Fine polishing liquid for diamond substrate, preparation method of fine polishing liquid and polishing method of diamond substrate

Abstract

The invention discloses fine polishing liquid for a diamond substrate, a preparation method of the fine polishing liquid and a polishing method of the diamond substrate, and relates to the technical field of diamond processing. The fine polishing liquid for the diamond substrate comprises a first fine polishing liquid or a second fine polishing liquid, the first fine polishing liquid comprises the following raw materials: 1-7 parts of a first grinding material, 0.1-1 part of a dispersing agent, 0.1-1 part of a suspending agent, 2-3 parts of an oxidizing agent and the balance of water, the total amount is 100 parts, and the first grinding material comprises diamond or aluminum oxide; the second fine polishing liquid comprises the following raw materials: 89-97 parts of a second grinding material, 0.1-1 part of a dispersing agent and 3-10 parts of an oxidizing agent, the total parts are 100, and the second grinding material comprises silica sol. The surface energy of the diamond substrate is improved through the oxidizing agent, the surface is softened, and the diamond substrate and the grinding material can be physically cut more easily; the dispersing agent and the suspending agent are added, so that abrasive particles are uniformly dispersed, and a relatively consistent machined surface is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond processing, and particularly relates to a fine polishing liquid for a diamond substrate, a preparation method thereof, and a polishing method for a diamond substrate. Background Art

[0002] As a material with extremely high hardness and brittle characteristics, diamond is widely used in various fields, such as electronics, optics, tool processing, etc. At present, processes such as cutting, grinding, and polishing of diamond crystals are required for the industrial utilization of diamond.

[0003] Common diamond polishing schemes generally include three processes: rough grinding, fine grinding, and fine polishing. Chemical mechanical polishing (CMP) is a super-precision polishing method, which is widely used in the planarization treatment of the surfaces of integrated circuit chips, computer hard disks, micro-electromechanical systems, optical glass, etc. However, due to the extremely high chemical inertness and hardness of diamond, conventional polishing liquids are difficult to achieve an ideal ultra-smooth surface and non-damaged surface. Therefore, there are almost no fine polishing liquids for diamond substrates on the market. At present, the main schemes for fine polishing of diamond are: energy beam polishing technology, laser polishing, ion beam polishing, plasma-assisted polishing, and laser-assisted polishing. Although these polishing methods have a high removal rate, due to the extremely high hardness of diamond, the accuracy after fine polishing using traditional polishing methods is limited, and the surface roughness of the processed workpiece is difficult to control below 10 μm. Moreover, traditional polishing methods may also cause thermal cracks or other damages to the diamond surface, which greatly limits the application of diamond.

[0004] Therefore, it is still of great significance for those skilled in the art to develop a fine polishing liquid for diamond substrates to overcome the defects of low polishing rate, low surface roughness, and poor surface quality existing in the diamond polishing process. Summary of the Invention

[0005] The main object of the present invention is to propose a fine polishing liquid for a diamond substrate, a preparation method thereof, and a polishing method for a diamond substrate, aiming to develop a fine polishing liquid for a diamond substrate to solve the problems of low polishing rate, low surface roughness, and poor product quality existing in the existing diamond polishing process.

[0006] To achieve the above object, the present invention proposes a fine polishing liquid for a diamond substrate, and the fine polishing liquid for a diamond substrate includes a first fine polishing liquid or a second fine polishing liquid, wherein: The first fine polishing liquid includes the following raw materials in parts by mass: 1-7 parts of a first abrasive, 0.1-1 part of a dispersant, 0.1-1 part of a suspending agent, 2-3 parts of an oxidant, and the balance is water, totaling 100 parts. The first abrasive includes diamond or alumina; The second fine polishing liquid comprises raw materials in the following parts by mass: 89-97 parts of a second abrasive, 0.1-1 part of a dispersant, and 3-10 parts of an oxidant, with a total of 100 parts. The second abrasive comprises silica sol.

[0007] In one embodiment, the fine polishing liquid for a diamond substrate comprises a first fine polishing liquid. In the first fine polishing liquid: The diamond has a particle size of 0.1-5 μm; and / or, The alumina has a particle size of 0.5-20 μm.

[0008] In one embodiment, the fine polishing liquid for a diamond substrate comprises a first fine polishing liquid. In the first fine polishing liquid: The dispersant comprises at least one of Disper850 dispersant, DisperST-400 dispersant, AD8030 dispersant, sodium pyrophosphate, sodium silicate, and potassium silicate; and / or, The suspending agent comprises at least one of xanthan gum, carbomer, sodium polyacrylate, and polyacrylamide; and / or, The oxidant comprises at least one of hydrogen peroxide, potassium ferrate, ammonium bifluoride, sodium hypochlorite, and ferric chloride.

[0009] In one embodiment, the fine polishing liquid for a diamond substrate comprises a second fine polishing liquid. In the second fine polishing liquid: The silica sol has a particle size of 60-150 nm.

[0010] In one embodiment, the fine polishing liquid for a diamond substrate comprises a second fine polishing liquid. In the second fine polishing liquid: The dispersant comprises at least one of Disper850 dispersant, DisperST-400 dispersant, AD8030 dispersant, sodium pyrophosphate, sodium silicate, and potassium silicate; and / or, The oxidant comprises at least one of hydrogen peroxide, potassium ferrate, ammonium bifluoride, sodium hypochlorite, and ferric chloride.

[0011] The present invention provides a method for preparing the fine polishing liquid for a diamond substrate as described above. The fine polishing liquid for a diamond substrate comprises a first fine polishing liquid. The method for preparing the fine polishing liquid for a diamond substrate comprises the following steps: A1. Mix water and a suspending agent to obtain a first mixed liquid; A2. Adjust the pH of the first mixed liquid to a first preset pH, and then mix the first mixed liquid, an oxidant, and a dispersant to obtain a second mixed liquid; A3. Mix the second mixed liquid and a first abrasive to obtain the fine polishing liquid for a diamond substrate.

[0012] In one embodiment, the pH value of the first preset pH is 8 to 10.

[0013] The present invention provides a method for preparing a fine polishing liquid for a diamond substrate, the fine polishing liquid for a diamond substrate includes a second fine polishing liquid, and the method for preparing the fine polishing liquid for a diamond substrate includes the following steps: B1. First, add a second abrasive to a blender, start the stirring kettle, then add an oxidant and a dispersant, and mix to obtain a third mixed liquid; B2. Adjust the pH of the third mixed liquid to a second preset pH to obtain the fine polishing liquid for a diamond substrate.

[0014] In one embodiment, the pH value of the second preset pH is 8 to 10.

[0015] The present invention provides a polishing method for a diamond substrate, including the following steps: C1. Provide a diamond substrate and a polishing pad; C2. Apply the fine polishing liquid to the polishing pad, and use the polishing pad to polish the diamond substrate to obtain a polished diamond substrate; Wherein, the fine polishing liquid adopts the fine polishing liquid for a diamond substrate described in the above technical solution or the fine polishing liquid prepared by the method for preparing the fine polishing liquid for a diamond substrate according to the above technical solution.

[0016] In the technical solution of the present invention, the provided fine polishing liquid for a diamond substrate selects one of diamond, alumina, and silica sol as the abrasive, and the dispersant is used to make the abrasive particles evenly dispersed, so as to obtain a relatively consistent processed surface during the fine polishing process of the workpiece; the suspending agent is used to prevent the abrasive from depositing at the bottom during the polishing process, ensuring the uniform distribution of the abrasive, thereby reducing the possibility of damage such as scratches and increased roughness on the workpiece surface; the oxidant reacts chemically with the diamond surface, thereby increasing the surface energy of the diamond substrate, softening the surface, making the diamond substrate easier to physically cut with the abrasive, which is beneficial to improving the removal rate, and after being treated with the oxidant, the surface of the diamond substrate is smoother and brighter, achieving the effect of brightening the processed part, which is beneficial to improving the surface quality of the workpiece. The fine polishing liquid provided by the technical solution of the present invention can be used in the fine polishing process of a diamond substrate, which can not only solve the problems of low polishing rate, low surface roughness, and poor surface quality, but also selects common materials as the raw materials of the fine polishing liquid, does not require complex modification of the abrasive, does not require strict control of the polishing process, has good stability, can be used for a long time, has the advantages of low cost and high efficiency, and is suitable for large-scale applications. Detailed Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0018] It should be noted that if there are directional indications (such as up, down, left, right, front, back,...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0019] In addition, if there are descriptions such as "first", "second", etc. involved in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0020] As a material with extremely high hardness and brittle characteristics, diamond is widely used in various fields, such as electronics, optics, tool processing, etc. At present, diamond crystals need to be cut, ground, polished and other processes to be industrially utilized. The common diamond polishing solutions generally include three processes: rough grinding, fine grinding and fine polishing.

[0021] Chemical mechanical polishing (CMP) is an ultra-precision polishing method, which is widely used in the planarization of the surfaces of integrated circuit chips, computer hard disks, micro-electromechanical systems, optical glass, etc. However, due to the extremely high chemical inertness and hardness of diamond, it is difficult for conventional polishing fluids to achieve an ideal ultra-smooth surface and non-damaged surface. Therefore, there are almost no fine polishing fluids for diamond substrates on the market. At present, the main solutions for fine polishing of diamond are: energy beam polishing technology, laser polishing, ion beam polishing, plasma-assisted polishing, and laser-assisted polishing. Although these polishing methods have a high removal rate, due to the extremely high hardness of diamond, the accuracy after fine polishing using traditional polishing methods is limited, and it is difficult to control the surface roughness of the processed workpiece below 10 μm. Moreover, traditional polishing methods may also cause thermal cracks or other damages to the diamond surface, thus greatly limiting the application of diamond. Therefore, it is still of great significance for those skilled in the art to solve the problems of low polishing rate and poor product quality existing in the diamond polishing process.

[0022] Based on the above background, the present invention provides a fine polishing fluid for a diamond substrate. The fine polishing fluid for a diamond substrate includes a first fine polishing fluid or a second fine polishing fluid, wherein: The first fine polishing fluid includes the following raw materials in parts by mass: 1-7 parts of a first abrasive, 0.1-1 part of a dispersant, 0.1-1 part of a suspending agent, 2-3 parts of an oxidizing agent, and the balance is water, totaling 100 parts. The first abrasive includes diamond or alumina; The second fine polishing fluid includes the following raw materials in parts by mass: 89-97 parts of a second abrasive, 0.1-1 part of a dispersant, 3-10 parts of an oxidizing agent, totaling 100 parts. The second abrasive includes silica sol.

[0023] The technical solution of the present invention selects one of diamond, alumina, and silica sol as the abrasive. The dispersant is used to make the abrasive particles disperse evenly, which is beneficial to obtaining a relatively consistent processed surface during the fine polishing process of the processed workpiece; the suspending agent is used to prevent the abrasive from depositing at the bottom during the polishing process, ensuring the uniform distribution of the abrasive and reducing the possibility of damage such as scratching and increased roughness to the workpiece surface; the oxidizing agent reacts with the diamond surface to generate an oxidation layer with higher reactivity and relatively softer properties, thereby increasing the surface energy of the diamond substrate, softening the surface, making it easier for the diamond substrate to physically cut with the abrasive, thus improving the polishing rate. Moreover, after being treated with the oxidizing agent, the surface is smoother and brighter, and the processed part can also be brightened, further improving the surface quality of the processed workpiece. The fine polishing fluid provided by the technical solution of the present invention can be used to solve the problems of low polishing rate and low surface roughness of the processed workpiece.

[0024] The fine polishing liquid for diamond substrates provided by the present invention does not require modification of the abrasive. By optimizing the components of the fine polishing liquid, diamond can be selected as the abrasive, or alumina or silica sol can also be used as the abrasive. After applying the prepared fine polishing liquid to the polishing of diamond substrates, the surface roughness of the processed workpieces is small. In addition, selecting diamond or alumina as the abrasive can reduce the risk of crystallization. Prolonged use is beneficial for cost control, and the processed workpieces are easy to clean and more environmentally friendly. Using silica sol as the abrasive has a high processing yield and low raw material cost. In addition, the fine polishing liquid for diamond substrates provided by the present invention can be recycled multiple times, which is beneficial for cost savings.

[0025] It should be noted that if there is too much abrasive, scratches will occur and the TTV (Total Thickness Variation) will increase; if there is too little first abrasive, the polishing rate will decrease; if there is too much oxidant, surface pits, orange peel, etc. will occur, and if there is too little oxidant, the polishing rate will decrease. Therefore, setting the dosages of the first abrasive, second abrasive, dispersant, and oxidant within the above ranges can reduce the scratching phenomenon during fine polishing and avoid too slow a polishing rate at the same time. If the dosage of the suspending agent is insufficient, sedimentation of abrasive particles may occur, resulting in uneven surface treatment of the workpiece; if the dosage of the suspending agent is too large, the viscosity of the fine polishing liquid will be too high, the relative movement between the abrasive particles and the workpiece surface will be hindered, the effective contact will be reduced, and the material removal efficiency will be lowered. Therefore, setting the dosage of the suspending agent within the above range can ensure both the rate and obtain a better processed surface.

[0026] In an embodiment of the present invention, the fine polishing liquid for diamond substrates includes a first fine polishing liquid. In the first fine polishing liquid, the median particle size D50 of the diamond is 0.1 - 5 μm. If the particle size exceeds the above range, the roughness and TTV will increase, increasing the risk of scratching; if it is lower than the above range, the polishing rate will be affected. The technical solution of the present invention sets the particle size of the diamond within the above range, which can achieve a higher polishing rate and obtain a better polishing effect at the same time.

[0027] In an embodiment of the present invention, the fine polishing liquid for diamond substrates includes a first fine polishing liquid. In the first fine polishing liquid, the median particle size D50 of the alumina is 0.5 - 20 μm. If the particle size exceeds the above range, the roughness and TTV will increase, increasing the risk of scratching; if it is lower than the above range, the polishing rate will be affected. Setting the particle size of the alumina within the above range can achieve a higher polishing rate and a better polishing effect at the same time.

[0028] In an embodiment of the present invention, the polishing liquid for diamond substrate comprises a first polishing liquid, in which the dispersant comprises at least one of Disper850 dispersant, DisperST-400 dispersant, AD8030 dispersant, sodium pyrophosphate, sodium silicate and potassium silicate. The dispersant is used to disperse the abrasive particles uniformly.

[0029] In an embodiment of the present invention, the polishing liquid for diamond substrate comprises a first polishing liquid, in which the suspending agent comprises at least one of xanthan gum, carbomer, sodium polyacrylate and polyacrylamide. The suspending agent is used to prevent abrasives from being deposited at the bottom during polishing, resulting in insufficient solid content of the actual abrasives, ensuring that the abrasives are evenly distributed, and that soft lumps do not occur, thereby causing scratches on the workpiece surface, increased roughness and other damages; insufficient solid content will also lead to a slow polishing process.

[0030] In an embodiment of the present invention, the polishing liquid for diamond substrate comprises a first polishing liquid, in which the oxidant comprises at least one of hydrogen peroxide, potassium ferrate, ammonium bifluoride, sodium hypochlorite and ferric chloride. The oxidant can chemically react with the surface of the diamond substrate, oxidize the surface layer into corresponding oxides, increase the surface energy of the diamond substrate, thereby softening the surface, making the diamond substrate easier to physically cut with the abrasive, and increasing the removal rate. After adding the oxidant treatment, the workpiece can also be brightened, further improving the surface quality of the workpiece.

[0031] In an embodiment of the present invention, the polishing liquid for diamond substrates includes a second polishing liquid, in which the median particle size D50 of the silica sol is 60-150 nm. Particle sizes beyond the above range will increase the roughness and TTV, increasing the risk of scratches, and those below the above range will affect the polishing rate. The technical solution of the present invention sets the particle size of the silica sol within the above range, which can achieve a higher polishing rate and obtain a better polishing effect.

[0032] In an embodiment of the present invention, the polishing liquid for diamond substrate comprises a second polishing liquid, in which the dispersant comprises at least one of Disper850 dispersant, DisperST-400 dispersant, AD8030 dispersant, sodium pyrophosphate, sodium silicate and potassium silicate. The dispersant is used to disperse the abrasive particles uniformly.

[0033] In an embodiment of the present invention, the fine polishing liquid for a diamond substrate includes a second fine polishing liquid. In the second fine polishing liquid, the oxidizing agent includes at least one of hydrogen peroxide, potassium ferrate, ammonium bifluoride, sodium hypochlorite, and ferric chloride. The oxidizing agent can chemically react with the surface of the diamond substrate to oxidize the surface layer into the corresponding oxide, increasing the surface energy of the diamond substrate, thereby softening the surface and making the diamond substrate more easily physically cut by the abrasive, improving the removal rate. Adding an oxidizing agent can also brighten the workpiece, further enhancing the surface quality of the processed workpiece.

[0034] The present invention provides a method for preparing the fine polishing liquid for a diamond substrate. The fine polishing liquid for a diamond substrate includes a first fine polishing liquid. The method for preparing the fine polishing liquid for a diamond substrate includes the following steps: A1. Mix water and a suspending agent to obtain a first mixed liquid; A2. Adjust the pH of the first mixed liquid to a first preset pH, and then mix the first mixed liquid, an oxidizing agent, and a dispersing agent to obtain a second mixed liquid; A3. Mix the second mixed liquid and a first abrasive to obtain the fine polishing liquid for a diamond substrate.

[0035] When diamond or alumina is selected as the abrasive, directly mixing raw materials such as the abrasive, dispersing agent, and oxidizing agent will result in insufficient mixing of the raw materials, and then deviation in the performance test of the obtained fine polishing liquid (such as viscosity, conductivity, etc.). The suspending agent will increase the viscosity, and the dispersing agent will decrease the viscosity. Adding them together will cause instability in the solution system and damage to the polishing liquid system. The technical solution of the present invention selects to first add the suspending agent, then add the oxidizing agent and the dispersing agent, and finally add the abrasive, which is beneficial for the abrasive to be fully dispersed and obtain a fine polishing liquid with stable performance.

[0036] In an embodiment of the present invention, the mixing of each raw material is carried out under stirring, wherein: In step A1, the rotation speed of the stirrer is 800 - 1000 rpm, and the stirring time is 15 - 20 min.

[0037] In step A2, the rotation speed of the stirrer is 1200 - 1600 rpm, and the stirring time is 15 - 20 min.

[0038] In step A3, the rotation speed of the stirrer is 1200 - 1600 rpm, and the stirring time is 15 - 20 min.

[0039] When diamond or alumina is selected as the abrasive, setting the frequency and stirring time of the stirring kettle within the above range can evenly disperse the abrasive and obtain a stable polishing liquid system.

[0040] In an embodiment of the present invention, the pH value of the first preset pH is 8 to 10. The main purpose of adjusting the pH of the first mixed solution to the first preset pH is to provide a pH environment in which the oxidant and the suspending agent can take effect. When the pH is too low, the suspension and dispersion effect may decrease, resulting in a poor surface effect; when the pH is too high, the oxidizing ability of the oxidant may decrease, resulting in a reduced rate.

[0041] In an embodiment of the present invention, an alkaline pH regulator is used to adjust the pH of the first mixed solution, and the alkaline pH regulator includes at least one of sodium hydroxide, potassium hydroxide, triethanolamine and ammonia water.

[0042] The present invention provides a method for preparing a fine polishing liquid for a diamond substrate, wherein the fine polishing liquid for a diamond substrate comprises a second fine polishing liquid, and the method for preparing the fine polishing liquid for a diamond substrate comprises the following steps: B1, first add the second abrasive into the mixer, start the stirring kettle, then add the oxidant and the dispersant, mix, and obtain the third mixed solution; B2. Adjusting the pH of the third mixed solution to a second preset pH to obtain the fine polishing solution for the diamond substrate.

[0043] When silica sol is used as an abrasive, the abrasive is first dispersed, and then a dispersant and an oxidant are added to mix the raw materials sufficiently, which is conducive to obtaining a stable polishing system. It should be noted that when silica sol is used as an abrasive, the silica sol can be directly selected from silica sol with a solid content of 40-60%, or the silica sol can be mixed with water to make the solid content of the silica sol reach 40-60%.

[0044] In an embodiment of the present invention, the step B1 specifically includes: Add abrasive into the mixer, stir for 15-20 minutes, then add oxidant and dispersant, stir for 15-20 minutes to obtain a third mixed solution; Wherein, the rotation speed of the stirrer is 1200~1600rpm.

[0045] By setting the frequency and stirring time of the stirring kettle within the above range, the abrasive can be evenly dispersed.

[0046] In an embodiment of the present invention, the pH value of the second preset pH is 8 to 10. The main function of adjusting the pH of the third mixed solution to the second preset pH is to make the abrasive have a better suspension and dispersion effect and provide a suitable pH environment for the oxidant. When the pH is too low, the suspension and dispersion effect may decrease, resulting in a poor surface effect; when the pH is too high, the oxidizing ability of the oxidant may decrease, resulting in a reduced removal rate. Therefore, setting the pH value of the second polishing liquid within the above range is conducive to maintaining a good suspension effect of the polishing liquid and obtaining a good processed surface.

[0047] In an embodiment of the present invention, an alkaline pH regulator is used to adjust the pH of the third mixed solution, and the alkaline pH regulator includes at least one of sodium hydroxide, potassium hydroxide, triethanolamine, and ammonia water.

[0048] The present invention provides a polishing method for a diamond substrate, comprising the following steps: C1. Provide a diamond substrate and a polishing pad; C2. Apply the fine polishing liquid to the polishing pad, and use the polishing pad to polish the diamond substrate to obtain a polished diamond substrate; Wherein, the fine polishing liquid adopts the fine polishing liquid for diamond substrate described in the above technical solution or the fine polishing liquid prepared by the preparation method of the fine polishing liquid for diamond substrate described in the above technical solution.

[0049] The fine polishing liquid provided by the present invention can be carried out according to the conventional grinding process. In an embodiment of the present invention, the polishing is carried out on a single-sided grinding machine. The workpiece is placed on a customized carrier, the fine polishing liquid is applied to the polishing pad, and then the diamond substrate is polished with the polishing pad containing the fine polishing liquid. After the polishing time ends, the workpiece is taken off and cleaned to obtain a polished diamond substrate. The process parameters of the polishing are: the upper rotation speed is 50 rpm, the lower rotation speed is 200 rpm, the pressure is 18 kg, and the time is set to 4 h.

[0050] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0051] Example 1 A fine polishing liquid for a diamond substrate, comprising: 10 g of diamond (particle size of 0.5 μm), 1 g of carbomer, 1 g of sodium pyrophosphate, 20 g of potassium ferrate, and 968 g of water.

[0052] The preparation method of the fine polishing liquid for a diamond substrate comprises the following steps: (1) Add 968 g of water and 1 g of carbomer to a blender to obtain a first mixed solution, and then adjust the pH value of the first mixed solution within 8-10 with sodium hydroxide; wherein, the rotation speed of the blender is 1000 rpm and it is stirred for 20 min; (2) Add 20 g of potassium ferrate and 1 g of sodium pyrophosphate to the first mixed solution in step (1), and stir at a rotation speed of 1500 rpm for 20 min to obtain a second mixed solution; (3) Add 10 g of diamond to the second mixed solution in step (2), and stir at a rotation speed of 1500 rpm for 20 min to obtain the fine polishing liquid for a diamond substrate.

[0053] Example 2 A fine polishing liquid for diamond substrates, comprising: 70 g of alumina (particle size 5 μm), 5 g of xanthan gum, 2 g of AD8030 dispersant, 30 g of sodium hypochlorite, and 893 g of water.

[0054] The preparation method of the fine polishing liquid for diamond substrates includes the following steps: (1) Add 893 g of water and 5 g of xanthan gum into a blender to obtain a first mixed liquid, and then adjust the pH value of the first mixed liquid within 8 - 10 with sodium hydroxide; wherein, the rotation speed of the blender is 1000 rpm and stir for 20 min; (2) Add 30 g of sodium hypochlorite and 2 g of AD8030 dispersant into the first mixed liquid in step (1), and stir at a rotation speed of 1500 rpm for 20 min to obtain a second mixed liquid; (3) Add 70 g of alumina into the second mixed liquid in step (2), and stir at a rotation speed of 1500 rpm for 20 min to obtain the fine polishing liquid for diamond substrates.

[0055] Example 3 A fine polishing liquid for diamond substrates, comprising: 966 g of silica sol (particle size 120 nm, solid content 40%), 4 g of potassium silicate, and 30 g of hydrogen peroxide (concentration 30%).

[0056] The preparation method of the fine polishing liquid for diamond substrates includes the following steps: (1) Add 966 g of silica sol into a blender and stir at a rotation speed of 1500 rpm for 20 min; then add 30 g of hydrogen peroxide and 4 g of potassium silicate, and stir at a rotation speed of 1500 rpm for 20 min to obtain a mixed liquid; (2) Add sodium hydroxide into the mixed liquid in step (1) to adjust the pH value of the system within the range of 8 - 10 to obtain the fine polishing liquid for diamond substrates.

[0057] Example 4 Compared with Example 2, the difference is that the xanthan gum is 10 g, the AD8030 dispersant is 10 g, and the water is 880 g.

[0058] Example 5 Compared with Example 3, the difference is that the silica sol is 890 g, the potassium silicate is 10 g, and the hydrogen peroxide is 100 g.

[0059] Example 6 Compared with Example 1, the difference is that the particle size of the diamond is 0.1 μm.

[0060] Example 7 Compared with Example 1, the difference lies in that the particle size of the diamond is 5 μm.

[0061] Example 8 Compared with Example 2, the difference lies in that the particle size of the alumina is 0.6 μm.

[0062] Example 9 Compared with Example 2, the difference lies in that the particle size of the alumina is 20 μm.

[0063] Example 10 Compared with Example 3, the difference lies in that the particle size of the silica sol is 60 nm.

[0064] Example 11 Compared with Example 3, the difference lies in that the particle size of the silica sol is 150 nm.

[0065] Comparative Example 1 Compared with Example 2, the difference lies in that sodium pyrophosphate is not added.

[0066] Comparative Example 2 Compared with Example 2, the difference lies in that carbomer is not added.

[0067] Comparative Example 3 Compared with Example 2, the difference lies in that the step of adjusting the pH with sodium hydroxide is not carried out.

[0068] Performance Test The diamond substrates were polished with the fine polishing liquids of Examples 1 - 11 and Comparative Examples 1 - 3. After polishing, the diamond substrates were washed and dried, and then the grinding rate and surface roughness were measured. The process parameters and test methods during polishing are as follows: Fine polishing: Grinding was carried out on a single - sided grinding machine. The process parameters were: the upper rotation speed was 50 rpm, the lower rotation speed was 200 rpm, the pressure was 18 kg, and the time was set to 4 h.

[0069] Test method for polishing rate: Use an analytical balance to test the mass of the diamond substrate. The calculation formula for the polishing rate is as follows: Polishing rate = △m * 10000 / (ρ * s * t), where △m (g) is the weight change of the workpiece during polishing, ρ is the density of the diamond substrate (ρ = 3.52 g / cm²), s is the surface area of the workpiece, and t is the polishing time. The test results are shown in Table 1.

[0070] Test method for surface roughness: Use a white - light interferometer to test the surface roughness. The test results are shown in Table 1.

[0071] Table 2 Test Results of the Fine Polishing Liquids of Examples 1 - 11 and Comparative Examples 1 - 3

[0072] As can be seen from Table 1, after polishing the diamond substrate with the fine polishing liquids of Examples 1-11, the roughness of the diamond substrate can be reduced, and the surface of the machined workpiece can be improved.

[0073] From the test results of Example 1 and Examples 6-7, Example 2 and Examples 8-9, Example 3 and Examples 10-11, it can be seen that increasing the abrasive particle size will increase the roughness; decreasing the particle size will reduce the polishing rate.

[0074] From the test results of Example 2 and Comparative Examples 1-3, the test result of Example 2 is better than that of Comparative Example 2, indicating that not using a suspending agent will deteriorate the surface quality of the machined workpiece. This is because without adding a suspending agent, the uniformity of the powder becomes poor. The test result of Example 1 is better than that of Comparative Example 1, indicating that not using a dispersant will deteriorate the surface quality of the machined workpiece. This is because without a dispersant, the dispersibility of the polishing liquid becomes poor, and uneven distribution of the abrasive particles leads to the generation of pits. The test result of Example 2 is better than that of Comparative Example 3, indicating that since Comparative Example 3 does not use an alkaline pH regulator to adjust the pH to 8-10, it will also lead to a poor surface after processing.

[0075] The above description is only an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformation made using the content of the specification of the present invention under the technical concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A fine polishing liquid for diamond substrates, characterized in that, The fine polishing liquid for diamond substrates includes a first fine polishing liquid or a second fine polishing liquid, where: The first fine polishing liquid includes raw materials in the following parts by mass: 1 - 7 parts of a first abrasive, 0.1 - 1 part of a dispersant, 0.1 - 1 part of a suspending agent, 2 - 3 parts of an oxidizing agent, with the balance being water, totaling 100 parts. The first abrasive includes diamond or alumina; The second fine polishing liquid includes raw materials in the following parts by mass: 89 - 97 parts of a second abrasive, 0.1 - 1 part of a dispersant, 3 - 10 parts of an oxidizing agent, totaling 100 parts. The second abrasive includes silica sol.

2. The fine polishing liquid for diamond substrate according to claim 1, wherein The fine polishing liquid for diamond substrates includes a first fine polishing liquid. In the first fine polishing liquid: The particle size of the diamond is 0.1 - 5 μm; and / or, The particle size of the alumina is 0.5 - 20 μm.

3. The fine polishing liquid for diamond substrate according to claim 1, characterized in that, The fine polishing liquid for diamond substrates includes a first fine polishing liquid. In the first fine polishing liquid: The dispersant includes at least one of Disper850 dispersant, DisperST - 400 dispersant, AD8030 dispersant, sodium pyrophosphate, sodium silicate, and potassium silicate; and / or, The suspending agent includes at least one of xanthan gum, carbomer, sodium polyacrylate, and polyacrylamide; and / or, The oxidizing agent includes at least one of hydrogen peroxide, potassium ferrate, ammonium bifluoride, sodium hypochlorite, and ferric chloride.

4. The fine polishing liquid for diamond substrate according to claim 1, wherein, The fine polishing liquid for diamond substrates includes a second fine polishing liquid. In the second fine polishing liquid: The particle size of the silica sol is 60 - 150 nm.

5. The fine polishing liquid for diamond substrates according to claim 1, wherein, The fine polishing liquid for diamond substrates includes a second fine polishing liquid. In the second fine polishing liquid: The dispersant includes at least one of Disper850 dispersant, DisperST - 400 dispersant, AD8030 dispersant, sodium pyrophosphate, sodium silicate, and potassium silicate; and / or, The oxidizing agent includes at least one of hydrogen peroxide, potassium ferrate, ammonium bifluoride, sodium hypochlorite, and ferric chloride.

6. A method for preparing a fine polishing liquid for a diamond substrate as described in claim 2 or 3, characterized in that, The fine polishing liquid for diamond substrates includes a first fine polishing liquid. The preparation method of the fine polishing liquid for diamond substrates includes the following steps: A1. Mix water and a suspending agent to obtain a first mixed liquid; A2. Adjust the pH of the first mixed liquid to a first preset pH, and then mix the first mixed liquid, an oxidizing agent, and a dispersant to obtain a second mixed liquid; A3. Mix the second mixed liquid and a first abrasive to obtain the fine polishing liquid for diamond substrates.

7. The preparation method of the fine polishing liquid for diamond substrates according to claim 6, characterized in that, The pH value of the first preset pH is 8 - 10.

8. A method for preparing a fine polishing liquid for a diamond substrate as described in claim 4 or 5, characterized in that, The fine polishing liquid for diamond substrates includes a second fine polishing liquid. The preparation method of the fine polishing liquid for diamond substrates includes the following steps: B1. First, add a second abrasive to a blender, start the stirring kettle, and then add an oxidizing agent and a dispersant and mix to obtain a third mixed liquid; B2. Adjust the pH of the third mixed liquid to a second preset pH to obtain the fine polishing liquid for diamond substrates.

9. The preparation method of the fine polishing liquid for diamond substrates according to claim 8, characterized in that, The pH value of the second preset pH is 8 - 10.

10. A polishing method for a diamond substrate, characterized in that, Includes the following steps: C1. Provide a diamond substrate and a polishing pad; C2. Apply the fine polishing liquid to the polishing pad, and use the polishing pad to polish the diamond substrate to obtain a polished diamond substrate; Among them, the fine polishing liquid is the fine polishing liquid for diamond substrates described in any one of claims 1 to 5, or the fine polishing liquid prepared by the preparation method of the fine polishing liquid for diamond substrates described in any one of claims 6 to 9.

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