Additive for water-based cutting cooling liquid for multi-wire cutting process and application

Abstract

The invention relates to an additive, in particular to an additive for a water-based cutting cooling liquid for a multi-wire cutting process and application of the additive, and particularly relates to an additive for a water-based cutting cooling liquid in the cutting process of hard and brittle materials such as semiconductors or solar silicon materials. The preparation method comprises the following steps: proportioning the following components in percentage by mass: 0.1-5% of hydrophilic micro powder; 20-85% of a hydrophilic solvent; 1-5% of a pH regulator; and the balance water. The foam phenomenon in the cutting process can be eliminated and relieved, the flow of cutting cooling liquid is stabilized, stable and continuous operation of cutting equipment is guaranteed, and the yield of silicon wafers and the like is improved.

Description

Technical Field

[0001] The invention relates to an additive, in particular to an additive for aqueous cutting coolant in a multi-wire cutting process and its application, and is particularly used as an additive for aqueous cutting coolant in a cutting process of hard and brittle materials such as semiconductors or solar silicon materials. Background Art

[0002] There are two main types of slicing technologies for glass and semiconductors: slurry cutting and diamond wire cutting. Since a large amount of heat is generated by friction during wire cutting, a cooling system is required to prevent wire breakage, a decrease in cutting quality, and even chipping. The cutting coolant used in the cooling system is a liquid that is sprayed on the cutting wire to lubricate, cool, and disperse abrasives or cut powders. The moving cutting wire brings the cutting coolant into the slicing gap to cool the slicing surface and the cutting wire. At the same time, the mechanical movement of the cutting wire is used to promptly remove the ground powder from the gaps between wafers and other objects to achieve a continuous and stable cutting effect.

[0003] With the technical progress of multi-wire cutting or cost control, steel wires are becoming thinner and thinner. At the same time, in order to improve cutting efficiency, in addition to increasing the speed of the steel wire, there is also a way to speed up the feeding speed. These changes in the cutting process require increasing the flow rate of the cutting fluid or cutting mortar. Because multi-wire cutting, whether it is a one-way cycle or a reciprocating cycle, uses the steel wire to push the abrasive to form a grinding motion on the object to be cut to achieve cutting. A large amount of heat is generated during the grinding process, and it is necessary to use the cutting coolant to absorb the heat to achieve cooling. Therefore, if the flow rate of the cutting fluid or cutting mortar remains unchanged, the heat taken away cannot keep up with the heat generated by the grinding motion. The cutting debris generated during the cutting process will not be wetted in time and carried out by the steel wire, causing the debris to stick to the surface. At the same time, the steel wire will also heat up quickly, resulting in a decrease in cutting ability, causing serious saw marks and dirt on the cutting surface such as the wafer, and also causing wire breakage.

[0004] Water is the substance with the highest thermal conductivity among non-metallic liquids, so increasing the water ratio in the water-based cutting fluid can improve its thermal conductivity and achieve a good cooling effect. The current wire diameter of wire cutting is about 60-120μm. The penetration and wetting of the gaps generated by cutting and the debris from grinding require the cutting fluid to have a relatively low surface tension. Therefore, in addition to water, the actual water-based cutting fluid usually contains water-soluble solvents and surfactants to achieve good permeability and wettability. While the surfactant reduces the surface tension, it also brings a negative problem to the cutting process, which is that it is easy to produce foaming. Because the cutting process requires the mortar to be sprayed above the cutting wire device, the spray can easily cause the mortar to foam, especially when the flow rate of the cutting mortar needs to be increased. More foam will be generated. Once the foam is generated and cannot be eliminated immediately, the flow of the mortar pump will be unstable, and even the mortar flowmeter alarm will appear, causing the cutting equipment to suddenly stop.

[0005] In order to eliminate the foam problem of water-based cutting coolant, it can be controlled by adding defoamers, etc., but it is still difficult to solve it fundamentally. Because non-silicone oil defoamers are weak; while silicone oils have good defoaming effects on pure water-based systems, they are not very ideal for water-based systems containing more solvents. In addition, silicone oil defoamers are prone to silicone oil demulsification and the risk of clogging the pipeline nozzle.

[0006] Therefore, there is a need for a technology that can solve the problem of unstable flow alarm or shutdown of the mortar pump caused by foaming of the cutting coolant without using silicone oil defoaming agents. Summary of the invention

[0007] The present invention mainly solves the deficiencies in the prior art and provides an additive and application for aqueous cutting coolant used in a multi-wire cutting process to solve the problem of foaming of aqueous cutting coolant during use, realize continuous operation of cutting equipment, and prevent the yield of cutting objects such as silicon wafers from decreasing.

[0008] The above technical problems of the present invention are mainly solved by the following technical solutions:

[0009] An additive for aqueous cutting coolant used in multi-wire cutting process:

[0010] The proportions are as follows:

[0011] Hydrophilic micro powder 0.1-5%; hydrophilic solvent 20-85%; pH adjuster 1-5%; water balance;

[0012] Its preparation method is:

[0013] First, prepare a hydrophilic solvent, add the hydrophilic micropowder thereto and stir evenly, then add water and pH buffer components and stir until uniform.

[0014] Preferably, the hydrophilic micropowder is silicon dioxide micropowder and / or titanium dioxide, and the particle size thereof ranges from 0.2 to 10 μm.

[0015] Preferably, the hydrophilic solvent is one or more of ethylene glycol (EG), propylene glycol (PG), diethylene glycol (DEG), dipropylene glycol (DPG), and polyethylene glycol (PEG, molecular weight less than 400).

[0016] Preferably, the pH adjuster is one or more of sodium dihydrogen phosphate and citric acid buffer, dipotassium hydrogen phosphate and citric acid buffer, disodium hydrogen phosphate and potassium dihydrogen phosphate buffer, citric acid and sodium citrate buffer, citric acid and potassium citrate buffer; the pH range of the pH adjuster is between 5.0 and 6.8.

[0017] An application of an additive for aqueous cutting coolant in a multi-wire cutting process, and its application scenarios are:

[0018] Add in the manufacture of water-based cutting coolant;

[0019] Or, add when preparing cutting mortar;

[0020] Or, add to the cutting mortar during the wire cutting process;

[0021] Or, add to the cutting fluid during the wire cutting process;

[0022] The amount of the additive used is a mass ratio of water-based cutting coolant to the additive of 100:1-5.

[0023] Aqueous cutting fluid additives often contain surfactants that can easily cause foaming. When the cutting fluid is sprayed to cool the wire saw, foam is generated, which can easily lead to unstable cutting fluid flow, causing flow meter alarms and even shutdowns. The additives of this technology can eliminate and reduce foaming without using silicone oil defoamers, stabilize the flow of cutting coolant, ensure stable and continuous operation of cutting equipment, and improve the yield of silicon wafers. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further specifically described below through embodiments.

[0025] The hydrophilic solvent of the present invention is a hydroxyl-containing organic solvent commonly used in aqueous cutting fluids. The additives using these hydrophilic solvents have good stability after being mixed with aqueous cutting fluids. The solvent can be one of ethylene glycol (EG), propylene glycol (PG), diethylene glycol (DEG), dipropylene glycol (DPG), polyethylene glycol (PEG, molecular weight less than 400), or a mixture of these solvents. It is best to choose a solvent type that is completely consistent with the cutting fluid. Its content is also best to be consistent with the solvent content ratio in the aqueous cutting fluid, so as to ensure that it does not affect the stability and application performance of the original product. Based on the above viewpoints, the additive solvent content is preferably 20-85%.

[0026] The hydrophilic micropowder of the present invention is a fine particle of nanometer to micrometer level, which can be stably dispersed in a hydrophilic solvent, and when the cutting fluid generates foam, it can promote the thinning and accelerated rupture of the foam liquid film containing hydrophilic particles, thereby reducing foam. The particle size of the above-mentioned micropowder is preferably in the range of 0.2-10.0μm. Although the micropowder exceeding 10um still shows a defoaming effect, it is easy to settle after being prepared as an additive. The hydrophilic micropowder used in the present invention includes: Saint Ann's spherical micropowder PG-50 (0.5μm), PG-500 (5μm), PG-1000 (10μm) and Ningbo Xinfu NTR-606 coating grade titanium dioxide (0.3μm).

[0027] The preparation method of the additive is as follows: first prepare a hydrophilic solvent, add the hydrophilic micropowder thereto and stir evenly, then add water and pH buffer components and stir until uniform.

[0028] Examples of the additives of the present invention are shown in Table 1, but the present invention is not limited to the following examples.

[0029] Table 1

[0030]

[0031]

[0032] The effects of the present invention are described below in conjunction with embodiments and experimental data.

[0033] However, the present invention is not limited to the following examples. The cutting fluids used are Sundash CL-821 and Sundash CL-8830, the proprietary products of Sundash Chemical (Co., Ltd.). Sundash CL-821 is a cutting coolant for free mortar, which is used as stock solution during cutting; Sundash CL-8830 is a diamond wire cutting fluid, which is generally used after being diluted 30-100 times with water.

[0034] Embodiment 1:

[0035] Prepare 200g of cutting coolant, take 190g of SUNDASH CL-821, add 10g of additive 1 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0036] Embodiment 2:

[0037] Prepare 200g of cutting coolant, take 198g of SUNDASH CL-821, add 2g of additive 2 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0038] Embodiment three:

[0039] Prepare 200g of cutting coolant, take 194g of SUNDASH CL-821, add 6g of additive 3 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0040] Embodiment 4:

[0041] Prepare 200g of cutting coolant, take 194g of SUNDASH CL-821, add 6g of additive 4 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0042] Embodiment five:

[0043] Prepare 200g of cutting coolant, take 194g of SUNDASH CL-821, add 6g of additive 5 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0044] Embodiment six:

[0045] Prepare 200g of cutting coolant, take 194g of SUNDASH CL-821, add 6g of additive 6 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height (ml). The data is shown in Table 2.

[0046] Embodiment seven:

[0047] Prepare 200g of cutting coolant, take 194g of SUNDASH CL-821, add 6g of additive 7 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0048] Embodiment eight:

[0049] Prepare 200g of cutting coolant, take 190g of SUNDASH CL-821, add 10g of additive 8 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0050] Embodiment nine:

[0051] Prepare 200g of cutting coolant, take 194g of SUNDASH CL-821, add 6g of additive 9 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0052] Embodiment ten:

[0053] Prepare 200g of cutting coolant, take 4g of SUNDASH CL-8830 and 186g of water, add 10g of additive 7 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0054] Embodiment eleven:

[0055] Prepare 200g of cutting coolant, take 4g of SUNDASH CL-8830 and 190g of water, then add 6g of additive 5 and stir evenly. Then pour into a 1000mL measuring cylinder, use the bubbling method to bubble the cutting coolant from the bottom of the measuring cylinder for 1 minute, and record the foam height. The data is shown in Table 2.

[0056] Table 2 Summary of foam height results of additive bubbling test

[0057]

[0058] It can be seen from Table 2 that, compared with the comparative example, the foam height of the bubbling test is significantly reduced after adding various additives.

Claims

1. An additive for aqueous cutting coolant in a multi-wire cutting process, characterized in that: The proportions are as follows: Hydrophilic micropowder 0.1-5%; hydrophilic solvent 20-85%; pH adjuster 1-5%; water as the balance.

2. The additive for aqueous cutting coolant in a multi-wire cutting process according to claim 1, characterized in that: The hydrophilic micropowder is silicon dioxide micropowder and / or titanium dioxide, and its particle size ranges from 0.2 to 10 μm.

3. The additive for aqueous cutting coolant in a multi-wire cutting process according to claim 1, characterized in that: The hydrophilic solvent is one or more of ethylene glycol (EG), propylene glycol (PG), diethylene glycol (DEG), dipropylene glycol (DPG), and polyethylene glycol (PEG, molecular weight less than 400).

4. The additive for aqueous cutting coolant in a multi-wire cutting process according to claim 1, characterized in that: The pH adjuster is one or more of sodium dihydrogen phosphate and citric acid buffer, dipotassium hydrogen phosphate and citric acid buffer, disodium hydrogen phosphate and potassium dihydrogen phosphate buffer, citric acid and sodium citrate buffer, citric acid and potassium citrate buffer; the pH range of the pH adjuster is between 5.0 and 6.

8.

5. The use of an additive for aqueous cutting coolant in a multi-wire cutting process according to claim 1, characterized in that: Its application scenarios are: adding in the manufacture of water-based cutting coolant; Or, add when preparing cutting mortar; Or, add to the cutting mortar during the wire cutting process; Or, add to the cutting fluid during the wire cutting process; The amount of the additive used is a mass ratio of water-based cutting coolant to the additive of 100:1-5.

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