Silicon carbide seed crystal bonding floating pressure plate and bonding method

Abstract

The invention relates to a silicon carbide seed crystal bonding floating pressure plate and a bonding method, and belongs to the technical field of seed crystal production, the silicon carbide seed crystal bonding floating pressure plate comprises a fixedly arranged lower graphite pressure plate, a first floating graphite pressure plate is arranged right above the lower graphite pressure plate, and the upper surface of the first floating graphite pressure plate is connected with an upper graphite fixing cylinder through a first connecting assembly; the lower surface of the first floating graphite pressure plate is connected with a second floating graphite pressure plate through a second connecting assembly, the first connecting assembly and the second connecting assembly are each composed of a plurality of graphite knuckle bearings arranged in a line, each graphite knuckle bearing is of a one-way swing structure, and the first connecting assembly and the second connecting assembly are arranged in a cross shape. The first floating graphite pressure plate can swing back and forth, the second floating graphite pressure plate can swing left and right, real-time compensation is carried out through self-adaptive swing of the two stages of floating pressure plates, it is ensured that the pressure plates are always tightly attached to the surface of the seed crystal, and pressure borne by all areas of the seed crystal in the pressurizing process is kept consistent.

Description

Technical Field

[0001] This invention relates to the field of seed crystal production technology, and in particular to a silicon carbide seed crystal bonding floating pressure plate and bonding method. Background Technology

[0002] Silicon carbide crystal is a compound semiconductor material composed of silicon and carbon in a 1:1 stoichiometric ratio. It has characteristics such as a large bandgap and a high critical breakdown field strength, making it an ideal material for manufacturing high-frequency, high-power, radiation-resistant, and light-resistant integrated devices. It is currently widely used in new energy vehicles, 5G communications, aerospace and other fields.

[0003] Currently, most silicon carbide crystals are grown using the liquid phase method. This method involves mixing silicon and carbon sources in stoichiometric or non-stoichiometric ratios and then subjecting the raw materials to a silicon-based molten liquid phase under high temperature and pressure conditions. Carbon elements dissolve in this liquid phase and reach a supersaturated state. Subsequently, using SiC seed crystals as the growth substrate, the Si-C atomic clusters dissolved in the liquid phase are deposited in an orderly manner on the surface of the seed crystal according to the crystal lattice orientation by controlling the temperature gradient and cooling rate, thus completing the crystal growth.

[0004] The initial step of the liquid phase method requires seed crystal bonding. During the pressurization and heating process, pressure is applied by placing a pressure plate on the seed crystal. During the coating and scraping of adhesive, uneven coating is very likely to occur, resulting in an uneven seed crystal surface. Furthermore, due to the non-parallelism or poor flatness of the upper and lower pressure plates caused by assembly or processing, insufficient pressure will result in uneven stress on the seed crystal surface, reducing the growth quality of silicon carbide. Summary of the Invention

[0005] To address the technical problems mentioned in the background section, this invention provides a floating pressure plate and bonding method for bonding silicon carbide seed crystals. The floating graphite pressure plate can better adapt to the non-parallelism of the upper and lower pressure plates caused by uneven processing or adhesive coating by swinging, thereby improving the growth quality of silicon carbide.

[0006] The technical solution of this invention is as follows: This invention provides a silicon carbide seed crystal bonding floating pressure plate, including a fixedly arranged lower graphite pressure plate, a first floating graphite pressure plate located directly above the lower graphite pressure plate, an upper graphite fixing cylinder connected to the upper surface of the first floating graphite pressure plate via a first connecting component, and a second floating graphite pressure plate connected to the lower surface of the first floating graphite pressure plate via a second connecting component. Both the first and second connecting components are composed of several graphite spherical bearings arranged in a straight line, the graphite spherical bearings having a unidirectional swing structure, and the first and second connecting components are arranged in a cross shape. The cross-shaped arrangement of the first and second connecting components, combined with the unidirectional oscillation characteristics of the graphite spherical bearing, allows the first floating graphite pressure plate to oscillate in the front-to-back direction, and the second floating graphite pressure plate to oscillate in the left-to-right direction. When there are problems such as uneven seed crystal surface caused by uneven adhesive coating, or non-parallelism or insufficient flatness of the upper and lower pressure plates due to assembly and processing, the adaptive oscillation of the two-stage floating pressure plates can provide real-time compensation, ensuring that the pressure plate and the seed crystal surface are always in close contact, and ensuring that the pressure on each area of ​​the seed crystal is consistent during the pressurization process, providing a uniform and stable force foundation for the subsequent growth of silicon carbide crystals.

[0007] Preferably, the graphite spherical bearing includes an outer ring and an inner ring. A bushing is fixedly installed inside the outer ring, and the inner ring rotatably resides within the bushing. A connecting shaft is fixedly connected to the inner ring, which in turn connects to a corresponding first or second floating graphite pressure plate. The bushing provides stable rotational support for the inner ring, reducing direct frictional loss between the inner and outer rings. The connecting shaft ensures a secure connection between the inner ring and the floating graphite pressure plate, guaranteeing precise transmission of oscillating forces and thus ensuring uniform pressure application to the seed crystal.

[0008] Preferably, two limiting parts are fixedly provided on the outer wall of the inner ring. The limiting parts are arranged circumferentially and are positioned opposite each other on both sides of the center of the inner ring. The limiting parts can limit the axial movement of the inner ring, prevent the inner ring from being displaced due to axial force during pressurization, ensure that the inner ring always swings unidirectionally within a preset radial range, maintain the coaxiality of the overall structure of the graphite spherical bearing, prevent axial displacement from affecting the bonding accuracy between the pressure plate and the seed crystal, and thus ensure the uniformity of force on the surface of the seed crystal.

[0009] Preferably, two limiting grooves are provided on the inner wall of the bushing along its circumference, and the limiting part is inserted into the limiting groove. This not only restricts the axial movement of the inner ring, but also provides guidance for the unidirectional swing of the inner ring, allowing the inner ring to rotate flexibly only along the extension direction of the limiting groove, preventing axial movement and deviation in non-target directions, ensuring that the swing adjustment of the first and second floating graphite pressure plates is stable and controllable, and improving the stability and accuracy of the seed crystal pressurization process.

[0010] Preferably, the outer wall of the inner ring is provided with a first groove and a second groove along the circumferential direction. The first groove is located at the middle of the outer wall of the inner ring, and a second groove is provided on each side of the first groove. The first and second grooves can reduce the contact area between the inner ring and the bushing, reduce the frictional resistance during the swing process, and make the inner ring rotate more flexibly and smoothly. At the same time, the grooves can store a small amount of graphite debris generated during the swing process, preventing debris accumulation from affecting the swing accuracy. They can also provide a buffer space for thermal expansion under high temperature conditions, preventing the structure from jamming due to thermal expansion and contraction.

[0011] Preferably, the second groove is close to the limiting part, and the second groove is located on the side of the limiting part close to the first groove. It can store a small amount of graphite debris generated during the swinging process, which can not only prevent the debris from falling off and contaminating the bonding interface, but also form a debris lubrication layer to reduce the coefficient of friction of the spherical surface.

[0012] Preferably, a first mounting seat is fixedly provided on the outer wall of the outer ring, and the first mounting seat has a plurality of first mounting holes; a connecting member is fixedly provided on the upper surface of both the first floating graphite pressure plate and the second floating graphite pressure plate, the connecting member including a second mounting seat, an ear fixedly provided on the second mounting seat, and a plurality of second mounting holes, the ear being fixedly connected to the connecting shaft. The first mounting seat and the second mounting seat provide a stable mounting structure for the connection between the graphite spherical bearing and the upper graphite fixed cylinder and the floating graphite pressure plate, the first mounting holes and the second mounting holes facilitate quick assembly and disassembly, and the fixed connection between the ear and the connecting shaft ensures the reliability of power transmission, allowing the swing adjustment of the floating pressure plate to respond promptly.

[0013] An adhesive bonding method, comprising: The silicon carbide seed crystals were subjected to gradient cleaning and drying. Mix graphite powder, silicon carbide micro powder and coupling agent evenly, add phenolic resin and stir; add anhydrous ethanol to the mixture, adjust the solid-liquid ratio to 1:0.8, and continue stirring until a uniform paste binder is formed. The adhesive is evenly coated on the upper surface of the lower graphite pressure plate, and the treated silicon carbide seed crystal is placed on the adhesive coating. The lower surface of the second floating graphite pressure plate is brought into contact with the upper surface of the silicon carbide seed crystal. The axial pressure is slowly increased and maintained. During the pressurization process, the first floating graphite pressure plate is adjusted by swinging back and forth through the first connecting component, and the second floating graphite pressure plate is adjusted by swinging left and right through the second connecting component. Transfer to a curing oven and cure in stages by increasing the temperature.

[0014] Gradient cleaning removes organic contaminants, oxide layers, and impurities from the seed crystal surface, ensuring a clean bonding interface between the seed crystal and the binder. A specially formulated binder, with graphite powder and silicon carbide micropowder components whose thermal expansion coefficients match those of the seed crystal and graphite pressure plate, along with a coupling agent, enhances the bonding strength of each component. During pressurization, the bidirectional oscillation of the two-stage floating pressure plate adaptively compensates for errors caused by uneven adhesive application and non-parallelism of the pressure plates, ensuring uniform stress on the seed crystal surface. Segmented heating and curing then form a dense and high-strength graphitized adhesive layer, significantly improving the strength and stability of the seed crystal bond and providing a high-quality seed crystal substrate for silicon carbide crystal growth.

[0015] Preferably, the gradient cleaning process for silicon carbide seed crystals is as follows: the seed crystals are sequentially immersed in acetone and ethanol solutions for ultrasonic cleaning for 15 minutes each, then immersed in hydrofluoric acid solution for 5 minutes, and finally rinsed with deionized water until neutral. Ultrasonic cleaning with acetone and ethanol effectively removes organic oil and residual impurities from the seed crystal surface. Hydrofluoric acid solution precisely peels off the surface oxide layer, preventing the oxide layer from affecting the bonding effect between the adhesive and the seed crystal. Rinsing with deionized water until neutral prevents residual acid from corroding the seed crystal or affecting the adhesive performance. The entire gradient cleaning process is gradual, ensuring that the seed crystal surface reaches a clean and impurity-free state, providing good interface conditions for subsequent bonding.

[0016] Preferably, the segmented heating and curing process is as follows: First stage: Heat from room temperature to 150℃ at a rate of 5℃ / min and hold for 2 hours to remove low-boiling-point components such as anhydrous ethanol from the adhesive. Second stage: Continue to heat to 300℃ at a rate of 3℃ / min, and hold for 3 hours to promote the cross-linking reaction of phenolic resin and form a preliminary adhesive structure. The third stage involves heating to 600℃ at a rate of 2℃ / min and holding for 4 hours to carbonize the phenolic resin and form a graphitized adhesive layer, thereby enhancing the bonding strength and high-temperature stability.

[0017] The segmented heating method avoids the rapid volatilization of low-boiling-point components in the adhesive, which can cause bubbles due to excessively rapid heating, or the stress generated at the bonding interface due to sudden temperature changes. The first stage thoroughly removes volatile components, the second stage allows the phenolic resin to fully crosslink and form a stable preliminary bonding structure, and the third stage forms a graphitized bonding layer through carbonization. This not only significantly improves the bonding strength but also gives the bonding layer excellent high-temperature stability and thermal conductivity, making it suitable for the high-temperature conditions of subsequent silicon carbide crystal growth. At the same time, it reduces defects at the bonding interface and ensures the quality of crystal growth.

[0018] As can be seen from the above technical solutions, the advantages of the present invention are: 1. The cross-shaped arrangement of the first and second connecting components, combined with the unidirectional swing characteristics of the graphite spherical bearing, allows the first floating graphite pressure plate to swing back and forth, and the second floating graphite pressure plate to swing left and right. When there are uneven seed crystal surfaces due to uneven adhesive coating, or problems such as non-parallelism or insufficient flatness of the upper and lower pressure plates due to assembly and processing, the adaptive swing of the two-stage floating pressure plates can provide real-time compensation, ensuring that the pressure plate and the seed crystal surface are always in close contact, and that the pressure on each area of ​​the seed crystal is consistent during the pressurization process, providing a uniform and stable force foundation for the subsequent growth of silicon carbide crystals.

[0019] 2. Gradient cleaning removes organic contaminants, oxide layers, and impurities from the seed crystal surface, ensuring a clean bonding interface between the seed crystal and the binder. The binder, formulated with a special formula, has graphite powder and silicon carbide micro-powder components whose thermal expansion coefficients match those of the seed crystal and graphite pressure plate. A coupling agent enhances the bonding strength of each component. During pressurization, the bidirectional oscillation of the two-stage floating pressure plate adaptively compensates for errors caused by uneven adhesive application and non-parallelism of the pressure plates, ensuring uniform stress on the seed crystal surface. Segmented heating and curing then form a dense and high-strength graphitized adhesive layer, significantly improving the strength and stability of the seed crystal bond and providing a high-quality seed crystal substrate for silicon carbide crystal growth. Attached Figure Description

[0020] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of the silicon carbide seed crystal bonding floating pressure plate according to one or more embodiments of the present invention. Figure 2 This is a schematic diagram of the structure of a graphite spherical bearing according to one or more embodiments of the present invention; Figure 3 This is a schematic diagram of the inner ring structure according to one or more embodiments of the present invention; Figure 4 This is a cross-sectional structural schematic diagram of the bushing according to one or more embodiments of the present invention; Figure 5 This is a schematic diagram of the connector according to one or more embodiments of the present invention; Figure 6 This is a cross-sectional schematic diagram of the lower graphite pressure plate according to one or more embodiments of the present invention; The components represented by the various reference numerals in the diagram are: 1. Upper graphite fixing cylinder; 2. First connecting assembly; 3. First floating graphite pressure plate; 4. Second connecting assembly; 5. Second floating graphite pressure plate; 6. Lower graphite pressure plate; 7. Outer ring; 8. Bushing; 9. Inner ring; 10. First mounting base; 11. First mounting hole; 12. Limiting part; 13. First groove; 14. Second groove; 15. Limiting groove; 16. Connecting piece; 17. Second mounting base; 18. Second mounting hole; 19. Ear; 20. Connecting shaft; 21. Silicon carbide seed crystal; 22. Lower graphite fixing cylinder. Detailed Implementation

[0022] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.

[0023] Example 1 In a typical embodiment of the present invention, such as Figures 1-6 As shown, a silicon carbide seed crystal bonding floating pressure plate is proposed, comprising: an upper graphite fixing cylinder 1, a first connecting assembly 2, a first floating graphite pressure plate 3, a second connecting assembly 4, a second floating graphite pressure plate 5, and a lower graphite pressure plate 6. The top end of the upper graphite fixing cylinder 1 is provided with an internal thread for connection to a moving mechanism via a threaded connection. The first floating graphite pressure plate 3 is located directly below the upper graphite fixing cylinder 1, and the second floating graphite pressure plate 5 is located directly below the first floating graphite pressure plate 3. The bottom of the upper graphite fixing cylinder 1 is connected to the first floating graphite pressure plate 3 via the first connecting assembly 2. Next, the bottom of the first floating graphite pressure plate 3 is connected to the second floating graphite pressure plate 5 through the second connecting component 4. The first connecting component 2 and the second connecting component 4 are both composed of several graphite spherical bearings arranged in a straight line. The graphite spherical bearings are unidirectional swing structures. The first connecting component 2 and the second connecting component 4 are arranged in a cross shape, so that the swing directions of the two rows of graphite spherical bearings are perpendicular. The lower graphite pressure plate 6 is fixedly set on the worktable, and the lower graphite pressure plate 6 is located directly below the second floating graphite pressure plate 5. The silicon carbide seed crystal 21 is placed on the upper surface of the lower graphite pressure plate 6.

[0024] In this embodiment, the first floating graphite pressure plate 3 can swing back and forth under the action of the first connecting component 2, and the second floating graphite pressure plate 5 can swing left and right under the action of the second connecting component 4. The swinging of the floating graphite pressure plate can better adapt to the situation where the upper and lower pressure plates are not parallel due to uneven processing, assembly or glue application, so that the silicon carbide seed crystal surface is uniformly pressed and the growth quality of silicon carbide is improved.

[0025] It is important to note that graphite spherical bearings cannot use universal joint structures. Universal joint structures have unnecessary movements such as rotation around the axis and tilting, which can not only cause the stress point of the seed crystal to shift (excessive or insufficient local pressure), but also disrupt the heat transfer uniformity of the graphite pressure plate. In addition, the contact points are usually point contact or small surface contact, which can easily lead to local stress concentration under high temperature and high pressure environments, resulting in spherical wear and deformation, which in turn affects the oscillation accuracy of the pressure plate and disrupts the uniformity of the seed crystal pressure.

[0026] like Figure 2 As shown, the graphite spherical bearing includes an outer ring 7, a bushing 8, and an inner ring 9. The outer ring 7 is fixed in position by bolts. The bushing 8 is fixedly installed inside the outer ring 7. The inner ring 9 is rotatably installed inside the bushing 8. The inner ring 9 is fixedly connected to a connecting shaft 20, so as to connect with the corresponding first floating graphite pressure plate 3 or second floating graphite pressure plate 5 through the connecting shaft 20.

[0027] In this embodiment, the bushing 8 and the outer ring 7 are fixed by an interference fit or a key connection to limit the relative rotation between them. Similarly, the inner ring 9 and the connecting shaft 20 are connected by an interference fit or a key connection. The bushing 8 can be replaced as needed, which effectively extends the service life of the graphite spherical bearing.

[0028] A first mounting base 10 is fixedly provided on the outer wall of the outer ring 7. The first mounting base 10 has several first mounting holes 11. The first mounting holes 11 are used for bolt installation, so that the first mounting base 10 is fixedly installed on the bottom of the upper graphite fixing cylinder 1 or the first floating graphite pressure plate 3 by bolt fixing.

[0029] like Figure 3 As shown, two limiting parts 12 are fixedly provided on the outer wall of the inner ring 9. The limiting parts 12 are arranged along the circumferential direction, and the two limiting parts 12 are arranged opposite to each other on both sides of the center of the inner ring 9. The limiting parts 12 are inserted into the bushing 8 and slidably connected with the bushing 8 to limit the movement of the inner ring 9 along the axial direction. A first groove 13 and a second groove 14 are provided on the outer wall of the inner ring 9. There is one first groove 13 and two second grooves 14. Both the first groove 13 and the second groove 14 are arranged along the circumferential direction. The first groove 13 is located at the middle position of the outer wall of the inner ring 9. The two second grooves 14 are distributed opposite to each other on both sides of the first groove 13. The second grooves 14 are close to the limiting parts 12 and are located on the side of the limiting parts 12 that are close to the first groove 13. The first groove 13 and the second groove 14 can store a small amount of graphite debris generated during the swinging process, which not only prevents the debris from falling off and contaminating the bonding interface, but also forms a debris lubrication layer to reduce the coefficient of spherical friction.

[0030] like Figure 4As shown, two limiting grooves 15 are provided on the inner wall of the bushing 8 along its circumference. The two limiting grooves 15 are arranged opposite to each other on both sides of the center of the bushing 8. The limiting grooves 15 correspond one-to-one with the limiting parts 12. The limiting parts 12 are inserted into the limiting grooves 15 and are slidably connected to the limiting grooves 15 so as to restrict the axial movement of the inner ring 9 through the cooperation of the limiting parts 12 and the limiting grooves 15.

[0031] In this embodiment, the edge cross-section of the limiting part 12 is semi-circular, and the corresponding cross-sectional shape of the limiting groove 15 matches that of the limiting part 12.

[0032] Both the upper surfaces of the first floating graphite pressure plate 3 and the second floating graphite pressure plate 5 are fixedly provided with connecting parts 16, so as to connect with the corresponding graphite spherical bearings through the connecting parts 16 and the connecting shaft 20. Figure 5 As shown, the connector 16 includes a second mounting base 17 and ears 19. There are two ears 19, which are fixedly disposed on the second mounting base 17. The second mounting base 17 has several second mounting holes 18 for bolt installation. The second mounting base 17 is fixedly connected to the corresponding first floating graphite pressure plate 3 or second floating graphite pressure plate 5 by bolt connection. The ears 19 are used for the installation of the connecting shaft 20.

[0033] In this embodiment, one ear 19 has a through hole and the other ear 19 has a threaded hole. The connecting shaft 20 passes through the through hole and is connected to the threaded hole by a threaded connection, thereby realizing the fixed connection between the connecting shaft 20 and the connecting member 16. The connecting shaft 20 is fixedly connected to the inner ring 9 by an interference fit or by a keyway on the connecting shaft 20.

[0034] The lower graphite pressure plate 6 is a fixed pressure plate, which also serves to conduct heat and provide a high-temperature environment, such as... Figure 6 As shown, a lower graphite pressure plate 6 is fixedly connected to a lower graphite fixing cylinder 22 at its bottom. The lower graphite fixing cylinder 22 has an internal thread, which is used to fix it to the worktable through a threaded connection, thereby fixing the position of the lower graphite pressure plate 6.

[0035] Example 2 In another typical embodiment of the present invention, an bonding method is provided for bonding silicon carbide seed crystals, comprising: Step 1: Pretreatment of the bonding device All graphite components were purged with high-purity argon gas to remove dust, oil and other impurities; all graphite components were then placed in a vacuum oven and dried for 2 hours at 120°C and a vacuum of ≤10Pa to remove surface moisture.

[0036] Step 2: Pretreatment of silicon carbide seed crystals Select 4H-SiC single crystal seed crystals with a size of 50-200mm and a thickness of 3-5mm. Use a metallographic microscope to screen seed crystals with no cracks, scratches, or impurities on the surface, and require a surface roughness Ra≤0.5μm.

[0037] The seed crystal was subjected to gradient cleaning, sequentially immersed in acetone and then ethanol solutions for 15 minutes each, using ultrasonic cleaning to remove organic contaminants from the surface. Next, the seed crystal was immersed in a 10% hydrofluoric acid solution for 5 minutes to remove the surface oxide layer. Finally, a solution with a resistivity ≥18 MΩ was used. Rinse the seed crystal surface with deionized water until neutral, i.e., pH=6.5-7.5; finally, place the seed crystal in a vacuum oven and dry it for 1 hour at 80℃ and vacuum degree ≤10Pa for later use.

[0038] Step 3: Preparation of adhesive Based on mass fractions, 60 parts of graphite powder, 30 parts of phenolic resin, 8 parts of silicon carbide micro powder, and 2 parts of coupling agent (KH-550) were selected. Among them, the particle size of graphite powder was 1-3μm and the purity was ≥99.99%, the softening point of phenolic resin was 80-100℃, and the particle size of silicon carbide micro powder was 0.5-1μm and was isomorphous with the seed crystal.

[0039] Graphite powder, silicon carbide micro powder and coupling agent are mixed evenly, phenolic resin is added and stirred for 15 minutes; anhydrous ethanol is added to the mixture to adjust the solid-liquid ratio to 1:0.8, and stirring is continued for 30 minutes until a uniform paste binder is formed. Let stand for 10 minutes to eliminate the air bubbles generated during stirring. The binder in this embodiment has a thermal expansion coefficient that matches that of graphite and silicon carbide after curing, no volatile pollutants at high temperature, and a bonding strength ≥8MPa.

[0040] Step 4: Applying adhesive and positioning the seed crystal The prepared adhesive is uniformly coated on the upper surface of the lower graphite pressure plate 6. The coating thickness is controlled to be 0.1-0.15mm, and the coating area is slightly larger than the bottom surface area of ​​the seed crystal, that is, the coating area extends 2-5mm beyond the edge of the seed crystal on one side. During the coating process, the scraper is kept moving at a uniform speed and scraped in the same direction. If air bubbles are found, they should be punctured with a needle tip and smoothed to ensure that the adhesive coating is free of pores and accumulation.

[0041] The pretreated silicon carbide seed crystal is placed stably on the adhesive coating, ensuring that the center of the seed crystal is aligned with the center of the lower graphite pressure plate 6, and that the distance between the edge of the seed crystal and the edge of the lower graphite pressure plate 6 is uniform, so as to avoid uneven local stress caused by seed crystal displacement.

[0042] Step 5: Floating Adaptive Pressure The height of the upper graphite fixing cylinder 1 is adjusted by the moving mechanism so that the lower surface of the second floating graphite pressure plate 5 contacts the upper surface of the seed crystal. The initial pressure is controlled at ≤0.5kN to avoid excessive initial pressure squeezing the adhesive and causing uneven coating thickness.

[0043] Initiate the pressurization process and slowly increase the axial pressure to 5-15kN. The axial pressure is adjusted according to the seed crystal size: 50mm seed crystal pressure is 5-8kN, and 200mm seed crystal pressure is 12-15kN. Hold the pressure for 5 minutes. During the pressurization process, the first floating graphite pressure plate 3 swings back and forth through the graphite spherical bearing of the first connecting component 2, and the second floating graphite pressure plate 5 swings left and right through the graphite spherical bearing of the second connecting component 4. This adaptively compensates for uneven glue application and non-parallelism caused by pressure plate processing and assembly errors, ensuring uniform pressure distribution on the seed crystal surface.

[0044] Step 6: Segmented heating and curing While maintaining the pressure, move the entire bonding device into the curing oven and cure it using a staged heating process: First stage: Heat from room temperature to 150℃ at a rate of 5℃ / min and hold for 2 hours to remove low-boiling-point components such as anhydrous ethanol from the adhesive. Second stage: Continue to heat to 300℃ at a rate of 3℃ / min, and hold for 3 hours to promote the cross-linking reaction of phenolic resin and form a preliminary adhesive structure. The third stage involves heating to 600℃ at a rate of 2℃ / min and holding for 4 hours to carbonize the phenolic resin and form a graphitized adhesive layer, thereby enhancing the bonding strength and high-temperature stability.

[0045] After curing, turn off the curing oven and allow the device to cool to room temperature with the oven at a rate of ≤4℃ / min to avoid thermal stress caused by sudden temperature changes between the seed crystal and the bonding layer. After cooling to room temperature, gradually release the pressure at a rate of 1kN / min to complete the bonding.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A silicon carbide seed crystal bonding floating pressure plate, comprising: The fixed lower graphite pressure plate (6) is characterized in that a first floating graphite pressure plate (3) is provided directly above the lower graphite pressure plate (6), the upper surface of the first floating graphite pressure plate (3) is connected to an upper graphite fixing cylinder (1) through a first connecting component (2), and the lower surface of the first floating graphite pressure plate (3) is connected to a second floating graphite pressure plate (5) through a second connecting component (4). The first connecting component (2) and the second connecting component (4) are both composed of several graphite joint bearings arranged in a straight line. The graphite joint bearings are unidirectional swing structures, and the first connecting component (2) and the second connecting component (4) are arranged in a cross shape.

2. The silicon carbide seed crystal bonding floating pressure plate according to claim 1, characterized in that, The graphite spherical bearing includes an outer ring (7) and an inner ring (9). A bushing (8) is fixedly provided inside the outer ring (7). The inner ring (9) is rotatably disposed inside the bushing (8). A connecting shaft (20) is fixedly connected to the inner ring (9). The connecting shaft (20) is connected to the corresponding first floating graphite pressure plate (3) or second floating graphite pressure plate (5).

3. The silicon carbide seed crystal bonding floating pressure plate according to claim 2, characterized in that, Two limiting parts (12) are fixedly provided on the outer wall of the inner ring (9). The limiting parts (12) are arranged along the circumferential direction and the two limiting parts (12) are arranged opposite to each other on both sides of the center of the inner ring (9).

4. The silicon carbide seed crystal bonding floating pressure plate according to claim 3, characterized in that, Two limiting grooves (15) are provided on the inner wall of the bushing (8) along its circumference, and the limiting part (12) is inserted into the limiting groove (15).

5. The silicon carbide seed crystal bonding floating pressure plate according to claim 3, characterized in that, The outer wall of the inner ring (9) is provided with a first groove (13) and a second groove (14) along the circumferential direction. The first groove (13) is located at the middle position of the outer wall of the inner ring (9), and a second groove (14) is provided on each side of the first groove (13).

6. The silicon carbide seed crystal bonding floating pressure plate according to claim 5, characterized in that, The second groove (14) is close to the limiting part (12), and the second groove (14) is located on the side of the limiting part (12) close to the first groove (13).

7. The silicon carbide seed crystal bonding floating pressure plate according to claim 2, characterized in that, A first mounting base (10) is fixedly provided on the outer wall of the outer ring (7), and a plurality of first mounting holes (11) are provided on the first mounting base (10); a connector (16) is fixedly provided on the upper surface of the first floating graphite pressure plate (3) and the second floating graphite pressure plate (5), the connector (16) includes a second mounting base (17), an ear (19) is fixedly provided on the second mounting base (17), a plurality of second mounting holes (18) are provided on the second mounting base (17), and the ear (19) is fixedly connected to the connecting shaft (20).

8. An adhesive bonding method, characterized in that, The floating pressure plate with silicon carbide seed crystal bonding as described in any one of claims 1-7 includes: The silicon carbide seed crystal (21) was subjected to gradient cleaning and drying; Mix graphite powder, silicon carbide micro powder and coupling agent evenly, add phenolic resin and stir; add anhydrous ethanol to the mixture, adjust the solid-liquid ratio to 1:0.8, and continue stirring until a uniform paste binder is formed. The adhesive is uniformly coated on the upper surface of the lower graphite pressure plate (6), and the treated silicon carbide seed crystal (21) is placed on the adhesive coating. Make the lower surface of the second floating graphite pressure plate (5) contact the upper surface of the silicon carbide seed crystal (21), slowly increase the axial pressure and hold the pressure. During the pressurization process, the first floating graphite pressure plate (3) is adjusted by swinging back and forth through the first connecting component (2), and the second floating graphite pressure plate (5) is adjusted by swinging left and right through the second connecting component (4). Transfer to a curing oven and cure in stages by increasing the temperature.

9. The bonding method according to claim 2, characterized in that, The gradient cleaning process of silicon carbide seed crystal (21) is as follows: the seed crystal is placed in acetone and ethanol solutions for ultrasonic cleaning for 15 minutes each, then the seed crystal is immersed in hydrofluoric acid solution for 5 minutes, and finally the surface of the seed crystal is rinsed with deionized water until neutral.

10. The bonding method according to claim 8, characterized in that, The segmented heating and curing process is as follows: First stage: Heat from room temperature to 150℃ at a rate of 5℃ / min and hold for 2 hours to remove low-boiling-point components such as anhydrous ethanol from the adhesive. Second stage: Continue to heat to 300℃ at a rate of 3℃ / min, and hold for 3 hours to promote the cross-linking reaction of phenolic resin and form a preliminary adhesive structure. The third stage involves heating to 600℃ at a rate of 2℃ / min and holding for 4 hours to carbonize the phenolic resin and form a graphitized adhesive layer, thereby enhancing the bonding strength and high-temperature stability.

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