Diamond wire cutting fluid for large-size thin monocrystalline silicon N-type solar photovoltaic wafers

Abstract

This invention discloses a diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of the N-type solar photovoltaic industry, relating to the field of monocrystalline silicon wafer cutting. It is composed of 20-35% by mass of a bisphenol-based block polyether dispersant, 5-10% of a super wetting agent, and water. Using a bisphenol-type alcohol as the initiator, it possesses a rigid steric structure, which facilitates the spatial extension of the grafted chain ends and prevents reduced dispersion efficiency and effectiveness due to the curling of the grafted chain ends themselves or between them. The dispersant is grafted with ethylene oxide and propylene oxide polyether segments at four molecular chain ends, with propylene oxide end-capping, resulting in low foaming and self-eliminating foam. During the cutting spray cycle, it does not generate excessive foam, thus avoiding the risk of overflow. The polyethylene oxide groups provide numerous dispersion and adsorption active sites, resulting in high dispersion efficiency. Simultaneously, the large molecular volume allows it to form a water-retaining and lubricating layer on the silicon wafer surface, effectively mitigating the problem of wire jamming during the lifting and retraction process after cutting.

Description

Technical Field

[0001] This invention relates to the field of monocrystalline silicon wafer cutting, and in particular to diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of the N-type solar photovoltaic industry. Background Technology

[0002] Currently, thinning technology places high demands on silicon wafer production capacity, and the demand for high-quality silicon wafers remains significant. The production and supply of high-quality silicon wafers are crucial for the development of the photovoltaic industry. Only by ensuring a sufficient supply of high-quality silicon wafers can the photovoltaic industry achieve large-scale production, reduce costs, improve efficiency, and thus promote sustainable development. Therefore, diamond wire multi-wire cutting fluid, a key auxiliary material in the diamond wire cutting process for large-size silicon wafers using thinning technology, directly affects the efficiency and quality of silicon wafer manufacturing. To improve the yield and efficiency of silicon wafer cutting, there is a greater need for enhanced performance of diamond wire multi-wire cutting fluid. Currently, especially in the cutting process of large-size thin silicon wafers, the silicon powder particles produced by multi-wire cutting have reduced particle size, increased specific surface area, and increased number of silicon powder particles. This places greater demands on the dispersion effect of dispersants and the wetting performance of wetting agents. However, existing multi-wire cutting fluids cause severe silicon powder agglomeration on the surface of silicon wafers, which also encapsulates the steel wires, resulting in a significant decrease in the cutting capacity of the steel wires and serious cutting and wire breakage. The severe silicon powder agglomeration on the surface of silicon wafers leads to a significant increase in silicon wafer fragmentation, microcracks, and cleaning contamination, which seriously affects the yield and quality of silicon wafers. Therefore, the silicon powder dispersion problem urgently needs to be solved. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of N-type solar photovoltaic, which addresses the shortcomings of the prior art.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of type N-type solar photovoltaic is composed of 20-35% by mass of bisphenol block polyether dispersant, 5-10% of super wetting agent and water.

[0006] As a further preferred embodiment of the present invention, the structure of the bisphenol block polyether dispersant is as follows:

[0007]

[0008] As a further preferred embodiment of the present invention, 4≤m≤10, 8≤n≤20, 12≤m+n≤30, and m and n are positive integers.

[0009] As a further preferred embodiment of the present invention, R1 is H, CH3 or CH2CH3; R2 is H, CH3 or CH2CH3.

[0010] As a further preferred embodiment of the present invention, the super wetting agent is one or more combinations of Evonik Tego Twin 4000, Tego Twin 4100, and Tego Twin 4200, which have strong wetting properties.

[0011] As a further preferred embodiment of the present invention, the water is EDI ultrapure water. Metal ions in the water increase the consumption of the cutting fluid and adsorb onto the silicon wafer surface, forming ionic contaminants that affect the yield of the texturing process. Using ultrapure water in the cutting fluid can reduce the consumption of cutting fluid components, reduce cleaning difficulty, and increase the yield of the cells after texturing.

[0012] As a further preferred embodiment of the present invention, the bisphenol block polyether dispersant is 25% and the super wetting agent is 8%.

[0013] The present invention has the following beneficial effects:

[0014] The bisphenol-type alcohol used in this invention has a rigid steric structure, which is conducive to the spatial extension of the grafted chain ends and is less likely to reduce dispersion efficiency and effect due to the curling of the grafted chain ends themselves or each other. The dispersant is grafted with ethylene oxide and propylene oxide polyether segments at the ends of four molecular chains, and is capped with propylene oxide. It has low foam and can eliminate foam. During the cutting spray cycle, it will not generate a large amount of foam and cause the risk of overflow. The polyethylene oxide groups have many dispersion and adsorption active sites and high dispersion efficiency. At the same time, the large molecular volume can form a water-retaining and lubricating layer on the silicon wafer surface, which has a good effect on the lifting and retraction process after cutting. It greatly overcomes the occurrence of lifting wire jamming and avoids secondary loss after silicon wafer cutting. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the bisphenol block polyether dispersant of the present invention;

[0016] Figure 2 These are the test data results of the formulation products of the present invention and commercially available competing products. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0018] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0019] like Figure 1 As shown in this application, a diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of N-type solar photovoltaic is composed of 20-35% by mass of bisphenol-based block polyether dispersant, 5-10% of super wetting agent, and the balance of EDI ultrapure water. Metal ions in the water increase the consumption of the cutting fluid and adsorb onto the silicon wafer surface, forming ionic contaminants that affect the yield of the texturing process. Using ultrapure water in the cutting fluid can reduce the consumption of cutting fluid components, reduce cleaning difficulty, and increase the yield of the cells after texturing.

[0020] The structure of bisphenol block polyether dispersants is as follows:

[0021]

[0022] Wherein, 4≤m≤10, 8≤n≤20, 12≤m+n≤30, and m and n are positive integers; R1 is H, CH3, or CH2CH3; R2 is H, CH3, or CH2CH3. The super wetting agent is one or more combinations of Evonik Tego Twin 4000, Tego Twin 4100, and Tego Twin 4200, exhibiting extremely strong wetting properties.

[0023] Example 1

[0024] When the content of bisphenol block polyether dispersant in the cutting fluid is 20% and the content of super wetting agent is 5%, the experimental results obtained by applying the cutting fluid of the present invention in the diamond wire cutting process of large-size silicon wafers are as follows: the lifting rod jamming rate is 0%, the A-grade slice rate is 96.23%, the first-pass A-grade rate is 95.86%, the contamination rate is 0.09%, and the edge chipping rate is 0.10%.

[0025] Example 2

[0026] When the content of bisphenol block polyether dispersant in the cutting fluid is 25% and the content of super wetting agent is 8%, the experimental results obtained by applying the cutting fluid of the present invention in the diamond wire cutting process of large-size silicon wafers are as follows: the lifting rod jamming rate is 0%, the A-grade slice rate is 96.57%, the first-pass A-grade rate is 96.02%, the contamination rate is 0.03%, and the edge chipping rate is 0.08%.

[0027] Example 3

[0028] When the content of bisphenol block polyether dispersant in the cutting fluid is 35% and the content of super wetting agent is 10%, the experimental results obtained by applying the cutting fluid of the present invention in the diamond wire cutting process of large-size silicon wafers are as follows: the wire jamming rate is 0%, the A-grade slice rate is 96.40%, the first-pass A-grade rate is 95.59%, the contamination rate is 0.08%, and the edge chipping rate is 0.11%.

[0029] Example 4

[0030] When m is 5, n is 10, and R1 is H and R2 is CH3 in the bisphenol block polyether dispersant, the experimental results obtained by applying the cutting fluid of the present invention in the diamond wire cutting process of large-size silicon wafers are as follows: the lifting rod jamming rate is 0, the A-grade slice rate is 96.38%, the first-pass A-grade rate is 95.83%, the contamination rate is 0.07%, and the edge chipping rate is 0.10%.

[0031] The experimental slicing equipment used in Examples 1-4 was the Yujing XQL921B. The silicon rod specifications were 182mm×182mm, the silicon rod length was 830mm, the silicon wafer thickness was 130um, the crystal rod type was N-type, and the experimental data were statistical data of 1000 silicon rods cut.

[0032] like Figure 2 As shown, the commercially available competitor YT has a wire-clamping rate of 2.5%, a wafer A-grade yield of 95.56%, a first-pass A-grade yield of 94.38%, a contamination rate of 0.43%, and a chipping rate of 0.52%. The commercially available competitor DB has a wire-clamping rate of 2.1%, a wafer A-grade yield of 95.52%, a first-pass A-grade yield of 94.41%, a contamination rate of 0.41%, and a chipping rate of 0.55%. The cutting fluid of this invention can reduce the cleaning contamination rate to less than 0.1%; the wire-clamping rate is 0%; and the first-pass A-grade yield of 182-size 130µm thick N-type silicon wafers is greater than 95%, and the wafer A-grade yield is greater than 96%, representing a significant improvement.

[0033] The bisphenol-type alcohol used in this invention has a rigid steric structure, which is conducive to the spatial extension of the grafted chain ends and is less likely to reduce dispersion efficiency and effect due to the curling of the grafted chain ends themselves or each other. The dispersant is grafted with ethylene oxide and propylene oxide polyether segments at the ends of four molecular chains, and is capped with propylene oxide. It has low foam and can eliminate foam. During the cutting spray cycle, it will not generate a large amount of foam and cause the risk of overflow. The polyethylene oxide groups have many dispersion and adsorption active sites and high dispersion efficiency. At the same time, the large molecular volume can form a water-retaining and lubricating layer on the silicon wafer surface, which has a good effect on the lifting and retraction process after cutting. It greatly overcomes the occurrence of lifting wire jamming and avoids secondary loss after silicon wafer cutting.

[0034] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of the N-type solar photovoltaic industry, characterized in that: It is composed of 20-35% by mass of bisphenol-based block polyether dispersant, 5-10% of super wetting agent, and water, wherein the water is EDI ultrapure water; the structure of the bisphenol-based block polyether dispersant is as follows: Wherein, 4≤m≤10, 8≤n≤20, 12≤m+n≤30, m and n are positive integers; R1 is H, CH3 or CH2CH3; R2 is H, CH3 or CH2CH3; The bisphenol block polyether dispersant uses bisphenol-type alcohols as initiators, grafts ethylene oxide and propylene oxide polyether segments at the four molecular chain ends, and ends with propylene oxide.

2. The diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of solar photovoltaic type N according to claim 1, characterized in that: The super wetting agent is one or a combination of Evonik's Tego Twin 4000, Tego Twin 4100, and Tego Twin 4200.

3. The diamond wire multi-wire cutting fluid for large-size thin monocrystalline silicon wafers of N-type solar photovoltaic according to claim 1, characterized in that: The bisphenol block polyether dispersant is 25%, and the super wetting agent is 8%.

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