A directional thermally conductive copper-based diamond composite material and its preparation method

Abstract

This invention provides a directional thermally conductive copper-based diamond composite material and its preparation method, belonging to the technical field of copper-based diamond composite materials. By constructing a "diamond particle size gradient + aluminum nitride / silicon carbide ceramic gradient," combined with multilayer powder injection molding and segmented vacuum hot pressing, the thermal conductivity and thermal expansion in the thickness direction are synergistically controlled: the upper layer of fine-grained diamond and a small amount of aluminum nitride forms a high thermal conductivity layer, the middle layer of medium-grained diamond and a relatively high amount of aluminum nitride acts as a thermal-mechanical buffer, and the lower layer of coarse-grained diamond and silicon carbide improves the expansion matching and sintering stability of the substrate side; sequential injection combined with interval time and thickness ratio control forms a continuous composition gradient and particle intercalation interface during debinding and densification processes, and through two-step heating, three-stage pressure, depressurization and slow cooling, and medium-temperature heat preservation, densification, interfacial reaction and residual stress release are taken into account, so that the copper-based diamond composite material maintains high thermal conductivity while having an adjustable expansion gradient and high structural reliability.

Description

Technical Field

[0001] This invention belongs to the technical field of copper-based diamond composite materials, and relates to a directional thermally conductive copper-based diamond composite material and its preparation method. Background Technology

[0002] Currently, copper-based diamond composite materials used in power device packaging and power module heat dissipation substrates mostly employ uniform proportions or relatively simple layered designs, relying primarily on increasing the overall diamond volume fraction to achieve high thermal conductivity. This approach lacks targeted gradient control in the thickness direction, making it difficult to simultaneously address the differences in heat dissipation paths and constraints between the chip's working surface and the substrate side. This results in insufficient overall thermal expansion matching, leading to reliability issues such as warping, stress concentration, and interface cracking during thermal cycling and long-term service. Furthermore, existing composite material interface design methods are relatively crude, often improving wettability and bonding strength by adding active elements like Ti to the copper matrix or applying a single metal plating to the diamond. This easily leads to high solid solution concentration or coarse precipitation of active elements in the matrix, significantly reducing the intrinsic thermal conductivity of the copper matrix. Moreover, the thickness and composition of the interface reaction layer are difficult to control precisely. Simultaneously, conventional pressing, hot pressing, or impregnation processes have limited capabilities in achieving complex gradient structures and near-net-shape forming, making it difficult to guarantee the quality of interlayer bonding interfaces and the stability of compositional distribution. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a directional thermally conductive copper-based diamond composite material and its preparation method. This application achieves precise control of thermal conductivity and coefficient of thermal expansion in the thickness direction by introducing a "diamond particle size gradient and aluminum nitride / silicon carbide ceramic synergistic gradient" into the system, combined with multilayer powder injection molding and segmented vacuum hot pressing sintering. The upper layer uses high-volume-fraction fine-grained diamond supplemented with a small amount of aluminum nitride to construct a high thermal conductivity layer; the middle layer uses medium-grained diamond and a relatively high amount of aluminum nitride to achieve thermal-mechanical buffering; and the lower layer uses coarse-grained diamond and silicon carbide to improve expansion matching and sintering stability near the substrate. Multilayer powder sequential injection combined with short intervals and thickness ratio control ensures a continuous composition gradient macroscopically and forms interlocking transition zones at the microscopic interface. Solvent degreasing and thermal degreasing result in a gradient preform with a more uniform pore distribution. Subsequently, a two-step heating, three-stage pressure, depressurization and slow cooling, and medium-temperature holding process was employed in vacuum hot pressing. This process achieved densification and the formation of an interface reaction layer involving Ti / Zr. Simultaneously, while the copper matrix still retained its plasticity, it released residual stress caused by the expansion difference between the diamond / ceramic and the copper matrix, reducing the risk of warping and cracking. The synergistic effect of interface metallization, layered addition of active alloy powder, enhanced phase gradient, multi-layer injection, and segmented hot pressing resulted in a copper-based diamond composite material that maintains high thermal conductivity while possessing an adjustable expansion gradient, high structural integrity, and high service reliability.

[0004] To achieve this objective, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a method for preparing a directional thermally conductive copper-based diamond composite material, the method comprising:

[0006] S1: Fine-grained diamond particles, medium-grained diamond particles, coarse-grained diamond particles, aluminum nitride particles, and silicon carbide particles are cleaned and dried separately, and then placed in a vacuum coating device. Physical vapor deposition is used to form a connecting film on the surface to obtain coated fine-grained diamond particles, coated medium-grained diamond particles, coated coarse-grained diamond particles, coated aluminum nitride particles, and coated silicon carbide particles.

[0007] S2: A first premix is ​​obtained by mixing fine-grained diamond particles, aluminum nitride particles, alloy powder, and metal matrix powder; a mixing binder is added to obtain a first mixture; and the mixture is melt-kneaded to obtain a first layer feed. A second premix is ​​obtained by mixing medium-grained diamond particles, aluminum nitride particles, alloy powder, and metal matrix powder; a mixing binder is added to obtain a second mixture; and the mixture is melt-kneaded to obtain a second layer feed. A third premix is ​​obtained by mixing coarse-grained diamond particles, silicon carbide particles, alloy powder, and metal matrix powder; a mixing binder is added to obtain a third mixture; and the mixture is melt-kneaded to obtain a third layer feed.

[0008] S3: After granulating the first layer feed, the second layer feed, and the third layer feed, respectively load them into the injection molding machine and inject them into the mold in sequence to obtain gradient injection preforms. Place the gradient injection preforms in n-heptane for degreasing to obtain solvent-degreased preforms. Place the solvent-degreased preforms in an inert gas environment for thermal degreasing to obtain degreased preforms.

[0009] S4: Place the degreased blank in a vacuum hot press furnace, heat it to the first temperature and apply the first pressure, then continue to heat it to the sintering temperature and increase the pressure to the second pressure and hold it at the temperature, then reduce the pressure to the third pressure and cool it to the third temperature at the cooling rate and hold it at the temperature, then cool it to room temperature and demold to obtain a directional thermally conductive copper-based diamond composite material.

[0010] As a preferred technical solution of the present invention, in step S1, the particle size of the fine diamond particles is 8-12 μm, for example, it can be 8.0 μm, 8.4 μm, 8.8 μm, 9.2 μm, 9.6 μm, 10.0 μm, 10.4 μm, 10.8 μm, 11.2 μm, 11.6 μm or 12.0 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0011] In some optional embodiments, the particle size of the medium-sized diamond particles is 40-60 μm, for example, it can be 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 56 μm, 58 μm or 60 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0012] In some optional embodiments, the coarse diamond particles have a particle size of 80-120 μm, for example, 80 μm, 84 μm, 88 μm, 92 μm, 96 μm, 100 μm, 104 μm, 108 μm, 112 μm, 116 μm or 120 μm, but are not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0013] In some optional embodiments, the aluminum nitride particles have a particle size of 5-30 μm, for example, 5.0 μm, 7.5 μm, 10.0 μm, 12.5 μm, 15.0 μm, 17.5 μm, 20.0 μm, 22.5 μm, 25.0 μm, 27.5 μm or 30.0 μm, but are not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0014] In some optional embodiments, the particle size of the silicon carbide particles is 5-30 μm, for example, it can be 5.0 μm, 7.5 μm, 10.0 μm, 12.5 μm, 15.0 μm, 17.5 μm, 20.0 μm, 22.5 μm, 25.0 μm, 27.5 μm or 30.0 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0015] In some optional embodiments, the thickness of the connecting film is 80-200 nm, for example, it can be 80 nm, 92 nm, 104 nm, 116 nm, 128 nm, 140 nm, 152 nm, 164 nm, 176 nm, 188 nm or 200 nm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0016] The connecting film is a metal film or a SiC-metal composite film. The metal film is any one or a combination of Ti, Cr, Zr, Mo, and W. When the connecting film is a metal film, it is deposited with a metal target and an inert gas. When the connecting film is a SiC-metal composite film, a carbon-containing gas is introduced and a metal-Si alloy target or a metal target and a silicon target are co-sputtered and deposited.

[0017] In some optional embodiments, the working pressure during physical vapor deposition is 0.3-1.0 Pa, for example, it can be 0.3 Pa, 0.35 Pa, 0.4 Pa, 0.45 Pa, 0.5 Pa, 0.55 Pa, 0.6 Pa, 0.65 Pa, 0.7 Pa, 0.75 Pa, 0.8 Pa, 0.85 Pa, 0.9 Pa, 0.95 Pa or 1.0 Pa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] In some alternative embodiments, the substrate temperature during physical vapor deposition is 80-200°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0019] As a preferred technical solution of the present invention, in step S2, the particle size of the alloy powder is 5-15μm, for example, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] The alloy powder is Cu-Ti alloy powder or Cu-Ti-Zr alloy powder; wherein the Cu-Ti alloy powder contains 4-8 wt.% Ti and the balance is Cu; the Cu-Ti-Zr alloy powder contains 3-6 wt.% Ti and 1-2 wt.% Zr and the balance is Cu.

[0021] In some optional embodiments, the volume fraction of the coated fine diamond particles in the first premix is ​​65-75%, for example, it can be 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74% or 75%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the volume fraction of coated aluminum nitride particles in the first premix is ​​1-5%, for example, it can be 1.0%, 1.4%, 1.8%, 2.2%, 2.6%, 3.0%, 3.4%, 3.8%, 4.2%, 4.6% or 5.0%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the volume fraction of alloy powder in the first premix is ​​1-3%, for example, it can be 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8% or 3.0%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] The metal matrix powder is any one of pure copper, Cu-Zr alloy, Cu-Cr alloy, or Cu-Cr-Zr alloy, wherein in the Cu-Cr alloy, Cr is 0.2-0.8 wt.% and the remainder is Cu; in the Cu-Zr alloy, Zr is 0.05-0.20 wt.% and the remainder is Cu; and in the Cu-Cr-Zr alloy, Cr is 0.2-0.6 wt.% and Zr is 0.05-0.15 wt.% and the remainder is Cu.

[0025] The metal matrix powder in the first premix is ​​used to supplement the balance.

[0026] In some alternative embodiments, the melt mixing temperature of the first mixture is 130-170°C, for example, it can be 130°C, 134°C, 138°C, 142°C, 146°C, 150°C, 154°C, 158°C, 162°C, 166°C or 170°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some alternative embodiments, the mass ratio of paraffin, polyethylene, and polypropylene in the mixed binder is (50-70):(10-25):(15-30), for example, (50, 52, 54, 56, 58, 60, 62, 64, 66, 68, or 70):(10.0, 11.5, 13.0, 14.5, 16.0, 17.5, 19.0, 20.5, 22.0, 23.5, or 25.0):(15.0, 16.5, 18.0, 19.5, 21.0, 22.5, 24.0, 25.5, 27.0, 28.5, or 30.0), but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the amount of binder mixed in the first layer feed is 8-12% of the mass of the first premix, for example, it can be 8.0%, 8.4%, 8.8%, 9.2%, 9.6%, 10.0%, 10.4%, 10.8%, 11.2%, 11.6% or 12.0%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the volume fraction of diamond particles in the coating of the second premix is ​​45-55%, for example, it can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the volume fraction of coated aluminum nitride particles in the second premix is ​​5-15%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the volume fraction of alloy powder in the second premix is ​​3-6%, for example, it can be 3.0%, 3.3%, 3.6%, 3.9%, 4.2%, 4.5%, 4.8%, 5.1%, 5.4%, 5.7% or 6.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the melt mixing temperature of the second mixture is 130-170°C, for example, 130°C, 134°C, 138°C, 142°C, 146°C, 150°C, 154°C, 158°C, 162°C, 166°C or 170°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the amount of binder mixed in the second layer feed is 8-12% of the second premix mass, for example, it can be 8.0%, 8.4%, 8.8%, 9.2%, 9.6%, 10.0%, 10.4%, 10.8%, 11.2%, 11.6% or 12.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the volume fraction of the coated coarse diamond particles in the third premix is ​​20-35%, for example, it can be 20.0%, 21.5%, 23.0%, 24.5%, 26.0%, 27.5%, 29.0%, 30.5%, 32.0%, 33.5% or 35.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the volume fraction of the coated silicon carbide particles in the third premix is ​​10-25%, for example, it can be 10.0%, 11.5%, 13.0%, 14.5%, 16.0%, 17.5%, 19.0%, 20.5%, 22.0%, 23.5% or 25.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the volume fraction of alloy powder in the third premix is ​​5-8%, for example, it can be 5.0%, 5.3%, 5.6%, 5.9%, 6.2%, 6.5%, 6.8%, 7.1%, 7.4%, 7.7% or 8.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the amount of binder mixed in the third layer feed is 8-12% of the mass of the third premix, for example, it can be 8.0%, 8.4%, 8.8%, 9.2%, 9.6%, 10.0%, 10.4%, 10.8%, 11.2%, 11.6% or 12.0%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the melt mixing temperature of the third mixture is 130-170°C, for example, it can be 130°C, 134°C, 138°C, 142°C, 146°C, 150°C, 154°C, 158°C, 162°C, 166°C or 170°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] As a preferred technical solution of the present invention, in step S3, the temperature of the barrel is 110-140℃, for example, it can be 110℃, 113℃, 116℃, 119℃, 122℃, 125℃, 128℃, 131℃, 134℃, 137℃ or 140℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] In some alternative embodiments, the temperature of the mold is 25-50°C, for example, it can be 25.0°C, 27.5°C, 30.0°C, 32.5°C, 35.0°C, 37.5°C, 40.0°C, 42.5°C, 45.0°C, 47.5°C or 50.0°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0041] In some alternative embodiments, the injection pressure is 80-120 MPa, for example, it can be 80 MPa, 84 MPa, 88 MPa, 92 MPa, 96 MPa, 100 MPa, 104 MPa, 108 MPa, 112 MPa, 116 MPa or 120 MPa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0042] In some optional embodiments, the time for sequentially injecting the first, second, and third layers of feed into the mold after granulation is 1-5 seconds, for example, it can be 1.0s, 1.4s, 1.8s, 2.2s, 2.6s, 3.0s, 3.4s, 3.8s, 4.2s, 4.6s, or 5.0s, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0043] In some alternative embodiments, the pressure holding time is 5-20s, for example, it can be 5.0s, 6.5s, 8.0s, 9.5s, 11.0s, 12.5s, 14.0s, 15.5s, 17.0s, 18.5s or 20.0s, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0044] In some optional embodiments, the settling time after the first layer of feed, the second layer of feed, and the third layer of feed are sequentially injected into the mold is 2-10 seconds, for example, it can be 2.0 seconds, 2.8 seconds, 3.6 seconds, 4.4 seconds, 5.2 seconds, 6.0 seconds, 6.8 seconds, 7.6 seconds, 8.4 seconds, 9.2 seconds, or 10.0 seconds, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] In some optional embodiments, the injection thickness ratio of the first, second, and third feed layers is 1:(0.8-1.2):(0.8-1.2), for example, it can be 1:(0.80, 0.84, 0.88, 0.92, 0.96, 1.00, 1.04, 1.08, 1.12, 1.16, or 1.20):(0.80, 0.84, 0.88, 0.92, 0.96, 1.00, 1.04, 1.08, 1.12, 1.16, or 1.20), but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0046] In some optional embodiments, the solvent degreasing temperature of the gradient injection preform is 50-65°C, for example, it can be 50.0°C, 51.5°C, 53.0°C, 54.5°C, 56.0°C, 57.5°C, 59.0°C, 60.5°C, 62.0°C, 63.5°C or 65.0°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0047] In some optional embodiments, the solvent degreasing time of the gradient injection preform is 10-14 h, for example, it can be 10.0 h, 10.4 h, 10.8 h, 11.2 h, 11.6 h, 12.0 h, 12.4 h, 12.8 h, 13.2 h, 13.6 h or 14.0 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0048] In some optional embodiments, the mass-to-volume ratio of the gradient injection preform to n-heptane is 1 g:(5-15) mL, for example, it can be 1 g:5 mL, 1 g:6 mL, 1 g:7 mL, 1 g:8 mL, 1 g:9 mL, 1 g:10 mL, 1 g:11 mL, 1 g:12 mL, 1 g:13 mL, 1 g:14 mL or 1 g:15 mL, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0049] In some optional embodiments, the heating rate of the hot degreasing treatment of the degreased blank is 1-2℃ / min, for example, it can be 1.0℃ / min, 1.1℃ / min, 1.2℃ / min, 1.3℃ / min, 1.4℃ / min, 1.5℃ / min, 1.6℃ / min, 1.7℃ / min, 1.8℃ / min, 1.9℃ / min or 2.0℃ / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0050] In some optional embodiments, the hot degreasing temperature of the degreased blank is 300-450°C, for example, it can be 300°C, 315°C, 330°C, 345°C, 360°C, 375°C, 390°C, 405°C, 420°C, 435°C or 450°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0051] In some optional embodiments, the hot degreasing time of the degreased blank is 2-4 hours, for example, it can be 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0052] As a preferred embodiment of the present invention, in step S4, the vacuum degree is 1.0 × 10⁻⁶. -2 -1.0×10 -4 Pa, for example, could be 1.0 × 10⁻⁶. -4 Pa, 1.09×10 -3 Pa, 2.08×10 -3 Pa, 3.07×10 -3 Pa, 4.06×10 -3 Pa, 5.05 × 10 -3 Pa, 6.04 × 10 -3 Pa, 7.03×10 -3 Pa, 8.02×10 -3 Pa, 9.01×10 -3 Pa or 1.0 × 10 -2 Pa, but not limited to the listed values, applies to other unlisted values ​​within the same range.

[0053] In some alternative embodiments, the rate of heating to the first temperature is 5-10°C / min, for example, it can be 5.0°C / min, 5.5°C / min, 6.0°C / min, 6.5°C / min, 7.0°C / min, 7.5°C / min, 8.0°C / min, 8.5°C / min, 9.0°C / min, 9.5°C / min or 10.0°C / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0054] In some alternative embodiments, the first temperature is 500-700°C, for example, it can be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C or 700°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0055] In some alternative embodiments, the first pressure is 5-15 MPa, for example, it can be 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa or 15 MPa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0056] In some optional embodiments, the sintering temperature is 880-930°C, for example, it can be 880°C, 885°C, 890°C, 895°C, 900°C, 905°C, 910°C, 915°C, 920°C, 925°C or 930°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0057] In some alternative embodiments, the second pressure is 15-25 MPa, for example, it can be 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa or 25 MPa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0058] In some optional embodiments, the holding time for sintering is 60-120 min, for example, it can be 60 min, 66 min, 72 min, 78 min, 84 min, 90 min, 96 min, 102 min, 108 min, 114 min or 120 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0059] In some alternative embodiments, the third pressure is 2-5 MPa, for example, it can be 2.0 MPa, 2.3 MPa, 2.6 MPa, 2.9 MPa, 3.2 MPa, 3.5 MPa, 3.8 MPa, 4.1 MPa, 4.4 MPa, 4.7 MPa or 5.0 MPa, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0060] In some alternative embodiments, the cooling rate is 3-10℃ / min, for example, it can be 3.0℃ / min, 3.7℃ / min, 4.4℃ / min, 5.1℃ / min, 5.8℃ / min, 6.5℃ / min, 7.2℃ / min, 7.9℃ / min, 8.6℃ / min, 9.3℃ / min or 10.0℃ / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0061] In some alternative embodiments, the third temperature is 400-600°C, for example, it can be 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C or 600°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0062] In some optional embodiments, the heat preservation time at the third temperature is 1-3 hours, for example, it can be 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h or 3.0h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0063] Secondly, the present invention provides a copper-based diamond composite material with directional thermal conductivity prepared by the preparation method described above.

[0064] This application simultaneously introduces diamond with different particle sizes and two types of ceramic fillers, aluminum nitride and silicon carbide, into the system, and achieves a synergistic gradient distribution of volume fraction in the three-layer structure to construct a composite reinforcement network that balances high thermal conductivity and expansion control. The upper layer is mainly composed of fine-grained diamond, supplemented with a small amount of aluminum nitride, forming a high thermal conductivity layer with a large specific surface area and dense contact network near the heat source. The middle layer uses medium-grained diamond combined with aluminum nitride, introducing a ceramic phase with mechanical and expansion coefficients between diamond and metal matrix while maintaining high thermal conductivity, thus acting as a thermal-mechanical buffer. The bottom layer uses a combination of coarse-grained diamond and silicon carbide, which reduces the number of interfaces and decreases the sensitivity to sintering shrinkage, while the linear expansion coefficient of silicon carbide is closer to that of diamond, which can improve thermal expansion matching near the substrate. By combining "diamond particle size gradient, ceramic type and content gradient", the performance is no longer adjusted by simply changing the volume fraction of diamond. Instead, by selecting and layering the second-phase ceramic, the thermal conductivity, thermal expansion coefficient and sintering shrinkage behavior of each layer are adjusted in a more detailed manner. This allows the material to meet the high thermal conductivity requirements while reducing the risk of cracking and interface failure caused by thermal stress and sintering deformation.

[0065] This application utilizes a multi-layer powder injection molding process, sequentially injecting different formulation feedstocks into the mold cavity while controlling the interlayer interval and thickness ratio. This allows for a continuous transition of the composition gradient on a macroscopic scale, while simultaneously forming interlocking transition zones at the microscopic interface. By granulating the three feedstocks separately and injecting them sequentially, and controlling the interlayer settling time to 2-10 seconds, a semi-cured shell of a certain thickness can be formed on the surface of the first injected layer while maintaining plasticity inside. Subsequently injected upper or lower feedstocks undergo localized blending and mechanical interlocking with the previous layer at the interface region under high pressure. Controlling the thickness ratio of the first, second, and third layers helps balance the shrinkage strain of each layer and reduces significant interfacial defects. The combined solvent degreasing and thermal degreasing pathway preferentially dissolves low-molecular-weight binders such as paraffin in n-heptane, retaining some of the PE / PP skeleton to maintain the preform morphology. Then, the residual binder is removed by slow heating and holding under an inert atmosphere, providing a degreased preform with a predetermined gradient structure and relatively uniform pore distribution for subsequent densification. Compared to sintering first and then machining to create gradients or pressing with simple laminates, the multilayer powder injection molding scheme of this application simultaneously completes the near-net-shape forming and interface interlocking of three layers of materials in one step, which is beneficial to improving the repeatability of gradient structures and the overall bonding quality.

[0066] This application employs a two-step heating and three-stage pressure control during the vacuum hot-pressing sintering stage, and incorporates medium-temperature holding and pressure reduction steps during the cooling process. This approach ensures densification and interfacial reactions while mitigating residual stress caused by the difference in thermal expansion coefficients between the diamond, ceramic, and copper matrices. In the first stage at 500-700℃ and 5-15MPa, the metal matrix powder first undergoes sintering neck growth and initial densification, forming a stable contact network between the reinforcing phases. Subsequently, the temperature is raised to 880-930℃ and the pressure is increased to 15-25MPa. In this temperature range, diffusion and plastic flow further close the pores and promote the diffusion of Ti / Zr from the alloy powder to the connecting film and the surface of the reinforcing phases, driving the formation and thickness increase of the interfacial reaction layer. After the heat treatment, the pressure is reduced to 2-5 MPa before cooling. Combined with a medium-temperature tempering at 400-600℃ for 1-3 hours, this allows the copper matrix to release some of the stress caused by thermal expansion mismatch through creep and recovery processes while it still retains some plasticity. This reduces the probability of macroscopic warping or microcracks after removal from the furnace. Compared to conventional hot pressing processes that involve rapid cooling after a single high-temperature pressure treatment, this segmented heating / pressure reduction / heat treatment strategy is more conducive to the synergy between densification, interfacial reaction, and stress relaxation, ensuring that the multiphase system maintains relatively stable dimensions and structural integrity even under high thermal conductivity requirements.

[0067] In this application, there is a certain synergistic relationship between interface metallization, layered addition of active alloy powder, gradient of reinforcing phase particle size and type, multilayer powder injection molding, and segmented hot pressing sintering. In the early stage, the interface is pre-designed using connecting films and alloy powders, enabling diamond, aluminum nitride, and silicon carbide to form a relatively reliable thermal-mechanical transfer interface with the copper matrix even at high volume fractions, thus providing a foundation for the high thermal conductivity layer and transition layer. The layered proportioning design of the reinforcing phase and alloy powder reduces the excessive solid solution of Ti / Zr in the matrix in the first layer, while utilizing its precipitation strengthening effect in the third layer to improve the matrix's load-bearing capacity, making the thermal conductivity and mechanical properties in the material thickness direction more in line with the actual service requirements. Multilayer powder injection and short time interval control not only create a gradual change in composition between layers but also achieve mechanical interlocking through particle interlocking in the microstructure, providing a continuous carrier for densification and interface reaction in subsequent hot pressing. The two-step heating and slow cooling regime of vacuum hot pressing, on this basis, completes densification and interface reaction while releasing thermal stress as much as possible, preventing the gradient structure from failing due to thermal cycling. Through the synergy of the above multiple stages, not only is a synergistic gradient of diamond / ceramic / active alloy powder introduced in the material composition, but also a matching interface and stress control path are constructed in the forming and sintering process, making it easier to ensure the reliability of copper-based diamond composite materials with directional thermal conductivity and adjustable thermal expansion gradient in engineering applications.

[0068] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0069] This application achieves adjustable thermal conductivity and coefficient of thermal expansion along the thickness direction through the synergy of a diamond particle size gradient and an aluminum nitride / silicon carbide ceramic synergistic filler gradient. The upper layer is dominated by fine-grained diamond, the middle layer introduces medium-grained diamond and a greater amount of aluminum nitride, and the lower layer uses coarse-grained diamond and silicon carbide. This results in higher thermal conductivity and lower expansion near the heat source, and better expansion matching and load-bearing capacity near the substrate. A balanced structural foundation is provided between thermal conductivity and crack resistance and warpage resistance.

[0070] This application utilizes a bonding film formed on the surfaces of diamond and aluminum nitride / silicon carbide, along with the layered addition of Ti / Zr-containing alloy powder, to facilitate the construction of a relatively stable interfacial transition layer. During hot pressing, the bonding film can undergo interfacial reactions with the surface of the reinforcing phase and the matrix, thereby improving the interfacial bonding state and helping to reduce interfacial thermal resistance. The alloy powder provides supplementary active elements, and by controlling its content through layering, it reduces solid solution damage of Ti / Zr in the copper matrix, balancing interfacial reliability and matrix thermal conductivity.

[0071] This application employs multi-layer powder injection molding to construct a three-layer gradient preform. By controlling the injection sequence of different feedstocks, the interlayer interval time, and the thickness ratio, the compositional gradient and structural gradient are integrated. Multi-layer powder injection molding completes the gradient distribution and interlayer particle interlocking in a one-step forming process, reducing processes such as lamination, re-sintering, or machining to etch the gradient, thereby reducing interface defects and fabrication errors.

[0072] This application employs segmented heating and multi-stage pressure in vacuum hot pressing sintering, and incorporates pressure reduction and medium-temperature holding steps during the cooling stage to ensure that densification, interfacial reaction, and residual stress release are mutually matched. Initial densification is achieved at lower temperatures and medium pressures, followed by increased pressure in a temperature range close to the solidus line of the copper alloy to enhance densification and interfacial reaction. Subsequent pressure reduction, slow cooling, and medium-temperature holding help reduce internal stress caused by the expansion mismatch between the diamond / ceramic and the copper matrix.

[0073] The various elements of this application work synergistically: interface metallization and layered alloy powder ensure that the highly filled reinforcing phase maintains high thermal conductivity while possessing a reliable interface; the gradient of particle size and ceramic type allows different layers to perform their respective functions in thermal conductivity, expansion, and load-bearing; multilayer powder injection molding and segmented hot pressing further realize the advantages of the above-mentioned formulation. Therefore, this application is expected to achieve an adjustable thermal expansion gradient in the thickness direction and good structural integrity while maintaining high overall thermal conductivity, making it suitable for applications of copper-based diamond composite materials with high requirements for thermal conductivity and dimensional stability. Detailed Implementation

[0074] 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 technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0075] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0076] Unless otherwise specified, the alloy powder and copper alloy used in the same embodiment are the same alloy powder and copper alloy.

[0077] Example 1

[0078] This embodiment provides a directional thermally conductive copper-based diamond composite material and its preparation method. The preparation method of the directional thermally conductive copper-based diamond composite material specifically includes the following steps:

[0079] S1: Fine diamond particles with a diameter of 10 μm, medium diamond particles with a diameter of 55 μm, coarse diamond particles with a diameter of 110 μm, aluminum nitride particles with a diameter of 25 μm, and silicon carbide particles with a diameter of 20 μm are cleaned and dried separately, and then placed in a vacuum coating apparatus. Physical vapor deposition is used to form a Ti / SiC composite film with a thickness of 150 nm on the surface, resulting in coated fine diamond particles, coated medium diamond particles, coated coarse diamond particles, coated aluminum nitride particles, and coated silicon carbide particles. The working pressure during physical vapor deposition is 0.5 Pa, and the substrate temperature is 80 °C.

[0080] S2: A first premix is ​​obtained by mixing fine-grained diamond particles, coated aluminum nitride particles, Cu-Ti alloy powder with a particle size of 12 μm, and pure copper powder. The volume fraction of the fine-grained diamond particles is 72%, the volume fraction of the coated aluminum nitride particles is 4%, the volume fraction of the alloy powder is 2.5%, and the remainder is pure copper powder. The alloy powder contains 4 wt.% Ti and the remainder is Cu. A mixing binder is added to obtain a first mixture, which is then melt-blended at 160°C to obtain a first layer of feedstock. The mixing binder is a compound of paraffin wax, polyethylene, and polypropylene in a mass ratio of 65:20:25, and the amount of the mixing binder added is 11% of the mass of the first premix. A second premix is ​​obtained by mixing medium-grained diamond particles, coated aluminum nitride particles, alloy powder, and pure copper powder. The first premix consists of 52% coarse-grained diamond particles, 12% coated aluminum nitride particles, 5% alloy powder, and the remainder is pure copper powder. A second mixture is obtained by adding a binder and then melt-blending at 165°C to obtain a second feedstock. The amount of the binder is 11.5% of the mass of the second premix. The second premix consists of 30% coated coarse-grained diamond particles, 20% coated silicon carbide particles, 7% alloy powder, and the remainder is pure copper powder. A third mixture is obtained by adding a binder and then melt-blending at 155°C to obtain a third feedstock. The amount of the binder is 10% of the mass of the third premix.

[0081] S3: The first, second, and third layers of feed material are granulated and then loaded into an injection molding machine. Under the conditions of barrel temperature 130℃, mold temperature 45℃, and injection pressure 110MPa, they are injected into the mold sequentially to obtain a gradient injection preform. The mold filling time is 4s, the holding pressure time is 18s, and each layer of feed material is allowed to stand for 8s after injection. The injection thickness ratio of the first, second, and third layers of feed material is 1:1.1:1.0. The gradient injection preform is placed in n-heptane at 62℃ for 13h to obtain a solvent-degreased preform. The mass-to-volume ratio of the gradient injection preform to n-heptane is 1g:12mL. The degreased preform is placed in an inert gas and heated to 400℃ at a heating rate of 1.8℃ / min for 3.5h to obtain a degreased preform.

[0082] S4: Place the degreased blank in a vacuum hot press furnace at 5×10 -3 Under vacuum of Pa, the temperature is increased to a first temperature of 650℃ at a heating rate of 8℃ / min, and then a first pressure of 12MPa is applied. The temperature is then increased to a sintering temperature of 910℃, and the pressure is increased to a second pressure of 22MPa and held for 100min. The pressure is then reduced to a third pressure of 4MPa and cooled to a third temperature of 550℃ at a cooling rate of 8℃ / min. The temperature is held for 2.5h and then cooled to room temperature. The resulting copper-based diamond composite material with directional thermal conductivity is then demolded.

[0083] Example 2

[0084] This embodiment provides a directional thermally conductive copper-based diamond composite material and its preparation method. The preparation method of the directional thermally conductive copper-based diamond composite material specifically includes the following steps:

[0085] S1: Fine diamond particles with a diameter of 8μm, medium diamond particles with a diameter of 40μm, coarse diamond particles with a diameter of 80μm, aluminum nitride particles with a diameter of 5μm, and silicon carbide particles with a diameter of 5μm are cleaned and dried separately, and then placed in a vacuum coating apparatus. Physical vapor deposition is used to form a Cr / SiC composite film with a thickness of 80nm on the surface to obtain coated fine diamond particles, coated medium diamond particles, coated coarse diamond particles, coated aluminum nitride particles, and coated silicon carbide particles. The working pressure during physical vapor deposition is 0.8Pa, and the substrate temperature is 150℃.

[0086] S2: A first premix is ​​obtained by mixing fine-grained diamond particles, aluminum nitride particles, Cu-Ti-Zr alloy powder with a particle size of 5 μm, and Cu-Cr-Zr alloy powder. The volume fraction of the fine-grained diamond particles is 65%, the volume fraction of the aluminum nitride particles is 1%, the volume fraction of the alloy powder is 1%, and the remainder is Cu-Cr-Zr alloy powder. The Cu-Ti-Zr alloy powder contains 4 wt.% Ti, 1.2 wt.% Zr, and the remainder is Cu. The Cu-Cr-Zr alloy powder contains 0.4 wt.% Cr, 0.10 wt.% Zr, and the remainder is Cu. A mixing binder is added to obtain a first mixture, which is then melt-blended at 130°C to obtain a first layer of feedstock. The mixing binder is a compound of paraffin wax, polyethylene, and polypropylene in a mass ratio of 50:10:15, and the amount of the mixing binder is 8% of the mass of the first premix. Medium-grained diamond particles, aluminum nitride particles, and Cu-Cr-Zr alloy powder with a particle size of 5 μm are then mixed to obtain a first layer of feedstock. A second premix is ​​obtained by mixing aluminum nitride particles, alloy powder, and metal matrix powder, wherein the volume fraction of coated medium-grained diamond particles is 45%, the volume fraction of coated aluminum nitride particles is 5%, the volume fraction of alloy powder is 3%, and the balance is Cu-Cr-Zr alloy powder. A mixing binder is added to obtain a second mixture, which is then melt-blended at 130°C to obtain a second feedstock; the amount of the mixing binder is 8% of the mass of the second premix. A third premix is ​​obtained by mixing coarse-grained coated diamond particles, coated silicon carbide particles, alloy powder, and metal matrix powder, wherein the volume fraction of coated coarse-grained diamond particles is 20%, the volume fraction of coated silicon carbide particles is 10%, the volume fraction of alloy powder is 5%, and the balance is Cu-Cr-Zr alloy powder. A mixing binder is added to obtain a third mixture, which is then melt-blended at 170°C to obtain a third feedstock; the amount of the mixing binder is 8% of the mass of the third premix.

[0087] S3: After granulation, the first, second, and third layers of feed material are loaded into the injection molding machine. Under the conditions of barrel temperature 110℃, mold temperature 25℃, and injection pressure 80MPa, they are injected into the mold sequentially to obtain a gradient injection preform. The mold filling time is 1s, the holding pressure time is 5s, and each layer of feed material is allowed to stand for 2s after injection. The injection thickness ratio of the first, second, and third layers of feed material is 1:0.8:0.8. The gradient injection preform is placed in n-heptane at 50℃ for 10h to obtain a solvent-degreased preform. The mass-volume ratio of the gradient injection preform to n-heptane is 1g:5mL. The degreased preform is placed in an inert gas and heated to 300℃ at a heating rate of 1℃ / min for 2h to obtain a degreased preform.

[0088] S4: Place the degreased blank in a vacuum hot press furnace at 1.0×10⁻⁶. -2Under vacuum of Pa, the temperature is increased to a first temperature of 500℃ at a heating rate of 5℃ / min, and then a first pressure of 5MPa is applied. The temperature is then increased to a sintering temperature of 880℃, and the pressure is increased to a second pressure of 15MPa and held for 60min. The pressure is then reduced to a third pressure of 2MPa and cooled to a third temperature of 400℃ at a cooling rate of 3℃ / min. After holding for 1h, the temperature is cooled to room temperature, and the copper-based diamond composite material with directional thermal conductivity is obtained by demolding.

[0089] Example 3

[0090] This embodiment provides a directional thermally conductive copper-based diamond composite material and its preparation method. The preparation method of the directional thermally conductive copper-based diamond composite material specifically includes the following steps:

[0091] S1: Fine diamond particles with a diameter of 11 μm, medium diamond particles with a diameter of 45 μm, coarse diamond particles with a diameter of 90 μm, aluminum nitride particles with a diameter of 10 μm, and silicon carbide particles with a diameter of 15 μm are cleaned and dried separately, and then placed in a vacuum coating apparatus. Physical vapor deposition is used to form a Ti / Mo composite film with a thickness of 100 nm on the surface to obtain coated fine diamond particles, coated medium diamond particles, coated coarse diamond particles, coated aluminum nitride particles, and coated silicon carbide particles. The working pressure during physical vapor deposition is 1.0 Pa, and the substrate temperature is 180 °C.

[0092] S2: A first premix is ​​obtained by mixing coated fine-grained diamond particles, coated aluminum nitride particles, Cu-Ti-Zr alloy powder with a particle size of 8μm, and Cu-Zr alloy powder. The volume fraction of the coated fine-grained diamond particles is 68%, the volume fraction of the coated aluminum nitride particles is 2%, the volume fraction of the alloy powder is 1.5%, and the remainder is Cu-Zr alloy powder. The Cu-Ti-Zr alloy powder contains 3 wt.% Ti, 2 wt.% Zr, and the remainder is Cu. The Cu-Zr alloy powder contains 0.1 wt.% Zr and the remainder is Cu. A mixing binder is added to obtain a first mixture, which is then melt-blended at 140°C to obtain a first layer of feedstock. The mixing binder is a compound of paraffin wax, polyethylene, and polypropylene in a mass ratio of 60:15:20, and the amount of the mixing binder added is 9% of the mass of the first premix. Medium-grained diamond particles and coated aluminum nitride particles are then mixed... A second premix is ​​obtained by mixing alloy powder and metal matrix powder, wherein the volume fraction of coated medium-grained diamond particles is 48%, the volume fraction of coated aluminum nitride particles is 8%, the volume fraction of alloy powder is 4%, and the balance is Cu-Zr alloy powder. A mixing binder is added to obtain a second mixture, which is then melt-blended at 145°C to obtain a second layer feedstock; the amount of the mixing binder is 9.5% of the mass of the second premix. A third premix is ​​obtained by mixing coated coarse-grained diamond particles, coated silicon carbide, alloy powder, and metal matrix powder, wherein the volume fraction of coated coarse-grained diamond particles is 25%, the volume fraction of coated silicon carbide particles is 15%, the volume fraction of alloy powder is 6%, and the balance is Cu-Zr alloy powder. A mixing binder is added to obtain a third mixture, which is then melt-blended at 140°C to obtain a third layer feedstock; the amount of the mixing binder is 11% of the mass of the third premix.

[0093] S3: The first, second, and third layers of feed material are granulated and then loaded into an injection molding machine. Under the conditions of barrel temperature 120℃, mold temperature 30℃, and injection pressure 90MPa, they are injected into the mold sequentially to obtain a gradient injection preform. The mold filling time is 2s, the holding pressure time is 10s, and each layer of feed material is allowed to stand for 5s after injection. The injection thickness ratio of the first, second, and third layers of feed material is 1:0.9:1.1. The gradient injection preform is placed in n-heptane at 55℃ for 11h to obtain a solvent-degreased preform. The mass-volume ratio of the gradient injection preform to n-heptane is 1g:8mL. The degreased preform is placed in an inert gas environment and heated to 350℃ at a heating rate of 1.2℃ / min for 2.5h to obtain a degreased preform.

[0094] S4: Place the degreased blank in a vacuum hot press furnace at 8×10 -4Under vacuum of Pa, the temperature is raised to a first temperature of 600℃ at a heating rate of 6℃ / min, and then a first pressure of 8MPa is applied. The temperature is then raised to a sintering temperature of 890℃, and the pressure is increased to a second pressure of 18MPa and held for 80min. The pressure is then reduced to a third pressure of 3MPa and cooled to a third temperature of 450℃ at a cooling rate of 5℃ / min. The temperature is held for 1.5h and then cooled to room temperature. The resulting copper-based diamond composite material with directional thermal conductivity is obtained by demolding.

[0095] Example 4

[0096] This embodiment provides a directional thermally conductive copper-based diamond composite material and its preparation method. The preparation method of the directional thermally conductive copper-based diamond composite material specifically includes the following steps:

[0097] S1: Fine diamond particles with a diameter of 12μm, medium diamond particles with a diameter of 60μm, coarse diamond particles with a diameter of 120μm, aluminum nitride particles with a diameter of 30μm, and silicon carbide particles with a diameter of 30μm are cleaned and dried separately, and then placed in a vacuum coating apparatus. A Zr metal film with a thickness of 200nm is formed on the surface by physical vapor deposition to obtain coated fine diamond particles, coated medium diamond particles, coated coarse diamond particles, coated aluminum nitride particles, and coated silicon carbide particles. The working pressure during physical vapor deposition is 0.3Pa, and the substrate temperature is 200℃.

[0098] S2: A first premix is ​​obtained by mixing fine-grained diamond particles, aluminum nitride particles, Cu-Ti alloy powder with a particle size of 15 μm, and Cu-Cr alloy powder. The volume fraction of the fine-grained diamond particles is 75%, the volume fraction of the aluminum nitride particles is 5%, the volume fraction of the Cu-Ti alloy powder is 3%, and the remainder is Cu-Cr alloy powder. The Cu-Ti alloy powder contains 8 wt.% Ti and the remainder is Cu, while the Cu-Cr alloy powder contains 0.2 wt.% Cr and the remainder is Cu. A mixing binder is added to obtain a first mixture, which is then melt-blended at 170°C to obtain a first layer of feedstock. The mixing binder is a compound of paraffin wax, polyethylene, and polypropylene in a mass ratio of 70:25:30, and the amount of the mixing binder added is 12% of the mass of the first premix. Medium-grained diamond particles, aluminum nitride particles, alloy powder, and metal matrix are then mixed. A second premix is ​​obtained by mixing bulk powders, wherein the volume fraction of coated medium-grained diamond particles is 55%, the volume fraction of coated aluminum nitride particles is 15%, the volume fraction of alloy powder is 6%, and the balance is Cu-Cr alloy powder. A mixing binder is added to obtain a second mixture, which is then melt-blended at 170°C to obtain a second feedstock; the amount of the mixing binder is 12% of the mass of the second premix. A third premix is ​​obtained by mixing coated coarse-grained diamond particles, coated silicon carbide particles, alloy powder, and metal matrix powder, wherein the volume fraction of coated coarse-grained diamond particles is 35%, the volume fraction of coated silicon carbide particles is 25%, the volume fraction of alloy powder is 8%, and the balance is Cu-Cr alloy powder. A mixing binder is added to obtain a third mixture, which is then melt-blended at 130°C to obtain a third feedstock; the amount of the mixing binder is 12% of the mass of the third premix.

[0099] S3: The first, second, and third layers of feed material are granulated and then loaded into an injection molding machine. Under the conditions of barrel temperature 140℃, mold temperature 50℃, and injection pressure 120MPa, they are injected into the mold sequentially to obtain a gradient injection preform. The mold filling time is 5s, the holding pressure time is 20s, and each layer of feed material is allowed to stand for 10s after injection. The injection thickness ratio of the first, second, and third layers of feed material is 1:1.2:1.2. The gradient injection preform is placed in n-heptane at 65℃ for 14h to obtain a solvent-degreased preform. The mass-volume ratio of the gradient injection preform to n-heptane is 1g:15mL. The degreased preform is placed in an inert gas and heated to 450℃ at a heating rate of 2℃ / min for 4h to obtain a degreased preform.

[0100] S4: Place the degreased blank in a vacuum hot press furnace at 1.0×10⁻⁶. -4Under vacuum of Pa, the temperature is raised to a first temperature of 700℃ at a heating rate of 10℃ / min, and then a first pressure of 15MPa is applied. The temperature is then raised to a sintering temperature of 930℃, and the pressure is increased to a second pressure of 25MPa and held for 120min. The pressure is then reduced to a third pressure of 5MPa and cooled to a third temperature of 600℃ at a cooling rate of 10℃ / min. After holding for 3h, the temperature is cooled to room temperature, and the copper-based diamond composite material with directional thermal conductivity is obtained by demolding.

[0101] Comparative Example 1

[0102] This comparative example provides a copper-based diamond composite material with directional thermal conductivity. The difference from Example 1 is that no coated aluminum nitride particles and coated silicon carbide particles are added in S2. Other operating steps and process parameters are exactly the same as in Example 1.

[0103] Comparative Example 2

[0104] This comparative example provides a copper-based diamond composite material with directional thermal conductivity. The difference from Example 1 is that the particle size of the diamond particles is uniformly set to 55 μm, while the other operating steps and process parameters are exactly the same as in Example 1.

[0105] Comparative Example 3

[0106] This comparative example provides a copper-based diamond composite material with directional thermal conductivity. The difference from Example 1 is that step S1 is omitted, and uncoated fine-grained diamond particles, medium-grained diamond particles, coarse-grained diamond particles, aluminum nitride particles, and silicon carbide particles are used directly. Other operating steps and process parameters are exactly the same as in Example 1.

[0107] Comparative Example 4

[0108] This comparative example provides a copper-based diamond composite material with directional thermal conductivity. The difference from Example 1 is that pure copper powder of the same particle size is used to replace Cu-Ti alloy powder in S2. Other operating steps and process parameters are exactly the same as in Example 1.

[0109] The performance of the directional thermally conductive copper-based diamond composite materials of Examples 1-4 and Comparative Examples 1-4 was tested, and the specific process is as follows:

[0110] Cut test pieces of different thicknesses and test the thermal conductivity of the first, second and third layers according to GB / T 22588-2008;

[0111] The three-point bending strength of the test sample was determined according to GB / T 232-2024.

[0112] The thermal cycling performance of the samples was tested according to GB / T 2423.22-2012;

[0113] According to GB / T 5163-2006, the bulk density of the test sample is calculated as the ratio of bulk density to theoretical density.

[0114] The test results are shown in Table 1.

[0115] Table 1. Performance test results of copper-based diamond composite materials with directional thermal conductivity in Examples 1-4 and Comparative Examples 1-4

[0116]

[0117] From the test results of Example 1 and Comparative Example 1 in Table 1, it can be seen that in S2, without the addition of aluminum nitride and silicon carbide, the high volume fraction diamond layer lacks the sintering regulation and expansion buffering effect of the ceramic transition phase between the matrix and the substrate. The sintering shrinkage is more uncoordinated, local stress concentration leads to an increase in internal residual porosity and micro-defects, and a decrease in density. Although the diamond filling amount is similar and the thermally conductive framework still exists, the middle and lower layers lack the synergistic thermal conductivity and expansion regulation of aluminum nitride and silicon carbide. The interface defects and porosity increase, resulting in a decrease in the thermal conductivity of each layer and the whole. In terms of three-point bending strength, the bending load-bearing capacity decreases due to the more brittle structure, interface stress concentration, and more porosity. Under thermal cycling conditions, the thermal expansion mismatch is severe, the warping is obvious, and thermal stress is more likely to accumulate at the pores and interfaces, triggering crack initiation and propagation, resulting in a decrease in thermal cycling performance.

[0118] As shown in Table 1, the test results of Example 1 and Comparative Example 2 reveal that unifying the diamond particle size to 55 μm eliminates the advantages of "fine, medium, and coarse" particles in terms of packing density, interface quantity control, and matching of shrinkage behavior across layers. This leads to a decrease in local packing efficiency and sintering shrinkage coordination, resulting in decreased density and more uneven distribution of internal microcracks and pores. In terms of thermal conductivity, the upper layer has a smaller specific surface area and less dense thermal channels due to the larger diamond particle size, while the lower layer has a higher number of interfaces, increased stress, and defects, causing a decrease in the thermal conductivity of each layer. Regarding three-point bending strength, uniform particle size makes stress distribution and crack propagation paths less conducive to preventing cracks, resulting in a decrease in macroscopic bending resistance. Under thermal cycling conditions, the absence of a reasonable particle size gradient and expansion gradient in the thickness direction leads to more concentrated thermal stress, increased warpage, and decreased thermal cycling performance.

[0119] As shown in Table 1, the test results of Example 1 and Comparative Example 3 indicate that when step S1 is omitted and uncoated fine-grained diamond particles, medium-grained diamond particles, coarse-grained diamond particles, aluminum nitride particles, and silicon carbide particles are used directly, the contact between diamond, aluminum nitride, and silicon carbide and the metal matrix is ​​mainly based on poor wetting mechanical contact. It is difficult to form a continuous and stable interface reaction layer during sintering. Micropores, microcracks, and debonding zones are easily formed near the interface. Although the overall compaction is acceptable, the volume of the effective compacted interface is reduced, resulting in a decrease in density and structural integrity. The interface thermal resistance increases, and the thermal conduction channels of each layer are interrupted by a large number of interface defects, resulting in a decrease in the thermal conductivity of the three layers. In terms of three-point bending strength, the interface bearing capacity is weak, and cracks are very easy to initiate at the interface and propagate along the interface, which deteriorates the macroscopic bending performance. In the thermal cycling test, due to the poor interface bonding and the difficulty in buffering the expansion mismatch through the stable interface layer, warping, delamination, and through cracks appear earlier, resulting in a decrease in thermal cycling performance.

[0120] As shown in Table 1, the test results of Example 1 and Comparative Example 4 indicate that in S2, pure copper powder of the same particle size was used to replace Cu-Ti alloy powder. The lack of active elements from the matrix side near the interface resulted in insufficient reaction between the connecting film and the surface of the reinforcing phase. The interface transition layer was thinner and discontinuous, weakening the healing effect on interface porosity and microcracks during sintering, leading to a decrease in overall density. Regarding thermal conductivity, although the coating still provides some interface improvement, the incomplete interface reaction layer, local debonding, and increased micropores reduced the actual thermal conductivity of each layer. In terms of three-point bending strength, the macroscopic bending performance decreased due to insufficient interface load-bearing capacity and the interface's tendency to become a crack source. Under thermal cycling conditions, the interface was more prone to microcracks and local delamination under repeated thermal stress, resulting in more significant warping and damage accumulation, and a decrease in thermal cycling performance.

[0121] 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 directional thermally conductive copper-based diamond composite material, characterized in that, The preparation method includes: S1: Fine diamond particles with a particle size of 8-12μm, medium diamond particles with a particle size of 40-60μm, coarse diamond particles with a particle size of 80-120μm, aluminum nitride particles, and silicon carbide particles are pretreated and then placed in a vacuum coating apparatus. Physical vapor deposition is used to form a connecting film with a thickness of 80-200nm on the surface, resulting in coated fine diamond particles, coated medium diamond particles, coated coarse diamond particles, coated aluminum nitride particles, and coated silicon carbide particles. S2: A first premix is ​​obtained by mixing fine-grained diamond particles, aluminum nitride particles, alloy powder, and metal matrix powder; a mixing binder is added to obtain a first mixture; and the mixture is melt-kneaded to obtain a first layer feed. A second premix is ​​obtained by mixing medium-grained diamond particles, aluminum nitride particles, alloy powder, and metal matrix powder; a mixing binder is added to obtain a second mixture; and the mixture is melt-kneaded to obtain a second layer feed. A third premix is ​​obtained by mixing coarse-grained diamond particles, silicon carbide particles, alloy powder, and metal matrix powder; a mixing binder is added to obtain a third mixture; and the mixture is melt-kneaded to obtain a third layer feed. The alloy powder is Cu-Ti alloy powder or Cu-Ti-Zr alloy powder; The volume fraction of the coated fine diamond particles in the first premix is ​​65-75%, the volume fraction of the coated aluminum nitride particles is 1-5%, and the volume fraction of the alloy powder is 1-3%. In the second premix, the volume fraction of the coated diamond particles is 45-55%, the volume fraction of the coated aluminum nitride particles is 5-15%, and the volume fraction of the alloy powder is 3-6%. The third premix contains 20-35% by volume of coated coarse diamond particles, 10-25% by volume of coated silicon carbide particles, and 5-8% by volume of alloy powder. S3: After granulating the first layer of feed, the second layer of feed, and the third layer of feed, inject them into the mold in sequence to obtain a gradient injection preform. Place the gradient injection preform in n-heptane to degrease it to obtain a solvent-degreased preform. Place the solvent-degreased preform in an inert gas and heat it to obtain a degreased preform. The settling time after the first layer of feed, the second layer of feed, and the third layer of feed are injected into the mold in sequence is 2-10 seconds; The injection thickness ratio of the first, second, and third layers of feed is 1:(0.8-1.2):(0.8-1.2); S4: Place the degreased blank in a vacuum hot press furnace, heat it to the first temperature of 500-700℃, apply the first pressure of 5-15MPa, then continue to heat it to the sintering temperature of 880-930℃ and increase the pressure to the second pressure of 15-25MPa and hold it at that temperature. After reducing the pressure to the third pressure of 2-5MPa, cool it to the third temperature of 400-600℃ at a cooling rate and hold it at that temperature. Then cool it to room temperature and demold to obtain a directional thermally conductive copper-based diamond composite material.

2. The method for preparing a directional thermally conductive copper-based diamond composite material according to claim 1, characterized in that, In S1: The aluminum nitride particles have a particle size of 5-30 μm; The silicon carbide particles have a particle size of 5-30 μm; The connecting film is a metal film or a SiC-metal composite film. The metal film is any one or a combination of Ti, Cr, Zr, Mo, and W. When the connecting film is a metal film, it is deposited with a metal target and an inert gas. When the connecting film is a SiC-metal composite film, a carbon-containing gas is introduced and a metal-Si alloy target or a metal target and a silicon target are co-sputtered and deposited.

3. The method for preparing a directional thermally conductive copper-based diamond composite material according to claim 1, characterized in that, In S2: The particle size of the alloy powder is 5-15 μm; The metal matrix powder is any one of pure copper, Cu-Zr alloy, Cu-Cr alloy or Cu-Cr-Zr alloy; The metal matrix powder in the first premix is ​​used to supplement the balance.

4. The method for preparing a directional thermally conductive copper-based diamond composite material according to claim 1, characterized in that, In S2: The melt mixing temperature of the first mixture is 130-170℃; The mass ratio of paraffin, polyethylene and polypropylene in the mixed binder is (50-70):(10-25):(15-30); The amount of binder added in the first layer of feed is 8-12% of the mass of the first premix.

5. The method for preparing a directional thermally conductive copper-based diamond composite material according to claim 1, characterized in that, In S2: The metal matrix powder in the second premix is ​​supplemented to the remaining amount; The melting and mixing temperature of the second mixture is 130-170℃; The amount of the binder added in the second layer of feed is 8-12% of the mass of the second premix.

6. The method for preparing a directional thermally conductive copper-based diamond composite material according to claim 1, characterized in that, In S2: The metal matrix powder in the third premix is ​​supplemented to the remaining amount; The amount of the mixed binder added in the third layer of feed is 8-12% of the mass of the third premix.

7. The method for preparing a directional thermally conductive copper-based diamond composite material according to claim 1, characterized in that, In S3: The time for injecting the first, second, and third layers of feed into the mold after granulation is 1-5 seconds. The solvent degreasing temperature of the gradient injection preform is 50-65℃; The mass-to-volume ratio of the gradient injection preform to n-heptane is 1g:(5-15)mL; The heating rate of the hot degreasing treatment of the preform after solvent degreasing is 1-2℃ / min; The hot degreasing temperature of the preform after solvent degreasing is 300-450℃.

8. The method for preparing a directional thermally conductive copper-based diamond composite material according to claim 1, characterized in that, In S4: The rate of heating to the first temperature is 5-10℃ / min; The cooling rate is 3-10℃ / min.

9. A copper-based diamond composite material with directional thermal conductivity prepared by the preparation method according to any one of claims 1-8.

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