Cutting fluid for cutting solar silicon wafer by diamond wire and preparation method of cutting fluid

Abstract

The invention relates to the technical field of silicon wafer cutting fluids, in particular to a cutting fluid for diamond wire cutting of a solar silicon wafer and a preparation method thereof.The preparation method includes the steps that raw materials are mixed, and the raw materials comprise, by weight, 60-70 parts of a solvent, 3-5 parts of an antioxidant, 8-12 parts of an anti-shearing agent, 5-8 parts of a dispersing agent, 4-6 parts of an extreme pressure lubricant and 0.5-1 part of a pH regulator; according to the cutting fluid, the oxidation resistance and the shear resistance can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon wafer cutting fluid, in particular to a cutting fluid for cutting solar silicon wafer by diamond wire and a preparation method thereof. BACKGROUND

[0002] The diamond wire is used to cut the solar silicon wafer, and has the characteristics of high efficiency and good quality of the cut silicon wafer, but the diamond wire cutting has higher requirements for the cutting fluid under the conditions of high cutting rate and high speed. In the process of cutting by the diamond wire, the molecular chain of the traditional cutting fluid is easy to break, resulting in a decrease in viscosity, a decrease in lubrication and cooling performance, and the heat generated by instantaneous cutting is easy to cause oxidation or carbonization of the cutting fluid, and to generate a gel-like substance.

[0003] In addition, the increase of the cutting rate accelerates the generation of silicon powder, which easily causes the residue of the mortar to cause dirty pieces and the like. SUMMARY

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a cutting fluid for cutting solar silicon wafer by diamond wire and a preparation method thereof, which solves the problem that the cutting fluid in the prior art cannot meet the needs of cutting solar silicon wafer by diamond wire.

[0005] The present application first provides a preparation method of a cutting fluid for cutting solar silicon wafer by diamond wire, which comprises mixing raw materials, the raw materials comprising the following substances by weight:

[0006] 60-70 parts of solvent, 3-5 parts of antioxidant, 8-12 parts of shear inhibitor, 5-8 parts of dispersant, 4-6 parts of extreme pressure lubricant, and 0.5-1 parts of pH adjuster;

[0007] The preparation of the shear inhibitor comprises:

[0008] 3-phenyl-1-oxetane, boron trifluoride ether complex and 1,4-butanediol, anhydrous dichloromethane are reacted to obtain a hydroxyl-terminated polymer;

[0009] Polyethylene glycol, hexamethylene diisocyanate, dibutyltin dilaurate and toluene are reacted to obtain isocyanate-terminated polyethylene glycol;

[0010] The hydroxyl-terminated polymer and the isocyanate-terminated polyethylene glycol are dissolved in toluene to obtain the shear inhibitor;

[0011] The preparation of the dispersant comprises: cup[4]arene and chloroacetic acid are reacted to obtain carboxylated cup[4]arene;

[0012] The cetyl polyoxyethylene ether and triethylamine are dissolved in anhydrous tetrahydrofuran, and 1,3-propane sultone is added to react to obtain a reaction solution containing cetyl polyoxyethylene sulfonate;

[0013] The polyacrylic acid is subjected to carboxyl activation under the action of a coupling agent, and then the reaction solution containing cetyl polyoxyethylene sulfonate is added to react, and then the carboxylated calix[4]arene is added to continue the reaction to obtain the dispersant.

[0014] In an embodiment, the solvent includes water and polyethylene glycol, and the weight ratio of the water and the polyethylene glycol is 1:(0.5-1).

[0015] In an embodiment, the antioxidant includes a first antioxidant and a second antioxidant, the first antioxidant is ammonium molybdate, and the preparation of the second antioxidant includes the following steps: galloyl chloride and vitamin E are subjected to condensation reaction to obtain gallic acid tocopherol ester; and the gallic acid tocopherol ester and sulfur trioxide pyridine are subjected to sulfonation to obtain the second antioxidant.

[0016] In an embodiment, the molar ratio of the cetyl polyoxyethylene ether and 1,3-propane sultone is 1:(0.4-0.6).

[0017] In an embodiment, the weight ratio of the polyacrylic acid, the reaction solution containing cetyl polyoxyethylene sulfonate, and the carboxylated calix[4]arene is 1.0:(1.2-2.0):(0.1-0.3).

[0018] In an embodiment, the coupling agent is an EDC and NHS coupling agent.

[0019] In an embodiment, the extreme pressure lubricant includes potassium phosphate ester.

[0020] In an embodiment, the pH regulator includes sodium citrate and triethanolamine.

[0021] In an embodiment, the weight ratio of the sodium citrate and the triethanolamine is 1.0:(0.8-1.2).

[0022] Another aspect of the present application also provides a cutting fluid for cutting solar silicon wafers by a diamond wire, which is prepared by the preparation method.

[0023] The cutting fluid for cutting solar silicon wafers by a diamond wire provided by the present application has the following beneficial effects: the antioxidant and the anti-shearing agent are synthesized, which can effectively improve the antioxidant performance of the cutting fluid, and improve the service life and stability of the cutting fluid. DETAILED DESCRIPTION

[0024] The application provides a cutting fluid for cutting solar silicon wafers by diamond wires.

[0025] The cutting fluid comprises a solvent, the solvent comprises water and polyethylene glycol, the water can be deionized water, the polyethylene glycol can be PEG-400, and the weight ratio of the water to the polyethylene glycol can be 1:(0.5-1). The use of the two solvents can balance the viscosity and wetting performance of the cooling liquid, and the use of the environmentally friendly solvents can reduce the use of organic solvents.

[0026] The cutting fluid comprises an antioxidant, the antioxidant comprises a first antioxidant and a second antioxidant, the first antioxidant is ammonium molybdate, and the preparation of the second antioxidant comprises the following steps.

[0027] S11: under nitrogen protection, 21.5 g of vitamin E is dissolved in 200 mL of anhydrous dichloromethane, then 7 mL of triethylamine and 0.5 g of 4-dimethylaminopyridine (DMAP) are added, and the mixture is cooled to 0 DEG C in an ice bath. 10.6 g of galloyl chloride is dissolved in 20 mL of dichloromethane, and then slowly added dropwise, and the reaction is carried out for 30 minutes, and the temperature is kept below 5 DEG C, to obtain a gallic acid tocopherol ester;

[0028] S12: under nitrogen protection, 20 g of gallic acid tocopherol ester and 12 g of sulfur trioxide pyridine are added to 200 mL of DMF, and the mixture is subjected to a sulfonation reaction for 6 hours, and the sulfonation temperature is kept below 5 DEG C, to obtain the second antioxidant.

[0029] In steps S11 and S12, the ester bond and the tocopherol structure are retained, the phenolic hydroxyl group is sulfonated, and a sulfonated gallic acid tocopherol ester is generated. The vitamin E is purchased from Chengdu Bishang Biotechnology Co., Ltd. The galloyl chloride is purchased from Yantai Shengkailun Chemical Technology Co., Ltd. (CAS No: 35388-10-4). The sulfur trioxide pyridine is purchased from Shanghai Macklin Biochemical Technology Co., Ltd. (CAS No: 26412-87-3).

[0030] The second antioxidant introduces a sulfonic acid group (-SO3H) which can significantly improve the water solubility of the second antioxidant, the negative charge of the sulfonic acid group helps to be adsorbed on the surface of the silicon wafer, enhances the stability of the antioxidant film, the phenol ring and the chroman ring of the tocopherol can synergistically antioxidant, and the sulfonated antioxidant can be uniformly dispersed to avoid precipitation.

[0031] The weight ratio of the first antioxidant and the second antioxidant is (3-5): 1, and the two antioxidants work in that the phenolic hydroxyl (-OH) and benzodihydropyran ring (vitamin E part) remaining in the second antioxidant can scavenge ·OH, ROO· and other free radicals, and the first antioxidant molybdate generates a MoO3 passivation layer on the surface of the steel wire to reduce the dissolution of metal ions.

[0032] The cutting fluid includes a shear-resistant agent. The shear-resistant agent is a block copolymer. The synthesis of the shear-resistant agent includes the following steps:

[0033] S21: 10g of 3-phenyl-1-oxetane is dissolved in 100ml of dichloromethane, 1.2ml of boron trifluoride ether complex (BF3·OEt2) dissolved in 10ml of dichloromethane is slowly added dropwise, stirring is carried out for 6 hours, the reaction temperature is not more than 5℃, then 1.35g of 1,4-butanediol dissolved in 20ml of dichloromethane is added and reacted for 30 minutes, and then the hydroxyl-terminated polymer is obtained through filtration and drying;

[0034] S22: 20g of polyethylene glycol with a molecular weight of 2000 is dissolved in 100ml of toluene, then 3.7g of hexamethylene diisocyanate and 0.1g of dibutyltin dilaurate are added, and the reaction is carried out at 80℃ for 4 hours under nitrogen protection to obtain isocyanate-terminated polyethylene glycol;

[0035] S23: 5.0g of the hydroxyl-terminated polymer and 20g of the isocyanate-terminated polyethylene glycol are dissolved in 100ml of toluene, and the reaction is carried out at 80℃ for 12 hours (FTIR monitoring-NCO peak disappears). After cooling, it is precipitated in 200ml of ether, filtered, and vacuum dried to obtain the shear-resistant agent.

[0036] In step S21, the 3-phenyl-1-oxetane is of Hangzhou Dongfan Chemical Co., Ltd. (CAS No.: 10317-13-2).

[0037] In the preparation of the shear-resistant agent, the polymer generated by ring-opening polymerization of 3-phenyl-1-oxetane contains rigid phenyl side chains, which form physical crosslinking points through π-π stacking or hydrophobic interaction, and flexible PEG segments provide freedom of movement and act as lubricants under shear force. In addition, the shear-resistant agent can also protect the sulfonated antioxidant. The phenyl side chain provides a rigid skeleton, and a physical crosslinking network is formed through π-π stacking or hydrogen bonding, which absorbs shear energy and reduces the stress directly acting on the molecular chain of the antioxidant. The shear-resistant agent wraps the sulfonated antioxidant molecule through hydrophobic interaction (poly(3-phenyl oxetane) block) or hydrogen bonding (PEG block) to form a buffer layer, reducing the direct destruction of shear force on the chemical bonds of the antioxidant, and prolonging its action time. The SO3 -The groups can form hydrogen bonds with the ether linkage of the PEG, enhancing the stability of the binding.

[0038] The cutting fluid includes a dispersant, and the dispersant is prepared under nitrogen protection.

[0039] The preparation of the dispersant includes the following steps:

[0040] S31: 5 g of calix[4]arene is dissolved in 50 mL of ethanol / water (1:1), 0.9 g of NaOH is added, and 2.12 g of chloroacetic acid dissolved in 10 mL of water is added dropwise to the above reaction solution, and the reaction is carried out at 80°C for 12 hours. After cooling, the pH is neutralized to pH=2 with hydrochloric acid, and a white precipitate is obtained. The carboxylated calix[4]arene is obtained by drying the precipitate and filtering (carboxyl peak ~1720 cm -1 ) is detected by IR).

[0041] S32: 10 g of cetyl polyoxyethylene ether (C 16 H 33 (OCH2CH2) n OH, n≈10, Sigma-Aldrich) and 2.2 mL of triethylamine are dissolved in 100 mL of anhydrous THF, and the solution is cooled to 0°C in an ice bath. 1.0 g of 1,3-propane sultone is dissolved in 10 mL of anhydrous THF, and the solution is added slowly to the reaction solution while keeping the temperature below 5°C. Then, the reaction is carried out at room temperature for 6 hours. After filtration and evaporation, a yellow viscous reaction solution is obtained, which is the reaction solution containing cetyl polyoxyethylene sulfonate.

[0042] S33: 2.0 g of polyacrylic acid (PAA, Mw~5000) is added to 50 ml of DMF, then 0.77 g of EDC and 0.46 g of NHS coupling agent are added, and the carboxyl group is activated at room temperature for 1 hour. Then, 3.2 g of the reaction solution of S32 is added for the first step of grafting, and the reaction is carried out at room temperature for 6 hours. Then, 0.28 g of carboxylated calix[4]arene of S31 is added for the second step of grafting, and the reaction is carried out for 12 hours. After the reaction is completed, the reaction solution is dialyzed to remove unreacted small molecules, and then freeze-dried to obtain the grafted polymer.

[0043] The dispersant includes a hydrophobic part of a cetyl long-chain (C 16 H 33 —) hydrophobic part, and a hydrophilic part of a polyoxyethylene chain (—(OCH2CH2) n —) and a sulfonate group, which can synergistically enhance the water solubility of the dispersant.

[0044] The dispersant can delay the settling rate of particles in the silicon wafer cutting liquid by grafting a cyclic molecule calix[4]arene on the side chain. The sulfonic acid group (-SO3H) and the carboxyl group (-COOH) in the dispersant provide charge repulsion after ionization. The rigid cavity of calix[4]arene and the extended conformation of the polyoxyethylene chain can prevent particle agglomeration.

[0045] In step S32, the hexadecyl polyoxyethylene ether is partially sulfonated, and the sulfonated part (-SO3-) provides hydrophilicity, and the sulfonated proportion is about 50%, and the remaining 50% of the hexadecyl polyoxyethylene ether retains a hydroxyl group, and the unsulfonated part is combined with the polyacrylic acid main chain in S33.

[0046] In step S33, the carboxylated calix[4]arene should not be excessive, otherwise it is easy to cause polymer aggregation. The weight ratio of the polyacrylic acid, the reaction solution containing hexadecyl polyoxyethylene sulfonate and the carboxylated calix[4]arene is 1.0:

[0047] (1.2-2.0):(0.1-0.3).

[0048] The hydrophobic cavity of calix[4]arene in the dispersant of the present application can also wrap sulfonated antioxidant molecules, reduce their contact with metal ions generated during cutting, and avoid catalytic oxidation failure. The hydroxyl group on the surface of the dispersant can form a hydrogen bond network with the phenolic hydroxyl group of the antioxidant, enhancing the efficiency of free radical capture. The calix[4]arene in the synthesis raw material of the dispersant is purchased from Shanghai Pingchuang Chemical Technology Co., Ltd. (CAS NO. 74568-07-3), and 1,3-propane sulfone lactone is purchased from Sigma-Aldrich Company (CAS No. 1120-71-4).

[0049] The cutting liquid comprises an extreme pressure lubricant, and the extreme pressure lubricant can comprise a potassium salt of phosphate ester.

[0050] The cutting liquid comprises a pH regulator, and the pH regulator can comprise sodium citrate and triethanolamine, and the weight ratio of the sodium citrate and triethanolamine is 1.0:(0.8-1.2), so that the pH value is stabilized between 8.5-9.5, the solubility and compatibility of the system are balanced, and the chelating performance to metal impurities is enhanced.

[0051] The technical solutions of the present application are further illustrated by specific examples.

[0052] Example 1

[0053] A cutting liquid for cutting solar silicon wafers by diamond wire, comprising the following components:

[0054] Solvent 60 parts, antioxidant 3 parts, shear inhibitor 8 parts, dispersant 5 parts, extreme pressure lubricant 4 parts, pH regulator 0.5 parts; wherein the solvent is water and polyethylene glycol 400, the weight ratio is 1:1, the weight ratio of the first antioxidant and the second antioxidant is 4:1, and the above raw materials are mixed to obtain the cutting fluid for cutting solar silicon wafer by diamond wire.

[0055] Example 2

[0056] A cutting fluid for cutting solar silicon wafer by diamond wire comprises the following components:

[0057] Solvent 70 parts, antioxidant 5 parts, shear inhibitor 12 parts, dispersant 8 parts, extreme pressure lubricant 6 parts, pH regulator 1 part; wherein the solvent is water and polyethylene glycol 400, the weight ratio is 1:1, the weight ratio of the first antioxidant and the second antioxidant is 4:1, and the above raw materials are mixed to obtain the cutting fluid for cutting solar silicon wafer by diamond wire.

[0058] Example 3

[0059] A cutting fluid for cutting solar silicon wafer by diamond wire comprises the following components:

[0060] Solvent 65 parts, antioxidant 4 parts, shear inhibitor 10 parts, dispersant 6 parts, extreme pressure lubricant 4 parts, pH regulator 0.5 parts; wherein the solvent is water and polyethylene glycol 400, the weight ratio is 1:1, the weight ratio of the first antioxidant and the second antioxidant is 4:1, and the above raw materials are mixed to obtain the cutting fluid for cutting solar silicon wafer by diamond wire.

[0061] Comparative Example 1

[0062] A cutting fluid for cutting solar silicon wafer by diamond wire comprises the following components:

[0063] Solvent 60 parts, dispersant 5 parts, extreme pressure lubricant 4 parts, pH regulator 0.5 parts; wherein the solvent is water and polyethylene glycol 400, the weight ratio is 1:1, and the above raw materials are mixed to obtain the cutting fluid for cutting solar silicon wafer by diamond wire.

[0064] Comparative Example 2

[0065] A cutting fluid for cutting solar silicon wafer by diamond wire comprises the following components:

[0066] Solvent 60 parts, antioxidant 3 parts, shear inhibitor 8 parts, dispersant 5 parts, extreme pressure lubricant 4 parts, pH adjuster 0.5 parts; wherein the solvent is water and polyethylene glycol 400, the weight ratio is 1:1, the weight ratio of the first antioxidant and the second antioxidant is 4:1, the dispersant is a commercially available Pluronic F127 dispersant, and the above raw materials are mixed to obtain a cutting fluid for cutting solar silicon wafers by diamond wire.

[0067] Comparative Example 3

[0068] Comparative Example 3 uses a commercially available cutting fluid in Derby.

[0069] Examples 1-3 and Comparative Examples 1-3 are evaluated for performance, and the evaluation results are shown in Tables 1 and 2.

[0070] (1) Suspension test: static sedimentation observation method, take 100 mL cutting fluid sample in a transparent cylinder, and place it in a 25℃ constant temperature environment. Initial liquid level H0, height H of the sedimentation layer after 24 hours.

[0071] Sedimentation rate (%) = H t / H0*100%;

[0072] (2) Antioxidant test: antioxidant test uses oven method, 50mL cutting fluid is placed in 80℃ constant temperature oven, continuous air is passed, sample is taken after 72 hours, and the following indexes are detected: acid value (AV): titration method measures free fatty acid content; peroxide value (POV): iodometric method measures hydroperoxide content.

[0073] (3) Wire breakage rate and dirt rate: after cutting 1.5 million silicon wafers, the wire breakage rate and dirt rate are counted. The statistical results are shown in Table 2.

[0074] Table 1 Performance evaluation table of Examples 1-3 and Comparative Examples 1-3

[0075]

[0076] Table 2 Wire breakage rate and dirt rate performance evaluation table of Examples 1-3 and Comparative Examples 1-3

[0077]

[0078] The dispersant used in the present application can effectively reduce the sedimentation rate of the cutting fluid by grafting a cyclic molecule on the side chain. As can be seen from Comparative Examples 1-3, the synergistic effect is best when the shear inhibitor: dispersant: antioxidant is 10:6:4, which can balance the performance and viscosity.

[0079] Compared with Comparative Example 1, the antioxidant phenothioglycolic acid tocopherol ester in the present application has a good synergistic effect with ammonium molybdate and an anti-shearing agent, significantly improves the anti-oxidation ability of the cutting fluid, and reduces the oxidative decomposition in a high-temperature environment. Comparative Example 2 uses a common PEO-PPO-PEO triblock copolymer dispersant, and the anti-settling effect is not as good as that of the cutting fluid of the present application.

[0080] The wire breakage rate and the dirt rate of Examples 1-3 are obviously better than those of the comparative examples, indicating that the cutting fluid of the present application effectively reduces the risk of diamond wire breakage and reduces the dirt problem on the surface of the silicon wafer through the synergistic effect of the anti-shearing agent and the dispersant.

[0081] The above examples only illustrate the principles and effects of the present application, and are not used to limit the present application. When the examples give numerical ranges, it should be understood that, unless otherwise stated by the present application, both endpoints of each numerical range and any number between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art. In addition to the specific methods, devices, materials used in the examples, any method, device and material of the prior art similar or equivalent to those described in the examples of the present application can also be used to implement the present application according to the mastery of the prior art by those skilled in the art and the description of the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A method for preparing a cutting fluid for diamond wire cutting of solar silicon wafers, characterized in that: The preparation method includes mixing raw materials, wherein the raw materials comprise the following substances in parts by weight: 60-70 parts solvent, 3-5 parts antioxidant, 8-12 parts anti-shear agent, 5-8 parts dispersant, 4-6 parts extreme pressure lubricant, and 0.5-1 part pH adjuster; The preparation of the anti-shear agent includes: The hydroxyl-terminated polymer was obtained by reacting 3-phenyl-1-oxetane, boron trifluoride diethyl ether complex, 1,4-butanediol, and anhydrous dichloromethane. Polyethylene glycol, hexamethylene diisocyanate, dibutyltin dilaurate and toluene are reacted to obtain polyethylene glycol with isocyanate end caps; The anti-shear agent is obtained by reacting hydroxyl-terminated polymer and isocyanate-terminated polyethylene glycol in toluene. The preparation of the dispersant includes: The carboxylated calix[4]arene was reacted with chloroacetic acid to obtain carboxylated calix[4]arene; Hexadecyl polyoxyethylene ether and triethylamine were dissolved in anhydrous tetrahydrofuran and 1,3-propane sulfonyl lactone was added to react and obtain a reaction solution containing hexadecyl polyoxyethylene sulfonate. The polyacrylic acid was activated by carboxyl group under the action of a coupling agent, and then the reaction solution containing hexadecyl polyoxyethylene sulfonate was added to carry out the reaction. Subsequently, the carboxylated calix[4] aromatic hydrocarbon was added to continue the reaction to obtain the dispersant.

2. The preparation method according to claim 1, characterized in that: The solvent comprises water and polyethylene glycol, wherein the weight ratio of water to polyethylene glycol is 1:(0.5-1).

3. The preparation method according to claim 1, characterized in that: The antioxidant includes a first antioxidant and a second antioxidant. The first antioxidant is ammonium molybdate, and the preparation of the second antioxidant includes the following steps: Galloyl chloride and vitamin E are condensed to obtain gallic acid tocopherol ester; the gallic acid tocopherol ester is sulfonated with sulfur trioxide pyridine to obtain the second antioxidant.

4. The preparation method according to claim 1, characterized in that: The molar ratio of hexadecyl polyoxyethylene ether to 1,3-propane sulfonyl lactone is 1:(0.4-0.6).

5. The preparation method according to claim 1, characterized in that: The weight ratio of the polyacrylic acid, the reaction solution containing hexadecyl polyoxyethylene sulfonate, and the carboxylated calix[4] aromatic hydrocarbon is 1.0:(1.2-2.0):(0.1-0.3).

6. The preparation method according to claim 1, characterized in that: The coupling agent is an EDC and NHS coupling agent.

7. The preparation method according to claim 1, characterized in that: The extreme pressure lubricant includes potassium phosphate salt.

8. The preparation method according to claim 1, characterized in that: The pH adjuster includes sodium citrate and triethanolamine.

9. The preparation method according to claim 8, characterized in that: The weight ratio of sodium citrate to triethanolamine is 1.0:(0.8-1.2).

10. A cutting fluid for diamond wire cutting of solar silicon wafers prepared by any of the preparation methods described in claims 1-9.

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