Oily diamond cutting fluid for silicon carbide wafer processing and preparation method thereof

Abstract

The invention discloses an oily diamond cutting fluid for silicon carbide wafer processing and a preparation method thereof, and relates to the technical field of precision grinding processing. The invention discloses oily diamond cutting fluid for silicon carbide wafer processing. The wear-resistant diamond lubricating oil is prepared from the following raw materials in parts by weight: 50 to 65 parts of modified base oil, 15 to 25 parts of modified diamond micro powder, 5 to 10 parts of polyisobutylene succinimide, 3 to 8 parts of polyethylene glycol oleate, 2 to 5 parts of molybdenum dialkyl dithiophosphate, 0.5 to 1.5 parts of benzotriazole, 0.5 to 2.5 parts of nano silicon dioxide, 0.3 to 0.8 part of antioxidant 264 and 0.5 to 1 part of hydroxyethyl methylacrylate. And 0.2 to 0.3 part of 1-butyl-3-methylimidazole lactate. The modified diamond micro-powder and the modified base oil in the oily diamond cutting fluid have synergistic interaction, and are matched with the multi-functional auxiliaries, so that the oily diamond cutting fluid is good in dispersion stability and free of agglomeration; during cutting, the lubricating wear resistance is high, the surface damage of the silicon carbide wafer can be reduced, and the machining precision is improved; the anti-oxidation performance at high temperature is excellent, the service life is long, preparation is efficient, and practicability is high.

Description

Technical Field

[0001] This invention relates to the field of precision grinding and machining technology, specifically to an oily diamond cutting fluid for silicon carbide wafer machining and its preparation method. Background Technology

[0002] Silicon carbide, as a third-generation wide-bandgap semiconductor material, possesses outstanding advantages such as high temperature resistance, high voltage resistance, and excellent high-frequency characteristics, leading to its increasingly widespread application in high-end fields such as new energy vehicles, 5G communications, and aerospace. Wafer dicing is a critical process in the manufacturing of silicon carbide devices, requiring the precise cutting of large ingots into thin wafers. This places stringent demands on the performance of the dicing fluid—it must not only have high-efficiency cutting capabilities but also ensure lubrication, cooling, and dispersion stability to prevent defects such as edge chipping, scratches, and surface contamination on the wafers.

[0003] Currently, commonly used cutting fluids for silicon carbide wafer processing are mainly divided into two categories: water-based and oil-based. Water-based cutting fluids are more environmentally friendly, but their lubrication and anti-settling capabilities are insufficient. During the cutting process, diamond powder agglomeration easily leads to a decrease in cutting efficiency, and their protective effect on the silicon carbide surface is limited, making it difficult to meet the requirements of high-precision processing. Although oil-based cutting fluids have better lubrication and cooling effects, the compatibility of their core components (base oil and diamond powder) still has shortcomings. The base oil used in traditional oil-based cutting fluids is mostly ordinary mineral oil, which has poor low-temperature fluidity and is prone to oxidation and deterioration at high temperatures, resulting in a short service life. Diamond powder, due to its strong surface inertness, has insufficient dispersion stability in oil-based systems, easily agglomerating into large particles, exacerbating wafer surface damage, and reducing the utilization rate of the cutting edge.

[0004] Furthermore, existing oil-based cutting fluids suffer from inadequate formulation of functional additives. Some products lack targeted anti-wear and anti-oxidation components, leading to high-temperature wear during cutting and premature tool wear. Other products exhibit stratification and precipitation after long-term storage or use due to poor compatibility between the dispersant and the system, further impacting processing accuracy and consistency. As silicon carbide wafers become larger and thinner, the requirements for the dispersion stability, lubrication, anti-wear properties, oxidation resistance, and compatibility of cutting fluids continue to increase. Existing cutting fluids are insufficient to meet the manufacturing demands of high-end silicon carbide devices. Therefore, developing an oil-based diamond cutting fluid that combines high-efficiency cutting, stable dispersion, and long-lasting durability through component modification and synergistic enhancement of functional additives has become an urgent need in the silicon carbide processing field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an oily diamond cutting fluid for silicon carbide wafer processing and its preparation method, solving the problems of diamond powder agglomeration, poor base oil compatibility, insufficient lubrication and wear resistance, and low processing accuracy in existing oily diamond cutting fluids.

[0006] To achieve the above objectives, the present invention provides the following technical solution: An oil-based diamond cutting fluid for silicon carbide wafer processing comprises the following raw materials in parts by weight: 50-65 parts modified base oil, 15-25 parts modified diamond micro powder, 5-10 parts polyisobutylene succinimide, 3-8 parts polyethylene glycol oleate, 2-5 parts molybdenum dialkyl dithiophosphate, 0.5-1.5 parts benzotriazole, 0.5-2.5 parts nano silica, 0.3-0.8 parts antioxidant 264, 0.5-1 part hydroxyethyl methacrylate, and 0.2-0.3 parts 1-butyl-3-methylimidazolium lactate.

[0007] Furthermore, the nano-silica has a particle size of 20-50nm, which can accurately fill the gaps in the system. Its surface is hydrophobically modified with methyltrimethoxysilane to improve its compatibility with oily systems, avoid agglomeration, and synergistically enhance dispersion stability with polyisobutylene succinimide. At the same time, it helps to build a dense oil film, reduce wafer surface scratches, and improve processing accuracy.

[0008] Furthermore, the modified diamond micro powder is prepared using the following specific steps: A1. Take diamond micro powder, add anhydrous ethanol, and ultrasonically disperse for 30 min to form a suspension. Add 30% hydrogen peroxide solution dropwise to the suspension, heat to 60-70℃ and stir at 400-500 r / min for 2 h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Redisperse the washed product in toluene, add silane coupling agent KH-550, purge with nitrogen, heat to 85-90℃, and reflux for 4 h. After cooling to room temperature, centrifuge, wash twice with toluene and once with anhydrous ethanol, and dry the product at 80℃ to constant weight to obtain the first modified diamond micro powder. Hydrogen peroxide oxidation introduces active functional groups, and silane coupling agent KH-550 is grafted to improve compatibility with oily systems and remove impurities, laying the foundation for subsequent modification. A2. Take the first modified diamond micro powder, disperse it in deionized water, and ultrasonically disperse it for 20 min. Add sodium dodecylbenzenesulfonate and stir at 600-700 r / min to form a stable suspension. Add acrylic acid and acrylamide to the suspension, mix well, and then add 10% ammonium persulfate solution. Heat to 70-75℃ and stir at 300-400 r / min for 5 h. During the reaction, add 5% sodium hydroxide solution to adjust the pH of the system to 6.5-7.0. After the reaction, centrifuge, wash the product with water until neutral, and dry at 80℃ to constant weight to obtain the second modified diamond micro powder. Sodium dodecylbenzenesulfonate helps with dispersion, and acrylic acid and acrylamide copolymerize to form an oleophilic coating layer, which inhibits agglomeration, buffers cutting impact, and extends the service life of the micro powder. A3. Dissolve tetrabutyl titanate in anhydrous ethanol and stir until homogeneous to obtain solution A. Dissolve aluminum trichloride in anhydrous ethanol to obtain solution B. Take the second modified diamond micropowder, disperse it in anhydrous ethanol and ultrasonically disperse for 30 min. Add solution A and solution B dropwise while stirring at 500-600 r / min for 1 h. Then add deionized water dropwise while stirring at 300-400 r / min for 3 h. Then heat to 80℃ and stir for 2 h. After the reaction is complete, add 10% sodium hydroxide solution to neutralize to pH=7 and then distill to recover the ethanol. Centrifuge the reaction product, wash it three times, dry it, and place it in a muffle furnace. Calcinate it at 500-550℃ for 2 h under a nitrogen atmosphere. After cooling, place the calcined product in a vacuum drying oven and dry it at 80℃ to constant weight to obtain modified diamond micropowder. Tetrabutyl titanate and aluminum trichloride hydrolyze to form a composite oxide coating layer. High-temperature calcination enhances the hardness and wear resistance of the micropowder and consolidates the dispersion stability.

[0009] Furthermore, the ratio of diamond micro powder, anhydrous ethanol, hydrogen peroxide solution, toluene, and silane coupling agent KH-550 in A1 is 100g:300-350mL:5-6mL:250-300mL:8-10g; the particle size of the diamond micro powder is 1-3μm.

[0010] Furthermore, the ratio of the first modified diamond micro powder, deionized water, sodium dodecylbenzenesulfonate, acrylic acid, acrylamide, and ammonium persulfate solution in A2 is 100g: 400-450mL: 2-3g: 12-15g: 8-10g: 1-1.5mL.

[0011] Furthermore, the ratio of tetrabutyl titanate, anhydrous ethanol, aluminum trichloride, second-modified diamond micro powder, and deionized water in A3 is 5-6g: 335-395mL: 3-4g: 100g: 5-6mL; wherein the ratio of anhydrous ethanol used to prepare solution A, solution B, and disperse the second-modified diamond micro powder is 20-25mL: 15-20mL: 300-350mL.

[0012] Furthermore, the modified base oil is prepared using the following specific steps: B1. Take hydrotreated paraffin-based mineral oil, add a molecular sieve catalyst and pass hydrogen gas through it. Maintain a pressure of 3-4 MPa and heat to 320-350℃ for 6 hours. After the reaction, filter to remove the catalyst, cool the mineral oil to 0-5℃, add a 1:1 volume ratio of methyl ethyl ketone-toluene mixed solvent, stir at 400-500 r / min for 2 hours, and then freeze at -10℃ for 4 hours to crystallize. Filter to remove wax crystals and distill to recover the solvent. Dry the product at 80℃ to constant weight to obtain the first modified base oil. Hydrotreating optimizes the molecular structure, and freezing crystallization removes wax crystals, improving the low-temperature fluidity and purity of the base oil and avoiding increased friction during cutting. B2. Take the first modified base oil, add polyethylene wax and maleic anhydride, heat to 180-190℃ and add dicumyl peroxide, continuously purge with nitrogen for protection, and stir at 400-500 r / min for 4 h; after the reaction is completed, cool to 120-130℃, add ethanolamine and stir for 2 h, and then dry the product at 80℃ to constant weight to obtain the second modified base oil; maleic anhydride grafting introduces polar groups, ethanolamine functionalization modification improves compatibility with additives, and enhances oil film adsorption and thermal stability. B3. Take the second modified base oil, heat it to 100-110℃, add ethyl silicate, stir at 400-500 rpm for 1 hour, then add 10% (w / w) dilute hydrochloric acid for catalytic hydrolysis for 2 hours; continue to add nano-boron nitride and nano-silica to the system, ultrasonically disperse for 30 minutes, heat to 150-160℃, and stir at 800-1000 rpm for 3 hours; after cooling to room temperature, add fatty acid amide, stir at 500-600 rpm for 30 minutes to obtain the modified base oil. Ethyl silicate hydrolysis forms a siloxane cross-linked structure, with nanoparticle embedding and reinforcement, improving high-temperature oxidation resistance and shear resistance, and optimizing lubrication and heat dissipation effects.

[0013] Furthermore, the modified base oil has a kinematic viscosity of 25-35 mmHg at 40°C. 2 / s, and after modification by ethyl silicate hydrolysis, the content of nano-sized siloxane crosslinked structures in the system accounts for 1.2-1.8% of the total mass of the base oil.

[0014] Furthermore, the ratio of hydrotreated paraffin-based mineral oil, molecular sieve catalyst, and methyl ethyl ketone-toluene mixed solvent in B1 is 100g:3-4g:6-7mL.

[0015] Furthermore, the ratio of the first modified base oil, polyethylene wax, maleic anhydride, dicumyl peroxide, and ethanolamine in B2 is 100g: 4-5g: 1.6-2g: 0.2-0.3g: 1-1.2g.

[0016] Furthermore, the ratio of the second modified base oil, ethyl silicate, dilute hydrochloric acid, nano boron nitride, nano silica, and fatty acid amide in B3 is 100g: 2-2.4g: 1.6-2mL: 0.6-0.8g: 0.2-0.5g: 0.4-0.6g. Here, the nano silica is the same component as the aforementioned nano silica, and its surface is hydrophobically modified with methyltrimethoxysilane, with a particle size of 20-50nm.

[0017] A method for preparing an oil-based diamond cutting fluid for silicon carbide wafer processing specifically includes the following steps: S1. Add 50-65 parts of modified base oil to a sealed reactor equipped with a reflux condenser, start stirring, set the speed to 300 r / min, and slowly heat to 60-70℃; add 0.3-0.8 parts of antioxidant 264 and 0.5-1.5 parts of benzotriazole to the system, and continue stirring for 30 min to ensure that the additives are completely dissolved to obtain a premixed oil phase; low-speed stirring and heating work together to promote the full dissolution of antioxidants and benzotriazole, avoiding uneven dispersion of additives that would affect the antioxidant effect, and reflux condensation prevents component volatilization; S2. Add 5-10 parts of polyisobutylene succinimide and 3-8 parts of polyethylene glycol oleate sequentially to the premixed oil phase. Increase the stirring speed to 800 r / min and the temperature to 80-85℃. Turn on the reflux condenser and continue stirring for 1 hour. Then add 2-5 parts of molybdenum dialkyl dithiophosphate and stir for 30 minutes. Subsequently, add 0.5-2.5 parts of nano silica and increase the stirring speed to 1500 r / min and stir for 30 minutes. Then perform high-speed homogenization at 8000 r / min for 5 minutes. The gradient speed increase and temperature increase promote the full integration of dispersant, lubricant and anti-wear agent. High-speed homogenization breaks up nano silica agglomerates, ensuring uniform dispersion and enhancing the stability and lubrication and anti-wear performance of the system. S3. Add 15-25 parts of modified diamond micro powder to the above system in 4 batches, with an interval of 15 minutes between each batch. During the addition process, turn on 300W ultrasonic dispersion and stirring in synergy, and maintain the stirring speed at 1200 r / min. After all the modified diamond micro powder has been added, continue ultrasonic stirring for 1 hour. Lower the system temperature to 50℃, adjust the stirring speed to 500 r / min, add 0.5-1 parts of hydroxyethyl methacrylate and 0.2-0.3 parts of 1-butyl-3-methylimidazolium lactate, and continue stirring for 30 minutes to fully integrate the functional additives into the system. Cool down to 50℃ to prevent high-temperature decomposition of the additives and ensure that hydroxyethyl methacrylate and 1-butyl-3-methylimidazolium lactate fully exert their oil film strengthening effect, thereby improving lubrication and heat dissipation. S4. Transfer the above mixture to a high-pressure homogenizer with a cooling jacket, set the pressure to 30-40 MPa, and perform two homogenization processes to further refine the dispersed phase. After each homogenization, cool the mixture with 15°C cold water for 10 minutes through the cooling jacket. After homogenization, transfer the system back to the reactor and allow it to cool naturally to room temperature. S5. Filter the system cooled to room temperature using a 200-mesh stainless steel filter and collect the filtered liquid, which is the oil-based diamond cutting fluid used for silicon carbide wafer processing.

[0018] Furthermore, in S3, the modified diamond micropowder is added in batches at a gradient ratio of 40%, 30%, 20%, and 10%, and ultrasonic dispersion is performed using a dual-frequency alternating ultrasonic mode of 20kHz and 40kHz, with an alternation cycle of 5 minutes, to ensure that the micropowder forms a uniform and stable suspended dispersion phase in the system. The gradient ratio feeding reduces agglomeration caused by excessively high micropowder concentration in the initial system; the dual-frequency alternating ultrasonic mode overcomes the limitations of single-frequency ultrasonication, achieving efficient dispersion of agglomerates of different sizes, ensuring no large particle agglomerates, and guaranteeing that the diamond micropowder cutting edge fully contacts the wafer during cutting, thereby improving processing accuracy and efficiency.

[0019] This invention provides an oil-based diamond cutting fluid for silicon carbide wafer processing and its preparation method, which has the following beneficial effects: 1. This invention constructs a stable oil-based dispersion system by performing three-stage gradient modification on diamond micropowder, combined with structural optimization of the modified base oil, and using polyisobutylene succinimide dispersant and hydrophobically modified nano-silica. The preparation process employs a synergistic process of alternating dual-frequency ultrasonication and gradient feeding and stirring, effectively preventing diamond micropowder agglomeration and ensuring its uniform suspension in the system. After long-term storage or recycling, the cutting fluid exhibits no stratification or sedimentation, and the diamond cutting edge remains exposed, continuously exerting high-efficiency cutting action. This significantly reduces the processing efficiency decline caused by micropowder agglomeration and extends the service life of the cutting fluid.

[0020] 2. After hydrorefining, grafting modification, and nanoparticle composite treatment, the modified base oil possesses both excellent lubricity and shear stability. Combined with dialkyl dithiophosphate molybdenum anti-wear agent, 1-butyl-3-methylimidazolium lactate, and hydroxyethyl methacrylate compound additives, it forms a dense and wear-resistant oil film at the cutting interface. This oil film effectively reduces the coefficient of friction between diamond micron powder and silicon carbide wafers and cutting tools, reducing impact forces during cutting and preventing defects such as chipping and scratches on the wafer. Simultaneously, the excellent adhesion of the oil film quickly dissipates cutting heat, preventing high-temperature-induced wafer surface deterioration and significantly improving the surface quality and dimensional accuracy of wafer processing.

[0021] 3. This invention, through the synergistic effect of antioxidant 264 and benzotriazole, combined with the cross-linking structure of nano-siloxanes and the doping modification of nano-boron nitride in the modified base oil, endows the cutting fluid with excellent high-temperature resistance and oxidation resistance. Under the high-temperature environment generated by high-speed silicon carbide wafer cutting, the cutting fluid is not prone to oxidation, abnormal viscosity increases, or acid value increases, and can maintain stable physicochemical properties over a long period. This characteristic not only avoids processing defects caused by cutting fluid deterioration but also reduces the frequency of cutting fluid replacement, lowers processing costs, and reduces contamination of processing equipment and wafers by deterioration products, making it suitable for the stringent processing requirements of high-end silicon carbide wafers.

[0022] 4. The cutting fluid preparation process of this invention employs staged temperature and speed control stirring, combined with high-pressure homogenization and precise filtration processes, to ensure full integration of all functional components and high batch-to-batch stability of the product. The synergistic design of modified diamond micron powder and modified base oil makes it suitable for both high-efficiency cutting of large-size silicon carbide ingots and the fine processing requirements of thin wafers. Simultaneously, all additives in the formula exhibit good compatibility, release no harmful substances, do not corrode equipment during use, and facilitate subsequent processing. This cutting fluid can be applied directly without modifying existing processing equipment, significantly lowering the application threshold for enterprises and possessing broad industrial application value. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: Preparation of an oily diamond cutting fluid for silicon carbide wafer processing. The specific preparation steps are as follows: S1. Add 50 parts of modified base oil to a sealed reactor equipped with a reflux condenser, start stirring, set the speed to 300 r / min, and slowly heat to 60℃; add 0.3 parts of antioxidant 264 and 0.5 parts of benzotriazole to the system, and continue stirring for 30 min to ensure that the additives are completely dissolved, and obtain the premixed oil phase; S2. Add 5 parts of polyisobutylene succinimide and 3 parts of polyethylene glycol oleate to the premixed oil phase in sequence. Increase the stirring speed to 800 r / min and the temperature to 80℃. Turn on the reflux condenser and continue stirring for 1 hour. Then add 2 parts of molybdenum dialkyl dithiophosphate and stir for 30 min. Then add 0.5 parts of nano silica, increase the stirring speed to 1500 r / min and stir for 30 min. Then perform high-speed homogenization at 8000 r / min for 5 min. S3. Add 15 parts of modified diamond micro powder to the above system in 4 batches, with each batch added in a gradient ratio of 40%, 30%, 20%, and 10%, with an interval of 15 minutes between each batch. During the addition process, turn on 300W ultrasonic dispersion and stirring in synergy, maintain the stirring speed at 1200 r / min, and use a dual-frequency alternating ultrasonic mode of 20 kHz and 40 kHz for ultrasonic dispersion, with an alternation cycle of 5 minutes. After all the modified diamond micro powder has been added, continue ultrasonic stirring for 1 hour. Lower the system temperature to 50℃, adjust the stirring speed to 500 r / min, add 0.5 parts of hydroxyethyl methacrylate and 0.2 parts of 1-butyl-3-methylimidazolium lactate, and continue stirring for 30 minutes to fully integrate the functional additives into the system. S4. Transfer the above mixture to a high-pressure homogenizer with a cooling jacket, set the pressure to 30 MPa, and perform two homogenization processes. After each homogenization, cool the mixture with 15°C cold water for 10 minutes through the cooling jacket. After homogenization, transfer the system back to the reactor and allow it to cool naturally to room temperature. S5. Filter the system cooled to room temperature using a 200-mesh stainless steel filter and collect the filtered liquid, which is the oil-based diamond cutting fluid used for silicon carbide wafer processing.

[0025] Example 2: Preparation of an oily diamond cutting fluid for silicon carbide wafer processing. The specific preparation steps are as follows: S1. Add 65 parts of modified base oil to a sealed reactor equipped with a reflux condenser, start stirring, set the speed to 300 r / min, and slowly heat to 70℃; add 0.8 parts of antioxidant 264 and 1.5 parts of benzotriazole to the system, and continue stirring for 30 min to ensure that the additives are completely dissolved to obtain a premixed oil phase; S2. Add 10 parts of polyisobutylene succinimide and 8 parts of polyethylene glycol oleate to the premixed oil phase in sequence. Increase the stirring speed to 800 r / min and the temperature to 85℃. Turn on the reflux condenser and continue stirring for 1 hour. Then add 5 parts of molybdenum dialkyl dithiophosphate and stir for 30 min. Then add 2.5 parts of nano silica, increase the stirring speed to 1500 r / min and stir for 30 min. Then perform high-speed homogenization at 8000 r / min for 5 min. S3. Add 25 parts of modified diamond micro powder to the above system in 4 batches, with each batch added in a gradient ratio of 40%, 30%, 20%, and 10%, with an interval of 15 minutes between each batch. During the addition process, turn on 300W ultrasonic dispersion and stirring in synergy, and maintain the stirring speed at 1200 r / min. Use a dual-frequency alternating ultrasonic mode of 20 kHz and 40 kHz for ultrasonic dispersion, with an alternation cycle of 5 minutes. After all the modified diamond micro powder has been added, continue ultrasonic stirring for 1 hour. Lower the system temperature to 50℃, adjust the stirring speed to 500 r / min, add 1 part of hydroxyethyl methacrylate and 0.3 parts of 1-butyl-3-methylimidazolium lactate, and continue stirring for 30 minutes to fully integrate the functional additives into the system. S4. Transfer the above mixture to a high-pressure homogenizer with a cooling jacket, set the pressure to 40 MPa, and perform two homogenization processes. After each homogenization, cool the mixture with 15°C cold water for 10 minutes through the cooling jacket. After homogenization, transfer the system back to the reactor and allow it to cool naturally to room temperature. S5. Filter the system cooled to room temperature using a 200-mesh stainless steel filter and collect the filtered liquid, which is the oil-based diamond cutting fluid used for silicon carbide wafer processing.

[0026] Example 3: Preparation of an oily diamond cutting fluid for silicon carbide wafer processing. The specific preparation steps are as follows: S1. Add 58 parts of modified base oil to a closed reactor equipped with a reflux condenser, start stirring, set the speed to 300 r / min, and slowly heat to 65℃; add 0.5 parts of antioxidant 264 and 1 part of benzotriazole to the system, and continue stirring for 30 min to ensure that the additives are completely dissolved to obtain a premixed oil phase; S2. Add 7 parts of polyisobutylene succinimide and 5 parts of polyethylene glycol oleate to the premixed oil phase in sequence. Increase the stirring speed to 800 r / min and the temperature to 82℃. Turn on the reflux condenser and continue stirring for 1 hour. Then add 3 parts of molybdenum dialkyl dithiophosphate and stir for 30 min. Then add 1.5 parts of nano silica, increase the stirring speed to 1500 r / min and stir for 30 min. Then perform high-speed homogenization at 8000 r / min for 5 min. S3. Add 20 parts of modified diamond micro powder to the above system in 4 batches, with each batch added in a gradient ratio of 40%, 30%, 20%, and 10%, with an interval of 15 minutes between each batch. During the addition process, turn on 300W ultrasonic dispersion and stirring in synergy, and maintain the stirring speed at 1200 r / min. Use a dual-frequency alternating ultrasonic mode of 20 kHz and 40 kHz for ultrasonic dispersion, with an alternation cycle of 5 minutes. After all the modified diamond micro powder has been added, continue ultrasonic stirring for 1 hour. Lower the system temperature to 50℃, adjust the stirring speed to 500 r / min, add 0.7 parts of hydroxyethyl methacrylate and 0.25 parts of 1-butyl-3-methylimidazolium lactate, and continue stirring for 30 minutes to fully integrate the functional additives into the system. S4. Transfer the above mixture to a high-pressure homogenizer with a cooling jacket, set the pressure to 35 MPa, and perform two homogenization processes. After each homogenization, cool the mixture with 15°C cold water for 10 minutes through the cooling jacket. After homogenization, transfer the system back to the reactor and allow it to cool naturally to room temperature. S5. Filter the system cooled to room temperature using a 200-mesh stainless steel filter and collect the filtered liquid, which is the oil-based diamond cutting fluid used for silicon carbide wafer processing.

[0027] Example 4: Preparation of modified diamond micro powder. The specific preparation steps are as follows: A1. Take 100g of diamond micro powder, add 300mL of anhydrous ethanol, and ultrasonically disperse for 30min to form a suspension. Add 5mL of 30% hydrogen peroxide solution to the suspension, heat to 60℃ and stir at 400r / min for 2h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Redisperse the washed product in 250mL of toluene, add 8g of silane coupling agent KH-550, purge with nitrogen for protection, heat to 85℃ and reflux for 4h. After cooling to room temperature, centrifuge, wash twice with toluene and once with anhydrous ethanol, and dry the product at 80℃ to constant weight to obtain the first modified diamond micro powder. A2. Take 100g of the first-modified diamond micro powder, disperse it in 400mL of deionized water, and sonicate it for 20min. Add 2g of sodium dodecylbenzenesulfonate and stir at 600r / min to form a stable suspension. Add 12g of acrylic acid and 8g of acrylamide to the suspension, mix well, and then add 1mL of 10% ammonium persulfate solution. Heat the mixture to 70℃ and stir at 300r / min for 5h. During the reaction, add 5% sodium hydroxide solution to adjust the pH of the system to 6.5. After the reaction is complete, centrifuge the product, wash it with water until neutral, and dry it at 80℃ to constant weight to obtain the second-modified diamond micro powder. A3. Dissolve 5g of tetrabutyl titanate in 20mL of anhydrous ethanol and stir until homogeneous to obtain solution A. Dissolve 3g of aluminum trichloride in 15mL of anhydrous ethanol to obtain solution B. Take 100g of the second modified diamond micro powder and disperse it in 300mL of anhydrous ethanol by ultrasonic dispersion for 30min. Add solution A and solution B dropwise and stir at 500r / min for 1h. Then add 5mL of deionized water and stir at 300r / min for 3h. Then heat to 80℃ and stir for 2h. After the reaction is completed, add 10% sodium hydroxide solution to neutralize to pH=7 and then distill to recover the ethanol. Centrifuge the reaction product, wash it 3 times, dry it and place it in a muffle furnace. Calcinate it at 500℃ for 2h under a nitrogen atmosphere. After cooling the calcined product, place it in a vacuum drying oven and dry it at 80℃ to constant weight to obtain modified diamond micro powder.

[0028] Example 5: Preparation of modified diamond micro powder. The specific preparation steps are as follows: A1. Take 100g of diamond micro powder, add 350mL of anhydrous ethanol, and ultrasonically disperse for 30min to form a suspension. Add 6mL of 30% hydrogen peroxide solution to the suspension, heat to 70℃ and stir at 500r / min for 2h. After the reaction, centrifuge and wash three times with anhydrous ethanol. Redisperse the washed product in 300mL of toluene, add 10g of silane coupling agent KH-550, purge with nitrogen for protection, heat to 90℃ and reflux for 4h. After cooling to room temperature, centrifuge, wash twice with toluene and once with anhydrous ethanol, and dry the product at 80℃ to constant weight to obtain the first modified diamond micro powder. A2. Take 100g of the first-modified diamond micro powder, disperse it in 450mL of deionized water, and sonicate it for 20min. Add 3g of sodium dodecylbenzenesulfonate and stir at 700r / min to form a stable suspension. Add 15g of acrylic acid and 10g of acrylamide to the suspension, mix well, and then add 1.5mL of 10% ammonium persulfate solution. Heat the mixture to 75℃ and stir at 400r / min for 5h. During the reaction, add 5% sodium hydroxide solution to adjust the pH of the system to 7.0. After the reaction is complete, centrifuge the product, wash it with water until neutral, and dry it at 80℃ to constant weight to obtain the second-modified diamond micro powder. A3. Dissolve 6g of tetrabutyl titanate in 25mL of anhydrous ethanol and stir until homogeneous to obtain solution A. Dissolve 4g of aluminum trichloride in 20mL of anhydrous ethanol to obtain solution B. Take 100g of the second modified diamond micro powder and disperse it in 350mL of anhydrous ethanol by ultrasonic dispersion for 30min. Add solution A and solution B dropwise and stir at 600r / min for 1h. Then add 6mL of deionized water and stir at 400r / min for 3h. Then heat to 80℃ and stir for 2h. After the reaction is completed, add 10% sodium hydroxide solution to neutralize to pH=7 and then distill to recover the ethanol. Centrifuge the reaction product, wash it 3 times, dry it and place it in a muffle furnace. Calcinate it at 550℃ for 2h under a nitrogen atmosphere. After cooling the calcined product, place it in a vacuum drying oven and dry it at 80℃ to constant weight to obtain modified diamond micro powder.

[0029] Example 6: Preparation of modified base oil. The specific preparation steps are as follows: B1. Take 100g of hydrotreated paraffin-based mineral oil, add 3g of molecular sieve catalyst and pass hydrogen gas through it. Maintain the pressure at 3MPa and heat to 320℃ for 6h. After the reaction is completed, filter to remove the catalyst, cool the mineral oil to 0℃, add 6mL of methyl ethyl ketone-toluene mixed solvent (volume ratio 1:1), stir at 400r / min for 2h, freeze at -10℃ for 4h to crystallize, filter to remove wax crystals and distill to recover the solvent, and dry the product at 80℃ to constant weight to obtain the first modified base oil. B2. Take 100g of the first modified base oil, add 4g of polyethylene wax and 1.6g of maleic anhydride, heat to 180℃ and add 0.2g of dicumyl peroxide, continuously purge with nitrogen for protection, and stir at 400r / min for 4h. After the reaction is completed, cool to 120℃, add 1g of ethanolamine and stir for 2h. Then dry the product at 80℃ to constant weight to obtain the second modified base oil. B3. Take 100g of the second modified base oil, heat it to 100℃ and add 2g of ethyl silicate. Stir at 400r / min for 1h, then add 1.6mL of 10% hydrochloric acid for catalytic hydrolysis for 2h. Continue to add 0.6g of nano boron nitride and 0.2g of nano silica to the system and ultrasonically disperse for 30min. Heat it to 150℃ and stir at 800r / min for 3h. After cooling to room temperature, add 0.4g of fatty acid amide and stir at 500r / min for 30min to obtain the modified base oil.

[0030] Example 7: Preparation of modified base oil. The specific preparation steps are as follows: B1. Take 100g of hydrotreated paraffin-based mineral oil, add 4g of molecular sieve catalyst and pass hydrogen gas through it. Maintain the pressure at 4MPa and heat to 350℃ for 6h. After the reaction is completed, filter to remove the catalyst, cool the mineral oil to 5℃, add 7mL of methyl ethyl ketone-toluene mixed solvent (volume ratio 1:1), stir at 500r / min for 2h, freeze at -10℃ for 4h to crystallize, filter to remove wax crystals and distill to recover the solvent, and dry the product at 80℃ to constant weight to obtain the first modified base oil. B2. Take 100g of the first modified base oil, add 5g of polyethylene wax and 2g of maleic anhydride, heat to 190℃ and add 0.3g of dicumyl peroxide, continuously purge with nitrogen for protection, and stir at 500r / min for 4h. After the reaction is completed, cool down to 130℃, add 1.2g of ethanolamine and stir for 2h. Then dry the product at 80℃ to constant weight to obtain the second modified base oil. B3. Take 100g of the second modified base oil, heat it to 110℃ and add 2.4g of ethyl silicate. Stir at 500r / min for 1h, then add 2mL of 10% hydrochloric acid for catalytic hydrolysis for 2h. Continue to add 0.8g of nano boron nitride and 0.5g of nano silica to the system and ultrasonically disperse for 30min. Heat it to 160℃ and stir at 1000r / min for 3h. After cooling to room temperature, add 0.6g of fatty acid amide and stir at 600r / min for 30min to obtain the modified base oil.

[0031] Comparative Example 1: An oily diamond cutting fluid for silicon carbide wafer processing was prepared. The specific preparation steps are as follows: The remaining steps remain unchanged, except that the modified diamond micro powder prepared in Example 4 used in Example 3 is replaced with unmodified diamond micro powder to prepare an oily diamond cutting fluid for silicon carbide wafer processing.

[0032] Comparative Example 2: An oily diamond cutting fluid for silicon carbide wafer processing was prepared. The specific preparation steps are as follows: The remaining steps remain unchanged, except that the modified base oil prepared in Example 7 used in Example 3 is replaced with unmodified hydrotreated paraffinic mineral oil to prepare an oily diamond cutting fluid for silicon carbide wafer processing.

[0033] Comparative Example 3: An oily diamond cutting fluid for silicon carbide wafer processing was prepared. The specific preparation steps are as follows: The remaining steps remain unchanged, except that the modified diamond micro powder prepared in Example 4 used in Example 3 is replaced with unmodified diamond micro powder, and the modified base oil prepared in Example 7 is replaced with unmodified hydrotreated paraffin-based mineral oil, to prepare an oily diamond cutting fluid for silicon carbide wafer processing.

[0034] Performance testing Test Project Test standards / methods Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Dispersion stability (3-month suspension rate) Natural settling method 88% 90% 92% 80% 82% 73% Dispersion stability (6-month suspension rate) Natural settling method 65% 69% 75% 48% 52% 39% Wafer surface roughness Ra (μm) GB / T3505-2009 0.12 0.10 0.08 0.25 0.21 0.33 Total thickness deviation (TTV) (μm) Cutting 6-inch silicon carbide wafers 4.5 4.2 3.8 5.2 4.9 5.8 Warp (μm) Cutting 6-inch silicon carbide wafers 8.5 8.0 7.2 10.5 9.8 11.2 Performance test results show that Examples 1-3 (the cutting fluids of this invention using modified diamond micron powder and modified base oil) are significantly superior to Comparative Examples 1-3 (products without modified micron powder, modified base oil, or both) in all key indicators: In terms of dispersion stability, the suspension rate of Examples reached 88%-92% after 3 months and 65%-75% after 6 months, which is much higher than that of the Comparative Examples (73%-82% and 39-52%, respectively); In terms of processing accuracy, the wafer surface roughness Ra of Examples is as low as 0.08-0.12μm, the total thickness deviation (TTV) is 3.8-4.5μm, and the warpage (WARP) is 7.2-8.5μm, all of which are better than that of the Comparative Examples (0.21-0.33μm, 4.9-5.8μm, and 9.8-11.2μm, respectively), which fully demonstrates that the modified components and synergistic process can effectively improve the dispersion stability and processing accuracy of the cutting fluid.

[0035] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. An oil-based diamond cutting fluid for silicon carbide wafer processing, characterized in that: It contains the following raw materials in parts by weight: 50-65 parts modified base oil, 15-25 parts modified diamond micro powder, 5-10 parts polyisobutylene succinimide, 3-8 parts polyethylene glycol oleate, 2-5 parts molybdenum dialkyl dithiophosphate, 0.5-1.5 parts benzotriazole, 0.5-2.5 parts nano silica, 0.3-0.8 parts antioxidant 264, 0.5-1 part hydroxyethyl methacrylate, and 0.2-0.3 parts 1-butyl-3-methylimidazolium lactate.

2. The oil-based diamond cutting fluid for silicon carbide wafer processing according to claim 1, characterized in that: The nano-silica has a particle size of 20-50 nm and its surface is hydrophobically modified with methyltrimethoxysilane.

3. The oil-based diamond cutting fluid for silicon carbide wafer processing according to claim 1, characterized in that: The modified diamond micro powder is prepared using the following specific steps: A1. Take diamond micro powder, add anhydrous ethanol, and ultrasonically disperse for 30 min to form a suspension. Add 30% hydrogen peroxide solution dropwise to the suspension, heat to 60-70℃ and stir at 400-500 r / min for 2 h. After the reaction is completed, centrifuge and wash 3 times with anhydrous ethanol. The washed product was redispersed in toluene, silane coupling agent KH-550 was added, nitrogen gas was introduced for protection, the temperature was raised to 85-90℃, and the reaction was refluxed for 4 hours. After cooling to room temperature, the product was centrifuged, washed twice with toluene and once with anhydrous ethanol, and dried at 80℃ to constant weight to obtain the first modified diamond micro powder. A2. Take the first modified diamond micro powder, disperse it in deionized water, and ultrasonically disperse it for 20 min. Add sodium dodecylbenzenesulfonate and stir at 600-700 r / min to form a stable suspension. Add acrylic acid and acrylamide to the suspension, mix well, and then add 10% ammonium persulfate solution. Heat the mixture to 70-75℃ and stir at 300-400 r / min for 5 h. During the reaction, add 5% sodium hydroxide solution to adjust the pH of the system to 6.5-7.

0. After the reaction is completed, centrifuge the product, wash it with water until neutral, and dry it at 80℃ to constant weight to obtain the second modified diamond micro powder. A3. Dissolve tetrabutyl titanate in anhydrous ethanol and stir until homogeneous to obtain solution A. Dissolve aluminum trichloride in anhydrous ethanol to obtain solution B. Take the second modified diamond micro powder, disperse it in anhydrous ethanol and ultrasonically disperse for 30 min. Add solution A and solution B dropwise and stir at 500-600 r / min for 1 h. Then add deionized water dropwise and stir at 300-400 r / min for 3 h. Then heat to 80℃ and stir for 2 h. After the reaction is completed, add 10% sodium hydroxide solution to neutralize to pH=7 and then distill to recover the ethanol. Centrifuge the reaction product, wash it 3 times, dry it and place it in a muffle furnace. Calcinate it at 500-550℃ for 2 h under a nitrogen atmosphere. After cooling the calcined product, place it in a vacuum drying oven and dry it at 80℃ to constant weight to obtain modified diamond micro powder.

4. The oil-based diamond cutting fluid for silicon carbide wafer processing according to claim 3, characterized in that: The ratio of diamond micro powder, anhydrous ethanol, hydrogen peroxide solution, toluene, and silane coupling agent KH-550 in A1 is 100g:300-350mL:5-6mL:250-300mL:8-10g; the particle size of the diamond micro powder is 1-3μm. The ratio of the first modified diamond micro powder, deionized water, sodium dodecylbenzenesulfonate, acrylic acid, acrylamide, and ammonium persulfate solution in A2 is 100g: 400-450mL: 2-3g: 12-15g: 8-10g: 1-1.5mL; The ratio of tetrabutyl titanate, anhydrous ethanol, aluminum trichloride, second-modified diamond micro powder, and deionized water in A3 is 5-6g: 335-395mL: 3-4g: 100g: 5-6mL; wherein the ratio of anhydrous ethanol used to prepare solution A, solution B, and disperse the second-modified diamond micro powder is 20-25mL: 15-20mL: 300-350mL.

5. The oil-based diamond cutting fluid for silicon carbide wafer processing according to claim 1, characterized in that: The modified base oil is prepared using the following specific steps: B1. Take hydrotreated paraffin-based mineral oil, add molecular sieve catalyst and pass hydrogen gas through it. Maintain pressure of 3-4 MPa and heat to 320-350℃ for 6 hours. After the reaction is completed, filter to remove the catalyst, cool the mineral oil to 0-5℃, add methyl ethyl ketone-toluene mixed solvent (volume ratio 1:1), stir at 400-500 r / min for 2 hours, freeze at -10℃ for 4 hours to crystallize, filter to remove wax crystals and distill to recover the solvent, and dry the product at 80℃ to constant weight to obtain the first modified base oil. B2. Take the first modified base oil, add polyethylene wax and maleic anhydride, heat to 180-190℃ and add dicumyl peroxide, continuously purge with nitrogen for protection, stir at 400-500 r / min for 4 h; after the reaction is completed, cool to 120-130℃, add ethanolamine and stir for 2 h, then dry the product at 80℃ to constant weight to obtain the second modified base oil. B3. Take the second modified base oil, heat it to 100-110℃ and add ethyl silicate. Stir at 400-500 r / min for 1 h, then add 10% by mass of dilute hydrochloric acid for catalytic hydrolysis for 2 h. Continue to add nano boron nitride and nano silica to the system and ultrasonically disperse for 30 min. Heat it to 150-160℃ and stir at 800-1000 r / min for 3 h. After cooling to room temperature, add fatty acid amide and stir at 500-600 r / min for 30 min to obtain the modified base oil.

6. The oil-based diamond cutting fluid for silicon carbide wafer processing according to claim 5, characterized in that: The modified base oil has a kinematic viscosity of 25-35 mmHg at 40°C. 2 / s, and after modification by ethyl silicate hydrolysis, the content of nano-sized siloxane crosslinked structures in the system accounts for 1.2-1.8% of the total mass of the base oil.

7. The oil-based diamond cutting fluid for silicon carbide wafer processing according to claim 5, characterized in that: The ratio of hydrogenated refined paraffinic mineral oil, molecular sieve catalyst, and methyl ethyl ketone-toluene mixed solvent in B1 is 100g: 3-4g: 6-7mL. The ratio of the first modified base oil, polyethylene wax, maleic anhydride, dicumyl peroxide, and ethanolamine in B2 is 100g: 4-5g: 1.6-2g: 0.2-0.3g: 1-1.2g; The ratio of the second modified base oil, ethyl silicate, dilute hydrochloric acid, nano boron nitride, nano silica, and fatty acid amide in B3 is 100g: 2-2.4g: 1.6-2mL: 0.6-0.8g: 0.2-0.5g: 0.4-0.6g. Here, the nano silica is the same component as the nano silica mentioned above, and its surface is hydrophobically modified with methyltrimethoxysilane, with a particle size of 20-50nm.

8. A method for preparing an oily diamond cutting fluid for silicon carbide wafer processing, characterized in that: Specifically, it includes the following steps: S1. Add 50-65 parts of modified base oil to a sealed reactor equipped with a reflux condenser, start stirring, set the speed to 300 r / min, and slowly heat to 60-70℃; add 0.3-0.8 parts of antioxidant 264 and 0.5-1.5 parts of benzotriazole to the system, and continue stirring for 30 min to ensure that the additives are completely dissolved, thus obtaining a premixed oil phase; S2. Add 5-10 parts of polyisobutylene succinimide and 3-8 parts of polyethylene glycol oleate to the premixed oil phase in sequence. Increase the stirring speed to 800 r / min and the temperature to 80-85℃. Turn on the reflux condenser and continue stirring for 1 hour. Then add 2-5 parts of molybdenum dialkyl dithiophosphate and stir for 30 min. Then add 0.5-2.5 parts of nano silica, increase the stirring speed to 1500 r / min and stir for 30 min. Then perform high-speed homogenization at 8000 r / min for 5 min. S3. Add 15-25 parts of modified diamond micro powder to the above system in 4 batches, with an interval of 15 minutes between each batch. During the addition process, turn on 300W ultrasonic dispersion and stirring in synergy, and maintain the stirring speed at 1200 r / min. After all the modified diamond micro powder has been added, continue ultrasonic stirring for 1 hour. Reduce the system temperature to 50℃, adjust the stirring speed to 500 r / min, add 0.5-1 parts of hydroxyethyl methacrylate and 0.2-0.3 parts of 1-butyl-3-methylimidazolium lactate, and continue stirring for 30 minutes to fully integrate the functional additives into the system. S4. Transfer the above mixture to a high-pressure homogenizer with a cooling jacket, set the pressure to 30-40 MPa, and perform two homogenization processes. After each homogenization, cool the mixture with 15°C cold water for 10 minutes through the cooling jacket. After homogenization, transfer the system back to the reactor and allow it to cool naturally to room temperature. S5. Filter the system cooled to room temperature using a 200-mesh stainless steel filter and collect the filtered liquid, which is the oil-based diamond cutting fluid used for silicon carbide wafer processing.

9. The method for preparing an oily diamond cutting fluid for silicon carbide wafer processing according to claim 8, characterized in that: The modified diamond micro powder in S3 is added in batches of 40%, 30%, 20%, and 10% in a gradient ratio. During ultrasonic dispersion, a dual-frequency alternating ultrasonic mode of 20kHz and 40kHz is used, with an alternation period of 5 minutes, to ensure that the micro powder forms a uniform and stable suspended dispersion phase in the system.