In-plane graphite-diamond-silicon carbide composite heat dissipation material and preparation method and application thereof

Abstract

The present application relates to the technical field of heat dissipation materials, and particularly relates to an in-plane graphite-diamond-silicon carbide composite heat dissipation material, a preparation method and application thereof. The present application mixes graded diamond powder and a binder, sequentially performs compression molding, degreasing treatment and water jet cutting to form a clamping groove array, and obtains a porous diamond preform; inserts a porous graphite sheet into the clamping groove array of the porous diamond preform, and obtains a graphite-diamond composite preform; performs chemical vapor infiltration on the graphite-diamond composite preform, in-situ generates silicon carbide, and obtains an in-plane graphite-diamond-silicon carbide composite heat dissipation material. The preparation method provided by the present application has high interface bonding strength and high vertical thermal conductivity, and the composite heat dissipation material has the characteristics of large size and ultra-thin, and can realize low-cost mass production.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation materials technology, specifically to an in-plane graphite-diamond-silicon carbide composite heat dissipation material, its preparation method, and its application. Background Technology

[0002] With the rapid development of artificial intelligence (AI), 5G communication, and new energy vehicle technologies, the heat flux density of high-end chips has exceeded 1400 W / cm². 2 The heat generation of electronic components increases exponentially, which severely restricts the performance and lifespan of these components. Therefore, developing novel thermal management materials with ultra-high vertical thermal conductivity and low coefficient of thermal expansion has become a key technical problem that urgently needs to be solved in this field.

[0003] Currently, in-plane oriented graphite composites and diamond-silicon carbide composites are recognized as the two most promising high-performance heat dissipation materials. The former has extremely high in-plane thermal conductivity, while the latter combines the advantages of excellent isotropic thermal conductivity and extremely low coefficient of thermal expansion.

[0004] For vertically oriented graphite composite heat dissipation materials, existing technologies typically employ the following process: artificial graphite sheets are vertically placed in a graphite mold with precision slots, and copper powder or resin is filled into the gaps between the graphite sheets. The composite material is then obtained through hot pressing and curing. However, this approach has significant drawbacks: firstly, the thermal expansion coefficients of graphite and the copper or resin matrix differ considerably, which is incompatible with semiconductor materials and easily leads to thermal stress; secondly, the interfacial thermal resistance between the graphite sheets and the matrix is ​​high, making it difficult to improve the vertical thermal conductivity of the composite material, which can only reach a maximum of approximately 400 W / (m·K), failing to meet the heat dissipation requirements of high power density.

[0005] For diamond-silicon carbide composite heat dissipation materials, existing technologies typically employ a liquid-phase melting infiltration method. This involves first pressing diamond micropowder into a preform, then placing it in a vacuum furnace and infiltrating it with liquid silicon. This allows the silicon to react in situ with the diamond, generating silicon carbide as the binder phase. However, this approach also has inherent drawbacks: the resulting composite material is brittle, has high processing costs, and is difficult to prepare large-size and ultra-thin samples, limiting its widespread application in practical applications.

[0006] Currently, there is no publicly available technology that can effectively composite in-plane oriented graphite with a diamond-silicon carbide matrix. Combining graphite materials with a diamond-silicon carbide matrix generally faces three core challenges: First, the poor interfacial bonding strength between graphite and the diamond-silicon carbide matrix hinders phonon transport at the interface, resulting in high interfacial thermal resistance. Second, the in-plane thermal conductivity of graphite is much higher than its thickness-direction thermal conductivity. When the composite material conducts heat vertically, the heat tends to dissipate along the in-plane path of the graphite rather than being conducted vertically, forming a bottleneck that restricts vertical thermal conductivity. Third, the fabrication process for large-size composite samples is still immature, making it difficult to ensure the uniformity of the microstructure. Due to these constraints, the thermal conductivity of finished products obtained by existing methods has consistently failed to exceed 600 W / (m·K), far from meeting the heat dissipation performance requirements of next-generation AI chips. Therefore, how to overcome the multiple technical bottlenecks mentioned above, such as interface bonding, heat conduction path design, and large-size uniform fabrication, and develop a novel composite heat dissipation material with a vertical thermal conductivity exceeding 600 W / (m·K) and a thermal expansion coefficient that matches that of semiconductor materials, has become a technical challenge that urgently needs to be tackled in this field. Summary of the Invention

[0007] Therefore, the purpose of this invention is to provide an in-plane graphite-diamond-silicon carbide composite heat dissipation material, its preparation method, and its applications. The composite heat dissipation material prepared by the method provided by this invention has high interfacial bonding strength and high vertical thermal conductivity. This composite heat dissipation material combines large size and ultra-thin characteristics, and can achieve low-cost mass production.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing an in-plane graphite-diamond-silicon carbide composite heat dissipation material, comprising the following steps: Graded diamond powder and binder are mixed and then subjected to pressing, degreasing and water jet cutting to form a slot array to obtain a porous diamond preform; the graded diamond powder includes coarse diamond particles with a particle size of 150~500μm, medium diamond particles with a particle size of 50~100μm and fine diamond particles with a particle size of 1~10μm. Porous graphite sheets are inserted into the slot array of the porous diamond preform to obtain a graphite-diamond composite preform; The graphite-diamond composite preform is subjected to chemical vapor infiltration to generate silicon carbide in situ, thereby obtaining an in-plane graphite-diamond-silicon carbide composite heat dissipation material.

[0009] Preferably, after the chemical vapor permeation, it further includes: The in-plane graphite-diamond-silicon carbide composite preform obtained by chemical vapor infiltration is sliced ​​to obtain in-plane graphite-diamond-silicon carbide composite sheets. A diamond layer is formed by chemical vapor deposition on the upper surface, lower surface, or both surfaces of the in-plane graphite-diamond-silicon carbide composite sheet.

[0010] Preferably, the mass fraction of coarse-grained diamond in the graded diamond powder is 55-65%, and the mass fraction of medium-grained diamond is 25-35%. The holding pressure for the pressing process is 120~180MPa, and the holding time is 0.5~10min; The degreasing treatment is carried out at a temperature of 800~1200℃ for 1~20h.

[0011] Preferably, the arrangement structure of the card slot array includes a parallel, honeycomb, or cross-grid pattern; The conditions for waterjet cutting include: the equipment used is a CNC high-pressure abrasive waterjet cutting machine; the working water pressure is 320~380MPa, the abrasive is garnet sand, the particle size of the abrasive is 240~320 mesh, the abrasive supply rate is 0.4~0.8kg / min, and the nozzle feed speed is 20~80mm / s; The card slot array has a length of 10~200mm, a width of 0.03~0.1mm, a depth of 10~100mm, a slot spacing of 0.05~0.3mm, and a sidewall verticality of 83~86°.

[0012] Preferably, the chemical vapor infiltration process conditions include: a silicon source comprising one or more of methyltrichlorosilane, silicon tetrachloride, dimethyldichlorosilane, trichlorosilane, and hexamethyldisilane, wherein the flow rate of the silicon source is 5-12 sccm; a carrier gas comprising hydrogen, wherein the flow rate of the carrier gas is 500-1200 sccm; a deposition temperature of 1100-1200℃; a deposition time of 6-15 h; and a reverse cycle of the silane-carrier gas mixture of 0.5-2 h.

[0013] Preferably, the slicing includes water-guided laser slicing, and the process conditions for water-guided laser slicing include: laser wavelength of 532nm, water beam diameter of 30~80μm, cutting feed speed of 15~50mm / s, and kerf taper <0.1°.

[0014] Preferably, the conditions for chemical vapor deposition include: the carbon source is methane; the carrier gas includes hydrogen; the carbon source accounts for 3-5% of the volume of the carrier gas; the deposition temperature is 830-980℃; and the working pressure is 6-20 kPa. The thickness of the diamond layer is 10~100μm.

[0015] Preferably, the surface layer of the in-plane graphite-diamond-silicon carbide composite sheet is activated by plasma etching before chemical vapor deposition.

[0016] The present invention also provides an in-plane graphite-diamond-silicon carbide composite heat dissipation material prepared by the preparation method described in the above technical solution.

[0017] The present invention also provides the application of the in-plane graphite-diamond-silicon carbide composite heat dissipation material described above in computing processing units, power semiconductor devices or aerospace electronic equipment.

[0018] This invention proposes an in-plane graphite-diamond-silicon carbide composite heat dissipation material and its moldless preparation method, aiming to solve the technical challenge of achieving large size, ultra-thinness, and low-cost mass production of ultra-high thermal conductivity composite heat dissipation materials in existing technologies. The method involves integral sintering, followed by abrasive waterjet cutting to create a porous diamond preform with vertical slots. The preformed slot array is then used to achieve precise moldless positioning and insertion of the porous graphite sheet. Subsequently, a chemical vapor infiltration process is used to generate a nanoscale SiC phase with both bonding and thermal bridging functions in situ within the preform. On one hand, the silicon carbide phase acts as a binder, filling the gaps between the porous graphite sheet and the diamond slots, binding them together through Si-C covalent bonds to achieve atomic-level covalent bonding between the graphite and diamond matrix. On the other hand, SiC acts as a thermal bridging phase, filling the interconnected pores within the porous graphite sheet to form a three-dimensional thermally conductive network penetrating the thickness of the graphite. A continuous, defect-free thermally conductive network composed of vertically oriented graphite sheets (dominant vertical thermal channels), diamond-silicon carbide matrix (auxiliary transverse thermal channels), and SiC thermal bridges (interface connection channels) has been successfully formed, creating a "main-auxiliary synergistic" three-dimensional thermally conductive network. This enables the mass production of in-plane graphite-diamond-silicon carbide composite heat dissipation materials, resulting in low-cost in-plane graphite-diamond-silicon carbide composite heat dissipation materials that combine ultra-high vertical thermal conductivity of 800~1200 W / (m·K) with large-size and ultra-thin characteristics.

[0019] This invention employs a process route of abrasive waterjet cutting of prefabricated slots + porous graphite sheet insertion + CVI deposition, which can prepare in-plane graphite-diamond-silicon carbide composite heat dissipation materials without any precision graphite molds.

[0020] The in-plane graphite-diamond-silicon carbide composite heat dissipation material prepared by this invention has an array of diamond fins integrally formed on the bottom edge. The diamond fins and the diamond substrate are of homogeneous and integrated structure. The diamond-silicon carbide array structure is located within the groove of the graphite fins and is arranged along the length direction. The groove cavity forms a built-in microchannel, which expands the contact area of ​​the coolant and enhances the liquid cooling heat transfer capability. Specifically, the in-situ built-in microchannel is formed in the diamond fin recesses, further increasing the contact area of ​​the water-cooling medium. The in-plane graphite-diamond-silicon carbide composite array inside the groove has both high thermal conductivity and cavity support functions, and enables heat to be quickly transferred from the substrate to the microchannel heat transfer area, which can accommodate both air cooling and liquid cooling conditions and is suitable for the high heat flux density heat dissipation requirements of high-power AI chips. Attached Figure Description

[0021] Figure 1 This is a process flow diagram for the preparation of in-plane graphite-diamond-silicon carbide composite heat dissipation material; Figure 2 This is a schematic diagram of the structure of an in-plane graphite-diamond-silicon carbide composite heat dissipation material (excluding the diamond layer). Detailed Implementation

[0022] This invention provides a method for preparing an in-plane graphite-diamond-silicon carbide composite heat dissipation material, comprising the following steps: Graded diamond powder and binder are mixed and then subjected to pressing, degreasing and water jet cutting to form a slot array to obtain a porous diamond preform; the graded diamond powder includes coarse diamond particles with a particle size of 150~500μm, medium diamond particles with a particle size of 50~100μm and fine diamond particles with a particle size of 1~10μm. Porous graphite sheets are inserted into the slot array of the porous diamond preform to obtain a graphite-diamond composite preform; The graphite-diamond composite preform is subjected to chemical vapor infiltration to generate silicon carbide in situ, thereby obtaining an in-plane graphite-diamond-silicon carbide composite heat dissipation material.

[0023] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0024] This invention mixes graded diamond powder and binder, and then sequentially performs pressing molding, degreasing treatment, and water jet cutting to form a slot array to obtain a porous diamond preform.

[0025] In this invention, the graded diamond powder comprises coarse diamond particles with a particle size of 150-500 μm, medium diamond particles with a particle size of 50-100 μm, and fine diamond particles with a particle size of 1-10 μm; the particle size of the coarse diamond particles can be 200-400 μm, or further 200-300 μm; the particle size of the medium diamond particles can be 60-90 μm, or further 60-80 μm; and the particle size of the fine diamond particles can be 2-8 μm, or further 3-5 μm. In this invention, the mass fraction of coarse diamond particles in the graded diamond powder can be 55-65%, or 58-62%, specifically 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, or 65%; the mass fraction of medium diamond particles in the graded diamond powder can be 25-35%, or 28-32%, specifically 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%. In this invention, the thermal conductivity of the coarse diamond particles can be 1200-1800 W / (m·K), or 1300-1700 W / (m·K), further 1350-1500 W / (m·K), specifically 1350 W / (m·K); the impurity content in the coarse diamond particles can be <0.1 wt%. In this invention, the thermal conductivity of the medium-grained diamond can be ≥800 W / (m·K), and can also be 800~1400 W / (m·K), and can be further 900~1300 W / (m·K); the impurity content in the medium-grained diamond can be <0.1 wt%. In this invention, the thermal conductivity of the fine-grained diamond can be ≥800 W / (m·K), and can also be 800~1300 W / (m·K), and can be further 900~1200 W / (m·K); the impurity content in the fine-grained diamond can be <0.1 wt%. Using the above-mentioned graded diamond powder, the porous diamond preform prepared in this invention has a thermal conductivity much higher than that of the SiC / Si3N4 ceramic matrix, thereby improving the vertical thermal conductivity of the in-plane graphite-diamond-silicon carbide composite heat dissipation material.

[0026] In this invention, the coarse-grained, medium-grained, and fine-grained diamonds can all be washed and dried before use. The washing process can be ultrasonic washing with anhydrous ethanol and acetone sequentially, or ultrasonic washing with isopropanol; the ultrasonic washing power can be 150-250W, specifically 180W or 200W; the ultrasonic washing time can be 10-20 minutes, or 12-15 minutes; the purpose of washing is to remove surface oil and impurities. The drying temperature can be 80-120℃, or 90-110℃, specifically 100℃; the drying time can be 1-2 hours, specifically 1.5 hours or 2 hours.

[0027] In this invention, the binder may include an aqueous solution of one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), carboxymethyl cellulose (CMC), polyvinyl butyral (PVB), and low-temperature phenolic resin; the degree of polymerization of the polyvinyl alcohol may be 1700±50, and the degree of alcoholysis of the polyvinyl alcohol may be 85~92%, or 86~91%, or further 87~90%, specifically 88% or 89%. In this invention, the solid content of the binder may be 5~15%, or 5~10%, or further 5~8%; the mass of the binder may be 2~5% of the mass of the graded diamond powder, or 2.5~4.5%, or further 3~4%.

[0028] In this invention, the mixing can be done using a three-dimensional mixer; the mixing temperature can be 25~30℃; the mixing speed can be 30~50rpm, or even 40rpm; the mixing time can be 1~5h, or even 2~4h, or even 3h.

[0029] After the mixing is completed, the present invention may further include passing the mixture through a 200-mesh sieve, with the undersize portion being the diamond mixed powder; the purpose of sieving is to remove agglomerates. The particle size distribution of the diamond mixed powder prepared by the present invention meets the design requirements, with no obvious agglomeration and good flowability.

[0030] In this invention, the holding pressure for compression molding can be 120-180 MPa, 130-170 MPa, 140-160 MPa, or specifically 150 MPa; the holding time for compression molding can be 0.5-10 min, 2-8 min, or specifically 5-6 min. In this invention, the pressure increase rate from atmospheric pressure to the holding pressure can be 1-5 MPa / s, 2-4 MPa / s, or specifically 3 MPa / s. In this invention, the compression molding can be performed using a fully automatic hydraulic press, and the pressure accuracy of the compression molding can be ±0.5 MPa; the compression molding operation can involve placing the diamond mixed powder in a steel mold with a release agent coated on the inner wall, smoothing it with a scraper, applying pressure with a pressure head, increasing the pressure to the holding pressure, and then performing pressure molding. In this invention, the release agent can include one or more of zinc stearate, stearic acid, paraffin emulsion, silicone oil, and polytetrafluoroethylene spray. In this invention, the cavity size of the steel mold can be (100~300) mm × (100~300) mm, or (150~200) mm × 150~200) mm; the surface roughness Ra of the steel mold can be <0.8 μm.

[0031] After the pressing and molding process is completed, the present invention may further include depressurizing to atmospheric pressure to obtain a diamond green blank. In the present invention, the depressurization rate may be 1~3 MPa / s, or it may be 2 MPa / s.

[0032] In this invention, the density of the diamond green blank can be ≥2.8 g / cm³. 3 It can also be 2.8~3.2g / cm³. 3 The diamond green blank prepared by this invention has a thickness uniformity error of <±5μm and is free from defects such as cracks, missing corners, and delamination.

[0033] In this invention, the holding temperature for the degreasing treatment can be 800~1200℃, or 900~1100℃, or even 1000~1100℃; the holding time for the degreasing treatment can be 1~20h, or 2~15h, or even 2~10h, specifically 2h, 3h, 4h, 5h, or 8h; the heating rate from room temperature to the holding temperature can be 5~20℃ / min, or even 10~15℃ / min; the degreasing treatment can be carried out under a protective atmosphere, which may include argon; the purity of the protective atmosphere can be ≥99.999%. In this invention, the degreasing treatment can be carried out in a vacuum atmosphere degreasing furnace; the specific operation of the degreasing treatment may include: placing the diamond green blank flat on a graphite tray, avoiding stacking, closing the furnace door, evacuating to below 10 Pa, introducing a protective atmosphere, bringing it to atmospheric pressure, raising the temperature and holding it at the specified temperature, performing the degreasing treatment, and then cooling it to room temperature with the furnace; the flow rate of the protective atmosphere can be 3~8 L / min, or 4~7 L / min, or even 5~6 L / min.

[0034] In this invention, the binder residue of the degreased diamond green blank obtained by the degreasing treatment is <0.1%, and the porosity is 20-30%, which can also be 23-28%, which can be further 24-26%, and specifically 25%; the average pore size of the degreased diamond green blank can be 1-5 μm, which can also be 2-4 μm, which can be further 2.5-3.5 μm, and specifically 3 μm; the air permeability of the degreased diamond green blank can be >1×10 -12 m 2 The flexural strength of the degreased diamond green blank can be >50MPa. The degreased diamond green blank prepared by this invention is free from deformation and cracking, and has interconnected pores.

[0035] In this invention, the arrangement structure of the slot array can include parallel, honeycomb, or cross-grid patterns. By setting different arrangement structures, this invention can adapt to different heat flow distribution requirements. Based on the hotspot distribution of the chip, non-uniform trench spacing can be designed to achieve targeted heat dissipation optimization. This invention can employ a non-uniform variable spacing arrangement based on the chip's hotspot distribution. In high heat flow areas, the density of the slot arrangement and the non-uniform variable spacing trenches can increase the number of channels and increase the coolant heat exchange area in the corresponding hotspot areas, precisely suppressing chip hotspot overheating.

[0036] In this invention, the length of the card slot array can be 10-200mm, or 50-150mm, specifically 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, or 200mm; the width of the card slot array can be 0.03-0.1mm, or 0.2-0.8mm, specifically 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm; The depth of the card slot array can be 10-100mm, or 30-80mm, specifically 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, or 100mm; the slot spacing of the card slot array can be 0.05-0.3mm, or 0.1-0.2mm, specifically 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, or 0.3mm; the card slots can be uniformly arranged or non-uniformly densified in hot spots; the verticality of the sidewalls of the card slot array can be 83-86°, or 84-85°, specifically 83°, 83.5°, 84°, 84.5°, 85°, 85.5°, or 86°. In this invention, the depth of the card slot can be 80-95% of the thickness of the diamond blank, or 85-90%. By controlling the matching relationship between the depth of the slot and the thickness of the diamond blank, this invention enables the slot to match the thickness and size of the entire degreased diamond blank, facilitating the through-type insertion of porous graphite sheets.

[0037] In this invention, the conditions for waterjet cutting may include: the equipment used is a CNC high-pressure abrasive waterjet cutting machine; the working water pressure is 320~380MPa, which can also be 330~370MPa, which can be further 340~360MPa, which can specifically be 350MPa; the abrasive is garnet sand, and the particle size of the abrasive is 240~320 mesh, which can also be 250~300 mesh, which can specifically be 250 mesh, 280 mesh, 300 mesh or 320 mesh; the abrasive supply rate is 0.4~0.8kg / min, which can also be 0.5~0.7kg / min, which can specifically be 0.6kg / min; the nozzle feed speed is 20~80mm / s, which can also be 30~70mm / s, which can be further 40~60mm / s, which can specifically be 50mm / s.

[0038] In this invention, the specific operation of waterjet cutting may include: fixing the degreased diamond blank on the waterjet CNC platform, calibrating the visual positioning based on the charge-coupled device (CCD), and importing the slot array CNC program; the waterjet nozzle moves at a constant speed to cut the through array slot from top to bottom, and after processing, the residual abrasive inside the slot is repeatedly rinsed with pure water and dried to remove water.

[0039] The groove array prepared by water jet cutting in this invention has a flat bottom without chipping, no thermal graphitization or microcracks, and no abrasive clogging the pores of the substrate inside the groove.

[0040] After obtaining a porous diamond preform, the present invention inserts porous graphite sheets into the slot array of the porous diamond preform to obtain a graphite-diamond composite preform.

[0041] In this invention, the porosity of the porous graphite sheet can be 5-30%, or 10-28%, or even 15-25%, specifically 18%, 19.5%, 20%, 20.3%, 20.8%, 22%, 24.3%, or 24.8%; the average pore size of the porous graphite sheet can be 1-5 μm, or 2-4 μm, or even 3 μm; the interconnectivity of the porous graphite sheet can be ≥90%; the degree of graphitization of the porous graphite sheet can be 95-99%, specifically 95.8% or 96.8%; the in-plane thermal conductivity of the porous graphite sheet can be 1500-1700 W / (m·K), or 1500-1650 W / (m·K), specifically 1520 W / (m·K) or 1620 W / (m·K). In this invention, the thickness of the porous graphite sheet can be 30~200μm, 50~150μm, 80~120μm, or specifically 100μm; the width of the slot can be 1~5μm larger than the thickness of the porous graphite sheet (i.e., the assembly gap between the porous graphite sheet and the slot is 1~5μm), 2~4μm, or even 3μm; this invention facilitates uniform filling of CVI-SiC by controlling the thickness of the porous graphite sheet and the width of the slot.

[0042] In this invention, the porous graphite sheet is obtained by laser cutting of porous graphite. The laser cutting conditions may include: a laser power of 10-50W, or 15-40W, or even 20-30W; a cutting speed of 50-300mm / s, or 100-250mm / s, specifically 100mm / s, 200mm / s, or 250mm / s; and a cutting accuracy of ±20μm, or ±10μm, or even ±5μm. The laser cutting operation may include: flattening and fixing the porous graphite on a laser cutting platform, importing a cutting pattern file, performing precision cutting, and after cutting, blowing away surface dust with compressed air.

[0043] In this invention, the insertion can be automated. The specific operation includes: using a high-precision automatic insertion machine with a positioning accuracy of ±1μm, fixing the porous diamond preform on the machine's worktable, arranging the porous graphite sheets neatly in the material box, starting the insertion machine, and using a CCD vision positioning system to identify the slot positions. The robotic arm grasps the porous graphite sheets, and the adsorption negative pressure can be -0.02~-0.06MPa (or -0.03~-0.05MPa, specifically -0.04MPa). The porous graphite sheets are inserted one by one into the slots with a pressure of 0.2~1N (or 0.3~0.8N, specifically 0.5N). After all insertions are completed, the insertion depth and perpendicularity of the porous graphite sheets are checked. There are no breaks or tilting phenomena, and the porous graphite sheets fall completely into the slots with a perpendicularity error of ±0.3°.

[0044] After obtaining the graphite-diamond composite preform, the present invention performs chemical vapor infiltration (CVI) on the graphite-diamond composite preform to generate silicon carbide in situ, thereby obtaining an in-plane graphite-diamond-silicon carbide composite heat dissipation material.

[0045] In this invention, the chemical vapor permeation process conditions may include: using a CVI reactor, specifically an isothermal CVI furnace; the silicon source includes one or more of methyltrichlorosilane (MTS), silicon tetrachloride (SiCl4), dimethyldichlorosilane (DMDCS), trichlorosilane (SiHCl3), and hexamethyldisilane (HMDS), wherein the purity of the silicon source can be 99.99%; the flow rate of the silicon source is 5~12 sccm, or 6~10 sccm, specifically 6 sccm or 8 sccm; the carrier gas includes hydrogen, wherein the purity of the carrier gas can be ≥99.999%; the flow rate of the carrier gas is 500~1200 sccm, or 600~1000 sccm, specifically 600 sccm. cm or 800 sccm; carrier gas / silicon source flow rate ratio ≥75, also 75~240, further 80~200, further 90~150, specifically 100 or 120; deposition temperature 1100~1200℃, also 1120~1180℃, further 1140~1160℃, specifically 1150℃; furnace temperature uniformity error <±5℃; deposition time 6~15h, also 8~12h, specifically 8h, 10h or 12h; reverse cycle of silane-carrier gas mixture 1~3h, also 1.5~2.5h, specifically 2h; reaction chamber pressure 5~10kPa, also 6~9kPa, further 7~8kPa. The reverse cycle of the silane-carrier gas mixture is 1~3h. The specific operation is as follows: the silicon source vapor and the carrier gas are pre-mixed to form a silane-carrier gas mixture. The mixture first flows into one side of the graphite-diamond composite preform, passes through all the through slots and the internal pores of the porous graphite, and then flows out from the other side. Every 1~3h, the pipeline flow direction is switched, and the mixture is changed to be introduced from the opposite side of the graphite-diamond composite preform, passes through all the slots and the internal pores of the porous graphite in reverse, and then discharged.

[0046] In this invention, the chemical vapor infiltration (CVI) operation may include: placing the graphite-diamond composite preform flat on a graphite fixture, ensuring the preform is perpendicular to the gas flow direction; placing the fixture in the homogenization zone of the CVI reactor; closing the furnace door; evacuating to below 1 Pa; introducing high-purity argon to atmospheric pressure; repeating the evacuation and argon purging operation 2-4 times (specifically 3 times); removing air from the furnace; raising the temperature to the deposition temperature; adjusting the reaction chamber pressure; opening the silane evaporator; heating the silane to generate silicon source vapor; introducing carrier gas; premixing the carrier gas and silicon source vapor to form a silane-carrier gas mixture; introducing the mixture into the reactor; controlling the silicon source vapor flow rate and carrier gas flow rate; starting the timer; switching the inlet and outlet directions of the silane-carrier gas mixture every 2 hours via a reversing valve; after deposition is complete, closing the silicon source valve; continuing to introduce carrier gas for protection; cooling with the furnace to 400-600°C (specifically 500°C); switching to argon protection; continuing to cool with the furnace to room temperature; opening the furnace door; and removing the sample. In this invention, the heating rate can be 3~8℃ / min, 4~7℃ / min, or even 5~6℃ / min. In this invention, the furnace cooling rate can be 1~5℃ / min, 2~4℃ / min, or even 2~3℃ / min.

[0047] In a specific embodiment of the present invention, the chemical vapor infiltration employs a symmetrically inlet isothermal CVI furnace. Independent inlet branches, two-position five-way solenoid valves, and mass flow controllers are respectively configured at the left and right ends of the furnace. The valves are automatically controlled by a PLC timing program, switching the gas flow inlet and outlet every 1-3 hours. The graphite-diamond composite preform is suspended in the homogenization zone within the furnace. The slots and the interior of the porous graphite form a continuous, narrow gas flow channel. Alternating inlet of silicon source vapor and carrier gas balances the silicon source concentration gradient along the channel, eliminating the defect of "excessive thickness at the inlet and insufficient deposition at the far end" in unidirectional deposition, achieving uniform growth of SiC films in all gaps and micropores. The deposition system uses low pressure combined with a large flow rate of excess high-purity carrier gas to dilute the silicon source, slowing down the violent decomposition of the silicon source. The carrier gas can etch away the instantaneously precipitated free silicon and carbon black particles, resulting in only selective gas-solid reaction on the graphite surface to generate single-phase SiC throughout the process. The low-temperature conditions of 1100-1200℃ do not cause diamond sp. 3 Through lattice etching and high-temperature graphite erosion, SiC is generated in situ only at the interface between the diamond slot and the porous graphite sheet, and within the pores of the porous graphite sheet. This allows for precise control of the SiC bonding layer and columnar thermal bridge thickness, while simultaneously leveraging Si-C covalent bonds to significantly enhance the interfacial bonding strength between the graphite and diamond matrix. This invention utilizes low-pressure, high-flow-rate carrier gas for chemical vapor infiltration, which can suppress the generation of byproducts such as free silicon powder and carbon black during the chemical vapor infiltration process.

[0048] In this invention, the pressure, silicon source flow rate, and carrier gas flow rate are stable and without fluctuation during the chemical vapor infiltration process. During chemical vapor infiltration, a SiC bonding layer can be generated in situ in the gap between the slot and the porous graphite sheet, and columnar SiC thermal bridges are formed inside the porous graphite sheet. The thickness of the SiC bonding layer can be 1~5μm, or 2~4μm, specifically 3μm; the diameter of the columnar SiC thermal bridge can be 1~5μm, or 2~4μm, specifically 3μm. In this invention, the in-plane graphite-diamond-silicon carbide composite preform obtained by chemical vapor infiltration is free from deformation and cracking, and the surface is free from obvious dust.

[0049] Traditional hot-pressing / vacuum high-pressure melting and infiltration equipment requires withstanding high pressure and temperature, resulting in equipment costs reaching millions of dollars. It can only process a few pieces per furnace load, leading to long production cycles. The preparation of ultra-thin samples requires specially customized molds, further increasing production costs and cycles, making it difficult to meet large-scale market demands. In contrast, the preparation method provided by this invention only requires a standard isothermal CVI furnace, with equipment costs only 1 / 10 to 1 / 5 of the former. The cavity can be designed to be large-sized, allowing for the simultaneous processing of 20 to 30 samples per furnace load. It can even be adapted to continuous CVI production lines, reducing overall production costs by 40 to 60%, completely solving the core pain point of difficult mass production of large-size, ultra-thin ultra-high thermal conductivity composite heat dissipation materials.

[0050] After completing the chemical vapor infiltration, the present invention may further include: dividing the in-plane graphite-diamond-silicon carbide composite preform obtained by the chemical vapor infiltration into slices to obtain in-plane graphite-diamond-silicon carbide composite sheets; and chemically vapor depositing a diamond layer (CVD diamond layer) on the upper surface, lower surface, or both upper and lower surfaces of the in-plane graphite-diamond-silicon carbide composite sheets.

[0051] In this invention, the slicing may include water-guided laser slicing. The process conditions for water-guided laser slicing may include: the equipment used includes a water-guided laser precision cutting machine; the laser wavelength is 532nm; the water beam diameter is 30~80μm, which can also be 40~70μm, or further 50~60μm; the cutting feed speed is 15~50mm / s, which can also be 20~45mm / s, or further 25~40mm / s, or further 30~35mm / s; and the kerf taper is <0.1°. In this invention, the operation of water-guided laser slicing may include: positioning and fixing the in-plane graphite-diamond-silicon carbide composite blank with a tooling, using a water-guided laser to slice along the length of the blank in an array, separating the whole piece according to the target thickness of the finished heat sink; rinsing the slicing gaps with pure water after processing, and air drying at room temperature. In this invention, during the water-guided laser slicing process, an array-type diamond fin structure can also be integrally formed on the bottom edge of a single piece. In this invention, the center-to-center distance between adjacent diamond fins in the array can be 0.1~0.3mm, or 0.15~0.25mm, specifically 0.2mm; the recessed cavities of adjacent diamond fins form independent liquid-cooled microchannels, the cross-sectional width of which can be 0.03~0.1mm, or 0.04~0.09mm, or further 0.05~0.08mm, specifically 0.06mm or 0.07mm; the depth of which can be 0.3~1mm, or 0.4~0.9mm, or further 0.5~0.8mm, specifically 0.6mm or 0.7mm; and the liquid-cooled microchannels are arranged to run through the entire length of the in-plane graphite-diamond-silicon carbide composite sheet.

[0052] This invention utilizes water-guided laser cold processing to form fins without thermal damage. The fin edges are free of diamond graphitization and microcracks, and the internal interconnected pores are fully preserved, ensuring continuous thermal conductivity in the fin area. The inner cavity of the diamond fin recess serves as a native integrated microchannel, eliminating the need for additional grooving. The microchannel is connected to the heat sink substrate, allowing coolant to flow freely within the channel and improving liquid cooling efficiency. The bottom of the composite heat dissipation material can be directly machined with a microchannel slot structure, achieving integration of the heat sink and the cold plate.

[0053] After the slab division is completed, the present invention may further include grinding and polishing the single composite blanks obtained from the slab division to obtain an in-plane graphite-diamond-silicon carbide composite sheet. In the present invention, the conditions for the double-sided precision grinding and polishing may include: attaching the single composite blank to a ceramic substrate, grinding sequentially using 400#, 800#, and 1500# diamond grinding wheels, and then performing double-sided precision polishing using diamond polishing fluid. In the present invention, the particle size of the diamond polishing fluid may be 0.03~0.1μm, or 0.04~0.09μm, or further 0.05~0.08μm, specifically 0.05μm, 0.06μm, or 0.07μm. In the present invention, the allowance removed from each side of the upper and lower surfaces during grinding and polishing may be 30~100μm, or 40~90μm, or further 50~80μm, specifically 50μm, 60μm, or 70μm. In this invention, the purpose of grinding and polishing is to remove the silicon carbide layer and other impurities from the surface.

[0054] In this invention, the thickness of the in-plane graphite-diamond-silicon carbide composite sheet can be 0.2~3mm, 0.5~2.5mm, or even 1~2mm.

[0055] In this invention, before chemical vapor deposition, the surface layer of the in-plane graphite-diamond-silicon carbide composite sheet can be activated by plasma etching.

[0056] In this invention, the process conditions for plasma etching activation may include: an etching atmosphere of high-purity hydrogen gas with a purity ≥99.999%; a working pressure of 4~15 kPa, which can also be 5~12 kPa, further 6~10 kPa, specifically 7 kPa, 8 kPa, 9 kPa, or 10 kPa; a plasma excitation power of 800~1800 W, which can also be 800~1500 W, further 800~1000 W, specifically 800 W, 900 W, 1000 W, 1100 W, 1200 W, 1300 W, 1400 W, 1500 W, 1600 W, 1700 W, or 1800 W; and an etching temperature of 750~950℃, which can also be 750~900℃, further 750~800℃, specifically 750℃. The etching temperature is 780℃, 800℃, 850℃, 900℃, or 950℃; the flow rate of the etching atmosphere is 3000~8000sccm, or 3000~5000sccm, or further 3000~4000sccm, specifically 3000sccm, 3500sccm, 4000sccm, 4500sccm, 5000sccm, 5500sccm, 6000sccm, 6500sccm, 7000sccm, 7500sccm, or 8000sccm; the etching holding time is 10~60min, or 10~50min, or further 10~40min, specifically 10min, 15min, 20min, 25min, 30min, 40min, 50min, or 60min.

[0057] In this invention, the etching activation operation may include: placing the in-plane graphite-diamond-silicon carbide composite sheet flat on a graphite stage of a CVD furnace, evacuating the sealed furnace to below 1 Pa, and replacing it with high-purity hydrogen 2-4 times (or 2-3 times); introducing an etching atmosphere, adjusting the pressure inside the furnace, turning on a microwave source to excite the etching atmosphere plasma, raising the temperature to the target etching temperature and holding it for etching, turning off the microwave source after etching, and uniformly cooling the temperature to below 600°C under the etching atmosphere. The temperature after cooling may also be 300-600°C, specifically 300°C, 400°C, 500°C, or 600°C.

[0058] In this invention, the conditions for chemical vapor deposition may include: the carbon source is methane; the carrier gas includes hydrogen; the volume fraction of the carbon source in the carrier gas may be 3-5%, or 4-5%; the deposition temperature is 830-980℃, or 850-950℃, or further 860-920℃, specifically 880℃ or 900℃; the working pressure is 6-20 kPa, or 8-18 kPa, or further 10-16 kPa, specifically 10 kPa, 12 kPa or 15 kPa; this invention does not have a special limitation on the deposition time, as long as a diamond layer with a thickness of 10-100 μm is obtained, the thickness of the diamond layer may be 20-90 μm, or further 30-80 μm, specifically 40 μm, 50 μm, 60 μm or 70 μm. In this invention, the thermal conductivity of the diamond layer can be 800~2000W / (m·K), or 1000~1800W / (m·K), or even 1200~1600W / (m·K), or specifically 1500W / (m·K).

[0059] In this invention, the chemical vapor deposition (CVD) operation may include: introducing a mixed gas of carbon source and carrier gas, adjusting the deposition pressure in the furnace, turning on the microwave source, plasma excitation, and depositing a diamond layer (continuous polycrystalline diamond film) in situ on the surface of the composite preform; controlling the deposition time according to the thickness of the diamond layer; after deposition, turning off methane, introducing only H2, and cooling to room temperature at a uniform rate of 5~20℃ / min (or 5~15℃ / min, or even 5~10℃ / min) under plasma conditions before unloading from the furnace. This invention, by chemically vapor depositing a dense, continuous CVD diamond layer onto the upper, lower, or both upper and lower surfaces of an in-plane graphite-diamond-silicon carbide composite sheet, forms a composite hierarchical structure of graphite-silicon carbide-diamond preform-surface CVD diamond. This further improves the overall surface thermal conductivity, wear resistance, and corrosion resistance of the composite heat dissipation material, and is suitable for brazing assembly.

[0060] Traditional vertical graphite-copper composite materials, using copper as the matrix, suffer from a severe mismatch between the coefficient of thermal expansion and that of silicon chips, leading to interface debonding after thermal cycling and poor reliability. Traditional mold-filling methods rely on high-precision graphite molds, making large-size fabrication difficult and resulting in high production costs. Liquid-phase melting infiltration methods suffer from high resistance to the penetration of liquid silicon in narrow vertical channels, leading to "over-infiltration at the edges and under-infiltration at the center" in large-size samples, with thermal conductivity deviations exceeding 20%. Hot-pressing processes are prone to graphite sheet tilting and misalignment due to powder impact, resulting in poor product consistency and an overall yield below 60%. Existing technologies, where graphite and the matrix are only mechanically bonded, suffer from severe "in-plane thermal resistance traps," preventing the full utilization of graphite's high thermal conductivity and making it difficult for isotropic graphite products to achieve thermal conductivity exceeding 150 W / (m·K). This invention, through abrasive waterjet cutting array slots + graphite sheet insertion + CVI process, completely avoids the problems of mold dependence, uneven melting and infiltration, and damage to the hot-pressed structure. It uses a diamond-silicon carbide substrate to achieve perfect thermal expansion matching with silicon chips. The yield rate of finished products is increased to over 95%, and the slot structure design is diverse. By adjusting the laser etching program, it can be adapted to any spacing, array, and irregular arrangement. At the same time, by generating a SiC thermal bridge network that penetrates the thickness of graphite in situ, it completely breaks through the "in-plane thermal resistance trap" and increases the vertical thermal conductivity of the composite material to 800~1200W / (m·K).

[0061] This invention also provides an in-plane graphite-diamond-silicon carbide composite heat dissipation material prepared by the method described in the above technical solution. The in-plane graphite-diamond-silicon carbide composite heat dissipation material provided by this invention has an array of diamond fins integrally formed on its bottom edge. The diamond fins and the diamond substrate are of homogeneous integrated structure. The grooves of the graphite fins contain an array structure of diamond and silicon carbide arranged along the length direction. The groove cavity forms a built-in microchannel, which expands the contact area with the coolant and enhances the liquid cooling heat transfer capacity.

[0062] This invention also provides the application of the in-plane graphite-diamond-silicon carbide composite heat dissipation material described above in computing processing units, power semiconductor devices, or aerospace electronic equipment. In this invention, the computing processing unit may include an AI chip or a server central processing unit (CPU); the power semiconductor device may include an insulated gate bipolar transistor (IGBT) power module, a silicon carbide power device, a gallium nitride radio frequency device, or an automotive power inverter; the aerospace electronic equipment may include a spaceborne processing chip, an airborne radar radio frequency component, an aerospace power module, an aerospace servo control circuit board, or a satellite payload heat dissipation substrate.

[0063] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0064] Example 1 according to Figure 1 The process flow diagram shown is prepared.

[0065] 1. Preparation of porous diamond preforms Step 1: Pretreatment and gradation of diamond powder. The specific operation is as follows: Coarse-grained diamond (particle size 200~300μm, impurity content <0.1wt%), medium-grained diamond (particle size 60~80μm, single crystal, impurity content <0.1wt%), and fine-grained diamond (particle size 3~5μm, single crystal, impurity content <0.1wt%) were ultrasonically cleaned with anhydrous ethanol and acetone at 200W for 15 min, respectively, and dried at 100℃ for 1.5 h. Then, the coarse-grained, medium-grained, and fine-grained diamonds were mixed at a mass ratio of 6:3:1 to obtain graded diamond powder. A 5% PVA aqueous solution was then added, and the mixture was stirred using a three-dimensional mixer at 25℃ and 40 rpm for 3 h. The mixture was then passed through a 200-mesh sieve; the portion passing through the sieve was the diamond mixed powder. The mass of the PVA aqueous solution was 3% of the mass of the graded diamond powder.

[0066] Step 2: Dry pressing to prepare diamond green blanks. The specific operation is as follows: A 150mm × 150mm steel mold is used, with the inner wall sprayed with zinc stearate release agent. The diamond powder mixture is placed in the mold and leveled. A fully automatic hydraulic press is used to increase the pressure to 150MPa at a rate of 3MPa / s, hold the pressure for 5 minutes, and then release the pressure at a rate of 2MPa / s to obtain the diamond green blank. The density of the diamond green blank is 3.0 g / cm³. 3 The thickness uniformity error is ±3μm, and there are no delamination cracks.

[0067] Step 3: High-temperature degreasing treatment. The specific operation is as follows: The diamond green blank is laid flat on a graphite tray. A vacuum atmosphere furnace is evacuated to 8 Pa, and high-purity argon gas (purity ≥99.999%) is introduced at a rate of 5 L / min to atmospheric pressure. The temperature is increased to 1000℃ (temperature control accuracy ±5℃) at a rate of 10℃ / min, held at this temperature for 2 hours, and then cooled in the furnace to obtain the degreased diamond green blank. The degreased diamond green blank has a PVA residue of 0.06 wt%, a porosity of 25.1%, an average pore size of 3.1 μm, a flexural strength of 55 MPa, and an air permeability of 1.2 × 10⁻⁶. -12 m 2 The degreased diamond blanks showed no deformation or cracking.

[0068] Step 4: Waterjet Cutting (Arraying). The specific steps are as follows: An array of through-grooves is cut on the surface of the porous diamond preform using an abrasive waterjet cutter. The preform is rinsed three times with pure water and dried at 80℃ for 1 hour to obtain the porous diamond preform. Process conditions: A CNC high-pressure abrasive waterjet cutter is used, with a working water pressure of 350 MPa. 280-mesh garnet abrasive is used, with a garnet abrasive supply rate of 0.6 kg / min and a nozzle feed speed of 50 mm / s. The grooves in the porous diamond preform are 150 mm long, 0.05 mm wide, and 50 mm deep, with a groove spacing of 0.2 mm. The dimensional error of the grooves is ±15 μm, the sidewall verticality is 84.5°, and there is no abrasive clogging or edge chipping.

[0069] 2. Laser-cut in-plane graphite sheet Step 5: Using a 355nm ultraviolet laser cutting machine at a power of 20W and a cutting speed of 200mm / s, the porous graphite was laser-cut. Surface dust was blown away with compressed air to obtain porous graphite sheets. The dimensions of the porous graphite sheets were 150mm × 50mm × (58±2)μm, with a cutting accuracy of ±5μm and no burrs or cracks on the edges. The graphitization degree of the porous graphite sheets was 96.8%, the in-plane thermal conductivity was 1620W / (m·K), the porosity was 20.3%, and the interconnectivity was 93%.

[0070] 3. Assembly of composite blanks Step 6: Automatic insertion of porous graphite sheets. The specific operation is as follows: A high-precision automatic insertion machine with CCD positioning slots is used. The suction negative pressure is -0.04MPa. The robotic arm inserts the porous graphite sheets one by one into the slots of the porous diamond preform with a pressure of 0.5N, obtaining a graphite-diamond composite preform (see structural schematic diagram). Figure 2 After insertion, the perpendicularity error of the porous graphite sheet was 0.3°, with no breakage, deformation, or tilting, and the insertion yield was 100%.

[0071] 4. Chemical Vapor Infiltration (CVI) Treatment and Post-processing Step 7: Using an isothermal forced flow CVI furnace, place the graphite-diamond composite preform perpendicular to the airflow direction in the uniform temperature zone, evacuate to 0.8 Pa, replace with argon three times, and raise the temperature to 1150℃ at 5℃ / min, with the furnace temperature uniformity ±3℃. The composite preform was loaded into a CVI reactor, and the pressure in the reaction chamber was adjusted to 8 kPa. The MTS evaporator was turned on, and the MTS was heated to 30°C to generate MTS vapor. Hydrogen gas with a flow rate of 800 sccm was introduced as a carrier gas. The hydrogen gas and MTS vapor (flow rate of 8 sccm) were mixed to form a silicon source-carrier gas mixture. The silicon source-carrier gas mixture entered the reactor, and the timing was started. The silicon source-carrier gas mixture first flowed into one side of the graphite-diamond composite preform, passed through all the through slots and the internal pores of the porous graphite, and then flowed out from the other side. Every 2 hours, the gas flow direction was switched by a reversing valve (i.e., the inlet and outlet directions of the silicon source-carrier gas mixture were exchanged). The deposition was carried out continuously for 10 hours. After the MTS was turned off, hydrogen gas was continued to be introduced, and the temperature was cooled to 500°C at a rate of 2°C / min. Argon gas protection was switched, and the furnace was cooled to room temperature to obtain the graphite-diamond-SiC composite preform. The CVI furnace employs a dual-end symmetrical air intake structure, with two air intake pipes equipped with electromagnetic reversing valves and a PLC timing control system, automatically reversing at a set 2-hour switching cycle. A silicon source-carrier gas mixture alternately passes through the slots and graphite pores on both sides of the preform, balancing the silicon source concentration within the narrow microchannels and ensuring uniform SiC deposition inside and outside the graphite. Low-pressure, high-flow-rate hydrogen at 8 kPa suppresses the generation of free silicon powder and carbon black byproducts. The 1150℃ deposition temperature selectively generates SiC only at the graphite interface, without damaging the diamond framework and porous graphite matrix. The SiC filling rate of the graphite-diamond-SiC composite preform is 89%, with good interfacial bonding, and the sample shows no deformation or cracking.

[0072] Step 8: Water-guided laser slicing and double-sided grinding and polishing. The specific steps are as follows: A water-guided laser (532nm green light, water beam diameter 50μm, feed speed 30mm / s) is used to slice the graphite-diamond-silicon carbide composite preform along its thickness direction, with each slice being 0.5mm thick. Then, 400#, 800#, and 1500# grinding wheels are used sequentially for grinding, followed by double-sided fine polishing with 0.5μm diamond polishing slurry. The removal amount on one side is 0.05mm, and the grinding pressure is 0.1MPa, resulting in an in-plane graphite-diamond-silicon carbide composite sheet. The surface roughness Ra of the in-plane graphite-diamond-silicon carbide composite sheet is 0.4μm, the thickness uniformity error is ±8μm, and there is no chipped graphitization. The dimensions of the in-plane graphite-diamond-silicon carbide composite sheet are 150mm × 150mm × 0.4mm.

[0073] The in-plane graphite-diamond-silicon carbide composite sheet has a vertical thermal conductivity of 1050 W / (m·K), an in-plane thermal conductivity of 820 W / (m·K), a flexural strength of 215 MPa, and a coefficient of thermal expansion of 2.3 × 10⁻⁶. -6 / K, with an interfacial bonding strength of 78MPa and a finished product yield of 96.2%.

[0074] Step 9: Deposition of the surface CVD diamond layer. The specific steps are as follows: Introduce an H2-CH4 mixed gas (CH4 accounts for 5% of the H2 volume), adjust the deposition pressure inside the furnace, turn on the microwave source, and initiate plasma excitation. Deposit a 30μm thick CVD diamond layer (continuous polycrystalline diamond film) in situ on the surface of the in-plane graphite-diamond-silicon carbide composite sheet. Control the deposition time according to the target film thickness. After deposition, turn off the methane supply and only introduce high-purity H2. Under plasma atmosphere conditions, cool to room temperature at a uniform rate of 10℃ / min and remove from the furnace to obtain the in-plane graphite-diamond-silicon carbide composite heat dissipation material. Deposition conditions: Deposition temperature is 880℃, working pressure is 15kPa; the thermal conductivity of the deposited CVD diamond layer is 1500W / (m·K). The surface of the in-plane graphite-diamond-silicon carbide composite heat dissipation material has a dense and continuous CVD diamond layer. The CVD diamond layer can be on the upper or lower surface or both surfaces of the in-plane graphite-diamond-silicon carbide composite sheet. The introduction of the CVD diamond layer can further improve the thermal conductivity and wear and corrosion resistance of the material, making it more suitable for brazing assembly.

[0075] The in-plane graphite-diamond-silicon carbide composite heat dissipation material prepared in this embodiment (with CVD diamond layers on both the upper and lower surfaces, tested at 25°C) has a thickness of 4.107 mm and a density of 3.325 g / cm³. 3 The vertical thermal conductivity is 815.61 W / (m·K), the specific heat capacity is 0.557 J / (g·℃), and the thermal diffusivity is 440.388 mm. 2 / s.

[0076] Example 2 Non-uniform variable-pitch fin microchannel composite heat sink (liquid-cooled enhanced type) Steps 1-3: The difference between Steps 1-3 and those in Example 1 is that the sample injection is performed using a degreased diamond blank with dimensions of 150mm × 150mm × 50mm.

[0077] Step 4: The slot array is a non-uniformly spaced, variable-spacing slot array. Process conditions: working water pressure is 360MPa, using 300-mesh garnet sand, and the garnet sand feed rate is 40mm / s. The slot width is 0.05mm, the depth is 50mm; the dimensional error is ±18μm, and the sidewall verticality is 84°.

[0078] Step 5: The only difference from Step 5 of Example 1 is that the thickness of the porous graphite sheet is 45 μm, the in-plane thermal conductivity is 1680 W / (m·K), and the porosity is 19.5%.

[0079] Steps 6 and 7 are the same as in Example 1.

[0080] Step 8: Integral molding of water-conducting fins and fins-microchannels, followed by double-sided grinding and polishing. The specific steps are as follows: The water-conducting laser cuts along an irregular trajectory, and the fins are simultaneously molded into an array of diamond fins on the bottom edge. The height of the diamond fins is 0.5mm, and the center-to-center distance between adjacent diamond fins is 0.5mm. The recessed cavities of adjacent diamond fins form independent liquid-cooled microchannels. The cross-sectional width of the liquid-cooled microchannel is 0.05mm, the depth is 0.5mm, and it extends along the length of the fin. The double-sided grinding and polishing operation is the same as in Example 1.

[0081] Step 9: The only difference from Step 9 in Example 1 is that the volume fraction of methane in hydrogen is 3%, the thermal conductivity of the deposited diamond layer is 1800 W / (m·K), and the thickness of the CVD diamond layer is 80 μm. The vertical thermal conductivity of the in-plane graphite-diamond-silicon carbide composite heat dissipation material is 1120 W / (m·K), and the local thermal conductivity of the chip hotspot area is improved by 15%. Under liquid cooling conditions (flow rate 1 L / min, water inlet temperature 25℃), the thermal resistance is reduced by 41% compared to the flat wafer, and the maximum chip temperature is reduced by 22℃.

[0082] The only difference between the flat sheet and the in-plane graphite-diamond-silicon carbide composite heat dissipation material in this embodiment is that the water-conducting segmentation and fin-microchannel integral molding in step 8 are omitted. The flat sheet is only used as a control group sample for performance comparison; the flat sheet has no diamond fins or through-flow liquid-cooled microchannels on its bottom edge, and relies on the overall plane for heat dissipation, without built-in liquid flow heat exchange channels.

[0083] The improvement in local thermal conductivity in the hot spot area of ​​the chip was obtained by fixed-point thermal conductivity detection using a laser flare instrument combined with infrared thermal imaging temperature field acquisition. The liquid cooling performance was tested using an electronic device steady-state thermal resistance test platform. The test conditions were set with a cooling water flow rate of 1L / min and a constant inlet water temperature of 25℃. A flat wafer was used as a control group. After the system reached thermal equilibrium, temperature data was collected and thermal resistance was calculated. The results showed that the thermal resistance of the sample with microchannel fin structure of the present invention was reduced by 41% compared with the flat wafer, and the chip's highest steady-state temperature was reduced by 22℃.

[0084] Example 3 Honeycomb arrangement double-sided CVD diamond composite heat sink (high reliability brazed type) Degreased diamond blanks were prepared according to steps 1-3 of Example 1.

[0085] Step 4: The only difference from Step 4 of Example 1 is that the card slot array is a regular hexagonal honeycomb arrangement, the center spacing of the card slots is 0.25mm, the width of the card slot is 0.06mm, the depth is 50mm, the verticality of the card slot wall is 83.5°, and the dimensional error is ±16μm.

[0086] Steps 5-6: The only difference from step 5 of Example 1 is that the porous graphite sheet has a thickness of 100 μm, an in-plane thermal conductivity of 1560 W / (m·K), a porosity of 20.8%, and is laser-cut into a honeycomb-fit porous graphite sheet.

[0087] The only difference between step 7 and step 7 in Example 1 is that the deposition time is 12 hours to ensure that the deep holes are fully filled.

[0088] Step 8: The only difference from Step 8 of Example 1 is that the thickness of the in-plane graphite-diamond-silicon carbide composite sheet is 0.5 mm.

[0089] Step 9: The only difference from Step 8 of Example 1 is that: the volume fraction of methane to hydrogen is 4%, the working pressure is 12 kPa; CVD diamond layers with a thickness of 50 μm are deposited on both the upper and lower surfaces, and the cooling rate is 5 °C / min. The vertical thermal conductivity of the in-plane graphite-diamond-silicon carbide composite heat dissipation material is 980 W / (m·K), the surface microhardness is 8200 HV; the brazing interface bonding strength is 125 MPa, suitable for high-temperature brazing assembly; the surface corrosion resistance is improved, and it can withstand strong acid and alkali conditions.

[0090] Example 4 Large-size composite heat sink with cross-grid design (large-area heat dissipation type) The degreased diamond green blank was prepared according to steps 1-3 of Example 1. The only difference from Example 1 is that the mold size is 200mm×200mm, the pressing pressure is 160MPa, and the holding time is 8min; the size of the degreased diamond green blank is 200mm×200mm×50mm, the porosity is 24.8%, and the bending strength is 52MPa.

[0091] Step 4: The only difference from Step 4 of Example 1 is that the slot array is in the form of an orthogonal grid, with a horizontal and vertical slot width of 0.05mm, a grid spacing of 0.2mm, and a slot depth of 50mm; the nozzle feed speed is 35mm / s; and the overall slot position accuracy is ±20μm.

[0092] Steps 5-6: The only difference from steps 5-6 in Example 1 is that the porous graphite sheet has a thickness of 100 μm, an in-plane thermal conductivity of 1560 W / (m·K), a porosity of 20.8%, and is cut into transverse and longitudinal porous graphite sheets to fit the grid, forming an orthogonal thermally conductive network.

[0093] Step 7: The only difference from Step 7 in Example 1 is that the deposition time is 11 hours to ensure uniform deposition at the center and edges of the large-sized blank.

[0094] Step 8: The only difference from Step 8 of Example 1 is that the size of the in-plane graphite-diamond-silicon carbide composite sheet is 200mm×200mm×0.3mm.

[0095] Step 9: The only difference from Step 9 in Example 1 is that the deposition temperature is 950℃, the working pressure is 12kPa, CVD diamond layers with a thickness of 50μm are deposited on both the upper and lower surfaces, and the cooling rate is 5℃ / min. Parameters are the same as in Example 1. The average vertical thermal conductivity of the in-plane graphite-diamond-silicon carbide composite heat dissipation material is 960W / (m·K), the difference in thermal conductivity between the center and the edge is <28W / (m·K), and the thermal conductivity uniformity is 97.2%; the in-plane temperature uniformity is ±1.5℃, suitable for the heat dissipation requirements of large-area AI chips.

[0096] Example 5 Ultra-thin densely packed parallel array composite heat sink (ultra-thin package adapter type) Step 1: Pretreatment and gradation of diamond powder. The specific operation is as follows: Coarse-grained diamond (150~200μm, impurity content <0.1wt%), medium-grained diamond (60~80μm, single crystal, thermal conductivity, impurity content <0.1wt%), and fine-grained diamond (3~5μm, single crystal, impurity content <0.1wt%) are ultrasonically cleaned with isopropanol at 180W for 12 min and dried at 90℃ for 2 h. Then, the coarse, medium, and fine-grained diamonds are mixed at a mass ratio of 55:35:10 to obtain graded diamond powder. A 4.5% PVB aqueous solution is then added, and the mixture is blended for 4 h at 22℃ and 35 rpm using a three-dimensional mixer. The mixture is then passed through a 250-mesh sieve; the undersize portion is the diamond mixed powder. The mass of the PVB aqueous solution is 2.5% of the mass of the graded diamond powder.

[0097] Step 2: The only differences from Step 2 in Example 1 are: the release agent is paraffin emulsion; the pressurization rate is 2 MPa / s, the holding pressure is 160 MPa, the holding time is 8 min, and the depressurization rate is 1.5 MPa / s; the density of the diamond green body is 3.05 g / cm³. 3 Thickness uniformity error ±2μm, no delamination cracks.

[0098] Step 3: The only difference from Step 3 in Example 1 is that the vacuum atmosphere furnace is evacuated to 6 Pa, and the flow rate of high-purity argon is 4 L / min; the temperature is increased to 1050℃ at 8℃ / min and held for 1.5 h; the residual PVB content of the degreased diamond green compact is 0.05 wt%, the porosity is 24.3%, the average pore size is 2.8 μm, the flexural strength is 58 MPa, and the air permeability is 1.1 × 10⁻⁶. -12 m 2 .

[0099] Step 4: The only difference from Step 4 of Example 1 is that: the card slot array is a closely spaced card slot array, the working water pressure is 360MPa, 320-mesh garnet sand is used, the garnet sand supply rate is 0.5kg / min, the nozzle feed speed is 35mm / s; the width of the card slot is 0.04mm, the depth is 30mm, and the slot spacing is 0.1mm; rinsed with pure water 4 times, dried at 85℃ for 1h; the dimensional error of the card slot is ±12μm, and the verticality of the sidewall is 85°.

[0100] Step 5: The only difference from Step 5 in Example 1 is that the laser cutting power is 15W, the cutting speed is 250mm / s, the size of the porous graphite sheet is 150mm×30mm, and the cutting accuracy is ±3μm. The thickness of the porous graphite sheet is 30μm±1.5μm, the degree of graphitization is 95.8%, the in-plane thermal conductivity is 1580W / (m·K), the porosity is 18.7%, and the interconnectivity is 91%.

[0101] Step 6: The only difference from Step 6 of Example 1 is that the pressure is 0.3N and the perpendicularity error of the porous graphite sheet after insertion is 0.2°.

[0102] Step 7: The only difference from Step 7 in Example 1 is that: the vacuum is reduced to 0.7 Pa, the temperature is increased to 1120 °C at 4 °C / min, the MTS evaporator temperature is controlled at 28 °C, the reaction chamber pressure is 8 kPa; the MTS vapor flow rate is 6 sccm, the H2 flow rate is 600 sccm, the deposition time is 8 h, and the temperature is cooled to 450 °C at 1.5 °C / min; after deposition, the SiC filling rate is 87%, and the interface bonding is good.

[0103] Step 8: The only difference from Step 8 in Example 1 is that: the water-guided laser uses 532nm green light, the water beam diameter is 40μm, the feed rate is 40mm / s, and the single-piece thickness is 0.22mm; double-sided fine polishing is performed using 0.3μm diamond polishing fluid, the single-sided removal amount is 0.03mm, and the polishing pressure is 0.08MPa; the surface roughness Ra of the in-plane graphite-diamond-silicon carbide composite sheet is 0.35μm, the thickness uniformity error is ±6μm, and there is no edge chipping or graphitization.

[0104] Step 9: The only difference from Step 9 in Example 1 is that the volume fraction of methane to hydrogen is 5%, the deposition temperature is 950°C, the working pressure is 12 kPa, a CVD diamond layer with a thickness of 50 μm is deposited on both the upper and lower surfaces, and the cooling rate is 5°C / min.

[0105] The in-plane graphite-diamond-silicon carbide composite heat dissipation material has a vertical thermal conductivity of 920 W / (m·K), an in-plane thermal conductivity of 760 W / (m·K), a bending strength of 195 MPa, and a total thickness of 0.16 mm. It is suitable for space-constrained heat dissipation scenarios such as 3D stacked chips and ultra-thin packages.

[0106] Example 6 The difference from Example 1 lies only in the addition of the following step between steps 6 and 7: plasma etching activation of the surface layer of the in-plane graphite-diamond-silicon carbide composite sheet. The specific operation is as follows: the in-plane graphite-diamond-silicon carbide composite sheet is placed flat on a graphite stage in a CVD furnace. The furnace is sealed and evacuated to below 1 Pa, and high-purity hydrogen is used for purging twice. High-purity hydrogen is introduced, the furnace pressure is adjusted, and a microwave source is turned on to excite hydrogen plasma. The temperature is raised to the target etching temperature and held for etching. After etching, the microwave source is turned off, and the temperature is uniformly lowered to 600°C under a hydrogen atmosphere. The plasma etching activation process conditions are: etching atmosphere is high-purity hydrogen (purity ≥ 99.999%), working pressure is 10 kPa, plasma excitation power is 800 W, etching temperature is 750°C, hydrogen flow rate is 3000 sccm, and etching holding time is 10 min.

[0107] The vertical thermal conductivity (CVD diamond layer on both the upper and lower surfaces) of the in-plane graphite-diamond-silicon carbide composite heat dissipation material prepared in this embodiment is 950 W / mK.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an in-plane graphite-diamond-silicon carbide composite heat dissipation material, comprising the following steps: Graded diamond powder and binder are mixed and then subjected to pressing, degreasing and water jet cutting to form a slot array to obtain a porous diamond preform; the graded diamond powder includes coarse diamond particles with a particle size of 150~500μm, medium diamond particles with a particle size of 50~100μm and fine diamond particles with a particle size of 1~10μm. Porous graphite sheets are inserted into the slot array of the porous diamond preform to obtain a graphite-diamond composite preform; The graphite-diamond composite preform is subjected to chemical vapor infiltration to generate silicon carbide in situ, thereby obtaining an in-plane graphite-diamond-silicon carbide composite heat dissipation material.

2. The preparation method according to claim 1, characterized in that, The chemical vapor permeation process further includes: The in-plane graphite-diamond-silicon carbide composite preform obtained by chemical vapor infiltration is sliced ​​to obtain in-plane graphite-diamond-silicon carbide composite sheets. A diamond layer is formed by chemical vapor deposition on the upper surface, lower surface, or both surfaces of the in-plane graphite-diamond-silicon carbide composite sheet.

3. The preparation method according to claim 1, characterized in that, The graded diamond powder contains 55-65% coarse-grained diamond and 25-35% medium-grained diamond by mass. The holding pressure for the pressing process is 120~180MPa, and the holding time is 0.5~10min; The degreasing treatment is carried out at a temperature of 800~1200℃ for 1~20h.

4. The preparation method according to claim 1, characterized in that, The arrangement structure of the card slot array includes parallel, honeycomb, or cross-grid patterns; The conditions for waterjet cutting include: the equipment used is a CNC high-pressure abrasive waterjet cutting machine; the working water pressure is 320~380MPa, the abrasive is garnet sand, the particle size of the abrasive is 240~320 mesh, the abrasive supply rate is 0.4~0.8kg / min, and the nozzle feed speed is 20~80mm / s; The card slot array has a length of 10~200mm, a width of 0.03~0.1mm, a depth of 10~100mm, a slot spacing of 0.05~0.3mm, and a sidewall verticality of 83~86°.

5. The preparation method according to claim 1, characterized in that, The chemical vapor infiltration process conditions include: a silicon source comprising one or more of methyltrichlorosilane, silicon tetrachloride, dimethyldichlorosilane, trichlorosilane, and hexamethyldisilane, wherein the flow rate of the silicon source is 5-12 sccm; a carrier gas comprising hydrogen, wherein the flow rate of the carrier gas is 500-1200 sccm; a deposition temperature of 1100-1200℃; a deposition time of 6-15 h; and a reverse cycle of the silane-carrier gas mixture of 0.5-2 h.

6. The preparation method according to claim 2, characterized in that, The slicing includes water-guided laser slicing, and the process conditions for water-guided laser slicing include: laser wavelength of 532nm, water beam diameter of 30~80μm, cutting feed speed of 15~50mm / s, and kerf taper <0.1°.

7. The preparation method according to claim 2, characterized in that, The conditions for chemical vapor deposition include: the carbon source is methane; the carrier gas includes hydrogen; the carbon source accounts for 3-5% of the volume of the carrier gas; the deposition temperature is 830-980℃; and the working pressure is 6-20 kPa. The thickness of the diamond layer is 10~100μm.

8. The preparation method according to claim 2 or 7, characterized in that, Before chemical vapor deposition, the surface layer of the in-plane graphite-diamond-silicon carbide composite sheet is first activated by plasma etching.

9. The in-plane graphite-diamond-silicon carbide composite heat dissipation material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the in-plane graphite-diamond-silicon carbide composite heat dissipation material according to claim 9 in computing processing units, power semiconductor devices, or aerospace electronic equipment.

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