[0011] Specifically, it includes:

[0012] S1, In an ice-water bath environment, TiH2 powder was dispersed in a sensitizing solution and stirred. The sensitizing solution was an aqueous solution containing stannous chloride and hydrochloric acid. After filtration and rinsing with ice water, the powder was immediately added to an activation solution and stirred. The activation solution was an aqueous solution containing palladium chloride and hydrochloric acid. After filtration again, the powder was rinsed alternately with ice water and anhydrous ethanol to obtain a wet activated filter cake. Copper sulfate pentahydrate, disodium EDTA, and 2,2'-bipyridine were dispersed in deionized water and the pH was adjusted to 11.9-12.1 with sodium hydroxide. After mixing evenly, the activated filter cake was added, stirred, and formaldehyde solution was added dropwise. The reaction was stopped when the deep blue color of the solution faded and approached colorless. The powder was filtered and washed successively with water and anhydrous ethanol. After vacuum drying, copper-coated titanium hydride composite powder was obtained.

[0013] S2, mix electrolytic copper powder, chromium powder, amorphous boron powder and silicon powder, and ball mill them in a glove box filled with high-purity argon in a carbide ball mill jar to obtain copper-based activating sintering aid;

[0014] S3. Sodium chloride, potassium chloride and tungsten powder are ground and mixed to prepare a molten salt medium. Diamond micro powder is added to the molten salt medium and mixed evenly. Under an argon atmosphere, the mixture is kept at a first temperature. After cooling, the salt is dissolved in deionized water. After stirring, the mixture is allowed to stand to allow the free tungsten powder to settle. The upper suspension is poured off, the supernatant is collected, and the free tungsten powder settled at the bottom is discarded. The above-mentioned graded washing operation is repeated 2-3 times until no obvious gray-black heavy slag appears at the bottom. The precipitate is collected and washed with anhydrous ethanol. Vacuum drying is performed to obtain tungsten-coated diamond. Tert-butanol, ethyl cellulose and oleic acid are mixed to obtain an organic carrier. Tungsten-coated diamond, electrolytic copper powder, copper-coated titanium hydride composite powder and copper-based activating sintering aid are added to the organic carrier. The mixture is ground to obtain a uniform slurry. The slurry is injected into a mold and centrifuged under a centrifugal force field. Then it is freeze-dried to obtain a green body with a copper-rich gradient structure at the bottom.

[0015] S4. The green blank is placed in a spark plasma sintering furnace and sintered to obtain a copper-diamond gradient composite material with high thermal conductivity.

[0016] In the preparation of copper-coated titanium hydride composite powder, the titanium hydride surface first undergoes sensitization and activation treatments. During the sensitization stage, stannous salt forms adsorbable reducing species on the particle surface under acidic conditions, removing some surface contaminants. During the activation stage, palladium salt is reduced on the surface and deposited as discrete palladium active sites. These sites serve as heterogeneous catalytic centers for the electroless plating reaction, lowering the reduction nucleation barrier for copper ions in the solution. In the electroless plating stage, alkaline conditions promote the oxidation of formaldehyde and the release of electrons. These electrons are transferred to copper complexes at the palladium active sites, allowing copper to preferentially nucleate and continuously grow on the particle surface to form a metallic coating. Bipyridine, acting as a stabilizer, inhibits homogeneous autocatalytic copper precipitation in the solution through coordination, improving the selective deposition of the plating solution on the powder surface. In the preparation of the copper-based activating sintering aid, copper, chromium, boron, and silicon are mechanically alloyed under an inert atmosphere. The ball milling process achieves particle refinement and composition homogenization through repeated cold welding and fracture. Under the conditions of increased lattice defects, dislocations and high-energy interfaces, it forms non-equilibrium solid solution or fine-scale multiphase structures. Such structures can enhance the driving force of atomic diffusion and interface migration during subsequent sintering. At the same time, boron and silicon may participate in the formation of local phase regions with low solidus lines in the copper matrix, thereby promoting particle rearrangement and pore closure during heating and pressurization.

[0017] In the step of molten salt-assisted tungsten infiltration onto the diamond surface, the chloride molten salt forms an ionic melt at high temperature, serving as a mass transfer and dispersion medium to reduce the agglomeration tendency of fine tungsten powder and enhance the contact probability between the tungsten powder and the diamond surface. Since this process is mainly based on physical adsorption and mechanical interlocking, tungsten is primarily carried on the diamond surface in the form of fine particles or thin layers. A small number of surface defect sites may experience localized interfacial reactions or solid-solid interdiffusion. In the step of preparing the centrifuged gradient green body, tert-butanol and ethyl cellulose form a rheologically controlled organic carrier, and oleic acid provides steric hindrance to reduce flocculation by forming an adsorption layer on the surface of the metal powder and the tungsten-coated diamond. During the centrifugation stage, the components migrate driven by density differences within the centrifugal acceleration field. The relatively larger density difference and achievable equivalent settling velocity of copper powder cause it to accumulate in the centrifugal direction, while the migration of diamond is limited due to its smaller density difference and finer particle size distribution, thus forming a continuously varying component distribution along the thickness direction.

[0018] In the spark plasma sintering step, the low-temperature section preferentially completes the thermal decomposition of organic components and the discharge of volatile products under vacuum and low contact pressure conditions, reducing gas retention in the pores. Simultaneously, titanium hydride begins to decompose and release hydrogen, which diffuses within the pores and reacts with the oxides on the copper powder surface, transforming the oxide film and exposing the metal surface to facilitate sintering neck formation. After heating and pressurization, mechanical alloying agents, through local softening or phase transformation, promote particle rearrangement, pore shrinkage, and increased diffusion flux. Combined with the localized thermal effect generated by the pulsed current and interfacial contact resistance, this accelerates neck growth and densification. In the interfacial reaction control section, active titanium from the decomposition of titanium hydride migrates to the diamond surface and tungsten-coated layer under short-range diffusion conditions, undergoing a solid-phase reaction with surface carbon and tungsten to form a thin-layer composite transition phase dominated by carbides. This transition phase provides a connection channel between the metal and diamond at the chemical bonding level, while its thickness is constrained by both temperature and holding time. The subsequent medium-temperature insulation section mainly involves stress relaxation and diffusion homogenization, which reduces the residual stress concentration caused by thermal expansion mismatch during the cooling process of the gradient structure, thereby improving the integrity of the macrostructure and service stability.

[0019] As a preferred embodiment of the present invention, in S1, the mass ratio of TiH2 powder, sensitizing solution, activating solution, copper sulfate pentahydrate, disodium EDTA, 2,2'-bipyridine, deionized water, and formaldehyde solution is (20-20.5):(407-418):(201-213):(40-41):(60-61):(0.02-0.03):(700-800):(30-31), for example, it can be (20, 20...). .05, 20.1, 20.15, 20.2, 20.25, 20.3, 20.35, 20.4, 20.45 or 20.5: (407, 408.1, 409.2, 410.3, 411.4, 412.5, 413.6, 414.7, 415.8, 416.9 or 418): (201, 202.2, 203.4, 204.6, 205.8, 207, 208.2, 209. 4. 210.6, 211.8 or 213: (40, 40.1, 40.2, 40.3, 40.4, 40.5, 40.6, 40.7, 40.8, 40.9 or 41): (60, 60.1, 60.2, 60.3, 60.4, 60.5, 60.6, 60.7, 60.8, 60.9 or 61): (0.02, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.027, 0.028, 0.029 or 0.03: (700, 710, 720, 730, 740, 750, 760, 770, 780, 790 or 800): (30, 30.1, 30.2, 30.3, 30.4, 30.5, 30.6, 30.7, 30.8, 30.9 or 31), but not limited to the listed values, other unlisted values ​​within this range also apply.

[0020] In some optional embodiments, the D50 of the TiH2 powder is <10 μm.

[0021] In some optional embodiments, the mass ratio of stannous chloride dihydrate, hydrochloric acid, and deionized water in the sensitizing solution is (2-2.2):(5-5.5):(400-410), and the concentration of the hydrochloric acid is 9-12M, for example, a mass ratio of (2.0, 2.02, 2.04, 2.06, 2.08, 2.1, 2.12, 2.14, 2.16, 2.18, or 2.2):(5, 5.05, 5.1, 5.15, 5.2, 5). 25, 5.3, 5.35, 5.4, 5.45 or 5.5: (400, 401, 402, 403, 404, 405, 406, 407, 408, 409 or 410), wherein the concentration of the hydrochloric acid is (9, 9.3, 9.6, 9.9, 10.2, 10.5, 10.8, 11.1, 11.4, 11.7 or 12) M, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0022] In some optional embodiments, the mass ratio of palladium chloride, hydrochloric acid, and deionized water in the activation solution is (0.1-0.12):(1-1.2):(200-210), and the concentration of the hydrochloric acid is 9-12M, for example, a mass ratio of (0.1, 0.102, 0.104, 0.106, 0.108, 0.11, 0.112, 0.114, 0.116, 0.118, or 0.12):(1.0, 1.02, 1.04, 1.06, 1... 0.08, 1.1, 1.12, 1.14, 1.16, 1.18 or 1.2: (200, 201, 202, 203, 204, 205, 206, 207, 208, 209 or 210), wherein the concentration of the hydrochloric acid is (9, 9.3, 9.6, 9.9, 10.2, 10.5, 10.8, 11.1, 11.4, 11.7 or 12) M, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0023] In some optional embodiments, the stirring time in the sensitizing solution is 2-3 min, for example, 2.0 min, 2.1 min, 2.2 min, 2.3 min, 2.4 min, 2.5 min, 2.6 min, 2.7 min, 2.8 min, 2.9 min or 3.0 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the stirring time in the activation solution is 3-4 min, for example, 3.0 min, 3.1 min, 3.2 min, 3.3 min, 3.4 min, 3.5 min, 3.6 min, 3.7 min, 3.8 min, 3.9 min or 4.0 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the mass fraction of sodium hydroxide is 20-25 wt.%, for example, it can be 20 wt.%, 20.5 wt.%, 21 wt.%, 21.5 wt.%, 22 wt.%, 22.5 wt.%, 23 wt.%, 23.5 wt.%, 24 wt.%, 24.5 wt.%, or 25 wt.%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] In some alternative embodiments, the 2,2'-bipyridine is pre-dissolved in anhydrous ethanol before use.

[0027] In some optional embodiments, the formaldehyde solution has a mass fraction of 35-37 wt.%, for example, it may be 35 wt.%, 35.2 wt.%, 35.4 wt.%, 35.6 wt.%, 35.8 wt.%, 36.0 wt.%, 36.2 wt.%, 36.4 wt.%, 36.6 wt.%, 36.8 wt.%, or 37 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the dripping time is 60-70 min, for example, it can be 60 min, 61 min, 62 min, 63 min, 64 min, 65 min, 66 min, 67 min, 68 min, 69 min or 70 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In a preferred embodiment of the present invention, in step S2, the mass ratio of electrolytic copper powder, chromium powder, amorphous boron powder, and silicon powder is (41.5-42):(5-5.2):(2.5-2.7):(1-1.1), for example, it can be (41.5, 41.55, 41.6, 41.65, 41.7, 41.75, 41.8, 41.85, 41.9, 41.95 or 42):(5, 5.02, 5.04, 5.06, 5.08, 5... 1, 5.12, 5.14, 5.16, 5.18 or 5.2: (2.5, 2.52, 2.54, 2.56, 2.58, 2.6, 2.62, 2.64, 2.66, 2.68 or 2.7): (1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09 or 1.1), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0030] In some optional embodiments, the D50 of the electrolytic copper powder is 10-12 μm, for example, it can be 10 μm, 10.2 μm, 10.4 μm, 10.6 μm, 10.8 μm, 11.0 μm, 11.2 μm, 11.4 μm, 11.6 μm, 11.8 μm or 12 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the chromium powder has a D50 of <45 μm.

[0032] In some optional embodiments, the silicon powder has a D50 of <10 μm.

[0033] In some alternative embodiments, the ball-to-material ratio of the ball mill is (18-22):1, for example, it can be (18, 18.4, 18.8, 19.2, 19.6, 20.0, 20.4, 20.8, 21.2, 21.6 or 22):1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the ball milling time is 40-60 hours, the ball milling speed is 300-400 r / min, and the ball milling process is intermittent. For example, the ball milling time can be (40, 42, 44, 46, 48, 50, 52, 54, 56, 58, or 60) hours, the ball milling speed can be (300, 310, 320, 330, 340, 350, 360, 370, 380, 390, or 400) r / min, and the ball milling process is intermittent. However, it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0035] In a preferred embodiment of the present invention, in step S3, the mass ratio of sodium chloride, potassium chloride, tungsten powder, and diamond micro powder is (50-51):(50-51):(10-10.5):(30-31), for example, it can be (50, 50.1, 50.2, 50.3, 50.4, 50.5, 50.6, 50.7, 50.8, 50.9 or 51):(50, 50.1, 50.2, 50.3, 50.4, 50.5, 50). 6, 50.7, 50.8, 50.9 or 51: (10.0, 10.05, 10.1, 10.15, 10.2, 10.25, 10.3, 10.35, 10.4, 10.45 or 10.5): (30, 30.1, 30.2, 30.3, 30.4, 30.5, 30.6, 30.7, 30.8, 30.9 or 31), but not limited to the listed values, other unlisted values ​​within this range also apply.

[0036] In some optional embodiments, the D50 of the tungsten powder is 1-3 μm, for example, it can be 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3.0 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the diamond powder comprises diamond powder with a D50 of 10 μm and diamond powder with a D50 of 5 μm in a mass ratio of 2:1.

[0038] In some alternative embodiments, the first temperature is 840-860°C, for example, it can be 840°C, 842°C, 844°C, 846°C, 848°C, 850°C, 852°C, 854°C, 856°C, 858°C or 860°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] In some optional embodiments, the holding time at the first temperature is 170-190 min, for example, it can be 170 min, 172 min, 174 min, 176 min, 178 min, 180 min, 182 min, 184 min, 186 min, 188 min or 190 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0040] In some optional embodiments, the mass ratio of tert-butanol, ethyl cellulose, oleic acid, tungsten-coated diamond, electrolytic copper powder, copper-coated titanium hydride composite powder, and copper-based activating sintering aid is (84-86):(4.5-5.5):(0.4-0.6):(20-20.5):(33-33.5):(3-3.2):(4-4.2), for example, it can be (84, 84.2, 84.4, 84.6, 84.8, 85.0, 85.2, 85.4, 85.6, 85.8 or 86):(4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5):(0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.5) 6, 0.58 or 0.6): (20, 20.05, 20.1, 20.15, 20.2, 20.25, 20.3, 20.35, 20.4, 20.45 or 20.5): (33, 33.05, 33.1, 33.15, 33.2, 33.25, 33.3, 33.35, 33.4, 33.45 or 33.5): (3.0 3.02, 3.04, 3.06, 3.08, 3.1, 3.12, 3.14, 3.16, 3.18 or 3.2): (4.0, 4.02, 4.04, 4.06, 4.08, 4.1, 4.12, 4.14, 4.16, 4.18 or 4.2), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0041] In some optional embodiments, the viscosity of the ethyl cellulose is specified as 10-50 mPa·s, measured at a specified concentration solution at 25°C. For example, it can be 10 mPa·s, 14 mPa·s, 18 mPa·s, 22 mPa·s, 26 mPa·s, 30 mPa·s, 34 mPa·s, 38 mPa·s, 42 mPa·s, 46 mPa·s, or 50 mPa·s, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] In some optional embodiments, the viscosity of the organic carrier at 25°C is 5000-8000 mPa·s, for example, it can be 5000 mPa·s, 5300 mPa·s, 5600 mPa·s, 5900 mPa·s, 6200 mPa·s, 6500 mPa·s, 6800 mPa·s, 7100 mPa·s, 7400 mPa·s, 7700 mPa·s or 8000 mPa·s, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0043] In some optional embodiments, the centrifugal acceleration of the centrifugal force field is 1500g-2000g, where g is the standard gravitational acceleration, for example, it can be 1500g, 1550g, 1600g, 1650g, 1700g, 1750g, 1800g, 1850g, 1900g, 1950g or 2000g, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0044] In some alternative embodiments, the centrifugation time is 8-12 min, for example, it can be 8.0 min, 8.4 min, 8.8 min, 9.2 min, 9.6 min, 10.0 min, 10.4 min, 10.8 min, 11.2 min, 11.6 min or 12.0 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0045] As a preferred technical solution of the present invention, in S4, the sintering procedure is as follows: under vacuum conditions, a contact pressure of 1.5-2.5 MPa is applied, the temperature is increased to 390-410℃ at 10℃ / min and held for 18-22 min to exhaust the air, then the temperature is increased to 540-560℃ at 30℃ / min and held for 18-22 min, then the contact pressure is linearly increased to 28-32 MPa and the temperature is increased to 840-860℃ at 100℃ / min and held for 4-6 min, then the contact pressure is further increased to 48-52 MPa and the temperature is increased to 900-920℃ at 50℃ / min and held for 5-8 min, finally the contact pressure is reduced to 4-6 MPa and the temperature is reduced to 740-760℃ and held for 30-45 min, and then cooled to room temperature with the furnace.For example, it could be: applying a contact pressure of (1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5) MPa under vacuum conditions, heating at 10℃ / min to (390, 392, 394, 396, 398, 400, 402, 404, 406, 408, or 410)℃ and holding at that temperature for (18, 18.4, 18.8, 19.2, 19.6, 20.0, 20.4, 20.8, 21.2, 21.6, or 22) min to remove the vent, then heating at 30℃ / min to (540, 542, 544, 5... Hold at 46, 548, 550, 552, 554, 556, 558, or 560℃ for (18, 18.4, 18.8, 19.2, 19.6, 20.0, 20.4, 20.8, 21.2, 21.6, or 22) min, then linearly increase the contact pressure to (28, 28.4, 28.8, 29.2, 29.6, 30.0, 30.4, 30.8, 31.2, 31.6, or 32) MPa and raise the temperature at 100℃ / min to (840, 842, 844, 846, 848, 850, 852, 854, 856, 858, or 86) MPa. Hold at 0℃ for (4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, or 6.0) min, then continue increasing the contact pressure to (48, 48.4, 48.8, 49.2, 49.6, 50.0, 50.4, 50.8, 51.2, 51.6, or 52) MPa and raise the temperature at 50℃ / min to (900, 902, 904, 906, 908, 910, 912, 914, 916, 918, or 920)℃ and hold for (5.0, 5.3, 5.6, 5.9, 6.2, 6.5, 6.8, 7.1, 7) min. 4, 7.7 or 8.0) min, then reduce the contact pressure to (4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8 or 6.0) MPa and cool to (740, 742, 744, 746, 748, 750, 752, 754, 756, 758 or 760) °C and hold for (30, 31.5, 33, 34.5, 36, 37.5, 39, 40.5, 42, 43.5 or 45) min, and cool with the furnace to room temperature. However, this is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0046] In a second aspect, the present invention provides a copper-diamond gradient composite material with high thermal conductivity prepared by the preparation method described in the first aspect.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention obtains copper-coated titanium hydride composite powder by low-temperature sensitization and activation of titanium hydride and stabilization electroless plating, so that reducing gas is released inside the material during sintering and participates in the transformation of copper powder oxide film, thereby reducing the obstacle of oxide film to diffusion bonding and sintering neck formation, and improving densification controllability; the copper-based sintering aid obtained by mechanical alloying promotes particle rearrangement and diffusion process under heating and pressurization conditions, so that the high-filled diamond system can achieve pore closure within a milder sintering window; a tungsten-rich carrying layer is introduced on the diamond surface by molten salt-assisted tungsten infiltration, and a controlled interface reaction occurs with active titanium and surface carbon during spark plasma sintering to form a thin-layer composite transition phase, which improves the stability of interface bonding and inhibits the increase in thermal resistance caused by excessive thickness of the reaction layer; a continuous gradient green blank is constructed by centrifugal differential sedimentation, so that the composite material forms a functional partition between a copper-rich connectable surface and a diamond-rich thermally conductive working layer, reducing residual stress concentration caused by thermal expansion mismatch, improving the reliability of thermal cycling and packaging connection, and is suitable for high heat flux density heat dissipation and power device packaging applications. Attached Figure Description

[0048] Figure 1 This is a physical image of the copper-diamond gradient composite material provided in Embodiment 1 of the present invention. Detailed Implementation

[0049] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0050] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0051] Example 1

[0052] This embodiment provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The preparation method specifically includes the following steps:

[0053] S1, in an ice-water bath environment, 20.0 g of TiH2 powder was dispersed in 418 g of sensitization solution and stirred for 3 min. The D50 of the TiH2 powder was <10 μm. The mass ratio of stannous chloride dihydrate, hydrochloric acid, and deionized water in the sensitization solution was 2.2:5:410, and the concentration of the hydrochloric acid was 12 M. After filtration and rinsing with ice water, the solution was immediately added to 213 g of activation solution and stirred for 3 min. The mass ratio of palladium chloride, hydrochloric acid, and deionized water in the activation solution was 0.12:1:210, and the concentration of the hydrochloric acid was 9 M. After filtration again and rinsing with alternating ice water and anhydrous ethanol, a wet activated filter cake was obtained. 41.0 g of copper sulfate pentahydrate, 60.0 g of disodium EDTA, and 0.03 g of... 2,2'-Bipyridine was dispersed in 700g of deionized water and the pH was adjusted to 11.9 with 25wt.% sodium hydroxide. The 2,2'-bipyridine was dissolved in anhydrous ethanol before use. After mixing evenly, the activated filter cake was added, stirred and 30.0g of 37wt.% formaldehyde solution was added dropwise. The reaction was stopped when the deep blue color of the solution faded and approached colorless. The mixture was filtered and washed successively with water and anhydrous ethanol. The mixture was then vacuum dried to obtain copper-coated titanium hydride composite powder.

[0054] S2, 42.0g of electrolytic copper powder, 5.0g of chromium powder, 2.7g of amorphous boron powder and 1.0g of silicon powder are mixed. The D50 of the electrolytic copper powder is 12μm, the D50 of the chromium powder is <45μm, and the D50 of the silicon powder is <10μm. The mixture is placed in a cemented carbide ball milling jar in a glove box filled with high-purity argon gas and ball milling is performed. The ball-to-material ratio is 22:1, the ball milling time is 40h, the ball milling speed is 400r / min, and the ball milling process is intermittent to obtain a copper-based activating sintering aid.

[0055] S3. A molten salt medium is prepared by grinding and mixing 51.0g of sodium chloride, 50.0g of potassium chloride, and 10.5g of tungsten powder. 30g of diamond micro-powder is added to the molten salt medium and mixed evenly. The tungsten powder has a D50 of 1μm, and the diamond micro-powder contains diamond micro-powder with a D50 of 10μm and diamond micro-powder with a D50 of 5μm in a mass ratio of 2:1. The mixture is heated at 860℃ for 170min under an argon atmosphere. After cooling, the salt is dissolved in deionized water, stirred, and allowed to stand for 40s to allow the free tungsten powder to settle. The upper suspension is poured off, the supernatant is collected, and the free tungsten powder settled at the bottom is discarded. This classification and washing operation is repeated twice until no obvious gray-black heavy slag appears at the bottom. The precipitate is collected, washed with anhydrous ethanol, and vacuum dried to obtain the final product. A tungsten-coated diamond was prepared by mixing 86g of tert-butanol, 4.5g of ethyl cellulose, and 0.6g of oleic acid to obtain an organic carrier. The viscosity of the ethyl cellulose was 50 mPa·s, measured at a specified concentration at 25°C. The viscosity of the organic carrier at 25°C was 5000 mPa·s. 20.5g of tungsten-coated diamond, 33.0g of electrolytic copper powder, 3.2g of copper-coated titanium hydride composite powder, and 4.0g of copper-based activating sintering aid were added to the organic carrier. The mixture was ground to obtain a uniform slurry. The slurry was injected into a mold and centrifuged for 12 minutes under a centrifugal force field with a centrifugal acceleration of 1500g, where g is the standard gravitational acceleration. Subsequently, the mixture was freeze-dried to obtain a green body with a copper-rich gradient structure at the bottom.

[0056] S4. The green blank is placed in a spark plasma sintering furnace and sintered to obtain a copper-diamond gradient composite material with high thermal conductivity. The sintering process is as follows: a contact pressure of 2.5 MPa is applied under vacuum, the temperature is increased to 390°C at 10°C / min and held for 22 min for degassing, then the temperature is increased to 560°C at 30°C / min and held for 18 min, then the contact pressure is linearly increased to 32 MPa and the temperature is increased to 840°C at 100°C / min and held for 6 min, then the contact pressure is further increased to 52 MPa and the temperature is increased to 900°C at 50°C / min and held for 8 min, finally the contact pressure is reduced to 4 MPa and the temperature is reduced to 760°C and held for 30 min, and then cooled to room temperature in the furnace. Figure 1 This is a physical image of the copper-diamond gradient composite material provided in this embodiment.

[0057] Example 2

[0058] This embodiment provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The preparation method specifically includes the following steps:

[0059] S1, in an ice-water bath environment, 20.5g of TiH2 powder was dispersed in 407g of sensitization solution and stirred for 2min. The D50 of the TiH2 powder was <10μm. The mass ratio of stannous chloride dihydrate, hydrochloric acid, and deionized water in the sensitization solution was 2.0:5.5:400, and the concentration of the hydrochloric acid was 9M. After filtration and rinsing with ice water, the mixture was immediately added to 201g of activation solution and stirred for 4min. The mass ratio of palladium chloride, hydrochloric acid, and deionized water in the activation solution was 0.10:1.2:200, and the concentration of the hydrochloric acid was 12M. After filtration again and rinsing with alternating ice water and anhydrous ethanol, a wet activated filter cake was obtained. 40.0g of copper sulfate pentahydrate, 61.0g of disodium EDTA, and 0.02g of... 2,2'-Bipyridine was dispersed in 800g of deionized water and the pH was adjusted to 12.1 with 20wt.% sodium hydroxide. The 2,2'-bipyridine was dissolved in anhydrous ethanol before use. After mixing evenly, the activated filter cake was added, stirred and 31.0g of 35wt.% formaldehyde solution was added dropwise. The reaction was stopped when the deep blue color of the solution faded and approached colorless. The mixture was filtered and washed successively with water and anhydrous ethanol. The mixture was then vacuum dried to obtain copper-coated titanium hydride composite powder.

[0060] S2, 41.5g of electrolytic copper powder, 5.2g of chromium powder, 2.5g of amorphous boron powder and 1.1g of silicon powder are mixed. The D50 of the electrolytic copper powder is 10μm, the D50 of the chromium powder is <45μm, and the D50 of the silicon powder is <10μm. The mixture is placed in a cemented carbide ball milling jar in a glove box filled with high-purity argon gas and ball-to-material ratio is 18:1. The ball milling time is 60h, the ball milling speed is 300r / min, and the ball milling process is intermittent to obtain a copper-based activating sintering aid.

[0061] S3. A molten salt medium is prepared by grinding and mixing 50.0g sodium chloride, 51.0g potassium chloride, and 10.0g tungsten powder. 31g diamond micropowder is added to the molten salt medium and mixed evenly. The tungsten powder has a D50 of 3μm, and the diamond micropowder contains diamond micropowder with a D50 of 10μm and diamond micropowder with a D50 of 5μm in a mass ratio of 2:1. The mixture is heated at 840℃ for 190min under an argon atmosphere. After cooling, the salt is dissolved in deionized water, stirred, and allowed to stand for 20s to allow the free tungsten powder to settle. The upper suspension is poured off, the supernatant is collected, and the settled free tungsten powder at the bottom is discarded. This classification and washing operation is repeated three times until no obvious gray-black heavy slag appears at the bottom. The precipitate is collected, washed with anhydrous ethanol, and vacuum dried. Tungsten-coated diamond was obtained. 84g of tert-butanol, 5.5g of ethyl cellulose, and 0.4g of oleic acid were mixed to obtain an organic carrier. The viscosity of the ethyl cellulose was 10 mPa·s, measured at a specified concentration at 25°C. The viscosity of the organic carrier at 25°C was 8000 mPa·s. 20.0g of tungsten-coated diamond, 33.5g of electrolytic copper powder, 3.0g of copper-coated titanium hydride composite powder, and 4.2g of copper-based activating sintering aid were added to the organic carrier. The mixture was ground to obtain a uniform slurry. The slurry was injected into a mold and centrifuged for 8 minutes under a centrifugal force field with a centrifugal acceleration of 2000g, where g is the standard gravitational acceleration. Subsequently, it was freeze-dried to obtain a green body with a copper-rich gradient structure at the bottom.

[0062] S4. The green blank is placed in a spark plasma sintering furnace and sintered to obtain a copper-diamond gradient composite material with high thermal conductivity. The sintering process is as follows: a contact pressure of 1.5 MPa is applied under vacuum, the temperature is increased to 410°C at 10°C / min and held for 18 min to remove air, then the temperature is increased to 540°C at 30°C / min and held for 22 min, then the contact pressure is linearly increased to 28 MPa and the temperature is increased to 860°C at 100°C / min and held for 4 min, then the contact pressure is further increased to 48 MPa and the temperature is increased to 920°C at 50°C / min and held for 5 min, finally the contact pressure is reduced to 6 MPa and the temperature is reduced to 740°C and held for 45 min, and then cooled to room temperature in the furnace.

[0063] Example 3

[0064] This embodiment provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The preparation method specifically includes the following steps:

[0065] S1, in an ice-water bath environment, 20.2g of TiH2 powder was dispersed in 410g of sensitization solution and stirred for 2.5min. The D50 of the TiH2 powder was <10μm. The mass ratio of stannous chloride dihydrate, hydrochloric acid, and deionized water in the sensitization solution was 2.1:5.2:405, and the concentration of the hydrochloric acid was 10M. After filtration and rinsing with ice water, the solution was immediately added to 210g of activation solution and stirred for 3.5min. The mass ratio of palladium chloride, hydrochloric acid, and deionized water in the activation solution was 0.11:1.1:205, and the concentration of the hydrochloric acid was 10M. The solution was filtered again and rinsed alternately with ice water and anhydrous ethanol to obtain a wet activated filter cake. 40.5g of copper sulfate pentahydrate, 60.5g of disodium EDTA, and 0.025g of... 2,2'-Bipyridine was dispersed in 750g of deionized water and the pH was adjusted to 12.0 with 22wt.% sodium hydroxide. The 2,2'-bipyridine was dissolved in anhydrous ethanol before use. After mixing evenly, the activated filter cake was added, stirred and 30.5g of 36wt.% formaldehyde solution was added dropwise. The reaction was stopped when the deep blue color of the solution faded and approached colorless. The mixture was filtered and washed successively with water and anhydrous ethanol. The mixture was then vacuum dried to obtain copper-coated titanium hydride composite powder.

[0066] S2, 41.8g of electrolytic copper powder, 5.1g of chromium powder, 2.6g of amorphous boron powder and 1.05g of silicon powder are mixed. The D50 of the electrolytic copper powder is 11μm, the D50 of the chromium powder is <45μm, and the D50 of the silicon powder is <10μm. The mixture is placed in a cemented carbide ball milling jar in a glove box filled with high-purity argon gas and ball-to-material ratio is 20:1. The ball milling time is 50h, the ball milling speed is 350r / min, and the ball milling process is intermittent to obtain a copper-based activated sintering aid.

[0067] S3. A molten salt medium is prepared by grinding and mixing 50.5g of sodium chloride, 50.5g of potassium chloride, and 10.2g of tungsten powder. 30.5g of diamond micro-powder is added to the molten salt medium and mixed evenly. The tungsten powder has a D50 of 2μm, and the diamond micro-powder contains diamond micro-powder with a D50 of 10μm and diamond micro-powder with a D50 of 5μm in a mass ratio of 2:1. The mixture is heated at 850℃ for 180min under an argon atmosphere. After cooling, the salt is dissolved in deionized water, stirred, and allowed to stand for 30s to allow the free tungsten powder to settle. The upper suspension is poured off, the supernatant is collected, and the settled free tungsten powder at the bottom is discarded. This classification and washing operation is repeated twice until no obvious gray-black heavy slag appears at the bottom. The precipitate is collected, washed with anhydrous ethanol, and vacuum dried. Tungsten-coated diamond was obtained. 85g of tert-butanol, 5.0g of ethyl cellulose, and 0.5g of oleic acid were mixed to obtain an organic carrier. The viscosity of the ethyl cellulose was 30 mPa·s, measured at a specified concentration at 25°C. The viscosity of the organic carrier at 25°C was 6000 mPa·s. 20.2g of tungsten-coated diamond, 33.2g of electrolytic copper powder, 3.1g of copper-coated titanium hydride composite powder, and 4.1g of copper-based activating sintering aid were added to the organic carrier. The mixture was ground to obtain a uniform slurry. The slurry was injected into a mold and centrifuged for 10 minutes under a centrifugal force field with a centrifugal acceleration of 1800g, where g is the standard gravitational acceleration. Subsequently, it was freeze-dried to obtain a green body with a copper-rich gradient structure at the bottom.

[0068] S4. The green blank is placed in a spark plasma sintering furnace and sintered to obtain a copper-diamond gradient composite material with high thermal conductivity. The sintering process is as follows: a contact pressure of 2.0 MPa is applied under vacuum, the temperature is increased to 400℃ at 10℃ / min and held for 20 min to exhaust the air, then the temperature is increased to 550℃ at 30℃ / min and held for 20 min, then the contact pressure is linearly increased to 30 MPa and the temperature is increased to 850℃ at 100℃ / min and held for 5 min, then the contact pressure is further increased to 50 MPa and the temperature is increased to 910℃ at 50℃ / min and held for 6 min, finally the contact pressure is reduced to 5 MPa and the temperature is reduced to 750℃ and held for 40 min, and then cooled to room temperature in the furnace.

[0069] Example 4

[0070] This embodiment provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The preparation method specifically includes the following steps:

[0071] S1, in an ice-water bath environment, 20.4 g of TiH2 powder was dispersed in 415 g of sensitizing solution and stirred for 2.8 min. The D50 of the TiH2 powder was < 10 μm. The mass ratio of stannous chloride dihydrate, hydrochloric acid, and deionized water in the sensitizing solution was 2.15:5.4:408, and the concentration of the hydrochloric acid was 11 M. After filtration and rinsing with ice water, the solution was immediately added to 206 g of activation solution and stirred for 3.8 min. The mass ratio of palladium chloride, hydrochloric acid, and deionized water in the activation solution was 0.105:1.15:208, and the concentration of the hydrochloric acid was 11 M. After filtration again and rinsing with alternating ice water and anhydrous ethanol, a wet activated filter cake was obtained. 40.8 g of copper sulfate pentahydrate, 60.8 g of disodium EDTA, and 0.028 g of... 2,2'-Bipyridine was dispersed in 780g of deionized water and the pH was adjusted to 12.0 with 24wt.% sodium hydroxide. The 2,2'-bipyridine was pre-dissolved in anhydrous ethanol before use. After mixing evenly, the activated filter cake was added, stirred, and 30.8g of 36.5wt.% formaldehyde solution was added dropwise. The reaction was stopped when the deep blue color of the solution faded and approached colorless. The mixture was filtered and washed successively with water and anhydrous ethanol. The mixture was then vacuum dried to obtain copper-coated titanium hydride composite powder.

[0072] S2, 41.6g of electrolytic copper powder, 5.15g of chromium powder, 2.65g of amorphous boron powder and 1.08g of silicon powder are mixed. The D50 of the electrolytic copper powder is 11.5μm, the D50 of the chromium powder is <45μm, and the D50 of the silicon powder is <10μm. The mixture is placed in a glove box filled with high-purity argon gas and then ball-milled in a carbide ball milling jar. The ball-to-material ratio is 19:1, the ball milling time is 55h, the ball milling speed is 320r / min, and the ball milling process is intermittent to obtain a copper-based activating sintering aid.

[0073] S3. A molten salt medium was prepared by grinding and mixing 50.8g of sodium chloride, 50.2g of potassium chloride, and 10.4g of tungsten powder. 30.8g of diamond micropowder was added to the molten salt medium and mixed thoroughly. The tungsten powder had a D50 of 2.5μm, and the diamond micropowder contained diamond micropowder with a D50 of 10μm and diamond micropowder with a D50 of 5μm in a mass ratio of 2:1. The mixture was heated at 855℃ for 185min under an argon atmosphere. After cooling, the salt was dissolved in deionized water, stirred, and allowed to stand for 25s to allow the free tungsten powder to settle. The upper suspension was poured off, the supernatant was collected, and the settled free tungsten powder at the bottom was discarded. This classification and washing operation was repeated three times until no obvious gray-black heavy slag appeared at the bottom. The precipitate was collected, washed with anhydrous ethanol, and vacuum dried to obtain the final product. A tungsten-coated diamond was prepared by mixing 85.5g of tert-butanol, 5.0g of ethyl cellulose, and 0.55g of oleic acid to obtain an organic carrier. The viscosity of the ethyl cellulose was 40 mPa·s, measured at a specified concentration at 25°C. The viscosity of the organic carrier at 25°C was 7000 mPa·s. 20.4g of tungsten-coated diamond, 33.4g of electrolytic copper powder, 3.15g of copper-coated titanium hydride composite powder, and 4.15g of copper-based activating sintering aid were added to the organic carrier. The mixture was ground to obtain a uniform slurry. The slurry was injected into a mold and centrifuged for 9 minutes under a centrifugal force field with a centrifugal acceleration of 1600g, where g is the standard gravitational acceleration. Subsequently, the mixture was freeze-dried to obtain a green body with a copper-rich gradient structure at the bottom.

[0074] S4. The green blank is placed in a spark plasma sintering furnace and sintered to obtain a copper-diamond gradient composite material with high thermal conductivity. The sintering process is as follows: a contact pressure of 1.8 MPa is applied under vacuum, the temperature is increased to 405°C at 10°C / min and held for 21 min for degassing, then the temperature is increased to 545°C at 30°C / min and held for 21 min. Subsequently, the contact pressure is linearly increased to 29 MPa and the temperature is increased to 855°C at 100°C / min and held for 4.5 min. The contact pressure is further increased to 49 MPa and the temperature is increased to 915°C at 50°C / min and held for 6.5 min. Finally, the contact pressure is reduced to 5.5 MPa and the temperature is reduced to 755°C and held for 35 min. The material is then cooled to room temperature in the furnace.

[0075] Comparative Example 1

[0076] This comparative example provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The difference between this example and Example 1 is that the copper-coated titanium hydride composite powder in S3 is replaced by an equal mass of electrolytic copper powder, while other process parameters and operating conditions are exactly the same as in Example 1.

[0077] Comparative Example 2

[0078] This comparative example provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The difference between this example and Example 1 is that tungsten-coated diamond is not used in S3, but instead, diamond micropowder of equal mass that has not undergone molten salt-assisted tungsten infiltration treatment is used. Other process parameters and operating conditions are exactly the same as in Example 1.

[0079] Comparative Example 3

[0080] This comparative example provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The difference between this example and Example 1 is that the copper-based activating sintering aid in S3 is replaced by an equal mass of electrolytic copper powder, while other process parameters and operating conditions are exactly the same as in Example 1.

[0081] Comparative Example 4

[0082] This comparative example provides a copper-diamond gradient composite material with high thermal conductivity and its preparation method. The difference between this example and Example 1 is that in S3, centrifugal molding under centrifugal force field is replaced by injecting slurry into a mold, allowing it to stand and then directly freeze-drying it. Other process parameters and operating conditions are exactly the same as in Example 1.

[0083] Thermal diffusivity was determined according to ASTM E1461, and thermal conductivity was calculated by combining density and specific heat capacity; relative density was tested according to ASTM B962; solderability was tested according to IEC 60068-2-69, and the results were based on wetting time.

[0084] The test results are shown in Table 1.

[0085] Table 1. Test results of copper-diamond gradient composite materials in Examples 1-4 and Comparative Examples 1-4

[0086] Thermal conductivity (W / (m·K)) Relative density (%) Wetting time (s) Example 1 604 99.2 1.7 Example 2 608 99.1 1.6 Example 3 610 99.4 2.0 Example 4 606 99.1 1.6 Comparative Example 1 510 98.4 3.4 Comparative Example 2 560 99.1 2.7 Comparative Example 3 470 98.6 3.5 Comparative Example 4 580 99.0 4.7

[0087] As shown in Table 1, compared to Example 1, Comparative Example 1 exhibits decreased thermal conductivity, decreased relative density, and increased wetting time; Comparative Example 2 exhibits decreased thermal conductivity, decreased relative density, and increased wetting time; Comparative Example 3 exhibits decreased thermal conductivity, decreased relative density, and increased wetting time; and Comparative Example 4 exhibits decreased thermal conductivity, decreased relative density, and increased wetting time. This is because in Comparative Example 1, without copper-coated titanium hydride, the lack of in-situ hydrogen evolution reduction and active Ti supply during sintering makes it difficult to remove the copper powder oxide film, hindering growth and leaving open pores, thus limiting interfacial reactions and increasing thermal resistance. In Comparative Example 2, without tungsten infiltration, the diamond surface lacks a W-rich carrier layer, making it easier for active Ti to react directly with carbon and form an uneven reaction layer, increasing local interfacial defects and thermal resistance, but worsening interfacial bonding and heat conduction pathways. In Comparative Example 3, after removing the mechanical alloying sintering aid, insufficient particle rearrangement and local softening phase result in reduced efficiency due to pore closure relying on solid-phase diffusion. After eliminating centrifugal differential settling in Comparative Example 4, the composition of the green blank tends to be homogeneous, making it difficult to form a continuous copper-rich bottom layer. Thermal expansion mismatch is concentrated in the cross section and easily induces microcracks.

[0088] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a copper-diamond gradient composite material with high thermal conductivity, characterized in that, The preparation method includes: S1, TiH2 powder is dispersed in a sensitizing solution and stirred. The sensitizing solution is an aqueous solution containing stannous chloride and hydrochloric acid. After filtration and rinsing with ice water, it is immediately added to an activation solution and stirred. The activation solution is an aqueous solution containing palladium chloride and hydrochloric acid to obtain a wet activated filter cake. Copper sulfate pentahydrate, disodium EDTA, and 2,2'-bipyridine are dispersed in deionized water, mixed evenly, and then added to the above wet activated filter cake. The mixture is stirred and formaldehyde solution is added dropwise to obtain copper-coated titanium hydride composite powder. S2, mix electrolytic copper powder, chromium powder, amorphous boron powder and silicon powder, and ball mill them in a glove box filled with high-purity argon in a carbide ball mill jar to obtain copper-based activating sintering aid; S3, sodium chloride, potassium chloride and tungsten powder are ground and mixed to prepare a molten salt medium. Diamond micro powder is added to the molten salt medium and mixed evenly and kept at a constant temperature to obtain tungsten-coated diamond. Tert-butanol, ethyl cellulose and oleic acid are mixed to obtain an organic carrier. Tungsten-coated diamond, electrolytic copper powder, copper-coated titanium hydride composite powder and copper-based activating sintering aid are added to the organic carrier. The mixture is ground to obtain a uniform slurry. The slurry is injected into a mold, centrifuged under a centrifugal force field and freeze-dried to obtain a green body with a bottom copper-rich gradient structure. S4. The green blank is placed in a spark plasma sintering furnace and sintered to obtain a copper-diamond gradient composite material with high thermal conductivity. The sintering procedure is as follows: under vacuum conditions, apply a contact pressure of 1.5-2.5 MPa, heat to 390-410℃ at 10℃ / min and hold for 18-22 min to exhaust the air, then heat to 540-560℃ at 30℃ / min and hold for 18-22 min, then linearly increase the contact pressure to 28-32 MPa and heat to 840-860℃ at 100℃ / min and hold for 4-6 min, then continue to increase the contact pressure to 48-52 MPa and heat to 900-920℃ at 50℃ / min and hold for 5-8 min, finally reduce the contact pressure to 4-6 MPa and cool to 740-760℃ and hold for 30-45 min, then cool to room temperature with the furnace.

2. The method for preparing a high thermal conductivity copper-diamond gradient composite material according to claim 1, characterized in that, In S1: The mass ratio of TiH2 powder, sensitizing solution, activating solution, copper sulfate pentahydrate, disodium EDTA, 2,2'-bipyridine, deionized water and formaldehyde solution is (20-20.5):(407-418):(201-213):(40-41):(60-61):(0.02-0.03):(700-800):(30-31).

3. The method for preparing a high thermal conductivity copper-diamond gradient composite material according to claim 1, characterized in that, In S1: The mass ratio of stannous chloride dihydrate, hydrochloric acid, and deionized water in the sensitizing solution is (2-2.2):(5-5.5):(400-410), and the concentration of hydrochloric acid is 9-12M.

4. The method for preparing a high thermal conductivity copper-diamond gradient composite material according to claim 1, characterized in that, In S1: The mass ratio of palladium chloride, hydrochloric acid, and deionized water in the activation solution is (0.1-0.12):(1-1.2):(200-210), and the concentration of the hydrochloric acid is 9-12M.

5. The method for preparing a high thermal conductivity copper-diamond gradient composite material according to claim 1, characterized in that, In S2: The mass ratio of electrolytic copper powder, chromium powder, amorphous boron powder and silicon powder is (41.5-42):(5-5.2):(2.5-2.7):(1-1.1).

6. The method for preparing a high thermal conductivity copper-diamond gradient composite material according to claim 1, characterized in that, In S3: The mass ratio of sodium chloride, potassium chloride, tungsten powder and diamond micro powder is (50-51):(50-51):(10-10.5):(30-31).

7. The method for preparing a high thermal conductivity copper-diamond gradient composite material according to claim 1, characterized in that, In S3: The mass ratio of tert-butanol, ethyl cellulose, oleic acid, tungsten-coated diamond, electrolytic copper powder, copper-coated titanium hydride composite powder to copper-based activating sintering aid is (84-86): (4.5-5.5): (0.4-0.6): (20-20.5): (33-33.5): (3-3.2): (4-4.2).

8. The method for preparing a high thermal conductivity copper-diamond gradient composite material according to claim 1, characterized in that, In S3: The centrifugal acceleration of the centrifugal force field is 1500g-2000g, where g is the standard gravitational acceleration.

9. A copper-diamond gradient composite material with high thermal conductivity is obtained by the preparation method according to any one of claims 1-8.

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