Ultrahigh heat conduction graphite-diamond / aluminum composite vapor chamber and preparation method thereof

Abstract

The invention discloses an ultrahigh heat conduction graphite-diamond / aluminum composite vapor chamber and a preparation method thereof. The composite vapor chamber comprises a high-thermal-conductivity graphite plate layer, an aluminum-based metal layer and diamond particles dispersed in the aluminum-based metal layer, the high-thermal-conductivity graphite plate layer is provided with a through hole structure, and the surface of the high-thermal-conductivity graphite plate layer is provided with a TiC transition layer and a Ti metal coating with micron-order thickness; the interiors, the upper layers, the lower layers and the peripheries of the through holes of the high-thermal-conductivity graphite plate layer are coated with aluminum-based metal layers; carbide layers are arranged on the surfaces of the diamond particles, and the diamond particles are distributed in a bimodal particle size mode and distributed in a volume fraction gradient mode in the direction perpendicular to the base plate. According to the preparation method, an assembly process of layer-by-layer powder laying and secondary cold pressing is adopted, and preparation of the diamond particle complex distribution configuration is achieved. Through three-phase composite system collaboration, gradient structure optimization and interface strengthening, the in-plane and z-axis heat conductivity is remarkably improved, the thermal expansion coefficient of the aluminum substrate is reduced, the interface bonding strength and long-term reliability are improved, and the ultrahigh heat flux density heat dissipation requirement can be met.

Description

Technical Field

[0001] This invention relates to an ultra-high thermal conductivity graphite-diamond / aluminum composite heat sink and its preparation method, belonging to the field of high-power electronic heat dissipation. Background Technology

[0002] As electronic devices evolve towards higher power density and miniaturization, heat dissipation systems face the challenge of instantaneous ultra-high heat flux densities (>800W / cm³). 2 The vapor chamber faces severe challenges. As a high-efficiency heat dissipation element, the core performance of the vapor chamber depends on the thermal conductivity, interfacial bonding strength, and thermal expansion matching of the composite materials used.

[0003] Patent document CN118670175A discloses an annealed pyrolytic graphite composite aluminum-based heat spreader. This aluminum-ultra-high thermal conductivity graphite composite system achieves lateral heat diffusion by embedding pyrolytic graphite into an aluminum substrate and utilizing the ultra-high in-plane thermal conductivity (1600-2000 W / (m·K)) of ultra-high thermal conductivity graphite. However, the thermal conductivity of this system in the thickness direction (z-axis) is extremely low (only 8-15 W / (m·K)), and the interfacial bonding strength between graphite and aluminum is low, making it prone to delamination failure after long-term thermal cycling.

[0004] Patent document CN115572875A discloses a method for preparing a diamond-reinforced graphite-aluminum high thermal conductivity composite material. By embedding diamond-aluminum cylinders inside the flake graphite, the normal thermal conductivity of the graphite-aluminum heat exchanger is improved. However, it does not improve the thermal conductivity of the aluminum layers on both sides of the graphite layer. At the same time, the chip connection area is still an aluminum substrate, and the thermal expansion coefficient of the aluminum substrate is about 23ppm / K, which is much larger than the thermal expansion coefficient of conventional semiconductor chips of 2~6ppm / K. This makes it easy for the chip to be stress cracked and detached after being welded on the aluminum substrate surface of the heat exchanger due to thermal expansion mismatch.

[0005] There are significant gaps in the existing technology: First, there is a lack of a three-phase synergistic composite design of ultra-high thermal conductivity graphite, diamond and aluminum, which makes it difficult to better balance in-plane heat diffusion and z-axis heat transfer; Second, the thermal conductivity and thermal expansion performance of the aluminum-based coating layer are not well designed, which causes the heat spreader to have thermal expansion mismatch problems in the application scenarios of ultra-high heat flux density chips.

[0006] Therefore, developing a composite substrate material that combines high in-plane thermal conductivity, high z-axis thermal conductivity, and low coefficient of thermal expansion has become an urgent problem to be solved. Summary of the Invention

[0007] This invention aims to overcome the defects of existing heat spreader materials, such as insufficient normal thermal conductivity, weak interfacial bonding, and thermal expansion mismatch, and provides an ultra-high thermal conductivity graphite-diamond / aluminum composite heat spreader and its preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A high thermal conductivity graphite-diamond / aluminum composite heat exchanger comprises a high thermal conductivity graphite layer, an aluminum-based metal layer, and diamond particles dispersed in the aluminum-based metal layer. The high thermal conductivity graphite plate has a through-hole structure, and a micron-thick TiC transition layer and a Ti metal coating are provided on the surface of the high thermal conductivity graphite plate. The through-holes, the upper and lower layers and the sides of the high thermal conductivity graphite plate are covered by an aluminum-based metal layer. The diamond particles dispersed in the aluminum-based metal layer serve as a reinforcing phase, accounting for 20-60% of the volume fraction. The thickness of the high thermal conductivity graphite plate layer is 0.5-3mm, the in-plane thermal conductivity is ≥1600 W / (m·K), the diameter of the through holes on the high thermal conductivity graphite plate layer is 3-8mm, and the center distance of the through holes is 10-20mm. The thickness of the aluminum-based metal layer is 0.5-1.5 mm; The diamond particles have a carbide layer on their surface and exhibit a bimodal particle size distribution, with coarse particles having a particle size of 100-200 μm and fine particles having a particle size of 10-50 μm. Furthermore, the diamond particles exhibit a volume fraction gradient distribution in the direction perpendicular to the substrate.

[0009] Preferably, the thickness of the TiC transition layer is 0.1-1 μm, and the thickness of the Ti metal coating is 0.5-3 μm.

[0010] Preferably, the carbide layer is selected from one of WC, TiC, and Cr2C3, and the thickness of the carbide layer is 50-500 nm.

[0011] Preferably, the gradient-distributed diamond particles are predominantly coarse-grained within the through-holes and near the high thermal conductivity graphite layer, accounting for >75% of the total volume of diamond particles in that region, with the diamond particles comprising 45-60% of the diamond / aluminum composite layer volume fraction (Vf1) in that region. Further preferably, the particles are predominantly fine-grained in regions far from the high thermal conductivity graphite layer, accounting for >75% of the total volume of diamond particles in that region, with the diamond particles comprising 20-30% of the total volume fraction (Vf2) in that region. More preferably, Vf1 / Vf2 = 1.5-3.0.

[0012] Preferably, the aluminum-based metal layer is a 6061 or 6063 series aluminum alloy.

[0013] A method for preparing the composite heat spreader includes the following steps: (1) A TiC transition layer and a Ti metal coating are formed on the surface of a high thermal conductivity graphite plate by vacuum evaporation or magnetron sputtering, and a carbide layer is formed on the surface of diamond particles. (2) Diamond particles with carbide layers are mixed with aluminum alloy powder, and the powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum alloy powder mixed layer. Layered diamond / aluminum green blanks and cylindrical diamond / aluminum green blanks are obtained by cold pressing. The pressure used for cold pressing is 50-100MPa. (3) The high thermal conductivity graphite plate layer obtained in step (1) and the diamond / aluminum green blank obtained in step (2) are assembled in a mold. The assembly sequence is layered diamond / aluminum green blank - high thermal conductivity graphite plate - cylindrical diamond / aluminum green blank - layered diamond / aluminum green blank. Then, a second cold pressing is performed to obtain high thermal conductivity graphite-diamond / aluminum green blank. The pressure used for the second cold pressing is 10-30MPa. (4) The high thermal conductivity graphite-diamond / aluminum green blank obtained in step (3) is subjected to vacuum hot pressing sintering and hot isostatic pressing sintering to finally obtain an ultra-high thermal conductivity graphite-diamond / aluminum composite heat exchange plate.

[0014] Preferably, the aluminum alloy powder used in step (2) has a particle size of 10-50 μm.

[0015] Preferably, in step (4), the process conditions for vacuum hot pressing sintering are: a vacuum degree of 10... -1 -10 -2 Pa, heating from room temperature to 550-600℃ at a heating rate of 5-10℃ / min, holding at that temperature for 10-30min; after holding at that temperature, pressurizing to 20-40MPa using a mechanical pressure head, holding at that temperature and pressure for 10-30min; then cooling under pressure to room temperature in the furnace.

[0016] Preferably, in step (4), the process conditions for hot isostatic pressing sintering are as follows: pressurize to 30-50 MPa in a nitrogen atmosphere at room temperature, heat to 500-550℃ at a rate of 3-6℃ / min, pressurize to 80-120 MPa, hold at temperature and pressure for 60-120 min, and then cool to room temperature under pressure in the furnace.

[0017] The beneficial effects of this invention are: Compared with the prior art, the present invention has the following beneficial effects: in-plane thermal conductivity >1500W / (m·K), z-axis thermal conductivity >40W / (m·K), significantly improving normal thermal conductivity; thermal expansion coefficient of aluminum-based welding surface at heat source <10ppm / K, surpassing the prior art; secondary cold pressing assembly technology precisely controls the complex distribution configuration of diamond particles and reduces the sintering temperature to below 600℃; the presence of high thermal conductivity graphite and diamond surface coatings effectively suppresses Al4C3 hydrolysis phase, resulting in excellent long-term stability of the composite substrate. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of the composite heat spreader in this invention. Detailed Implementation

[0019] like Figure 1 The diagram shown is a schematic cross-sectional view of the composite heat exchanger in this invention. The composite heat exchanger of this invention comprises a high thermal conductivity graphite plate layer, an aluminum-based metal layer, and diamond particles dispersed in the aluminum-based metal layer. The high thermal conductivity graphite plate layer has a through-hole structure, and a micron-thick TiC transition layer and a Ti metal plating layer are provided on its surface. The through-holes, upper and lower layers, and surrounding surfaces of the high thermal conductivity graphite plate layer are all covered by the aluminum-based metal layer. The diamond particles dispersed in the aluminum-based metal layer serve as a reinforcing phase, accounting for 20-60% of the volume.

[0020] In the composite heat spreader of the present invention, the thermal conductivity of the high thermal conductivity graphite plate layer is ≥1600 W / (m·K), and the thickness is 0.5-3mm. It serves as a heat spreader layer to achieve rapid lateral heat diffusion. The graphite layer is provided with a through-hole structure (hole diameter 5-8mm, hole center distance 10-20mm) for normal thermal conduction enhancement and mechanical strengthening.

[0021] Aluminum-based metal layer ( Figure 1 The aluminum layer shown provides formability and interface buffering. In addition to various auxiliary structures, the thickness of the plate is 0.5-1.5mm. By adding diamond particles as a reinforcing phase, its coefficient of thermal expansion (CTE) can be adjusted to 7-10ppm / K, which matches the thermal expansion of mainstream chip materials.

[0022] Diamond particles are dispersed in the aluminum-based metal layer to form a z-axis thermally conductive channel, accounting for 20-60% of the volume fraction. They adopt a bimodal particle size distribution (coarse particles with a diameter of 100-200 μm provide the main path; fine particles with a diameter of 10-50 μm fill the gaps and regulate the thermal expansion coefficient of the aluminum-based metal layer). The diamond particles also exhibit a concentration gradient distribution perpendicular to the substrate. In the through-holes and near the high thermal conductivity graphite plate layer, the concentration of diamond particles (the volume fraction of diamond particles in the diamond / aluminum composite layer in that region) Vf1 = 45-60%, while in the region far from the high thermal conductivity graphite plate layer, the concentration of diamond particles (the volume fraction of diamond particles in the diamond / aluminum composite layer in that region) Vf2 = 20-30%, with Vf1 / Vf2 = 1.5-3.0, to avoid abrupt changes in thermal resistance.

[0023] To enhance interfacial bonding, the surface of the high thermal conductivity graphite plate layer is coated with a double interfacial layer, including a TiC transition layer (thickness of 0.1-1μm) and a Ti metal coating (thickness of 1-4μm), which can reduce the aluminum melt contact angle from >90° to <30°; the surface of the diamond particles is coated with a carbide layer selected from WC, TiC, and Cr2C3 (thickness of 50-500nm), which can suppress the formation of Al4C3 hydrolysis phase.

[0024] The present invention also provides a method for preparing the above-mentioned composite heat spreader, comprising the following steps: (i) A TiC transition layer and a Ti metal coating are formed on the surface of a high thermal conductivity graphite plate by vacuum evaporation or magnetron sputtering, and a WC, TiC, and Cr2C3 carbide layer is formed on the surface of diamond particles. (ii) Diamond particles with a carbide layer and aluminum alloy powder are mixed according to the diamond particle size distribution and volume ratio. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green blanks and cylindrical diamond / aluminum green blanks are obtained by cold pressing. The aluminum alloy powder used is 6061 or 6063 series aluminum alloy with a particle size of 10-50μm. The pressure used for cold pressing is 50-100MPa. (iii) The high thermal conductivity graphite plate layer and diamond / aluminum green blank obtained in steps (i) and (ii) are assembled in a mold. The assembly sequence is layered diamond / aluminum green blank - high thermal conductivity graphite plate - cylindrical diamond / aluminum green blank - layered diamond / aluminum green blank. Then, a second cold pressing is performed to obtain high thermal conductivity graphite-diamond / aluminum green blank. The pressure used for the second cold pressing is 10-30 MPa. (iv) The high thermal conductivity graphite-diamond / aluminum green blank obtained in step (iii) is subjected to vacuum hot pressing sintering / hot isostatic pressing sintering to finally obtain an ultra-high thermal conductivity graphite-diamond / aluminum composite heat exchange plate.

[0025] The vacuum hot pressing sintering process conditions are: vacuum degree of 10. -1 -10 -2 The process involves heating from room temperature to 550-600℃ at a rate of 5-10℃ / min, holding at that temperature for 10-30 min; then pressurizing to 20-40 MPa using a mechanical press head, holding at that temperature and pressure for 10-30 min; finally cooling under pressure to room temperature in the furnace. The hot isostatic pressing (HIP) sintering process conditions are as follows: pressurizing to 30-50 MPa in a nitrogen atmosphere at room temperature, heating to 500-550℃ at a rate of 3-6℃ / min, then pressurizing to 80-120 MPa, holding at that temperature and pressure for 60-120 min, and finally cooling under pressure to room temperature in the furnace.

[0026] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0027] Example 1 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 3 mm, hole spacing 15 mm). A TiC transition layer (thickness 0.5 μm) and a Ti metal coating (thickness 2 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum base metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 200 nm).

[0028] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.8mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.3mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0029] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 50MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 10MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0030] Vacuum hot pressing sintering: vacuum degree is 10 -1 -10 -2 Pa, heated from room temperature to 580℃ at a heating rate of 8℃ / min, held for 30min; after holding, pressurized to 30MPa by a mechanical pressure head, held for 20min; then cooled to room temperature under pressure in the furnace.

[0031] Performance testing: In-plane thermal conductivity 1580W / (m·K), z-axis thermal conductivity 48W / (m·K), coefficient of thermal expansion 8.2ppm / K, material flexural strength 28MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0032] Example 2 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 3 mm, hole spacing 15 mm). A TiC transition layer (thickness 0.1 μm) and a Ti metal coating (thickness 1 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum-based metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 100 nm).

[0033] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.8mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.3mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0034] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 50MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 10MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0035] Vacuum hot pressing sintering: vacuum degree is 10 -1 -10 -2 Pa, heated from room temperature to 580℃ at a heating rate of 8℃ / min, held for 30min; after holding, pressurized to 30MPa by a mechanical pressure head, held for 20min; then cooled to room temperature under pressure in the furnace.

[0036] Performance testing: In-plane thermal conductivity 1560W / (m·K), z-axis thermal conductivity 46W / (m·K), coefficient of thermal expansion 8.5ppm / K, material flexural strength 27MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0037] Example 3 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 3 mm, hole spacing 15 mm). A TiC transition layer (thickness 0.5 μm) and a Ti metal coating (thickness 2 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum base metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 200 nm).

[0038] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.4mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.7mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0039] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 50MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 10MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0040] Vacuum hot pressing sintering: vacuum degree is 10 -1 -10 -2 Pa, heated from room temperature to 580℃ at a heating rate of 8℃ / min, held for 30min; after holding, pressurized to 30MPa by a mechanical pressure head, held for 20min; then cooled to room temperature under pressure in the furnace.

[0041] Performance testing: In-plane thermal conductivity 1540 W / (m·K), z-axis thermal conductivity 43 W / (m·K), coefficient of thermal expansion 7.6 ppm / K, material flexural strength 27 MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0042] Example 4 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 3 mm, hole spacing 15 mm). A TiC transition layer (thickness 0.5 μm) and a Ti metal coating (thickness 2 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum base metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 200 nm).

[0043] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.8mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.3mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0044] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 80MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 20MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0045] Vacuum hot pressing sintering: vacuum degree is 10 -1 -10 -2 Pa, heated from room temperature to 580℃ at a heating rate of 8℃ / min, held for 30min; after holding, pressurized to 30MPa by a mechanical pressure head, held for 20min; then cooled to room temperature under pressure in the furnace.

[0046] Performance testing: In-plane thermal conductivity 1590 W / (m·K), z-axis thermal conductivity 50 W / (m·K), coefficient of thermal expansion 8.0 ppm / K, material flexural strength 29 MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0047] Example 5 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 3 mm, hole spacing 15 mm). A TiC transition layer (thickness 0.5 μm) and a Ti metal coating (thickness 2 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum base metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 200 nm).

[0048] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.8mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.3mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0049] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 50MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 10MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0050] Vacuum hot pressing sintering: vacuum degree is 10 -1 -10 -2 Pa, heated from room temperature to 600℃ at a heating rate of 8℃ / min, held for 30min; after holding, pressurized to 30MPa by a mechanical pressure head, held for 20min; then cooled to room temperature under pressure in the furnace.

[0051] Performance testing: In-plane thermal conductivity 1590 W / (m·K), z-axis thermal conductivity 49 W / (m·K), coefficient of thermal expansion 8.0 ppm / K, material flexural strength 29 MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0052] Example 6 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 6 mm, hole spacing 12 mm). A TiC transition layer (thickness 0.5 μm) and a Ti metal coating (thickness 2 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum base metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 200 nm).

[0053] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.8mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.3mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0054] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 50MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 10MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0055] Vacuum hot pressing sintering: vacuum degree is 10 -1 -10 -2 Pa, heated from room temperature to 580℃ at a heating rate of 8℃ / min, held for 30min; after holding, pressurized to 30MPa by a mechanical pressure head, held for 20min; then cooled to room temperature under pressure in the furnace.

[0056] Performance testing: In-plane thermal conductivity 1540 W / (m·K), z-axis thermal conductivity 51 W / (m·K), coefficient of thermal expansion 8.2 ppm / K, material flexural strength 30 MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0057] Example 7 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 3 mm, hole spacing 15 mm). A TiC transition layer (thickness 0.5 μm) and a Ti metal coating (thickness 2 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum base metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 200 nm).

[0058] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.8mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.3mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0059] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 50MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 10MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0060] Hot isostatic pressing sintering: pressurize to 50 MPa in a nitrogen atmosphere at room temperature, heat to 520°C at a rate of 4°C / min, pressurize to 100 MPa, hold at temperature and pressure for 80 min, and then cool to room temperature in the furnace under pressure.

[0061] Performance testing: In-plane thermal conductivity 1600W / (m·K), z-axis thermal conductivity 50W / (m·K), coefficient of thermal expansion 8.0ppm / K, material flexural strength 29MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0062] Example 8 Raw material preparation: High thermal conductivity graphite plate (200×200×1.0mm) is selected. 3 The in-plane thermal conductivity is 1700 W / (m·K). The plate has a pre-set through-hole structure (hole diameter 3 mm, hole spacing 15 mm). A TiC transition layer (thickness 0.5 μm) and a Ti metal coating (thickness 2 μm) are sequentially formed on the surface of the high thermal conductivity graphite plate by magnetron sputtering. The aluminum base metal layer uses 6061 series aluminum alloy powder (particle size 10-50 μm). The diamond particles have a bimodal particle size distribution, with coarse particles of 100-200 μm and fine particles of 10-50 μm, and are all treated with W plating (coating thickness 200 nm).

[0063] Diamond / aluminum gradient distribution design: Near the high thermal conductivity graphite plate layer area (thickness 0.8mm) and inside the graphite through-holes: the diamond volume fraction Vf1 is 55%, of which coarse particles account for 80% and fine particles account for 20%; Far from the high thermal conductivity graphite plate layer area (thickness 0.3mm): the diamond volume fraction Vf2 is 25%, of which fine particles account for 90%, satisfying Vf1 / Vf2=2.2.

[0064] Green compact pressing and assembly: Diamond and aluminum alloy powders are mixed according to the volume and particle size ratio designed based on the diamond / aluminum gradient distribution. The powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum powder mixed layer. Layered diamond / aluminum green compacts and cylindrical diamond / aluminum green compacts are obtained by cold pressing under 50MPa pressure. After combining the diamond / aluminum green compacts with high thermal conductivity graphite plates, a second cold pressing is performed under 10MPa pressure to obtain high thermal conductivity graphite-diamond / aluminum green compacts.

[0065] Hot isostatic pressing sintering: pressurize to 50 MPa in a nitrogen atmosphere at room temperature, heat to 550°C at a rate of 4°C / min, pressurize to 100 MPa, hold at temperature and pressure for 80 min, and then cool to room temperature in the furnace under pressure.

[0066] Performance testing: In-plane thermal conductivity 1620 W / (m·K), z-axis thermal conductivity 52 W / (m·K), coefficient of thermal expansion 7.8 ppm / K, material flexural strength 30 MPa, no delamination after 500 thermal cycles (-40℃~125℃).

[0067] Comparative Example 1 Preparation method: The high thermal conductivity graphite plate structure and surface treatment, diamond surface coating, cold pressing process and sintering process are the same as in Example 1, except that the diamond particles are uniformly distributed in the aluminum-based metal layer in a 1:1 ratio of coarse to fine particles (volume fraction 40%), without gradient design.

[0068] Performance testing: In-plane thermal conductivity 1480 W / (m·K), z-axis thermal conductivity 35 W / (m·K); coefficient of thermal expansion 12 ppm / K, 46% higher than Example 1; material flexural strength 23 MPa; slight delamination after thermal cycling.

[0069] Comparative Example 2 Preparation method: The high thermal conductivity graphite plate was not treated with TiC transition layer and Ti metal coating, and the diamond particles were not coated on the surface. The other raw materials, gradient distribution design, cold pressing process and sintering process were the same as in Example 1.

[0070] Performance testing: In-plane thermal conductivity 1500W / (m·K), z-axis thermal conductivity 32W / (m·K), material bending strength only 20MPa; coefficient of thermal expansion 10.2ppm / K, obvious delamination after 100 thermal cycles, hydrolysis rate up to 18%.

[0071] Comparative Example 3 Preparation method: No diamond particles were used for filling. The other raw materials, surface treatment, cold pressing process and sintering process were the same as in Example 1.

[0072] Performance testing: In-plane thermal conductivity 1510 W / (m·K), z-axis thermal conductivity 15 W / (m·K), coefficient of thermal expansion 18 ppm / K, material bending strength 21 MPa; Due to the lack of diamond reinforcement phase, the normal thermal conductivity of the aluminum-based metal layer is significantly lower than that of Example 1, while the coefficient of thermal expansion is significantly higher than that of Example 1.

[0073] The above embodiments and comparative examples demonstrate that the present invention, through the three-phase synergistic design of a high thermal conductivity graphite plate layer, a bimodal particle size diamond reinforcing phase, and an aluminum-based metal layer, combined with gradient structure optimization and interface coating reinforcement, significantly improves the in-plane and z-axis thermal conductivity of the composite heat exchanger, and optimizes the thermal expansion matching and interface bonding strength. In contrast, designs without gradient distribution, interface coating, or diamond reinforcing phase will lead to a significant decrease in the thermal performance, mechanical properties, and long-term reliability of the composite heat exchanger, further verifying the superiority of the technical solution of the present invention.

Claims

1. A graphite-diamond / aluminum composite heat spreader with ultra-high thermal conductivity, characterized in that, It includes a high thermal conductivity graphite plate layer, an aluminum-based metal layer, and diamond particles dispersed in the aluminum-based metal layer, wherein, The high thermal conductivity graphite plate has a through-hole structure, and a micron-thick TiC transition layer and a Ti metal coating are provided on the surface of the high thermal conductivity graphite plate. The through-holes, the upper and lower layers, and the sides of the high thermal conductivity graphite plate are covered by an aluminum-based metal layer. The diamond particles dispersed in the aluminum-based metal layer serve as a reinforcing phase, accounting for 20-60% of the volume fraction. The thickness of the high thermal conductivity graphite plate layer is 0.5-3mm, the in-plane thermal conductivity is ≥1600 W / (m·K), the diameter of the through holes on the high thermal conductivity graphite plate layer is 3-8mm, and the center distance of the through holes is 10-20mm. The thickness of the aluminum-based metal layer is 0.5-1.5 mm; The diamond particles have a carbide layer on their surface and exhibit a bimodal particle size distribution, with coarse particles having a particle size of 100-200 μm and fine particles having a particle size of 10-50 μm. Furthermore, the diamond particles exhibit a volume fraction gradient distribution in the direction perpendicular to the substrate.

2. The ultra-high thermal conductivity graphite-diamond / aluminum composite heat spreader according to claim 1, characterized in that, The thickness of the TiC transition layer is 0.1-1 μm, and the thickness of the Ti metal coating is 0.5-3 μm.

3. The ultra-high thermal conductivity graphite-diamond / aluminum composite heat spreader according to claim 1 or 2, characterized in that, The carbide layer is selected from one of WC, TiC, and Cr2C3, and the thickness of the carbide layer is 50-500 nm.

4. The ultra-high thermal conductivity graphite-diamond / aluminum composite heat spreader according to any one of claims 1-3, characterized in that, The gradient-distributed diamond particles are predominantly coarse-grained in the through-holes and near the high thermal conductivity graphite plate layer, accounting for >75% of the volume of diamond particles in this region, and the volume fraction Vf1 of diamond particles in this region is 45-60%; while in the region far from the high thermal conductivity graphite plate layer, fine-grained particles are predominantly fine-grained, accounting for >75% of the volume of diamond particles in this region, and the volume fraction Vf2 of diamond particles in this region is 20-30%.

5. The ultra-high thermal conductivity graphite-diamond / aluminum composite heat spreader according to claim 4, characterized in that, Vf1 / Vf2 = 1.5 - 3.

0.

6. The ultra-high thermal conductivity graphite-diamond / aluminum composite heat spreader according to any one of claims 1-3, characterized in that, The aluminum-based metal layer is a 6061 or 6063 series aluminum alloy.

7. A method for preparing the composite heat spreader according to any one of claims 1-6, characterized in that, Includes the following steps: (1) A TiC transition layer and a Ti metal coating are formed on the surface of a high thermal conductivity graphite plate by vacuum evaporation or magnetron sputtering, and a carbide layer is formed on the surface of diamond particles. (2) Diamond particles with carbide layers are mixed with aluminum alloy powder, and the powder is spread layer by layer to obtain a gradient distribution of diamond particles / aluminum alloy powder mixed layer. Layered diamond / aluminum green blanks and cylindrical diamond / aluminum green blanks are obtained by cold pressing. The pressure used for cold pressing is 50-100MPa. (3) The high thermal conductivity graphite plate layer obtained in step (1) and the diamond / aluminum green blank obtained in step (2) are assembled in a mold. The assembly sequence is layered diamond / aluminum green blank - high thermal conductivity graphite plate - cylindrical diamond / aluminum green blank - layered diamond / aluminum green blank. Then, a second cold pressing is performed to obtain high thermal conductivity graphite-diamond / aluminum green blank. The pressure used for the second cold pressing is 10-30MPa. (4) The high thermal conductivity graphite-diamond / aluminum green blank obtained in step (3) is subjected to vacuum hot pressing sintering and hot isostatic pressing sintering to finally obtain an ultra-high thermal conductivity graphite-diamond / aluminum composite heat exchange plate.

8. The method for preparing the composite heat spreader according to claim 7, characterized in that, The aluminum alloy powder used in step (2) has a particle size of 10-50 μm.

9. The method for preparing the composite heat spreader according to claim 7, characterized in that, In step (4), the process conditions for vacuum hot pressing sintering are: vacuum degree of 10. -1 -10 -2 Pa, heating from room temperature to 550-600℃ at a heating rate of 5-10℃ / min, holding at that temperature for 10-30min; after holding at that temperature, pressurizing to 20-40MPa using a mechanical pressure head, holding at that temperature and pressure for 10-30min; then cooling under pressure to room temperature in the furnace.

10. The method for preparing the composite heat spreader according to claim 7, characterized in that, In step (4), the process conditions for hot isostatic pressing sintering are as follows: pressurize to 30-50 MPa in a nitrogen atmosphere at room temperature, heat to 500-550℃ at a rate of 3-6℃ / min, pressurize to 80-120 MPa, hold at temperature and pressure for 60-120 min, and then cool to room temperature under pressure in the furnace.

Images