Stable suspension water-based diamond grinding fluid and preparation method thereof

Abstract

The invention discloses a stably suspended water-based diamond grinding fluid and a preparation method thereof. The grinding fluid comprises the following components in percentage by mass: 0.4-0.8% of diamond micro powder, 1-5% of a Gemini type polyether quaternary ammonium salt surfactant, 0.1-2% of a pH regulator, 1-6% of a suspending agent, 0.01-0.2% of a preservative, 20-60% of a solvent and 10-40% of deionized water, and the sum of the mass percentages is 100%. The water-based diamond grinding fluid is high in grinding rate, small in TTV and high in grinding material dispersion stability, has the advantage of being not prone to sedimentation compared with a traditional water-based diamond grinding fluid, is safer, more environmentally friendly and easy to clean compared with an oily grinding fluid, and can avoid quality and potential safety hazards caused by temperature rise due to long-time operation.

Description

Technical Field

[0001] The invention belongs to the field of sapphire substrate grinding and processing, and in particular relates to a stable suspended aqueous diamond grinding liquid and a preparation method thereof. Background Art

[0002] At present, in the preparation of blue light LEDs, the heteroepitaxial method is usually used to grow gallium nitride materials. In commercialized LEDs, sapphire is used as the substrate material for epitaxial growth in most cases. Since sapphire materials have poor thermal conductivity, in order to prevent excessive temperature rise in the active area of ​​the LED from affecting its light output characteristics and life, the sapphire substrate must be back-thinned after completing processes such as electrode preparation to improve the heat dissipation performance of the device. In addition, since the Mohs hardness of sapphire is 9.0, in order to meet the requirements of subsequent processes such as dicing and splitting, the thickness of the substrate also needs to be thinned to a certain extent. Generally, the thickness of the epitaxial wafer needs to be thinned from more than 500 μm to around 100 μm or thinner. Since sapphire has a high hardness, the above-mentioned back thinning and polishing work usually takes a long time, so the processing efficiency and quality of back thinning and polishing become a key issue. There are two main steps to reduce the thickness of the sapphire substrate from about 500μm to about 100μm: first, use a 50-70μm grinding wheel on a lateral thinning machine to grind off about 300μm of thickness; then use a polishing machine (Xiuhe, NTS, WEC, etc.) for different grinding disks (tin / copper disks) and use suitable sapphire grinding fluid (water / oil) to polish the back of the chip, and finally reduce it from 150μm to about 100μm.

[0003] At present, the commonly used grinding fluids on the market can be divided into two types: water-based and oily. Oily grinding fluids generally have the advantages of high grinding rate and better workpiece surface processing quality. Therefore, oily grinding fluids are relatively more widely used. However, when grinding and polishing, the heat generated by continuous mechanical grinding friction under high pressure cannot be dissipated in time, causing the temperature of the grinding disc to rise rapidly with the increase of grinding time. The high temperature of the grinding disc will cause the disc surface to deform, and eventually cause the defect of large TTV of the substrate. At the same time, oily liquids are difficult to clean. If the back-end is not cleaned cleanly and the grinding fluid remains on the sapphire wafer, it will also affect the subsequent LED process.

[0004] Aqueous diamond polishing fluid has the advantages of being safe, environmentally friendly, easy to clean, and having low post-processing costs. However, the diamonds in the aqueous diamond polishing fluid tend to quickly settle to the bottom of the container, and need to be shaken again before use, which affects production efficiency. With the development and optimization of the aqueous diamond polishing fluid system, its grinding rate and grinding quality are also gradually improving. At present, it has a trend of gradually replacing oily polishing fluids to occupy the mainstream position in the LED industry. The patent (CN 105440953 A) discloses an aqueous diamond polishing fluid with continuous abrasive suspension. The invention treats diamond abrasives by using a surface modification method of alkylphenol polyoxyethylene ether to achieve long-term suspension of diamond abrasives. However, the alkylphenol polyoxyethylene ether used in it is a controlled substance in the European Union and does not meet the environmental protection regulations required by more and more LED factories today. Summary of the invention

[0005] The present invention aims to provide a stable suspended aqueous diamond grinding liquid and a preparation method thereof. The grinding liquid has the advantages of high grinding removal rate, small TTV, good abrasive dispersion, stable suspension and not easy to settle, environmental protection and safety, simple and fast production process, and high economic benefit.

[0006] To achieve the above object, the present invention adopts the following technical solution: A stable suspended aqueous diamond polishing liquid and a preparation method thereof, characterized in that the liquid is composed of the following raw materials in percentage by mass, with the sum of the percentages by mass being 100%: Diamond powder: 0.4-0.8%; Gemini type polyether quaternary ammonium salt surfactant: 1-5%; pH adjuster 0.1-2%; Suspension 1-6%; Preservative 0.01-0.2%; Solvent 20-60%; Deionized water 10-40%; The general structural formula of the Gemini type polyether quaternary ammonium salt surfactant is as follows: , wherein n is an integer between 1 and 10. The preparation thereof comprises the following steps: (1) Synthesis of dodecyltrimethylammonium chloride Take dodecyl dimethyl tertiary amine and isopropanol in a mass ratio of 1:4, stir for 10 minutes, mix thoroughly at room temperature, then add 36% concentrated hydrochloric acid, wherein the molar ratio of the effective component of hydrochloric acid to dodecyl dimethyl tertiary amine is 1.1:1, stir and react for 30 minutes to obtain dodecyl trimethyl ammonium chloride; (2) Synthesis of Gemini-type polyether quaternary ammonium salt surfactant The temperature of the reaction system was raised to 80°C, and epichlorohydrin and dodecyl polyoxyethylene ether tertiary amine were slowly added, and the addition was completed within 30 min. After the reaction was completed for 8 h, the heating was stopped to obtain a light yellow viscous transparent liquid. The liquid was cooled to room temperature, and the solvent, water and some impurities were removed by reduced pressure distillation at 60-70°C. The liquid was cooled, recrystallized with acetone for 3-5 times, and dried in vacuo to obtain the Gemini type polyether quaternary ammonium salt surfactant.

[0007] Furthermore, the diamond powder is a mixture of diamond A and diamond B; the diamond A and diamond B are one of single crystal diamond, polycrystalline diamond, polycrystalline diamond, and polycrystalline diamond. A mixture of polycrystalline diamond and polycrystalline diamond is preferred. The mass ratio of polycrystalline diamond to polycrystalline diamond is 8:1 to 4:1. When mixed diamond is used as an abrasive, due to the large surface area and volume of large-particle diamond abrasives, materials can be removed quickly and grinding efficiency can be improved, especially when removing excess materials in the initial grinding stage. Small-particle abrasives help reduce scratches and surface damage that may be caused by grinding with large-particle abrasives, and can enter areas that are difficult to reach with large-particle abrasives for finer polishing.

[0008] Further, the single crystal diamond particle size is 1-20 μm, the polycrystalline diamond particle size is 0.5-10 μm, the polycrystalline diamond particle size is 1-30 μm, and the polycrystalline diamond particle size is 1-30 μm. Preferably, the polycrystalline diamond particle size is 4-8 μm, and the polycrystalline diamond particle size is 0.5-1 μm.

[0009] Further, the pH regulator is one or more of isopropanolamine, diisopropylamine, diglycolamine, triethanolamine, N-butyldiethanolamine, ammonia, boric acid, acetic acid, acrylic acid, citric acid, and phytic acid, and the preferred pH value of the grinding liquid is in the range of 7-10. In a weakly alkaline environment with a pH value range of 7-10, the positive charge density of the Gemini type polyether quaternary ammonium salt surfactant is the highest, and its hydrophilic head group (usually a quaternary ammonium cation) becomes more hydrophilic, thereby enhancing its surface activity in aqueous solution, being able to more effectively adsorb on the particle surface and form a stable micelle structure, and promoting the dispersion of particles. However, too high a pH value may affect the stability of the quaternary ammonium salt, causing it to hydrolyze, thereby reducing its surface activity.

[0010] Furthermore, the suspending agent is one or more of saponified polyvinyl alcohol, hydroxymethyl cellulose, polymethacrylate, ethylene propylene copolymer, hydroxypropyl methyl fiber, montmorillonite, polyether polyester modified phosphate, organic bentonite, octadecyl acrylate-styrene-maleic anhydride, fumed silica, modified polyurea, polyvinyl pyrrolidone, xanthan gum, gelatin, sodium dodecylbenzene sulfonate, and non-ionic associative polyurethane, preferably montmorillonite.

[0011] Furthermore, sodium montmorillonite K-10 is preferred. The cations between the layers of sodium montmorillonite are sodium, which has higher cation exchange performance. + The charge density is relatively small, the hydration energy is lower, the hydration ability is stronger, and the expansion is better, which enhances the adsorption capacity of montmorillonite, and can adsorb more water molecules or other polar molecules, and is easier to disperse into a colloidal state to form a stable suspension. Montmorillonite K-10 is a special montmorillonite product. It has undergone special chemical treatment and processing. Compared with ordinary montmorillonite, montmorillonite K-10 has higher purity, better dispersibility and higher specific surface area, which improves the consistency and reliability of the product.

[0012] Furthermore, the preservative is one or more of sodium benzoate, sodium chloride, phenoxyethanol, and isothiazolinone, preferably sodium benzoate. The main reason for adding preservatives to the grinding liquid is to inhibit the growth of microorganisms and prevent the grinding liquid from being corrupted and deteriorating during use or storage. The activity of microorganisms may cause the decomposition of organic matter in the grinding liquid to produce metabolites, which may change the pH value, viscosity and chemical composition of the grinding liquid, thereby affecting the suspension and dispersibility of the abrasive particles. At the same time, microorganisms may form biofilms on the surface of the abrasive particles, change the surface properties of the particles, and reduce the friction and wear between the abrasive and the workpiece. As a preservative, sodium benzoate has an inhibitory effect on a variety of microorganisms, including bacteria, molds and yeasts; it is stable in the air, not easy to decompose, and has a low cost and is widely used.

[0013] Further, the solvent is one or more of ethylene glycol, polyethylene glycol, polypropylene glycol, and glycerol, preferably ethylene glycol and polyethylene glycol. Ethylene glycol as a solvent can synergistically dissolve a variety of substances (such as sodium benzoate), and after mixing with water, it can significantly reduce the freezing point of water and adapt to low-temperature environments. Ethylene glycol also has a certain lubricating effect, which can reduce the friction between the abrasive and the workpiece during the grinding process, reduce wear, and improve grinding efficiency. Polyethylene glycol can increase the viscosity of the grinding liquid, thereby improving the suspension of abrasive particles, reducing sedimentation, and maintaining the uniformity of the grinding liquid. Its long-chain molecular structure can provide a lubricating effect, reduce friction and wear during the grinding process, and also help to improve the wettability of the grinding liquid to the workpiece surface, so that the grinding liquid can better penetrate into the workpiece surface and improve the grinding efficiency.

[0014] Furthermore, the resistivity of the deionized water is greater than 16 MΩ·cm.

[0015] The method for preparing the above-mentioned stable suspended aqueous diamond polishing liquid comprises the following steps: (1) Mix deionized water and solvent and stir for 5-10 minutes; (2) Adding Gemini polyether quaternary ammonium salt surfactant and preservative to the solution obtained in step (1), stirring for 10-30 minutes; (3) adding a pH adjuster and a suspending agent to the solution obtained in step (2) to adjust the pH to 7-10; (4) Add diamond powder to the solution obtained in step (3), and stir ultrasonically for 20-30 min at an ultrasonic frequency of 28 kHz, an ultrasonic current of 2-4 A, and a stirring speed of 300-500 rpm.

[0016] The beneficial effects of the present invention are: (1) The Gemini type polyether quaternary ammonium salt surfactant molecule used in the present invention has two hydrophilic head groups and two hydrophobic chains. This structure enables it to form micelles in aqueous solution, significantly reducing the surface tension of the aqueous solution, thereby facilitating the dispersion of particles. Its hydrophilic head group carries a positive charge, and when adsorbed on the surface of solid particles, it can generate electrostatic repulsion to prevent aggregation between particles. The two hydrophobic chains are tightly connected by the connecting group, and the adsorption layer formed on the surface of the particles can produce a steric hindrance effect, further preventing particle aggregation. Therefore, the addition of the Gemini type polyether quaternary ammonium salt surfactant can improve the stability of the dispersion system and prevent the sedimentation and aggregation of the abrasive during long-term storage. At the same time, the Gemini type polyether quaternary ammonium salt surfactant has good biodegradability and is safer and more environmentally friendly.

[0017] (2) The present invention provides a stable suspended aqueous polishing fluid, which has the advantages of being easy to clean and having low post-processing costs compared to oily polishing fluids. Compared to traditional aqueous polishing fluids, it has the advantages of particles being difficult to settle and having stable suspension and dispersion properties.

[0018] (3) The stable suspended aqueous diamond grinding liquid provided by the present invention is used in the grinding and polishing of thinning the back side of LED sapphire, and has the advantages of small TTV, high removal rate, shallow scratches on the sapphire surface, and low fragmentation rate, which greatly improves the processing efficiency of sapphire and enhances the grinding benefit.

[0019] (4) The stable suspended aqueous diamond grinding fluid provided by the present invention has a simple production process, is easy to produce on an industrial scale, and has high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a synthetic step for dodecyltrimethylammonium chloride.

[0021] Figure 2 This is a synthesis step for Gemini type polyether quaternary ammonium salt surfactant.

[0022] Figure 3 Schematic diagram of the static stratification of the grinding liquid.

[0023] Figure 4 Schematic diagram of the scratches on the sapphire wafer after grinding under metallographic microscope. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The exemplary implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0025] A stable suspended aqueous diamond polishing fluid, which is composed of the following raw materials in percentage by weight, based on the sum of the percentages by weight being 100%: Diamond powder: 0.4-0.8%, Gemini type polyether quaternary ammonium salt surfactant: 1-5%, pH adjuster: 0.1-2%, Suspension agent: 1-6%, Preservatives: 0.01-0.2%, Solvent: 20-60%, Deionized water: 10-40%; The general structure of Gemini polyether quaternary ammonium salt surfactant is as follows: , where n is an integer from 1 to 10.

[0026] Its preparation comprises the following steps: (1) Synthesis of dodecyltrimethylammonium chloride Take dodecyl dimethyl tertiary amine and isopropanol in a mass ratio of 1:4, stir for 10 minutes at room temperature to fully mix, then add 36% concentrated hydrochloric acid, where the mass ratio of the effective component of hydrochloric acid to dodecyl dimethyl tertiary amine is 1:2, stir and react for 30 minutes to obtain dodecyl trimethyl ammonium chloride, such as Figure 1 shown.

[0027] (2) Synthesis of Gemini-type polyether quaternary ammonium salt surfactant The temperature of the reaction system was raised to 80 °C, and epichlorohydrin and dodecyl polyoxyethylene ether tertiary amine were slowly added to the obtained dodecyl trimethyl ammonium chloride to react, wherein the mass ratio of dodecyl trimethyl ammonium chloride, epichlorohydrin and dodecyl polyoxyethylene ether tertiary amine was 5:2:20, and the addition was completed within 30 min. After 8 h of reaction, the heating was stopped to obtain a light yellow viscous transparent liquid, which was cooled to room temperature and subjected to reduced pressure distillation at 60 °C to remove the solvent, water and some impurities, cooled to room temperature, and recrystallized with acetone for 4 times. The Gemini type polyether quaternary ammonium salt surfactant (n=9) was obtained, and its structural characterization data are as follows: 1 H NMR (300 MHz, DMSO- d6 ), δ: 0.88 (m, 6H, CH3), 1.26 (m, 32H, CH2), 1.29 (m, 4H, CH2), 1.71 (m, 4H, CH2), 3.22 (t, 4H, CH2), 3.30 (m, 6H, CH3), 3.41 (m, 4H, CH2), 3.50 (t, 4H, CH2), 3.52 (m, 64H, CH2), 3.54 (m, 4H, CH2), 3.70 (t, 4H, CH2), 3.81 (t, 4H, CH2), 4.77 (s, 1H, OH), 4.84 (m, 1H, CH), 5.40 (s, 2H, OH); 13 C NMR (125 MHz, DMSO- d6 ), δ: 14.1, 22.7, 25.4, 26.4, 26.8, 29.3,, 29.6, 31.9, 52.9, 54.8, 58.4, 58.7, 61.2, 61.3, 65.0, 65.,9, 70.1, 70.3, 70.4; HRMS calculated value C 69 H 144 O 21 N2Cl2 (M+H) + : 1407.5, measured value: 1408.5 The components and mass ratios of the aqueous diamond polishing liquids of Examples 1-7 are shown in Table 1: Table 1 Components and contents of different aqueous diamond polishing fluids in Examples 1-7

[0028] The preparation method of the stably suspended aqueous diamond polishing fluid of Example 1-7 is as follows: Weigh each component according to the weight ratio, mix deionized water and solvent and stir for 10 minutes, add Gemini polyether quaternary ammonium salt surfactant and preservative and stir for another 20 minutes; then add pH adjuster and suspending agent to adjust the pH to 7-10; add diamond powder to the above solution and ultrasonically stir for 30 minutes, with an ultrasonic frequency of 28 khz, an ultrasonic current of 4A, and a stirring speed controlled at 500 rpm to prepare a uniformly dispersed aqueous diamond polishing fluid.

[0029] The components and mass ratios of the stable suspended aqueous diamond polishing fluids of Comparative Examples 1-8 are shown in Table 2: Table 2 Components and contents in different aqueous diamond polishing fluids of Comparative Examples 1-8

[0030] The preparation method of Comparative Examples 1-8 is consistent with that of Examples 1-7.

[0031] Comprehensive performance tests were performed on Examples 1-7 and Comparative Examples 1-8: (1) Performance 1: Suspension days test Store the grinding liquid at room temperature away from light. When the abrasive material settles and layers from the shaken state to about 1 / 8 of the liquid level, it will no longer continue to settle. Figure 3 The storage time required for sedimentation to the layer was recorded as the evaluation standard of suspension performance.

[0032] (2) Performance 2: Material removal rate test: Step 1: Use a micrometer thickness gauge to measure the thickness of the sapphire sheet before grinding (accurate to 4 significant figures). Measure 5 locations in the top, bottom, left, right and center of the sapphire sheet in turn, test each point 3 times, and record the average value; Use solid wax to stick the sapphire sheet on the ceramic plate, place it on the grinder for grinding, and the grinding parameters are: speed 70r / min; pressure: 100kg; time: 10min; flow rate: 4ml / min; Step 2: After grinding, heat the sapphire sheet at 100℃ and remove it. Use wax remover, water, and IPA to clean the sapphire sheet. Use a 1000mm thickness gauge to test 5 locations of the sapphire sheet again and record the average value.

[0033] Material removal rate = average thickness difference before and after μm / time min (3) Performance 3: Scratch test: Metallographic microscope photo Figure 4 As shown, the left one is a diagram showing acceptable scratch levels, and the right one is a diagram showing unacceptable scratch levels.

[0034] (4) Performance 4: TTV test: Among the five points after grinding in the performance 1 test, the difference between the maximum thickness and the minimum thickness is taken as the TTV value μm.

[0035] Table 3 Comprehensive performance test results of grinding fluid

[0036] From Table 1, Table 2, and Table 3, it can be seen that the polishing liquids of Examples 2-5 can achieve the characteristics of long-lasting and stable suspension of abrasives, faster removal rate, low surface damage, and small TTV.

[0037] Compared with Example 2, Comparative Example 1 and Comparative Example 2 do not use diamond powder for mixing, and the material removal rate is relatively low.

[0038] Compared with Example 2, Comparative Example 3 did not add Gemini polyether quaternary ammonium salt surfactant, and the suspension sedimentation rate was faster. At the same time, due to the poor dispersibility of the abrasive (diamond powder), partial agglomeration occurred, resulting in an unqualified scratch degree.

[0039] Compared with Example 2, Comparative Example 5 did not add a suspending agent, and the suspension sedimentation rate was relatively fast.

[0040] Compared with Example 2, Comparative Example 7 did not add a pH regulator, which reduced the activity of the Gemini polyether quaternary ammonium salt surfactant, and the suspension sedimentation and scratch degree performance were poor.

[0041] Compared with Example 2, in Comparative Example 8, no preservative was added, and the long-term stability of the liquid medicine was affected, resulting in a shortened suspension sedimentation life.

[0042] The suspension and sedimentation performance of the grinding liquid is affected by the synergistic effect of the Gemini polyether quaternary ammonium salt surfactant, the suspending agent, and the pH regulator. The suspending agent can form a gel in water, adsorb the diamond powder in the grinding liquid, and fix it. The Gemini polyether quaternary ammonium salt surfactant can be dispersed in water, produce a steric hindrance effect, and further prevent the aggregation and sedimentation of particles. The pH regulator is the Gemini polyether quaternary ammonium salt surfactant to improve the weak alkaline environment and enhance the surface activity of the Gemini polyether quaternary ammonium salt surfactant in water. The three play a complementary role.

[0043] The material removal rate and scratches of the grinding liquid are mainly affected by the type of abrasive and the dispersion performance of the abrasive in the solution. From the perspective of abrasive particle size, the material removal rate is slower when using abrasives with low particle size, and vice versa when using abrasives with high particle size. From the perspective of abrasive types, the use of polycrystalline diamond and polycrystalline diamond also has obvious advantages over ordinary single crystals or polycrystalline-like crystals, because polycrystalline diamond and polycrystalline diamond are isotropic, and after they break after grinding, they can still form porous cutting edges inside, and the grinding life of the grinding particles is longer. From the perspective of abrasive dispersion, abrasives with poor dispersion performance will agglomerate in the solution, which will reduce the effective number of grinding particles, resulting in a decrease in grinding rate and heavier grinding scratches.

[0044] The TTV of the grinding fluid is mainly affected by the viscosity of the grinding. The viscosity of the grinding fluid increases with the increase of the amount of suspending agent added. The grinding fluid with higher viscosity is prone to produce higher disk temperature during grinding. High disk temperature is easy to cause the disk surface to deform, thus affecting the TTV index. Therefore, the addition of suspending agent in the grinding fluid needs to be controlled within a reasonable range.

[0045] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A stable suspended aqueous diamond polishing liquid, characterized in that: Assuming the sum of the mass percentages is 100%, the raw materials used and their mass percentages are: Diamond powder: 0.4-0.8%; Gemini type polyether quaternary ammonium salt surfactant: 1-5%; pH adjuster 0.1-2%; Suspension 1-6%; Preservatives 0.01-0.2%; Solvent 20-60%; Deionized water 10-40%; The general structural formula of the Gemini type polyether quaternary ammonium salt surfactant is: ， Wherein n is an integer between 1 and 10.

2. The stable suspension aqueous diamond polishing liquid according to claim 1, characterized in that: The diamond powder is a mixture of diamond A and diamond B; the diamond A and diamond B are one of single crystal diamond, polycrystalline diamond, polycrystalline diamond, and polycrystalline diamond.

3. The stable suspension aqueous diamond polishing liquid according to claim 2, characterized in that: The particle size of the single crystal diamond is 1-20 μm, the particle size of the polycrystalline diamond is 0.5-10 μm, the particle size of the polycrystalline diamond is 1-30 μm, and the particle size of the polycrystalline diamond is 1-30 μm.

4. The stable suspension aqueous diamond polishing liquid according to claim 1, characterized in that: The pH regulator is one or more of isopropanolamine, diisopropylamine, diglycolamine, triethanolamine, N-butyldiethanolamine, ammonia water, boric acid, acetic acid, acrylic acid, citric acid and phytic acid.

5. The stable suspension aqueous diamond polishing liquid according to claim 1, characterized in that: The suspending agent is one or more of saponified polyvinyl alcohol, hydroxymethyl cellulose, polymethacrylate, ethylene propylene copolymer, hydroxypropyl methyl fiber, montmorillonite, polyether polyester modified phosphate, organic bentonite, octadecyl acrylate-styrene-maleic anhydride, fumed silica, modified polyurea, polyvinyl pyrrolidone, xanthan gum, gelatin, sodium dodecylbenzene sulfonate, and non-ionic associative polyurethane.

6. The stable suspension aqueous diamond polishing liquid according to claim 1, characterized in that: The preservative is one or more of sodium benzoate, sodium chloride, phenoxyethanol and isothiazolinone.

7. The stable suspension aqueous diamond polishing liquid according to claim 1, characterized in that: The solvent is one or more of ethylene glycol, polyethylene glycol, polypropylene glycol and glycerol.

8. The stable suspension aqueous diamond polishing liquid according to claim 1, characterized in that: The resistivity of the deionized water is greater than 16 MΩ·cm.

9. The method for preparing a stable suspended aqueous diamond polishing liquid as claimed in claim 1, characterized in that: The following steps are involved: (1) Mix deionized water and solvent and stir for 5-10 minutes; (2) Adding Gemini polyether quaternary ammonium salt surfactant and preservative to the solution obtained in step (1), and stirring for 10-30 minutes; (3) adding a pH adjuster and a suspending agent to the solution obtained in step (2) to adjust the pH to 7-10; (4) Add diamond powder to the solution obtained in step (3), and stir ultrasonically for 20-30 min at an ultrasonic frequency of 28 kHz, an ultrasonic current of 2-4 A, and a stirring speed of 300-500 rpm.

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