Studies On The Experiment In Ultrasonic Fine Atomization CMP Of Optical Quartz Glass

Optical quartz glass is widely used in optical,military,aerospace and other fields because of its good transmittance,high filtering transmittance,small internal defects and stable chemical properties.It is a common material for optical systems such as microscopes and astronomical telescopes.Optical quartz glass is a kind of hard brittle material.It is easy to appear surface defects such as breakage,crack and scratch when using traditional processing method,which can’t meet the use standard of optical components.In the field of ultra precision machining,chemical mechanical polishing（CMP）is widely used in the planarization of hard and brittle materials because of its high efficiency and global planarization.On the basis of CMP,ultrasonic fine atomization was used to polish JGS1optical quartz glass.Taking the surface roughness and material removal rate as evaluation indexes,single factor test,polishing fluid component content optimization test and polishing process parameter optimization test were carried out successively,and the test results were analyzed theoretically,and finally the suitable optical properties were determined.Finally,the formula of special polishing slurry and polishing process parameters of quartz glass atomization polishing are introduced.（1）Through the design of single factor test,this paper finally selected SiO₂ of 50 nm size as abrasive,citric acid as complexing agent,polyvinylpyrrolidone（PVP）as surfactant,guanidine carbonate as cosolvent,KOH and HNO₃ as pH regulator.According to the experimental results,the concentration range of each additive was preliminarily determined,and the action mechanism of each additive was analyzed;（2）The influence of each component on the atomization polishing effect was investigated by orthogonal experiment,and the content of each component in the polishing solution was optimized.Then the removal mechanism of optical quartz glass was analyzed.The experimental results show that the concentration of SiO₂ and pH value have great influence on the polishing effect.The optimal formula of polishing fluid is:SiO₂ abrasive mass fraction 19%,citric acid content 1.4%,guanidine carbonate content 0.2%,PVP content0.9%,pH=11;（3）The influence of each polishing parameter（polishing pressure,flow rate and disc speed）on the polishing effect of optical quartz glass was investigated by single factor experiment that use the optimized slurry.Then,orthogonal experiment was designed to study the influence degree of each parameter on the polishing effect.Finally,the process parameters were optimized.The experimental results show that the polishing pressure has the greatest influence on the surface roughness and material removal rate of the optical quartz glass wafer,followed by the polishing disc speed,and the mist flow rate has the least influence on the polishing effect.The results show that the best process parameters are as follows:the polishing pressure is 4.2 psi,the flow rate of atomizing polishing fluid is 12.5 m L/min and the rotation speed of polishing disc is 70 r/min;（4）The traditional polishing and ultrasonic atomization polishing were compared by experiments.The other experimental conditions were the same except for the slurry flow rate.The spray flow rate was 12.5 m L/min,and the corresponding traditional polishing method was 85 m L/min.The experimental results show that the material removal rate of the wafer is slightly lower than that of the traditional polishing method,but the surface quality of the two polishing methods is similar,and the amount of atomizing polishing fluid is only 1/7 of that of the traditional polishing method.The results show that ultrasonic atomization polishing has its unique advantages under low flow rate of polishing fluid,and has the advantages of economic and environmental protection.