A diamond heat sink sheet and a method of manufacturing the same

Abstract

This invention relates to the field of diamond heat sinks, specifically a diamond heat sink and its preparation method, comprising: in-situ growth of a silicon carbide nanowire array on a diamond surface; sputtering a titanium carbide layer on the diamond surface using magnetron sputtering to obtain a titanium carbide / silicon carbide nanowire array composite structure; placing solder paste between the diamond and a metal sheet to form a brazed component, wherein the titanium carbide / silicon carbide nanowire array composite structure in the brazed component faces the side of the solder paste; and finally vacuum brazing. This invention has good process compatibility, is easy to realize industrial application, and effectively solves the problems of weak interface bonding, high thermal stress, and high interface thermal resistance when connecting diamond films and metals. It has important application value for heat dissipation of high-power electronic devices.

Description

Technical Field

[0001] This invention relates to the field of diamond heat sink sheets, specifically to a diamond heat sink sheet and its preparation method. Background Technology

[0002] Diamond, with its unique crystal structure and excellent physicochemical properties, is considered one of the most promising materials for high thermal conductivity. At room temperature, the thermal conductivity of synthetic diamond can reach 2000 W / (m·K), far exceeding that of traditional metals, making it a promising candidate for applications in high-power electronic devices, microwave equipment, and high-performance laser systems—fields where heat generation is critical. With the continuous increase in device power density and integration, utilizing the high thermal conductivity of diamond for heat dissipation has become a key issue in materials science and engineering.

[0003] Currently, chemical vapor deposition (CVD) is one of the mainstream methods for preparing high-quality diamond materials. This process can produce large-size, high-quality diamond materials with controllable thickness. In practical heat sink applications, diamonds are usually bonded to metals to form diamond composite sheets. The bonding state between the diamond and the metal affects the thermal conductivity and mechanical strength of the composite sheet. Currently, diamonds face two main problems in practical applications: First, the diamond surface is difficult to wet with ordinary solder, making bonding with the metal substrate challenging. Second, the solder layer itself has low thermal conductivity, resulting in high interfacial thermal resistance between the diamond and the metal substrate, affecting overall heat dissipation efficiency. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a diamond heat sink sheet and its preparation method.

[0005] The technical solution adopted is as follows: A method for preparing a diamond heat sink includes the following steps: S1: In-situ growth of silicon carbide nanowire arrays on diamond surface; S2: Titanium carbide / silicon carbide nanowire array composite structure was obtained by sputtering a titanium carbide layer on a diamond surface using magnetron sputtering. S3: Placing solder paste between diamond and metal sheet to form a brazed part, wherein the titanium carbide / silicon carbide nanowire array composite structure in the brazed part faces the side of the solder paste, and finally vacuum brazing is performed.

[0006] As a preferred embodiment of the present invention, S1 is specifically as follows: A catalytic metal layer is generated on the surface of diamond, and then the catalytic metal layer is treated with microwave plasma to obtain a catalytic metal nanoparticle layer. Finally, a silicon carbide nanowire array is prepared by vapor deposition.

[0007] In a preferred embodiment of the present invention, the catalytic metal layer is any one of iron, nickel, cobalt, gold, platinum, chromium, lanthanum, terbium, or aluminum. The choice of metal catalyst directly affects the morphology, diameter, crystal orientation, and yield of silicon carbide nanowires. Selecting a suitable catalyst in conjunction with specific process conditions (such as temperature, precursor, substrate, etc.) is key to precisely controlling the performance of nanowires.

[0008] As a preferred embodiment of the present invention, the catalytic metal layer is obtained using magnetron sputtering, electron beam evaporation, or atomic layer deposition. These methods can all form a catalytic metal layer with uniform thickness and good adhesion on the diamond surface.

[0009] In a preferred embodiment of the present invention, the plasma used for microwave plasma treatment of the catalytic metal layer is any one or a combination of two or more of hydrogen plasma, oxygen plasma, nitrogen plasma, argon plasma, and fluorine plasma. Microwave plasma treatment can "disperse" the continuous catalytic metal layer into nanoscale catalytic metal particles, which serve as nucleation centers for subsequent silicon carbide nanowire growth.

[0010] As a preferred embodiment of the present invention, the method for preparing silicon carbide nanowire arrays by vapor deposition is as follows: Diamond with a catalytic metal nanoparticle layer is placed in a vapor deposition apparatus. Under argon protection, the vapor deposition apparatus is heated to the reaction temperature at a rate of 5-10℃ / min. Then, hydrogen and silicon source gas are introduced and maintained at this temperature for 1-10 hours. After that, the hydrogen and silicon source gas are stopped, and the apparatus is allowed to cool down naturally.

[0011] In a preferred embodiment of the present invention, the silicon source gas is tetramethylsilane or tetraethylsilane, or a chlorosilane formed by replacing at least one hydrogen atom of tetramethylsilane or tetraethylsilane with a chlorine atom. Selecting a silicon source gas is a multi-objective trade-off process. Silanes are the most common choice, chlorosilanes are often used in specific industries such as polysilicon, while organosilicon sources have advantages in simplifying processes and improving specific properties (such as dielectric properties).

[0012] In a preferred embodiment of the present invention, the reaction temperature is 1150-1250°C. This temperature range covers the typical temperature window for the chemical vapor deposition growth of silicon carbide nanowires.

[0013] In a preferred embodiment of the present invention, the solder paste is composed of metal powder and organic additives, wherein the metal powder is composed of silver powder, copper powder, titanium powder, and indium powder. Silver-copper-titanium solder paste is a commonly used active solder. The titanium element in it reacts with the titanium carbide / silicon carbide nanowire array composite structure and the diamond matrix at high temperatures, forming a strong metallurgical bond. The introduction of indium can alter the microstructure of the interfacial reaction layer, resulting in a finer multilayer structure and thus a higher bonding strength between the solder and the silicon carbide nanowire array.

[0014] As a preferred embodiment of the present invention, the vacuum brazing method is as follows: first, the temperature is increased to 400-500℃ at a heating rate of 1-5℃ / min and held for 10-30 minutes; then, the temperature is increased to 760-780℃ at a heating rate of 10-20℃ / min and held for 10-30 minutes. This segmented heating and holding process helps the organic additives to volatilize and dissipate, while simultaneously allowing the solder to fully melt and complete the interfacial reaction.

[0015] The beneficial effects of this invention are: This invention provides a method for preparing a diamond heat sink sheet. By growing a silicon carbide nanowire array in situ on the diamond surface, the theoretical thermal conductivity of silicon carbide nanowires can reach up to 490 W / (m·K), and the axial thermal conductivity is excellent. The vertical array grown in situ can form a directional and continuous heat conduction channel between the diamond film and the metal, effectively reducing the thermal resistance at the interface, and forming a mechanical interlocking structure with the brazed joint to improve its mechanical strength.

[0016] Silicon carbide nanowire arrays exhibit excellent thermochemical stability, maintaining structural stability at high temperatures and resisting oxidation, graphitization, or structural collapse. Therefore, the diamond heat sink of this invention can operate for extended periods at higher temperatures, making it suitable for heat dissipation in high-power-density, high-temperature electronic devices. Furthermore, silicon carbide nanowires can withstand higher brazing temperatures, which facilitates complete solder melting and interfacial reactions, resulting in denser brazed joints.

[0017] Magnetron sputtering of titanium carbide layers can improve the bonding strength between silicon carbide nanowires and diamond films, preventing damage during subsequent brazing. Furthermore, it has good chemical compatibility with titanium in the solder paste, which helps improve the wettability of the solder and form a uniform and dense brazed joint.

[0018] Active brazing technology is used to form a transition layer between diamond and metal, which fills the gap between diamond and metal, compensates for the interfacial stress caused by the difference in the coefficients of thermal expansion between the two, alleviates stress concentration in thermal cycling through plastic deformation, improves joint strength, and prevents joint cracking.

[0019] All steps of this invention can be implemented on existing equipment, with good process compatibility and easy industrial application. By constructing a titanium carbide / silicon carbide nanowire array composite structure on the surface of a diamond film, the technical problems of weak interfacial bonding, high thermal stress, and high interfacial thermal resistance when connecting diamond films with metals are effectively solved. A diamond heat sink with both high shear strength and high thermal conductivity is obtained, which has important application value for heat dissipation of high-power electronic devices. Detailed Implementation

[0020] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters. Example 1:

[0021] A method for preparing a diamond heat sink includes the following steps: S1: A 10mm × 10mm × 0.5mm polycrystalline diamond film (prepared by MPCVD) was selected as the substrate and ground and polished to achieve a surface finish Ra of 50nm. The polycrystalline diamond film was then ultrasonically cleaned for 15 minutes each in acetone, anhydrous ethanol, and deionized water to remove surface grease and contaminants. After cleaning, the diamond film was dried with high-purity nitrogen. An iron catalytic metal layer was deposited on the surface of the cleaned diamond film using magnetron sputtering. The magnetron sputtering process parameters were: base vacuum 5 × 10⁻⁶ m² / m². -4 The sputtering pressure was 0.5 Pa, the sputtering power was 150 W, and the sputtering time was 1 min. The thickness of the resulting iron catalytic metal layer was approximately 10 nm. A diamond film with the deposited iron catalytic metal layer was placed in a microwave plasma chemical vapor deposition (CPCVD) apparatus. After vacuuming, plasma treatment was performed with the following parameters: microwave power 800 W, working gas hydrogen, gas flow rate 100 ml / min, treatment temperature 600 °C, and treatment time 5 min. Under the bombardment and reduction effects of hydrogen plasma, the continuous iron film underwent dewetting, forming uniformly distributed iron nanoparticles.

[0022] The microwave was then turned off and the room temperature was restored. The deposition chamber was evacuated, and argon gas was introduced as a protective gas at a flow rate of 200 ml / min. The equipment was then heated to 1200 °C at a rate of 8 °C / min. Hydrogen and tetramethylsilane were then introduced at flow rates of 1500 ml / min and 0.5 ml / min, respectively. The temperature was maintained at this level for 5 hours. Under the catalytic action of the iron nanoparticles, carbon and silicon atoms generated by the cracking of tetramethylsilane were deposited on the surface of the iron nanoparticles to form silicon carbide nanowires. The silicon carbide nanowires grew in a direction perpendicular to the diamond surface, forming a silicon carbide nanowire array. The introduction of hydrogen and tetramethylsilane was then stopped, and the equipment was allowed to cool naturally to room temperature.

[0023] S2: Place the diamond film with the silicon carbide nanowire array grown on it into a magnetron sputtering apparatus to sputter a titanium carbide layer. The sputtering process parameters are: base vacuum 5×10⁻⁶. -4 The working gas was high-purity argon (99.999% purity), the sputtering targets were titanium and carbon targets with 99.99% purity, the sputtering pressure was 0.5 Pa, the sputtering power was 400 W, and the sputtering time was 10 min. Finally, a titanium carbide / silicon carbide nanowire array composite structure was obtained on the diamond film surface.

[0024] S3: The solder paste used in this embodiment is AgCuInTi active solder paste, which consists of metal powder and organic additives in a mass ratio of 85:15, and by weight percentage: silver powder 59%, copper powder 22.5%, indium powder 17%, and titanium powder 1.5%. The silver powder particle size is 5-10μm, the copper powder particle size is 5-10μm, the indium powder particle size is 10-20μm, and the titanium powder particle size is 10-20μm. The organic additives consist of terpineol, ethyl cellulose, and stearic acid in a mass ratio of 90:8:2. The AgCuInTi active solder paste is obtained by thoroughly grinding the mixture using a three-roll mill. A 10mm×10mm×1mm oxygen-free copper sheet is selected as the metal substrate. The oxygen-free copper sheet is ultrasonically cleaned sequentially with acetone and anhydrous ethanol, then immersed in a 5% dilute sulfuric acid solution to remove the surface oxide layer, rinsed thoroughly with deionized water, and dried with nitrogen. The prepared AgCuInTi active solder paste was uniformly coated onto the surface of an oxygen-free copper sheet using screen printing, with a solder paste layer thickness of approximately 100 μm. The diamond film with the titanium carbide / silicon carbide nanowire array composite structure prepared in step S2 was placed on the oxygen-free copper sheet coated with solder paste, ensuring the titanium carbide / silicon carbide nanowire array composite structure faced the solder side. Gently pressing was applied to ensure good contact, and the film was clamped with a jig to form a brazed component. The assembled connector was then placed in a vacuum brazing furnace. The furnace was evacuated to a vacuum level of 5 × 10⁻⁶. -3Pa, the temperature is increased from room temperature to 450℃ at a rate of 3℃ / min, and held for 20min to allow the organic additives in the solder paste to fully volatilize and be discharged. Then, the temperature is increased to 770℃ at a rate of 15℃ / min, held for 15min, and finally cooled to room temperature with the furnace. Example 2:

[0025] The method is basically the same as in Example 1, except that in S1, a nickel catalytic metal layer is deposited on the surface of the cleaned diamond film by magnetron sputtering. Example 3:

[0026] The method is basically the same as in Example 1, except that in S1, a cobalt catalytic metal layer is deposited on the surface of the cleaned diamond film using magnetron sputtering. Example 4:

[0027] The process is basically the same as in Example 1, except that the vacuum brazing process in S3 is as follows: Place the assembled connectors into a vacuum brazing furnace and evacuate the furnace to a vacuum level of 5 × 10⁻⁶. -3 Pa, raise the temperature from room temperature to 400℃ at a rate of 1℃ / min, hold for 30min to allow the organic additives in the solder paste to fully volatilize and be discharged, then continue to raise the temperature to 780℃ at a rate of 20℃ / min, hold for 10min, and finally cool to room temperature with the furnace. Example 5:

[0028] The process is basically the same as in Example 1, except that the vacuum brazing process in S3 is as follows: Place the assembled connectors into a vacuum brazing furnace and evacuate the furnace to a vacuum level of 5 × 10⁻⁶. -3 Pa, raise the temperature from room temperature to 500℃ at a rate of 5℃ / min, hold for 10min to allow the organic additives in the solder paste to fully volatilize and be discharged, then continue to raise the temperature to 760℃ at a rate of 10℃ / min, hold for 30min, and finally cool to room temperature with the furnace.

[0029] Comparative Example 1: It is basically the same as Example 1, except that the diamond film surface does not contain the titanium carbide / silicon carbide nanowire array composite structure.

[0030] A method for preparing a diamond heat sink includes the following steps: S1: A polycrystalline diamond film with dimensions of 10mm×10mm×0.5mm (obtained by MPCVD method) was selected as the substrate and ground and polished to achieve a surface finish Ra of 50nm. The polycrystalline diamond film was then ultrasonically cleaned for 15min each in acetone, anhydrous ethanol and deionized water to remove surface grease and contaminants. The cleaned diamond film was then dried with high-purity nitrogen.

[0031] S2: The solder paste used in this comparative example is AgCuInTi active solder paste, which consists of metal powder and organic additives in a mass ratio of 85:15, and by weight percentage: silver powder 59%, copper powder 22.5%, indium powder 17%, and titanium powder 1.5%. The silver powder particle size is 5-10μm, the copper powder particle size is 5-10μm, the indium powder particle size is 10-20μm, and the titanium powder particle size is 10-20μm. The organic additives consist of terpineol, ethyl cellulose, and stearic acid in a mass ratio of 90:8:2. The AgCuInTi active solder paste is obtained by thoroughly grinding the mixture using a three-roll mill. A 10mm×10mm×1mm oxygen-free copper sheet is selected as the metal substrate. The oxygen-free copper sheet is ultrasonically cleaned sequentially with acetone and anhydrous ethanol, then immersed in a 5% dilute sulfuric acid solution to remove the surface oxide layer, rinsed thoroughly with deionized water, and dried with nitrogen. The prepared AgCuInTi active solder paste was uniformly coated onto the surface of an oxygen-free copper sheet using screen printing, with a paste layer thickness of approximately 100 μm. The diamond film from step S1 was placed on the solder paste-coated oxygen-free copper sheet, gently pressed to ensure good contact, and clamped with a jig to form a brazed component. The assembled connector was then placed in a vacuum brazing furnace. A vacuum was evacuated to a furnace vacuum level of 5 × 10⁻⁶. -3 Pa, the temperature is increased from room temperature to 450℃ at a rate of 3℃ / min, and held for 20min to allow the organic additives in the solder paste to fully volatilize and be discharged. Then, the temperature is increased to 770℃ at a rate of 15℃ / min, held for 15min, and finally cooled to room temperature with the furnace.

[0032] Comparative Example 2: It is basically the same as Example 1, except that the diamond film surface does not contain silicon carbide nanowire arrays.

[0033] A method for preparing a diamond heat sink includes the following steps: S1: A polycrystalline diamond film with dimensions of 10mm×10mm×0.5mm (obtained by MPCVD method) was selected as the substrate and ground and polished to achieve a surface finish Ra of 50nm. The polycrystalline diamond film was then ultrasonically cleaned for 15min each in acetone, anhydrous ethanol and deionized water to remove surface grease and contaminants. The cleaned diamond film was then dried with high-purity nitrogen.

[0034] S2: Place the diamond film into a magnetron sputtering apparatus to sputter a titanium carbide layer. The sputtering process parameters are: background vacuum 5×10⁻⁶. -4 The working gas was high-purity argon (99.999% purity), the sputtering targets were titanium and carbon targets with 99.99% purity, the sputtering pressure was 0.5 Pa, the sputtering power was 400 W, and the sputtering time was 10 min. Finally, a titanium carbide layer was obtained on the surface of the diamond film.

[0035] S3: The solder paste used in this comparative example is AgCuInTi active solder paste, which consists of metal powder and organic additives in a mass ratio of 85:15, and by weight percentage: silver powder 59%, copper powder 22.5%, indium powder 17%, and titanium powder 1.5%. The silver powder particle size is 5-10μm, the copper powder particle size is 5-10μm, the indium powder particle size is 10-20μm, and the titanium powder particle size is 10-20μm. The organic additives consist of terpineol, ethyl cellulose, and stearic acid in a mass ratio of 90:8:2. The AgCuInTi active solder paste is obtained by thoroughly grinding the mixture using a three-roll mill. A 10mm×10mm×1mm oxygen-free copper sheet is selected as the metal substrate. The oxygen-free copper sheet is ultrasonically cleaned sequentially with acetone and anhydrous ethanol, then immersed in a 5% dilute sulfuric acid solution to remove the surface oxide layer, rinsed thoroughly with deionized water, and dried with nitrogen. The prepared AgCuInTi active solder paste was uniformly coated onto the surface of an oxygen-free copper sheet using screen printing, with a solder paste layer thickness of approximately 100 μm. The diamond film prepared in step S2 was placed on the oxygen-free copper sheet coated with solder paste, with the titanium carbide layer facing the solder side. Gently pressing was applied to ensure good contact, and the piece was clamped using a jig to form a brazed component. The assembled connector was then placed in a vacuum brazing furnace. The furnace was evacuated to a vacuum level of 5 × 10⁻⁶. -3 Pa, the temperature is increased from room temperature to 450℃ at a rate of 3℃ / min, and held for 20min to allow the organic additives in the solder paste to fully volatilize and be discharged. Then, the temperature is increased to 770℃ at a rate of 15℃ / min, held for 15min, and finally cooled to room temperature with the furnace.

[0036] Comparative Example 3: It is basically the same as Example 1, except that the diamond film surface does not contain titanium carbide.

[0037] A method for preparing a diamond heat sink includes the following steps: S1: A 10mm × 10mm × 0.5mm polycrystalline diamond film (prepared by MPCVD) was selected as the substrate and ground and polished to achieve a surface finish Ra of 50nm. The polycrystalline diamond film was then ultrasonically cleaned for 15 minutes each in acetone, anhydrous ethanol, and deionized water to remove surface grease and contaminants. After cleaning, the diamond film was dried with high-purity nitrogen. An iron catalytic metal layer was deposited on the surface of the cleaned diamond film using magnetron sputtering. The magnetron sputtering process parameters were: base vacuum 5 × 10⁻⁶ m² / m². -4The sputtering pressure was 0.5 Pa, the sputtering power was 150 W, and the sputtering time was 1 min. The thickness of the resulting iron catalytic metal layer was approximately 10 nm. A diamond film with the deposited iron catalytic metal layer was placed in a microwave plasma chemical vapor deposition (CPCVD) apparatus. After vacuuming, plasma treatment was performed with the following parameters: microwave power 800 W, working gas hydrogen, gas flow rate 100 ml / min, treatment temperature 600 °C, and treatment time 5 min. Under the bombardment and reduction effects of hydrogen plasma, the continuous iron film underwent dewetting, forming uniformly distributed iron nanoparticles.

[0038] The microwave was then turned off and the room temperature was restored. The deposition chamber was evacuated, and argon gas was introduced as a protective gas at a flow rate of 200 ml / min. The equipment was then heated to 1200 °C at a rate of 8 °C / min. Hydrogen and tetramethylsilane were then introduced at flow rates of 1500 ml / min and 0.5 ml / min, respectively. The temperature was maintained at this level for 5 hours. Under the catalytic action of the iron nanoparticles, carbon and silicon atoms generated by the cracking of tetramethylsilane were deposited on the surface of the iron nanoparticles to form silicon carbide nanowires. The silicon carbide nanowires grew in a direction perpendicular to the diamond surface, forming a silicon carbide nanowire array. The introduction of hydrogen and tetramethylsilane was then stopped, and the equipment was allowed to cool naturally to room temperature.

[0039] S2: The solder paste used in this embodiment is AgCuInTi active solder paste, which consists of metal powder and organic additives in a mass ratio of 85:15, and by weight percentage: silver powder 59%, copper powder 22.5%, indium powder 17%, and titanium powder 1.5%. The silver powder particle size is 5-10μm, the copper powder particle size is 5-10μm, the indium powder particle size is 10-20μm, and the titanium powder particle size is 10-20μm. The organic additives consist of terpineol, ethyl cellulose, and stearic acid in a mass ratio of 90:8:2. The AgCuInTi active solder paste is obtained by thoroughly grinding the mixture using a three-roll mill. An oxygen-free copper sheet with dimensions of 10mm × 10mm × 1mm is selected as the metal substrate. The oxygen-free copper sheet is ultrasonically cleaned sequentially with acetone and anhydrous ethanol, then immersed in a 5% dilute sulfuric acid solution to remove the surface oxide layer, rinsed thoroughly with deionized water, and dried with nitrogen. The prepared AgCuInTi active solder paste was uniformly coated onto the surface of an oxygen-free copper sheet using screen printing, with a solder paste layer thickness of approximately 100 μm. The diamond film with a silicon carbide nanowire array prepared in step S1 was placed on the oxygen-free copper sheet coated with solder paste, ensuring the titanium carbide / silicon carbide nanowire array composite structure faced the solder side. Gently pressing was applied to ensure good contact, and the assembly was clamped to form a brazed joint. The assembled joint was then placed in a vacuum brazing furnace. The furnace was evacuated to a vacuum level of 5 × 10⁻⁶. -3Pa, the temperature is increased from room temperature to 450℃ at a rate of 3℃ / min, and held for 20min to allow the organic additives in the solder paste to fully volatilize and be discharged. Then, the temperature is increased to 770℃ at a rate of 15℃ / min, held for 15min, and finally cooled to room temperature with the furnace.

[0040] Comparative Example 4: The comparison example is basically the same as Example 1, except that the active solder paste does not contain indium powder, that is, the solder paste used in this comparison example is AgCuTi active solder paste.

[0041] Performance testing Samples for performance testing were prepared according to the methods in Examples 1-5 and Comparative Examples 1-4 of the present invention.

[0042] The room temperature shear strength of the brazed joint of the specimen was determined using an electronic universal testing machine. The specimen was fixed on the testing machine with a special fixture and shear test was performed at a loading rate of 0.5 mm / min. The maximum failure load was recorded and the shear strength was calculated.

[0043] The thermal diffusivity of the brazed joint was tested using a laser flare meter (NETSCH-LFA 467HT).

[0044] The results of the above performance tests are shown in Table 1 below: As shown in Table 1, the technical solution of the present invention effectively solves the technical problems of weak interfacial bonding, high thermal stress, and high interfacial thermal resistance when diamond films are connected to metals by constructing a titanium carbide / silicon carbide nanowire array composite structure on the surface of diamond films. This results in a diamond heat sink with both high shear strength and high thermal conductivity, which has important application value for heat dissipation of high-power electronic devices.

[0045] Examples 2 (nickel catalyst layer) and 3 (cobalt catalyst layer) are basically the same as Example 1 (iron catalyst layer) in terms of process, except for the catalytic metal. Nickel and cobalt have slightly lower catalytic activity for silicon carbide nanowire growth than iron. Therefore, the quality of the silicon carbide nanowire array (such as orientation, density, and degree of graphitization) may be slightly worse, resulting in slightly weaker mechanical interlocking with the solder and thermal conductivity compared to the iron catalytic system. Consequently, the shear strength and thermal diffusivity are slightly lower than in Example 1.

[0046] Comparative Example 1 (Titanium Carbide / Silicon Carbide Nanowire Array Composite Structure): No intermediate layer was present on the diamond surface; AgCuInTi solder was directly brazed to the diamond. Due to poor interfacial bonding between the diamond and the metal solder and high thermal resistance, the shear strength and thermal diffusivity were significantly lower than in the Example.

[0047] Comparative Example 2 (Titanium carbide layer only, no silicon carbide nanowire array): The interface is chemically bonded only by titanium carbide, lacking the mechanical anchoring and three-dimensional thermally conductive network of silicon carbide nanowire array. The performance is significantly lower than that of Example 1, but still better than Comparative Example 1 which has no intermediate layer at all.

[0048] Comparative Example 3 (Silicon carbide nanowire array only, without titanium carbide layer): The interface lacks titanium carbide transition. The residual iron catalyst used in the growth of silicon carbide nanowire array may affect the brazing interface. Although silicon carbide nanowire array still has a certain mechanical anchoring and three-dimensional thermal conductive network effect, its performance is significantly lower than that of Example 1, but it is still better than Comparative Example 1 which has no intermediate layer at all.

[0049] Comparative Example 4 (solder paste is AgCuTi, without In): The absence of In reduces wettability and interfacial reactivity, and the performance is significantly lower than that of Example 1.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a diamond heat sink sheet, characterized in that, include: S1: In-situ growth of silicon carbide nanowire arrays on diamond surface; S2: Titanium carbide / silicon carbide nanowire array composite structure was obtained by sputtering a titanium carbide layer on a diamond surface using magnetron sputtering. S3: Placing solder paste between diamond and metal sheet to form a brazed part, wherein the titanium carbide / silicon carbide nanowire array composite structure in the brazed part faces the side of the solder paste, and finally vacuum brazing is performed.

2. The method for preparing a diamond heat sink sheet as described in claim 1, characterized in that, S1 is as follows: A catalytic metal layer is generated on the diamond surface, and then the catalytic metal layer is treated with microwave plasma to obtain a catalytic metal nanoparticle layer. Finally, a silicon carbide nanowire array is prepared by vapor deposition.

3. The method for preparing a diamond heat sink sheet as described in claim 2, characterized in that, The catalytic metal layer is any one of iron, nickel, cobalt, gold, platinum, chromium, lanthanum, terbium, or aluminum.

4. The method for preparing a diamond heat sink sheet as described in claim 2, characterized in that, The catalytic metal layer was obtained using magnetron sputtering, electron beam evaporation, or atomic layer deposition.

5. The method for preparing a diamond heat sink sheet as described in claim 2, characterized in that, The method for preparing silicon carbide nanowire arrays by vapor deposition is as follows: Diamond with a catalytic metal nanoparticle layer is placed in a vapor deposition apparatus. Under argon protection, the vapor deposition apparatus is heated to the reaction temperature at a rate of 5-10℃ / min. Then, hydrogen and silicon source gas are introduced and maintained at this temperature for 1-10 hours. After that, the hydrogen and silicon source gas are stopped, and the apparatus is allowed to cool down naturally.

6. The method for preparing a diamond heat sink sheet as described in claim 5, characterized in that, The silicon source gas is tetramethylsilane or tetraethylsilane, or a chlorosilane formed by replacing at least one hydrogen atom of tetramethylsilane or tetraethylsilane with a chlorine atom.

7. The method for preparing a diamond heat sink sheet as described in claim 5, characterized in that, The reaction temperature is 1150-1250℃.

8. The method for preparing a diamond heat sink sheet as described in claim 1, characterized in that, The solder paste is composed of metal powder and organic additives, wherein the metal powder is composed of silver powder, copper powder, titanium powder and indium powder.

9. The method for preparing a diamond heat sink sheet as described in claim 1, characterized in that, The vacuum brazing method is as follows: First, heat the temperature to 400-500℃ at a heating rate of 1-5℃ / min and hold for 10-30 minutes. Then, heat the temperature to 760-780℃ at a heating rate of 10-20℃ / min and hold for 10-30 minutes.

10. A diamond heat sink sheet, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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