Graphene surface modified SiC high-thermal-conductivity substrate

Abstract

The invention provides a preparation method of a graphene surface modified SiC high thermal conductivity substrate. The method comprises the following steps: 1, selecting a high-purity SiC and graphene material support body; wherein both the SiC and the graphene are small cubes with the size of 5mm * 5mm * 5mm, the contact surface of the SiC and the brazing filler metal is mechanically polished, and the surface roughness Ra value after polishing is in the range of 0.2-0.5 mu m. And cleaning the surfaces of SiC and graphene by using an ultrasonic cleaning solution, and removing oil stains, oxides and other impurities. The cleaning time is 10-40 minutes, and the temperature is controlled between 20 DEG C and 70 DEG C. And secondly, a sandwich structure is assembled according to the base metal / brazing filler metal foil / base metal structure, and a to-be-welded piece is obtained. The assembled sample is put into a vacuum brazing furnace, brazing circulation starts from 20 DEG C, the temperature is increased to 400 DEG C to 500 DEG C at the speed of 10 DEG C / min, and then the temperature is increased to the target temperature interval of 800 DEG C to 1000 DEG C at the speed of 10 DEG C / min. And after the temperature reaches a target temperature interval, preserving heat for 10 minutes, and cooling to room temperature along with the furnace. And an innovative technical path is provided for research and development of the multifunctional heat management substrate.

Description

Technical Field

[0001] This invention relates to a method for preparing a graphene-modified SiC high thermal conductivity substrate, specifically addressing the problem of rapidly increasing current density in compact high-power electronic devices. This research provides a novel solution by proposing a thermal conductivity enhancement method based on atomic-level bonding optimization at the SiC / graphene heterostructure interface. This addresses the difficulties in interface bonding and poor process adaptability, as well as how to ensure the graphene layer can fully exert its heat dissipation enhancement effect. This method improves the overall thermal conductivity of the heat sink, opening up new avenues for developing multifunctional thermal management substrates. Background Technology

[0002] Currently, compact, high-power electronic devices are causing a sharp increase in current density, with localized heat loads reaching 3-5 times that of traditional devices, severely reducing operational reliability and exposing small-sized chips to a high risk of thermal failure. Graphene, with its excellent thermal conductivity, has become an ideal material choice for high-performance heat dissipation applications. Regarding graphene bonding, existing methods mostly employ physical lamination or polymer bonding, but these technologies suffer from high interfacial thermal resistance and low bonding strength. Notably, research on the interfacial bonding between graphene and silicon carbide is still relatively lacking, particularly regarding whether graphene can effectively enhance heat dissipation and its specific mechanisms of action, which remain key scientific questions requiring systematic research and theoretical explanation. To address these issues, this study proposes the following approach: Analyzing the interfacial behavior of graphene and silicon carbide, it was discovered that the nanoscale transition structure formed at the junction through interfacial bonding technology can achieve atomic-level tight bonding with the substrates on both sides. During the research, it was unexpectedly discovered that under specific process conditions (840℃ / 10min), a nanoscale transition structure and other thermally conductive phases formed at the interface, and the interfacial chemical reaction formed atomic-level bonding, effectively promoting in-plane high-frequency phonon coupling and significantly reducing the phonon scattering probability, thus achieving near-unimpeded phonon transmission. This anomalous phenomenon challenges existing interfacial heat transfer theories. By utilizing graphene to functionalize the surface of silicon carbide heat dissipation substrates, a new approach has been opened for the development of multifunctional thermal management substrates. Methods: 1. High-purity SiC and graphene materials were selected as supports. Both SiC and graphene were small cubes with dimensions of 5mm*5mm*5mm. The contact surfaces of SiC and solder were mechanically polished, and the surface roughness Ra value after polishing should be controlled within the range of 0.2-0.5μm. Ultrasonic cleaning fluid was used to clean the surfaces of SiC and graphene to remove oil, oxides, and other impurities. The cleaning process lasted 10-40min, and the temperature was controlled between 20-70℃. II. Then, assemble the substrate / brazing foil / substrate structure into a sandwich structure to obtain the component to be welded. III. Brazing process: Place the assembled sample into a vacuum brazing furnace. The brazing cycle starts at 20°C, heating to 400°C at a rate of 10°C / min, and then increasing the temperature to the target temperature range at a rate of 5°C / min. After reaching the target temperature range, hold at that temperature for 10 minutes and then cool to room temperature with the furnace. The brazing method of this invention can effectively reduce the interfacial thermal resistance, allowing the graphene layer to fully exert its heat dissipation enhancement effect, rapidly dissipating heat from the heat sink surface, thereby significantly improving the overall thermal management performance of the integrated component. Summary of the Invention

[0003] This invention aims to address the difficulties in bonding graphene and silicon carbide heterostructures using traditional methods, and to solve the problem of how to fully utilize the heat dissipation enhancement effect of the graphene layer to significantly improve the overall thermal conductivity of integrated components. It provides a method for preparing a graphene-modified SiC high thermal conductivity substrate, which significantly improves interfacial heat transfer efficiency. It is accomplished through the following steps:

[0004] I. Pre-treatment of experimental materials:

[0005] (1) Select high-purity SiC and graphene materials as supports. Both SiC and graphene are small cubes with dimensions of 5mm*5mm*5mm. Mechanically grind the contact surfaces of SiC and the solder, ensuring the surface roughness Ra value is controlled within the range of 0.2-0.5μm. Use ultrasonic cleaning fluid to clean the surfaces of SiC and graphene, removing oil, oxides, and other impurities. The cleaning process lasts 10-40 minutes, with the temperature controlled between 20-70℃.

[0006] (2) Then, assemble the base material / solder foil / base material structure into a sandwich structure to obtain the workpiece to be welded.

[0007] II. Brazing process:

[0008] (1) The brazing process cycle starts at 20°C, heats up to 400°C at a rate of 10°C / min, and then heats up to the target temperature range at a rate of 5°C / min.

[0009] (2) After the temperature reaches the target temperature range, keep it at that temperature for 10 minutes and then cool it down to room temperature with the furnace.

[0010] The beneficial effects of this invention are:

[0011] (1) This study successfully achieved efficient bonding between graphene and SiC: Compared with many previous interface connection methods that failed to form effective chemical bonds, by optimizing the interface connection process, a stable atomic-level chemical bond was established between the two for the first time, thereby significantly improving the interface heat transfer performance.

[0012] (2) Combining experimental and theoretical research, the optimal thermal conductivity (vertical direction) of the heat sink prepared in the experiment reached 201.59 W·m. -1 ·K -1 It is about 40% higher than that of unmodified silicon carbide; the peak heating rate reaches 1.8℃ / s, which is nearly 300% higher than that of unmodified silicon carbide.

[0013] (3) Therefore, the nanoscale transition structure formed at the junction can achieve atomic-level tight bonding with the substrates on both sides. This structure effectively promotes in-plane high-frequency phonon coupling through stable interatomic bonding, significantly reduces the phonon scattering probability, and thus achieves almost unimpeded phonon transmission.

[0014] (4) This method has made a breakthrough in the field of graphene-silicon carbide interface connection, which has not been systematically explored before, and solved the key problem of synergistic optimization of graphene-SiC interface bonding and heat transfer. It reveals that the interface phonon coupling and heat transport channel construction are the inherent laws of graphene's effectiveness in enhancing heat dissipation, and at the same time confirms the feasibility of this interface connection strategy in the actual thermal management application of SiC heat dissipation substrates, opening up a new way for the development of multifunctional thermal management substrates. Attached Figure Description

[0015] Figure 1 like Figure 1 As shown in figure a, this study employs a thermal conductivity enhancement method based on atomic-level bonding optimization of the SiC / graphene heterostructure interface. Using SEM / EDS characterization techniques, the microstructure evolution of the solder / substrate interface, the formation kinetics of the reaction layer, and the formation mechanism of intermetallic compounds such as TiC were systematically investigated. Notably, under optimized process conditions, a nanoscale transition structure (…) was formed at the interface. Figure 1 b) It established atomic-level bonding with the substrates on both sides. Figure 1 c). This structure significantly promotes high-frequency phonon coupling in the in-plane direction ( Figure 1 d) This improves the overall heat transfer efficiency. The optimal composite material exhibits 201.59 W·m -1 ·K -1 The brazed structure exhibits superior thermal conductivity, significantly improved compared to traditional physical bonding and polymer adhesive methods. Furthermore, it demonstrates excellent heat dissipation performance, with cooling efficiencies 18.2% and 40.0% higher than those of the thermal grease-bonded sample and the air-gap reference sample, respectively. These outstanding properties highlight its broad application prospects in advanced thermal management systems. Figure 2 To achieve brazing at lower temperatures (800℃ and 820℃), Figure 2 (ab) The joint exhibits obvious poor bonding characteristics: discontinuous areas exist at the interface, the solder does not adequately wet the substrate, and incompletely melted solder particles are visible in some areas. When the temperature rises to 840℃ ( Figure 2 At temperature c), the solder completely melts, forming a dense and uniform interface. Particularly noteworthy is that at this temperature, the solder exhibits perfect spreading and coverage of the graphene matrix, resulting in an optimized interface structure with regular geometry and minimal defects. When the temperature is further increased to 860℃ ( Figure 2In step d), the brazing filler metal overheats, resulting in irregular joint morphology and a significant decrease in interface bonding quality.

[0016] Figure 3 The in-plane thermal conductivity test results, used to assess sample performance, show that this study focused on analyzing the thermal properties of samples prepared using three different process parameters: 820℃ (sample 1), 840℃ (sample 2), and 860℃ (sample 3). Thermophysical characterization revealed that the measured densities of samples 1-3 were 3.963 g / cm³. 3 3.503 g / cm 3 and 3.653 g / cm 3 ( Figure 3 a) The corresponding thermal diffusivity is 97.86 mm. 2 / s, 95.88mm 2 / s and 88.39mm 2 / s( Figure 3 b). The specific heat capacities of samples 1-3 were determined to be 0.51 J / (kg·K), 0.61 J / (kg·K), and 0.53 J / (kg·K), respectively, through testing. Figure 3 d). According to Fourier's law of thermal conductivity, the in-plane thermal conductivity of samples 1-3 was calculated to be 198.26 W / (m·K), 201.59 W / (m·K), and 170.23 W / (m·K), respectively. Figure 3 c). Experimental results show that the brazed sample at 840℃ (sample 2) exhibits the best overall performance, thanks to its specific heat capacity (0.61 J / (kg·K)) and density (3.503 g / cm³). 3 ) and thermal diffusivity (95.88 mm) 2 A synergistic effect of / s) was achieved, resulting in a thermal conductivity of 201.59 W / (m·K). Experimental results show that sample 2, prepared by brazing at 840℃, exhibits the best overall performance. This is attributed to its specific heat capacity (0.61 J / (kg·K)) and density (3.503 g / cm³). 3 ) and thermal diffusivity (95.88 mm) 2 Through the synergistic effect of brazing parameters, this sample achieved an excellent thermal conductivity of 201.59 W / (m·K), a significant improvement over samples prepared under other process conditions. This performance improvement is mainly attributed to the dense microstructure and optimized interfacial bonding state formed under these process parameters, which effectively reduced phonon scattering and enhanced heat transfer efficiency. This result provides important process optimization guidance for the preparation of high-performance heat dissipation materials for electronic devices, highlighting the crucial role of precise control of brazing parameters in improving the thermophysical properties of composite materials.

[0017] Figure 4The results are from temperature testing and infrared thermal imaging analysis. This study evaluated the thermal performance of three different sample configurations (optimal welded sample, thermal grease-bonded sample, and air-gap sample). Figure 4 (d) shows that the optimal welded sample consistently exhibited the highest heating rate during the first 20 seconds of the heating phase, reaching a peak heating rate of approximately 1.8 °C / s, especially after the initial acceleration process. Its excellent thermal conductivity is a key factor in achieving superior heating performance. Simultaneously, the heating curves indicate that all three samples reached a stable surface peak temperature of 68 °C. Notably, this temperature range is highly consistent with the peak temperatures measured under the same heating conditions for independent monolayer graphene films. This consistency in thermal behavior suggests that the graphene layer likely plays a dominant role in thermal regulation within the composite structure, with its superior in-plane thermal conductivity promoting rapid and uniform heat distribution, ultimately leading to temperature convergence under different structural configurations. In the heating-cooling cycle test, infrared thermal imaging was used to capture the thermal distribution characteristics of the three sample configurations, and the experimental results are as follows: Figure 4 As shown in (b) and 4(c), a systematic heating and cooling test was conducted on a series of samples with different interface structures. Sample a exhibited the darkest color and the fastest temperature drop during both the heating and cooling phases. Initially (t = 0 s), the surface temperature field of all samples was uniformly distributed (average temperature 29.0 °C), consistent with the ambient temperature of the laboratory. After heating started, the optimal welded sample exhibited excellent thermal response characteristics at t = 3 s, with its central region brightness value significantly higher than other samples (corresponding temperature 49.2 °C). By t = 5 s, the welded sample reached its highest temperature of 55.1 °C, while the thermal grease-bonded sample and the air gap sample reached 49.2 °C and 48.3 °C, respectively. The welded sample reached thermal equilibrium at t = 18 s and maintained a stable maximum temperature of 68.2 °C. In contrast, the thermal grease-bonded sample and the air gap sample reached their peak temperatures at 22 s and 30 s, respectively.

[0018] During the cooling phase, the optimized welded sample again exhibited the highest cooling rate, with surface brightness decreasing to 47.6% of its initial value at t=180s. At t=270s, the surface temperature of the welded sample stabilized at 29.5℃, with negligible difference (<0.5℃) from the ambient temperature (29℃). Meanwhile, the air gap sample and the thermal grease-bonded sample maintained residual temperatures of 30.2℃ and 31.2℃, respectively, at the same time. The superior heating and cooling response characteristics of the optimal welded sample were evaluated using a constant power heating test system (primarily focusing on dynamic heating characteristics and thermal equilibrium state). Its thermal equilibrium temperature stage, as a key indicator for evaluating heat dissipation performance, directly reflects the long-term thermal stability of the material under actual working conditions.

[0019] Figure 4(e) shows a comparative XRD analysis of the original monolayer graphene and the optimally welded sample. The XRD results show that the intensity changes of the carbon-related diffraction peaks of the two groups of samples are highly consistent, indicating that the atomic-level bonding process did not cause significant damage to the graphene crystal structure. Figure 4 XRD characterization results in (f) indicate that the atomic-level bonding layer of the optimal weld joint mainly consists of Ag, Cu, C, and Ti phases, with Ag-C and Ag-Ti compounds present. Significant interdiffusion of elements was observed at the interface between the solder and the substrate. In the weld region, the synergistic effect of Ag, Cu, and Ti effectively eliminates the microstructural discontinuities at the graphene-solder interface. This multi-component interface engineering strategy successfully reduces the concentration of interface defects, significantly suppresses the adverse effects of contact thermal resistance, and thus optimizes the thermal conductivity of the heterojunction interface. The characterization results further show that the phase evolution mechanism during the atomic-level bonding process is mainly attributed to the directional segregation and reaction behavior of Ti—Ti preferentially reacts with graphene to form a stable Ti-C transition layer, significantly enhancing the interfacial bonding strength.

[0020] This performance improvement stems from a triple mechanism: first, the formation of the brazed joint effectively reduces contact thermal resistance; second, optimized process temperature ensures a uniform and dense interfacial reaction layer; and third, the intrinsic thermal conductivity of the metal brazing filler metal is significantly higher than that of organic adhesives and air. These findings provide important experimental evidence for selecting high thermal conductivity joining processes.

[0021] As can be seen, during the thermal cycling test, this study used infrared thermal imaging technology to analyze the thermal field of three typical interface structures: (1) a sample with an air gap intermediate layer, (2) a silicone grease bonded assembly, and (3) an optimized welded sample. The systematic heating and cooling test revealed that during the heating stage, the optimized welded sample showed a rapid response in 3 seconds (49.2℃ in the central area). The welded sample reached 55.1℃ in 5 seconds, which was significantly higher than that of the silicone grease bonded assembly (49.2℃) and the air gap sample (48.3℃). The welded sample reached thermal equilibrium first in 20 seconds. During the cooling stage, the thermal radiation intensity of the welded sample dropped to 47.6% of the initial value in 180 seconds, and the surface temperature stabilized at 29.5℃ in 270 seconds (temperature difference from the environment <0.5℃). In contrast, the comparative sample showed obvious thermal hysteresis (30.2℃ for the air gap and 31.2℃ for the silicone grease). The optimized welded sample showed a significant advantage in dynamic response. Detailed Implementation

[0022] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments. Specific implementation method one:

[0024] I. Pre-treatment of experimental materials:

[0025] (1) Select high-purity SiC and graphene materials as supports. Both SiC and graphene are small cubes with dimensions of 5mm*5mm*5mm. Mechanically grind the contact surfaces of SiC and the solder, ensuring the surface roughness Ra value is controlled within the range of 0.2-0.5μm. Use ultrasonic cleaning fluid to clean the surfaces of SiC and graphene, removing oil, oxides, and other impurities. The cleaning process lasts 10-40 minutes, with the temperature controlled between 20-70℃.

[0026] (2) Then, assemble the base material / solder foil / base material structure into a sandwich structure to obtain the workpiece to be welded.

[0027] II. Brazing process:

[0028] (1) Place the assembled sample into a vacuum brazing furnace. The brazing cycle starts at 20°C and heats to 400°C at a rate of 10°C / min. Then, the temperature is increased to the target temperature range at a rate of 5°C / min.

[0029] (2) After the temperature reaches the target temperature range, keep it at that temperature for 10 minutes and then cool it down to room temperature with the furnace.

[0030] The beneficial effects of this embodiment are:

[0031] 1. To ensure the strength of the brazed joint, the surface of the welding area must have sufficient roughness to promote the wetting and adhesion of the solder. Surface treatment with a Ra value in the range of 0.2-0.5μm can ensure good wettability while avoiding uneven solder flow caused by excessive surface roughness.

[0032] 2. Establish a three-stage ultrasonic cleaning process of ethanol → acetone → deionized water to reduce the content of surface contaminants, which plays a crucial role in the brazing process.

[0033] 3. The gradient heating program uses a three-stage temperature control curve: room temperature → 400℃ (10℃ / min) to ensure gradual stress release; 400℃ → target temperature to precisely control the interface reaction target temperature.

[0034] 4. Precise control of surface roughness is achieved by using a multi-stage diamond grinding disc (800-3000 grit) gradient grinding process.

[0035] 5. Welding in a vacuum environment prevents oxides in the air from contaminating the welding area, ensuring the purity of the joint. Vacuum level setting (5×10⁻⁶) -3 A suitable vacuum time (10 min) helps the solder to fully fill the composite layer and achieve good wetting.

[0036] 6. The use of a base material / brazing foil / base material structure enables uniform temperature distribution and effective stress release under thermo-mechanical synergistic control.

[0037] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the material dimensions in step one (1) are as follows: both SiC and graphene are small cubes with dimensions of 10mm*10mm*10mm. Everything else is the same as in Specific Implementation Method One.

[0038] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: the cleaning process in step 1 (1) lasts for 10-15 minutes, and the temperature is controlled between 35-40℃. The rest is the same as Specific Implementation Method 1 to 2.

[0039] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the brazing cycle starts at 20°C and heats up to the target temperature range of 800-860°C at a rate of 5°C / min. The rest is the same as Specific Implementation Methods One to Three.

[0040] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: when heating to the target temperature range of 800-860℃ at a rate of 10℃ / min, it is held at 600℃ for 10 minutes. Everything else is the same as Specific Implementation Methods One to Four.

[0041] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the temperature is increased to 400°C at a rate of 10°C / min, and then increased to the target temperature range at a rate of 10°C / min. Otherwise, it is the same as Specific Implementation Methods One to Five.

[0042] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: after the temperature reaches the target temperature range in step two (2), it is kept at that temperature for 50 minutes and then cooled to room temperature with the furnace. The rest is the same as Specific Implementation Methods One to Six.

[0043] The beneficial effects of the present invention are verified using the following embodiments:

[0044] Example 1:

[0045] A method for preparing a graphene-modified SiC high thermal conductivity substrate, comprising the following steps:

[0046] I. Pre-treatment of experimental materials:

[0047] (1) Select high-purity SiC and graphene materials as supports. Both SiC and graphene are small cubes with dimensions of 5mm*5mm*5mm. Mechanically grind the contact surfaces of SiC and the solder, ensuring the surface roughness Ra value is controlled within the range of 0.2-0.5μm. Use ultrasonic cleaning fluid to clean the surfaces of SiC and graphene, removing oil, oxides, and other impurities. The cleaning process lasts 10-40 minutes, with the temperature controlled between 20-70℃.

[0048] (2) Then, assemble the base material / solder foil / base material structure into a sandwich structure to obtain the workpiece to be welded.

[0049] II. Brazing process:

[0050] (1) Place the assembled sample into a vacuum brazing furnace. The brazing cycle starts at 20°C and heats to 400°C at a rate of 10°C / min. Then, the temperature is increased to the target temperature range at a rate of 5°C / min.

[0051] (2) After the temperature reaches the target temperature range, keep it at that temperature for 10 minutes and then cool it down to room temperature with the furnace.

[0052] In step 1, the material dimensions are as follows: both iC and graphene are small cubes with dimensions of 5mm*5mm*5mm;

[0053] Step 1: Mechanically grind the contact surface between SiC and Al / SiC. The surface roughness Ra value after grinding should be controlled within the range of 0.2-0.5μm.

[0054] Step 1: The cleaning process lasts for 10-15 minutes, with the temperature controlled between 25-30℃.

[0055] In step 1.2, the components are assembled into a sandwich structure according to the base material / solder foil / base material structure to obtain the workpiece to be welded.

[0056] Step 2: The assembled sample is placed in a vacuum brazing furnace. The brazing cycle starts at 20°C and is heated to 400°C at a rate of 10°C / min. Then, the temperature is increased to the target temperature range at a rate of 5°C / min.

[0057] After the temperature reaches the target temperature range in step 2, keep it at that temperature for 10 minutes and then cool it to room temperature with the furnace.

[0058] Figure 2The results of the temperature rise test to examine the sample performance show that this study evaluated the thermal performance of the brazed joint using a constant power heating experimental system, focusing on the dynamic heating characteristics and thermal equilibrium state—with the equilibrium temperature phase serving as a key indicator for evaluating heat dissipation performance, as it directly reflects the long-term thermal stability of the material under actual working conditions. The sample prepared at the optimized brazing temperature of 840℃ exhibited superior comprehensive thermal performance. Compared to the glued sample and the air gap sample, this sample showed the fastest heating rate in the dynamic heating test, attributed to its enhanced heat transfer capacity, enabling the system to reach the target temperature more quickly under the same heating conditions. This performance improvement stems from a three-pronged mechanism: firstly, the formation of the brazed joint effectively reduces the contact thermal resistance (measured value 1.2 × 10⁻⁶). -9 m 2 Firstly, optimized process temperature ensured a uniform and dense interfacial reaction layer (HRTEM showed a 2-3 nm thick TiC transition layer). Secondly, the intrinsic thermal conductivity of the metal solder (150 nm mean electron free path for Ag-Cu solid solution) was significantly higher than that of organic adhesives and air. These findings provide important experimental evidence for selecting high thermal conductivity bonding processes, and the underlying mechanisms will be further elucidated through subsequent microstructure characterization.

[0059] Figure 3 The results are shown in the infrared thermal imaging analysis. It can be seen that during the thermal cycling test, this study used infrared thermal imaging technology to analyze the thermal field of three typical interface structures: (1) the sample with an air gap intermediate layer, (2) the silicone grease bonded assembly, and (3) the optimized welded sample. The systematic heating and cooling test revealed that during the heating stage, the optimized welded sample showed a rapid response in 3 seconds (49.2℃ in the central area). The welded sample reached 55.1℃ in 5 seconds, which was significantly higher than that of the silicone grease bonded assembly (49.2℃) and the air gap sample (48.3℃). The welded sample reached thermal equilibrium first in 20 seconds. During the cooling stage, the thermal radiation intensity of the welded sample dropped to 47.6% of the initial value in 180 seconds, and the surface temperature stabilized at 29.5℃ in 270 seconds (temperature difference from the environment <0.5℃). In contrast, the comparison sample showed obvious thermal hysteresis (30.2℃ for the air gap and 31.2℃ for the silicone grease). The optimized welded sample showed a significant advantage in dynamic response.

Claims

1. A method for preparing a graphene-modified SiC high thermal conductivity substrate, characterized in that... It was accomplished in the following ways: I. Pre-treatment of experimental materials: (1) Select high-purity SiC and graphene materials as supports. Both SiC and graphene are small cubes with dimensions of 5mm*5mm*5mm. The contact surfaces of SiC and solder are mechanically polished, and the surface roughness Ra value after polishing should be controlled within the range of 0.2-0.5μm. Use ultrasonic cleaning fluid to clean the surfaces of SiC and graphene, removing oil, oxides, and other impurities. The cleaning process lasts 10-40 minutes, and the temperature is controlled between 20-70℃. (2) Then, assemble the base material / solder foil / base material structure into a sandwich structure to obtain the workpiece to be welded. II. Brazing process: (1) The brazing process cycle starts at 20°C and heats up to about 400°C to 500°C at a rate of 10°C / min. Then, it is heated up to the target temperature range of 800-1000°C at a rate of 10°C / min. (2) After the temperature reaches the target temperature range, keep it at that temperature for 10 minutes and then cool it down to room temperature with the furnace.

2. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: The material dimensions in step one (1) are as follows: SiC and graphene are both small cubes with dimensions of 5mm*5mm*5mm.

3. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: Step 1 (1) Mechanically grind the contact surface between SiC and the solder. The surface roughness Ra value after grinding should be controlled within the range of 0.2-0.5μm.

4. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: Step 1 (1) The cleaning process lasts for 10-40 minutes, and the temperature is controlled between 20-70℃.

5. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: Step 1 (2) Assemble the base material / brazing foil / base material into a sandwich structure to obtain the workpiece to be welded.

6. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: Step 2 (1) The brazing cycle starts at 20°C and heats up to the target temperature range of 800-860°C at a rate of 10°C / min.

7. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: The vacuum level of the vacuum environment described in step two (1) is 10. -1 Pa~10 -4 Pa.

8. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: In step 2 (1), when heating to the target temperature range of 800-860℃ at a rate of 10℃ / min, hold at 400℃ for 10min.

9. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: In step 2 (1), the temperature is increased to 400°C at a rate of 10°C / min, and then increased to the target temperature range at a rate of 5°C / min.

10. The vacuum furnace brazing method for connecting SiC and graphene materials based on AgCuTi solder as an intermediate layer according to claim 1, characterized in that: After the temperature reaches the target temperature range in step 2 (2), keep it at that temperature for 20 minutes and then cool it to room temperature with the furnace.

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