Cooling liquid for diamond wire cutting of solar silicon wafer and preparation method of cooling liquid

Abstract

The invention relates to the technical field of silicon wafer cooling liquid, in particular to cooling liquid for diamond wire cutting of a solar silicon wafer and a preparation method thereof.The preparation method comprises the steps that raw materials are mixed, and the raw materials comprise, by weight, 70-80 parts of a solvent, 5-8 parts of a dispersing agent, 3-5 parts of a wetting agent, 0.2-0.5 part of a heat conduction agent and 0.1-0.2 part of a pH regulator; the cooling liquid can effectively reduce the line breaking rate and the smudginess rate of silicon wafer cutting.

Description

A coolant for diamond wire cutting of solar silicon wafers and its preparation method Technical Field

[0001] This invention relates to the field of silicon wafer coolant technology, and in particular to a coolant for diamond wire cutting of solar silicon wafers and its preparation method. Background Technology

[0002] Using diamond wire to cut silicon wafers can effectively improve production efficiency and reduce production costs. However, due to the faster cutting speed, the friction between the diamond wire and the silicon wafer generates a large amount of heat, leading to increased wire breakage and contamination rates. Therefore, there is an urgent need to develop a coolant suitable for diamond wire cutting of solar silicon wafers to reduce the heat generated by friction between the diamond wire and the silicon wafer during the cutting process, reduce the breakage rate, and extend the life of the diamond wire. Nano-alumina has good thermal conductivity, but it suffers from problems such as the tendency of inorganic nanoparticles to agglomerate and poor dispersion stability in the cutting fluid. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a coolant for diamond wire cutting of solar silicon wafers and a method for preparing the same, so as to solve the problem that the coolant in the prior art is difficult to meet the requirements of diamond wire cutting of solar silicon wafers.

[0004] This invention first provides a method for preparing a coolant for diamond wire cutting of solar silicon wafers. The preparation method includes mixing raw materials, which include the following substances in parts by weight: 70-80 parts solvent, 5-8 parts dispersant, 3-5 parts wetting agent, 0.2-0.5 parts thermal conductive agent, and 0.1-0.2 parts pH adjuster; the solvent includes water and polyethylene glycol, and the weight ratio of water to polyethylene glycol is (2-3):1; the dispersant includes acrylic acid-maleic anhydride copolymer, and the wetting agent includes a first wetting agent, which is an alkyl alcohol polyoxyethylene ether; The thermal conductive agent is a modified nano-alumina dispersion. The preparation of the modified nano-alumina dispersion includes the following steps: (1) reacting nano-alumina with aminopropyltriethoxysilane to obtain amino nano-alumina; (2) reacting amino nano-alumina with glutaraldehyde to obtain aldehyde-modified nano-alumina, reacting the aldehyde-modified nano-alumina with 2-hydroxy-4-aminobutyric acid and then reducing it to obtain modified nano-alumina, dispersing the modified nano-alumina in water to obtain the modified nano-alumina dispersion. The solid content of the modified nano-alumina dispersion is 10%~20%.

[0005] In one embodiment, the nano-alumina is pretreated by soaking it in dilute nitric acid and hydrogen peroxide.

[0006] In one embodiment, the nano-alumina is a hydrophilic γ- The particle size is 20~50nm, and the specific surface area is greater than 100m². 2 / g.

[0007] In one embodiment, sodium borohydride is used as the reducing agent for the reduction.

[0008] In one embodiment, the wetting agent includes a second wetting agent, the preparation of which includes the following steps: (1) reacting 5-(hydroxymethyl)benzene-1,2,3-triol and epichlorohydrin to obtain a chloroether intermediate; (2) reacting 2-hydroxyethyl carbamate and the chloroether intermediate to obtain the second wetting agent.

[0009] In one embodiment, the weight ratio of the first wetting agent to the second wetting agent is (3~5):1.

[0010] In one embodiment, the weight ratio of 5-(hydroxymethyl)benzene-1,2,3-triol to epichlorohydrin is 100:(65~80), and the weight ratio of the chloroether intermediate to the 2-hydroxyethyl carbamate is 100:(90~110).

[0011] In one embodiment, the coolant includes 0.2 to 0.3 parts of defoamer.

[0012] In one embodiment, the method for preparing the defoamer includes the following steps: (1) polycondensing isobutylenetrimethoxysilane to obtain a condensate; (2) reacting the condensate with polypropylene glycol monoglycidyl ether to obtain the defoamer.

[0013] In another aspect, the present invention provides a coolant for diamond wire cutting of solar silicon wafers prepared by the method described above.

[0014] The coolant provided by this invention for cutting solar silicon wafers with diamond wire has the following beneficial effects: By synthesizing a modified nano-alumina dispersion, this invention can effectively transfer heat during the diamond wire cutting process, thereby reducing the wire breakage rate and contamination rate during the diamond wire cutting process. Detailed Implementation

[0015] This invention provides a coolant for diamond wire cutting of solar silicon wafers, the coolant having good dispersibility, cooling properties, and lubrication properties.

[0016] The coolant includes a solvent, which may be water and polyethylene glycol, and the weight ratio of water to polyethylene glycol may be (2~3):1, for example 2.5:1.

[0017] The coolant includes a dispersant, which may be an acrylic acid-maleic anhydride copolymer purchased from Shanghai Maclean, CAS No.: 26677-99-6.

[0018] The coolant includes a wetting agent, which may include a first wetting agent and a second wetting agent. The first wetting agent may be an alkyl alcohol polyoxyethylene ether, such as Real Madrid Technology's AEO-7 model.

[0019] The preparation of the second wetting agent may include the following steps: (1) In a dry reaction flask, add 100 parts by weight of 5-(hydroxymethyl)benzene-1,2,3-triol, 500 parts by weight of anhydrous 1,4-dioxane solvent and 10 parts by weight of triethylamine, and stir in an ice-water bath for 30 minutes. Then, slowly add 75 parts by weight of epichlorohydrin. After the addition is complete, slowly raise the temperature to 55°C and continue the reaction for 6 hours. Monitor the disappearance of the starting material spot by TLC. After the reaction is complete, filter and remove the solvent by rotary evaporation to obtain the chloroether intermediate.

[0020] (2) In another reaction flask, add 95 parts by weight of 2-hydroxyethyl carbamate and 400 parts by weight of N,N-dimethylformamide (DMF) solvent, and stir for 30 minutes. Then add 15 parts by weight of anhydrous potassium carbonate, dissolve the chloroether intermediate obtained in the previous step in 200 parts by weight of DMF, and slowly add it dropwise to the reaction system using a constant pressure dropping funnel. After the addition is complete, raise the temperature to 80°C and react for 10 hours.

[0021] After the reaction is complete, the reaction solution is poured into a large amount of ice water to precipitate the solid. The solid is then filtered, and the filter cake is washed three times with water. Finally, the solid is purified by column chromatography or recrystallization to obtain the final second wetting agent. This second wetting agent is a polyphenolic wetting agent, which has good anchoring and wetting effects on silica powder. The phenolic hydroxyl groups in the second wetting agent have a strong coordination chelating ability for metal ions and also have a certain rust-preventing effect.

[0022] The weight ratio of the first wetting agent to the second wetting agent is (3~5):1.

[0023] 5-(hydroxymethyl)benzene-1,2,3-triol was purchased from Henan Lien Chemical Products Co., Ltd., CAS: 68325-64-4. 2-hydroxyethyl carbamate was purchased from Shanghai Yuanye Biotechnology Co., Ltd., CAS No.: 5395-01-7.

[0024] The coolant includes a thermal conductive agent, which is a modified nano-alumina dispersion. The preparation of the modified nano-alumina dispersion includes the following steps: (1) Pretreatment: 100 parts by weight of nano-alumina ( Particles with a diameter of 20-50 nm were soaked in a mixed solution of dilute nitric acid (5 wt%) and hydrogen peroxide (30 wt%) (volume ratio 1:1) at 60 °C for 2 hours, filtered, washed with deionized water until neutral, and vacuum dried at 120 °C for later use.

[0025] (2) Silanization to introduce amino groups: 100 parts by weight of the pretreated nano-alumina were dispersed in 500 parts of anhydrous toluene and sonicated for 30 minutes. Under nitrogen protection and stirring, 8 parts of aminopropyltriethoxysilane were added. The temperature was raised to 110°C and refluxed for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, and the product was separated by centrifugation and washed three times with anhydrous ethanol to remove unreacted silane, yielding amino-alumina nano-alumina (… ), and vacuum dried at 60℃.

[0026] (3) Aldehydeation: 100 parts by weight of The alumina was dispersed in 400 parts of phosphate buffer solution (0.1M, pH=7.4) and ultrasonically dispersed for 30 minutes. Then, 5 parts of glutaraldehyde aqueous solution (50 wt%) were slowly added with stirring, and the reaction was carried out at 40°C for 6 hours. After the reaction was complete, the alumina was centrifuged and thoroughly washed with water to obtain aldehyde-modified nano-alumina. ).

[0027] (4) Grafting: Graft 100 parts by weight of The alumina was redispersed in 500 parts of deionized water and sonicated for 30 minutes. 20 parts by weight of 2-hydroxy-4-aminobutyric acid were added and stirred to dissolve. The pH was adjusted to 9-10 with sodium hydroxide solution, and the reaction was carried out at 60°C for 8 hours. After the reaction was complete, 5 parts of sodium borohydride were added, and the mixture was stirred and reduced at room temperature for another 2 hours. The alumina was centrifuged, washed three times each with alternating water and ethanol, and then vacuum dried at 60°C to obtain nano-alumina grafted with 2-hydroxy-4-aminobutyric acid.

[0028] After the reaction was completed, the reaction solution was dialyzed. Finally, the solid content of the dialyzed modified nano-alumina dispersion was adjusted to 10%~20% (w / w). The modified nano-alumina has certain electrostatic repulsion and steric hindrance benefits, which improves the dispersibility of alumina in the cutting fluid.

[0029] Nano-alumina was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. 2-Hydroxy-4-aminobutyric acid was purchased from Shanghai Baishun, CAS No.: 13477-53-7.

[0030] In some embodiments, the coolant includes an antifoaming agent, the preparation of which includes the following steps: (1) Preparation of silicone resin prepolymer: In a reaction flask equipped with a water separator, 100 parts by weight of isobutylenetrimethoxysilane, 300 parts by weight of toluene solvent, and 3 parts by weight of p-toluenesulfonic acid (p-TSA) are added as an acid catalyst. Under nitrogen protection, the temperature is slowly raised to 75°C and the reaction is stirred for 4 hours. After purification processes such as neutralization, washing, and separation, a silicone resin condensate solution containing active Si-OH groups is obtained.

[0031] Specifically, in step (1), infrared spectroscopy analysis can be used to track the reaction process and reach the predetermined Si-OH content. That is, the reaction can be terminated by neutralizing the catalyst to prevent further condensation.

[0032] (2) Epoxy ring-opening grafting reaction: Polypropylene glycol monoglycidyl ether (Mn=2000) with a molar ratio of 1:1.05 to Si-OH groups was added to the above system, along with 0.2% by mass of dibutyltin dilaurate as a catalyst. Under nitrogen protection, the temperature was raised to 100℃ and the reaction was carried out for 4 hours. The reaction was monitored by FTIR, and the intensity of the epoxy characteristic peak was monitored. When the peak essentially disappeared, the reaction was considered complete. After purification, the organosilicon-polyether copolymer was obtained.

[0033] The defoamer, linked by hydrophilic polyether segments to an oleophilic silicone resin backbone, enhances its uniformity and stable dispersion in the cutting fluid. The isobutylenetrimethoxysilane was purchased from Shaanxi Xinyan Bomei (CAS No. 18292-38-1).

[0034] The coolant includes a pH adjuster, which may be an alcohol amine, such as triethanolamine.

[0035] The present invention will be further illustrated by specific embodiments below.

[0036] Example 1: 70 parts solvent, 5 parts dispersant, 3 parts wetting agent, 0.2 parts thermal conductive agent, and 0.1 parts pH adjuster; the weight ratio of water to PEG-400 in the solvent is 3:1, the dispersant is acrylic acid-maleic anhydride copolymer, the wetting agent is alkyl alcohol polyoxyethylene ether, the thermal conductive agent is modified nano-alumina dispersion, the solid content in the dispersion is 10%, and the pH adjuster is triethanolamine.

[0037] Example 2: 80 parts solvent, 8 parts dispersant, 5 parts wetting agent, 0.5 parts thermal conductive agent, and 0.2 parts pH adjuster; the weight ratio of water to PEG-400 in the solvent is 3:1, the dispersant is acrylic acid-maleic anhydride copolymer, the wetting agent is alkyl alcohol polyoxyethylene ether, the thermal conductive agent is modified nano-alumina dispersion, the solid content in the dispersion is 10%, and the pH adjuster is triethanolamine.

[0038] Example 3: 80 parts solvent, 8 parts dispersant, 5 parts wetting agent, 0.5 parts thermal conductive agent, 0.3 parts defoamer, and 0.2 parts pH adjuster; the weight ratio of water to PEG-400 in the solvent is 3:1, the dispersant is acrylic acid-maleic anhydride copolymer, the wetting agent is alkyl alcohol polyoxyethylene ether, the thermal conductive agent is modified nano-alumina dispersion, the solid content in the dispersion is 10%, and the pH adjuster is triethanolamine.

[0039] Example 4: 80 parts solvent, 8 parts dispersant, 5 parts wetting agent, 0.5 parts thermal conductive agent, and 0.2 parts pH adjuster; the weight ratio of water to PEG-400 in the solvent is 3:1; the dispersant is acrylic acid-maleic anhydride copolymer; the wetting agent is a first wetting agent - alkyl alcohol polyoxyethylene ether and a second wetting agent, with a weight ratio of 3:1 between the first and second wetting agents; the thermal conductive agent is modified nano-alumina dispersion, with a solid content of 10% in the dispersion; and the pH adjuster is triethanolamine.

[0040] Example 5: 80 parts solvent, 8 parts dispersant, 5 parts wetting agent, 0.5 parts thermal conductive agent, 0.3 parts defoamer, and 0.2 parts pH adjuster; the weight ratio of water to PEG-400 in the solvent is 3:1; the dispersant is acrylic acid-maleic anhydride copolymer; the wetting agent is a first wetting agent - alkyl alcohol polyoxyethylene ether and a second wetting agent, with a weight ratio of 3:1 between the first and second wetting agents; the thermal conductive agent is modified nano-alumina dispersion, with a solid content of 10% in the dispersion; and the pH adjuster is triethanolamine.

[0041] Comparative Example 1: 80 parts solvent, 8 parts dispersant, 5 parts wetting agent, and 0.2 parts pH adjuster; the weight ratio of water to PEG-400 in the solvent was 3:1, the dispersant was acrylic acid-maleic anhydride copolymer, the wetting agent was alkyl alcohol polyoxyethylene ether, and the pH adjuster was triethanolamine.

[0042] The performance of the coolants obtained in the examples and comparative examples was compared with that of commercially available coolants. The specific data are shown in Table 1.

[0043] Test conditions: 210mm silicon rod, 40μm diamond wire, wire speed 2400 m / min, average value of 1.5 million pieces cut.

[0044] Table 1 Performance data of silicon wafer dicing

[0045] As can be seen from Table 1, Example 3, which added defoamer, has better foam control, the silica powder is less likely to adhere, and the dirt rate is effectively improved. Example 4, which added a second wetting agent, reduced friction and particle agglomeration due to rust prevention and anchoring effects, and the wire breakage rate was improved. Example 5, which added both a second wetting agent and defoamer, has the best overall performance.

[0046] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art. In addition to the specific methods, devices, and materials used in the embodiments, based on the knowledge of those skilled in the art and the description of the present invention, any prior art methods, devices, and materials similar to or equivalent to those described, used, and materials in the embodiments of the present invention can be used to implement the present invention. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a coolant for diamond wire cutting of solar silicon wafers, characterized in that: The preparation method includes mixing raw materials, which include the following substances in parts by weight: 70-80 parts solvent, 5-8 parts dispersant, 3-5 parts wetting agent, 0.2-0.5 parts thermal conductive agent, and 0.1-0.2 parts pH adjuster; the solvent includes water and polyethylene glycol, and the weight ratio of water to polyethylene glycol is (2-3):1; the dispersant includes acrylic acid-maleic anhydride copolymer, and the wetting agent includes a first wetting agent, which is an alkyl alcohol polyoxyethylene ether; the thermal conductive agent is a modified nano-alumina dispersion. The preparation of the modified nano-alumina dispersion includes the following steps: (1) reacting nano-alumina with aminopropyltriethoxysilane to obtain amino nano-alumina; (2) reacting amino nano-alumina with glutaraldehyde to obtain aldehyde-modified nano-alumina, reacting the aldehyde-modified nano-alumina with 2-hydroxy-4-aminobutyric acid and then reducing it to obtain modified nano-alumina, dispersing the modified nano-alumina in water to obtain the modified nano-alumina dispersion, wherein the solid content of the modified nano-alumina dispersion is 10%~20%.

2. The preparation method according to claim 1, characterized in that: The nano-alumina undergoes a pretreatment process, which includes soaking the nano-alumina in dilute nitric acid and hydrogen peroxide.

3. The preparation method according to claim 1, characterized in that: The nano-alumina is hydrophilic γ- The particle size is 20~50nm, and the specific surface area is greater than 100m². 2 / g.

4. The preparation method according to claim 1, characterized in that: The reduction process uses sodium borohydride as the reducing agent.

5. The preparation method according to claim 1, characterized in that: The wetting agent includes a second wetting agent, and the preparation of the second wetting agent includes the following steps: (1) Add 5-(hydroxymethyl)benzene-1,2,3-triol and epichlorohydrin to react and obtain a chloro ether intermediate; (2) React 2-hydroxyethyl carbamate and the chloro ether intermediate to obtain the second wetting agent.

6. The preparation method according to claim 5, characterized in that: The weight ratio of the first wetting agent to the second wetting agent is (3~5):

1.

7. The preparation method according to claim 5, characterized in that: The weight ratio of 5-(hydroxymethyl)benzene-1,2,3-triol to epichlorohydrin is 100:(65~80), and the weight ratio of the chloroether intermediate to the 2-hydroxyethyl carbamate is 100:(90~110).

8. The preparation method according to claim 1, characterized in that: The coolant includes 0.2 to 0.3 parts of defoamer.

9. The preparation method according to claim 8, characterized in that: The defoamer is prepared by the following steps: (1) isobutylenetrimethoxysilane is condensed to obtain a condensate; (2) the condensate is reacted with polypropylene glycol monoglycidyl ether to obtain the defoamer.

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

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