Diamond micro-powder sharp corner corrosion and passivation method, diamond abrasive and application of diamond abrasive

Abstract

The invention provides a diamond micro-powder sharp corner corrosion and passivation method which comprises the following steps: mixing raw materials consisting of aluminum powder, Ni-B (20) alloy and diamond micro-powder, and heating the mixture to 700-750 DEG C in a protective atmosphere, so that the molten Al-Ni-B alloy corrodes the diamond micro-powder sharp corner. The invention further provides the diamond abrasive prepared by the method. Meanwhile, the invention further provides application of the diamond abrasive in the field of wafer grinding.

Description

Technical Field

[0001] This invention relates to a method for passivating sharp corners of diamond micropowder through corrosion, belonging to the field of grinding materials. Background Technology

[0002] With the increasing demands for precision component processing quality, the high-precision processing of hard and brittle materials such as sapphire, single-crystal silicon, glass, gallium nitride, and ferromagnetic ferrite requires surface roughness at the nanometer level and the lowest possible surface residual stress. Therefore, ultra-precision grinding before the polishing process of components has become a current research hotspot.

[0003] Traditional high-grade diamond micron powder is mostly octahedral and dodecahedral (see...) Figure 1 Diamond abrasive grains have multiple sharp points. During grinding, the diamond abrasive is positioned between the workpiece and the grinding disc, creating relative displacement between them. The rolling diamond glides across the workpiece surface, producing a plowing effect and removing material. However, grinding machines, as grinding equipment, experience vibration during operation. Simultaneously, the grinding disc also vibrates due to dynamic imbalance. When using traditional diamond as the abrasive material to grind relatively hard and brittle materials like single-crystal silicon, the sharp points of the diamond abrasive can easily penetrate too deeply into the workpiece surface under mechanical vibration, resulting in deep and coarse grinding textures. Furthermore, the concentrated cutting stress at the cutting edge causes numerous pits to form on the workpiece surface, making it difficult to achieve a high-quality workpiece surface.

[0004] Therefore, reducing the sharp corners in diamond abrasives is beneficial to improving the surface quality of workpieces.

[0005] Patent application CN115433582A discloses a method for etching diamond. This method can prepare diamond particles with a porous surface structure, and the depth of the etching pits on the diamond particle surface can be easily controlled by changing process parameters, thereby altering the self-sharpening and grinding performance of the etched diamond particles. During grinding, the diamond particles obtained by this method operate with multiple grinding edges at the micro-nano scale. Compared to traditional single-edge diamond grinding, the size of the grinding edges is smaller, but the number is increased, allowing for the dispersion of grinding heat and stress, which is beneficial for improving the surface quality. Simultaneously, the porous structure of the diamond significantly reduces its compressive strength and significantly improves its self-sharpening properties, effectively increasing grinding efficiency.

[0006] Patent application CN114472882A discloses a method for directional etching of diamond surfaces. This method processes diamond particles while increasing their surface roughness and achieving uniform crystal surface etching, while maintaining all required diamond particle properties. Its key feature is the selection of different etching powders based on the specific requirements of the etched surface, and precise control of the etching degree through precise control of reaction time and temperature. The method is simple to operate, uses readily available materials, is pollution-free, and has low cost. It can simultaneously process diamonds of different particle sizes, enabling large-scale production to meet demand.

[0007] However, none of the above methods could achieve the passivation of sharp corners of diamond abrasive powder. Summary of the Invention

[0008] The first objective of this invention is to provide a method for passivating the sharp corners of diamond abrasive powder, wherein the diamond abrasive powder prepared by this method has significantly passivated sharp corners.

[0009] The second objective of this invention is to provide a diamond abrasive powder prepared by the method described above.

[0010] A third objective of this invention is to provide an application of the aforementioned diamond abrasive powder.

[0011] This invention is achieved through the following technical solution: A method for passivating diamond micropowder sharp corners by etching includes mixing raw materials composed of aluminum powder, Ni-B (20) alloy and diamond micropowder, and heating them to 700-750°C under a protective atmosphere, so that the molten Al-Ni-B alloy etches the sharp corners of the diamond micropowder.

[0012] The average particle size of the diamond abrasive powder is 1-50 micrometers. The raw materials comprise, by weight percentage, 25-35 wt% diamond micro powder, 60-70 wt% aluminum powder and 3-6 wt% Ni-B(20) alloy powder.

[0013] The medium used in the mixing process includes ethyl acetate; The weight of the medium used in the mixing process is 1.2-1.8 times that of the raw materials; The protective atmosphere includes argon; The mixing includes stirring; The stirring speed is 500-600 rpm.

[0014] After the raw materials are mixed, the process also includes vacuum drying and molding steps; The vacuum drying temperature is 30-35℃; The binder used in the molding process includes a methylcellulose solution; The amount of the methylcellulose solution added is 3-5 wt% of the raw material; The concentration of the methylcellulose solution is 3-4 wt%; The molding pressure is 100-110 MPa.

[0015] The heating process includes raising the temperature to 600-630°C at a rate of 3-5°C / min, holding the temperature for 1-2.5 hours, and then raising the temperature to 700-750°C at a rate of 3-5°C / min and holding the temperature for 5-12 hours.

[0016] The method for passivating sharp corners of diamond abrasive powder also includes a cleaning step; The cleaning process includes soaking in 15% dilute hydrochloric acid, rinsing with water until the rinse water is neutral, ultrasonicating in anhydrous ethanol, and drying. The drying temperature is 100-120℃; The frequency of the ultrasound is 3500-4000Hz.

[0017] A diamond abrasive is obtained by passivation through the diamond micro-powder sharp-angle corrosion passivation method.

[0018] The diamond abrasive described herein is used for grinding wafers or ferromagnetic ferrites.

[0019] The wafer includes sapphire wafers, single-crystal silicon wafers, glass wafers, or gallium nitride wafers.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The diamond micro powder processed by the method provided by this invention will have its sharp corners rounded off by a blunting surface.

[0021] The diamond abrasive prepared by this invention can process the surface roughness of wafers to the nanometer level and reduce the surface residual stress of wafers.

[0022] The diamond abrasive prepared by this invention can avoid the formation of large-sized crushing pits on the workpiece surface due to the stress concentration of cutting at the sharp corner of the abrasive when grinding single-crystal silicon semiconductor materials. At the same time, the grinding texture is shallow and fine, and the single-crystal silicon wafer after grinding can obtain a higher quality grinding surface. Attached Figure Description

[0023] Figure 1 SEM images of commercially available W10 diamond micropowder before corrosion are shown; the images show that this type of diamond is mostly octahedral and dodecahedral, and the diamond micropowder has many sharp corners; Figure 2The image shows the microstructure of the etched W10 diamond powder prepared in Example 1. The image shows that after etching, the sharp corners of the diamond powder became rounded, which indicates that the method provided in Example 1 can effectively round the sharp corners of the diamond powder. Figure 3 The image shows the surface microstructure of a single-crystal silicon wafer polished with W10 diamond micropowder prepared in Example 1 after etching; the image shows that the polishing texture of the single-crystal silicon wafer polished with W10 diamond micropowder prepared in Example 1 is fine and no large pits appear on the polished surface. Figure 4 The image shows the surface microstructure of a monocrystalline silicon wafer polished with commercially available W10 diamond micropowder. The image shows that the surface of the monocrystalline silicon wafer polished with commercially available W10 diamond micropowder has coarse polishing lines and large pits on the polished surface. Detailed Implementation

[0024] This invention provides a method for passivating the sharp corners of diamond micropowder through corrosion. The method involves using a molten Al-Ni-B alloy at high temperature to corrode the diamond micropowder, thereby passivating the sharp corners. The sharp corners of the diamond micropowder are corroded because the Al-Ni-B alloy contains a large amount of aluminum, which has a low melting point. At 700-750℃, aluminum liquefies (its melting point is around 660℃), subsequently forming a eutectic with nickel and boron, thus forming a molten Al-Ni-B alloy. The outer electron structure of the Ni atoms in the molten Al-Ni-B alloy is 3d. 8 4S 2 The d-shell electrons of a Ni atom have two unpaired electrons, which will affect the spline electrons of diamond. 3Electrons in hybrid orbitals exert an attractive force, inducing the breakage of C-C bonds in the atomic crystal diamond. Since carbon atoms are soluble in molten aluminum, the carbon atoms resulting from the breakage of these C-C bonds on the diamond surface dissolve into the Al-Ni-B alloy melt. This dissolution creates carbon vacancies on the diamond surface. The carbon atoms in the Al-Ni-B alloy have a radius and electronegativity similar to those in diamond, allowing them to fill these vacancies, maintain the electroneutrality of the diamond crystal surface, and reduce the potential energy required for carbon atoms to dissolve in the Al-Ni-B alloy melt. Therefore, the solubility of carbon atoms in the Al-Ni-B alloy melt is greatly increased, promoting greater dissolution of diamond within the melt. In diamond micron powder, the specific surface area of ​​the sharp corners is much larger than that of ordinary crystal faces. Since the reaction between diamond and Al-Ni-B alloy melt is a multiphase interfacial reaction, its reaction rate is directly proportional to the specific surface area. Therefore, carbon at the sharp corners of the diamond micron powder dissolves more easily in the molten Al-Ni-B alloy. Thus, this method can passivate the sharp corners of diamond micron powder through corrosion, resulting in diamond abrasives that are closer to a spherical shape.

[0025] Because the raw materials and diamonds used in this method are easily oxidized at high temperatures, the method must be carried out under a protective atmosphere. Specifically, this protective atmosphere can be argon. Alternatively, nitrogen and other inert gases that do not participate in the reaction, such as helium, can also be used.

[0026] The method provided by this invention can process diamond micro powder of various particle sizes. Based on the requirements of semiconductor wafer processing, this invention preferably selects diamond micro powder with an average particle size of 1-50 micrometers.

[0027] This invention selects aluminum powder and Ni-B(20) alloy powder as raw materials from the perspective of easy availability of raw materials. In essence, this invention can be achieved by selecting aluminum powder, Ni powder and B powder as raw materials, or by using aluminum-nickel alloy powder and boron powder, or by using aluminum-nickel-boron alloy powder as raw materials.

[0028] Specifically, when aluminum powder and Ni-B(20) alloy powder are used as raw materials, the raw materials include 25-35wt% diamond micro powder, 60-70wt% aluminum powder and 3-6wt% Ni-B(20) alloy powder.

[0029] To ensure a more uniform mixing of the various components in the raw materials, this invention first weighs diamond, aluminum powder, and Ni-B(20) alloy powder according to a specific ratio, and then uses ethyl acetate as the raw material dispersion medium to mix the components. Ethyl acetate has good chemical stability and will not react chemically with the raw materials. At the same time, ethyl acetate has good wettability with diamond, and can effectively disperse diamond during the mixing process. Other esters or other organic substances that will not react chemically with the raw materials can also achieve this invention. The mixed slurry is vacuum dried at a temperature of 30-40°C. Under vacuum, ethyl acetate evaporates rapidly, and the vacuum condition prevents the oxidation of aluminum powder and nickel-boron alloy powder. Methylcellulose solution is added to the dried powder as a temporary binder, and the powder is then placed into a steel mold and pressed into shape on a press. A relatively high pressure of 90-110 MPa is used for powder forming, which ensures sufficient contact between diamond, aluminum powder, and nickel powder.

[0030] Obviously, other mixing methods, such as dry ball milling, wet ball milling, or simple stirring, can also achieve mixing. This invention can also be achieved without shaping the raw materials. Even if the diamond, aluminum powder, and Ni-B(20) alloy powder are not mixed evenly, at high temperatures, after the aluminum-nickel-boron melts, the molten aluminum-nickel-boron will slowly form a uniform alloy melt and evenly wet the diamond micropowder. Pre-mixing the raw materials evenly results in higher corrosion efficiency, more uniform corrosion, and relatively better effects.

[0031] Specifically, the weight of the medium used in the mixing process is 1.2-1.8 times that of the raw material; during the mixing of the components in the raw material using ethyl acetate as the dispersion medium, the suspension can be stirred. The stirring speed is 500-600 rpm.

[0032] Specifically, the amount of methylcellulose solution added is 3-5 wt% of the raw material; the concentration of the methylcellulose solution is 3-4 wt%.

[0033] Specifically, during heating, the shaped raw material can be placed in a corundum crucible with boron nitride release agent on the inner wall, and then the crucible is placed in a controlled atmosphere furnace and heated to 600-630℃ at a rate of 3-5℃ / min under a protective atmosphere (such as argon), and held for 1-2 hours. Holding at this temperature can promote uniform temperature inside and outside of the shaped raw material. Then, the temperature is increased to 700-750℃ at a rate of 3-5℃ / min and held for 5-12 hours. When the temperature is higher than 660℃, the aluminum powder in the diamond passivation powder block begins to melt into molten aluminum. When the holding temperature starts at 700-750℃, the Ni-B(20) alloy powder in the diamond passivation powder block begins to melt into the molten aluminum liquid to form a molten Al-Ni-B alloy. After holding at 700-750℃ for a period of time, the sharp corners in the diamond micro powder will dissolve in the alloy melt under the action of the molten Al-Ni-B alloy.

[0034] The heat-treated bulk material is washed in excess hydrochloric acid to dissolve any remaining alloy. The filtered powder is then thoroughly cleaned to obtain diamond abrasive with blunted corners. The hydrochloric acid concentration used for cleaning is 15%. After soaking, the material is rinsed with water until the rinse water is neutral. It is then ultrasonically dried in anhydrous ethanol. The drying temperature is 100-120℃; the ultrasonic frequency is 3500-4000Hz.

[0035] This invention also provides a diamond abrasive, which is obtained by passivation using the aforementioned diamond micropowder sharp-corner etching passivation method. Due to the passivation of the sharp corners, this diamond abrasive is suitable for grinding materials with high surface roughness requirements, such as wafers. It can also be applied to grinding ferromagnetic ferrites. Specifically, the wafer includes sapphire wafers, single-crystal silicon wafers, glass wafers, or gallium nitride wafers.

[0036] The present invention will be further described below with reference to specific embodiments.

[0037] Example 1 The formula for diamond passivation powder blocks is as follows: Diamond powder (W10 average particle size 2 micrometers) 30wt%, aluminum powder (80 mesh) 66wt%, Ni-B(20) alloy powder 4wt%.

[0038] The specific corrosion steps are as follows: Weigh out the raw materials according to the specified proportions and pour them into a sealed mixing tank. Add ethyl acetate at 1.5 times the weight of the raw materials to the mixing tank, seal the tank, and purge with argon gas for protection. Mix using a spiral agitator at a speed of 600 rpm. After mixing for 1 hour, pour out the slurry. Place the slurry in a vacuum drying oven and vacuum dry it at 30°C. After the slurry is completely dry, pour the dried powder into a mortar and add 3% (by weight of the powder) of a 4% methylcellulose solution. Mix thoroughly by hand and then pass through a 40-mesh sieve to obtain the molding material for diamond passivation treatment powder blocks.

[0039] The molding material is put into a steel mold and pressed into shape under a pressure of 110 MPa on a press. After demolding, a block material is obtained. The block material is placed in a vacuum drying oven, vacuum dried at room temperature, and then stored under vacuum conditions for later use.

[0040] The obtained diamond passivation powder was placed in a corundum crucible with boron nitride release agent on the inner wall. The crucible was then placed in a controlled atmosphere furnace and heated to 600°C at a rate of 5°C / min under an argon protective atmosphere. The temperature was held for 2 hours, and then heated to 750°C at a rate of 5°C / min. The temperature was held for 5 hours. After the furnace was closed, the crucible was allowed to cool naturally in the electric furnace. When the furnace temperature was below 200°C, the furnace door was opened for cooling. When the temperature was below 70°C, the crucible was removed from the furnace, and the sintered diamond passivation powder was taken out of the crucible.

[0041] Sintered diamond passivation powder blocks were immersed in an excess of 15% dilute hydrochloric acid solution. After the reaction stopped, vacuum filtration was used to filter out the solid phase in the acid solution. Then, the filtered solid phase was repeatedly soaked and rinsed with deionized water. When the pH of the deionized water rinsing solution was neutral, rinsing was stopped. The powder material was placed in an ultrasonic cleaner and ultrasonically cleaned at a frequency of 4000 Hz for 1 hour using anhydrous ethanol as the medium. The powder was then removed and dried at 120 degrees Celsius to obtain diamond abrasive with sharp corner passivation.

[0042] When the diamond abrasive prepared in Example 1 of this invention is used to perform 150-micron grinding and thinning on a 6-inch single-crystal silicon wafer under 90N pressure, the grinding texture on the surface of the single-crystal silicon wafer prepared by the diamond abrasive of this invention is finer, and no large-sized pits appear on the grinding surface (see Example 1). Figure 3 The surface roughness is Ra 0.15 micrometers. The surface of silicon wafers processed with commercially available W10 diamond has coarse grinding marks and large pits (see...). Figure 4The surface roughness was Ra 0.64 micrometers. The surface stress value of the silicon wafer directly polished after grinding the W10 diamond micropowder prepared in Example 1 was quantitatively measured. Referring to GB / T 34899-2017, a silicon wafer with a 20 μm thick layer removed by HF chemical etching was used as a standard stress-free wafer for Raman spectroscopy calibration. The wavenumber of the standard silicon wafer was 520.012 cm⁻¹. -1 Ten points were selected on the sample to be tested, and each point was measured once. The average value of the ten test points was taken as the wavenumber corresponding to the Raman peak of the sample. The average Raman frequency shift of the sample was calculated using the formula δ = -464.64 × Δλ (where δ represents the surface stress of the silicon wafer in MPa; Δλ represents the difference between the wavenumber of the Raman peak of the tested sample and that of the standard silicon wafer at 520.012 cm⁻¹). -1 The residual stress of the polished wafer was calculated to be -4.5 MPa based on the difference in wavenumbers, while the surface stress of the silicon wafer polished directly after grinding with ordinary W10 diamond micropowder was -55 MPa. These data indicate that grinding the single-crystal silicon wafer with the diamond abrasive prepared in Example 1 followed by polishing results in a surface with lower stress values.

[0043] Example 2 The formula for diamond passivation powder blocks is as follows: Diamond powder (W10) 25wt%, aluminum powder (80 mesh) 70wt%, Ni-B(20) alloy powder 5wt%.

[0044] Weigh out the raw materials according to the specified proportions and pour them into a sealed mixing tank. Add ethyl acetate at 1.2 times the weight of the raw materials to the mixing tank, seal the tank, and purge with argon gas for protection. Mix using a spiral agitator at a speed of 600 rpm. After mixing for 1 hour, pour out the slurry. Place the slurry in a vacuum drying oven and vacuum dry it at 30°C. After the slurry is completely dry, pour the dried powder into a mortar and add 5% (by weight of the powder) of a 4% methylcellulose solution. Mix thoroughly by hand and then pass through a 40-mesh sieve to obtain the molding material for diamond passivation treatment powder blocks.

[0045] The molding material is put into a steel mold and pressed into shape under a pressure of 110 MPa on a press. After demolding, a block material is obtained. The block material is placed in a vacuum drying oven, vacuum dried at room temperature, and then stored under vacuum conditions for later use.

[0046] The obtained diamond passivation powder was placed in a corundum crucible with boron nitride release agent on the inner wall. The crucible was then placed in a controlled atmosphere furnace and heated to 600°C at a rate of 5°C / min under an argon protective atmosphere. The temperature was held for 2 hours, and then heated to 750°C at a rate of 5°C / min. The temperature was held for 5 hours. After the furnace was closed, the crucible was allowed to cool naturally in the electric furnace. When the furnace temperature was below 200°C, the furnace door was opened for cooling. When the temperature was below 70°C, the crucible was removed from the furnace, and the sintered diamond passivation powder was taken out of the crucible.

[0047] Sintered diamond passivation powder blocks were immersed in an excess of 15% dilute hydrochloric acid solution. After the reaction stopped, vacuum filtration was used to filter out the solid phase in the acid solution. Then, the filtered solid phase was repeatedly soaked and rinsed with deionized water. When the pH of the deionized water rinsing solution was neutral, rinsing was stopped. The powder material was placed in an ultrasonic cleaner and ultrasonically cleaned at a frequency of 4000 Hz for 1 hour using anhydrous ethanol as the medium. The powder was then removed and dried at 120 degrees Celsius to obtain diamond abrasive with sharp corner passivation.

[0048] When the diamond abrasive prepared in Example 2 of this invention is used to perform 150-micron grinding and thinning on a 6-inch single-crystal silicon wafer under a pressure of 90N, the surface texture of the resulting single-crystal silicon wafer is finer, no large-sized pits appear on the ground surface, and the surface roughness is Ra 0.11 microns. The average residual stress of the silicon wafer directly polished after grinding with the abrasive prepared in Example 2 is -4.7MPa (calculated using the same method as in Example 1).

[0049] Example 3 The formula for diamond passivation powder blocks is as follows: Diamond powder (W10) 35wt%, aluminum powder (80 mesh) 60wt%, Ni-B(20) alloy powder 5wt%.

[0050] Weigh each raw material according to the specified proportions and pour them into a sealed mixing tank. Add ethyl acetate at 1.8 times the weight of the raw materials to the mixing tank, seal the mixing tank, and purge with argon gas for protection. Mix using a spiral agitator at 550 rpm for 1 hour, then pour out the slurry. Place the slurry in a vacuum drying oven and vacuum dry it at 30 degrees Celsius. After the slurry is completely dry, pour the dried powder into a mortar and add 4% (by weight of the powder) of a 3% methylcellulose solution. Mix thoroughly by hand and then pass through a 40-mesh sieve to obtain the molding material for diamond passivation treatment powder blocks.

[0051] The molding material is put into a steel mold and pressed into shape under a pressure of 110 MPa on a press. After demolding, a block material is obtained. The block material is placed in a vacuum drying oven, vacuum dried at room temperature, and then stored under vacuum conditions for later use.

[0052] The obtained diamond passivation powder was placed in a corundum crucible with boron nitride release agent on the inner wall. The crucible was then placed in a controlled atmosphere furnace and heated to 600°C at a rate of 5°C / min under an argon protective atmosphere. The temperature was held for 2 hours, and then heated to 700°C at a rate of 4°C / min. The temperature was held for 5 hours. After the furnace was closed, the crucible was allowed to cool naturally in the electric furnace. When the furnace temperature was below 200°C, the furnace door was opened for cooling. When the temperature was below 70°C, the crucible was removed from the furnace, and the sintered diamond passivation powder was taken out of the crucible.

[0053] Sintered diamond passivation powder blocks were immersed in an excess of 15% dilute hydrochloric acid solution. After the reaction stopped, vacuum filtration was used to filter out the solid phase in the acid solution. Then, the filtered solid phase was repeatedly soaked and rinsed with deionized water. When the pH of the deionized water rinsing solution was neutral, rinsing was stopped. The powder material was placed in an ultrasonic cleaner and ultrasonically cleaned at a frequency of 3500 Hz for 1 hour using anhydrous ethanol as the medium. The powder was then removed and dried at 100 degrees Celsius to obtain diamond abrasive with sharp corner passivation.

[0054] When the diamond micropowder prepared in Example 3 was used to grind and thin a 6-inch single-crystal silicon wafer to 150 micrometers under a pressure of 90N, the resulting single-crystal silicon wafer had a finer grinding texture, no large-sized pits on the grinding surface, and a surface roughness of Ra 0.13 micrometers. The average residual stress of the silicon wafer directly polished after grinding with the diamond abrasive prepared in Example 4 was -4.0 MPa (calculated using the same method as in Example 1).

[0055] Example 4 The formula for diamond passivation powder blocks is as follows: Diamond powder (W10) 34wt%, aluminum powder (80 mesh) 60wt%, Ni-B(20) alloy powder (W20) 6wt%.

[0056] Weigh each raw material according to the specified proportions and pour them into a sealed mixing tank. Add ethyl acetate at 1.6 times the weight of the raw materials to the mixing tank, seal the tank, and purge with argon gas for protection. Mix using a spiral agitator at 500 rpm for 1 hour, then pour out the slurry. Place the slurry in a vacuum drying oven and vacuum dry it at 30°C. After the slurry is completely dry, pour the dried powder into a mortar and add 4% (by weight of the powder) of a 5% methylcellulose solution. Mix thoroughly by hand and then pass through a 40-mesh sieve to obtain the molding material for diamond passivation treatment powder blocks.

[0057] The molding material is put into a steel mold and pressed into shape under a pressure of 100MPa on a press. After demolding, a block material is obtained. The block material is placed in a vacuum drying oven, vacuum dried at room temperature, and then stored under vacuum conditions for later use.

[0058] The obtained diamond passivation powder was placed in a corundum crucible with boron nitride release agent on the inner wall. The crucible was then placed in a controlled atmosphere furnace and heated to 620°C at a rate of 3°C / min under an argon protective atmosphere, and held for 2.5 hours. The temperature was then increased to 750°C at a rate of 4°C / min and held for 6 hours. After the furnace was closed, the crucible was allowed to cool naturally in the electric furnace. When the furnace temperature was below 200°C, the furnace door was opened for cooling. When the temperature was below 70°C, the crucible was removed from the furnace, and the sintered diamond passivation powder was taken out of the crucible.

[0059] Sintered diamond passivation powder blocks were immersed in an excess of 15% dilute hydrochloric acid solution. After the reaction stopped, vacuum filtration was used to filter out the solid phase in the acid solution. Then, the filtered solid phase was repeatedly soaked and rinsed with deionized water. When the pH of the deionized water rinsing solution was neutral, rinsing was stopped. The powder material was placed in an ultrasonic cleaner and ultrasonically cleaned at a frequency of 4000Hz for 1 hour using anhydrous ethanol as the medium. The powder was then removed and dried at 120℃ to obtain diamond abrasive with sharp corner passivation.

[0060] When the diamond abrasive prepared in Example 4 was used to perform 150-micron grinding and thinning on a 6-inch single-crystal silicon wafer under 90N pressure, the resulting wafer had a finer grinding texture, no large pits, and a surface roughness of Ra 0.16 microns. The average residual stress of the silicon wafer directly polished after grinding with the diamond abrasive prepared in Example 4 was -4.3 MPa (calculated using the same method as in Example 1).

Claims

1. A method for passivating sharp corners with diamond micropowder through etching, characterized in that: The process includes mixing raw materials consisting of aluminum powder, Ni-B(20) alloy and diamond micro powder, and heating them to 700-750°C under a protective atmosphere to allow the molten Al-Ni-B alloy to corrode the sharp corners of the diamond micro powder.

2. The method for passivating sharp corners of diamond abrasive powder as described in claim 1, characterized in that: The average particle size of the diamond abrasive powder is 1-50 micrometers.

3. The method for passivating sharp corners of diamond abrasive powder as described in claim 1, characterized in that: The raw materials comprise, by weight percentage, 25-35 wt% diamond micro powder, 60-70 wt% aluminum powder and 3-6 wt% Ni-B(20) alloy powder.

4. The method for passivating sharp corners of diamond abrasive powder as described in claim 1, characterized in that: The medium used in the mixing process includes ethyl acetate; The weight of the medium used in the mixing process is 1.2-1.8 times that of the raw materials; The protective atmosphere includes argon; The mixing includes stirring; The stirring speed is 500-600 rpm.

5. The method for passivating sharp corners of diamond abrasive powder as described in claim 1, characterized in that: After the raw materials are mixed, the process also includes vacuum drying and molding steps; The vacuum drying temperature is 30-35℃; The binder used in the molding process includes a methylcellulose solution; The amount of the methylcellulose solution added is 3-5 wt% of the raw material; The concentration of the methylcellulose solution is 3-4 wt%; The molding pressure is 100-110 MPa.

6. The method for passivating sharp corners of diamond abrasive powder as described in claim 1, characterized in that: The heating process includes raising the temperature to 600-630°C at a rate of 3-5°C / min, holding the temperature for 1-2.5 hours, and then raising the temperature to 700-750°C at a rate of 4-5°C / min and holding the temperature for 5-6 hours.

7. The method for passivating sharp corners of diamond abrasive powder as described in claim 1, characterized in that: It also includes a cleaning step; The cleaning process includes soaking in 15% dilute hydrochloric acid, rinsing with water until the rinse water is neutral, ultrasonicating in anhydrous ethanol, and drying. The drying temperature is 100-120℃; The frequency of the ultrasound is 3500-4000Hz.

8. A diamond abrasive, characterized in that: The diamond micron powder sharp corner corrosion passivation method described in claim 1 is used to passivate the diamond.

9. The application of the diamond abrasive as described in claim 8, characterized in that: It is used for grinding wafers or ferromagnetic ferrites.

10. The application of the diamond abrasive as described in claim 9, characterized in that: The wafer includes sapphire wafers, single-crystal silicon wafers, glass wafers, or gallium nitride wafers.

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