Process and mechanism of magnetorheological variable gap dynamic pressure planarization finishing

Abstract

In order to improve the magnetorheological polishing efficiency of photoelectric wafer and realize its ultra smooth planarization, the magnetorheological variable gap dynamic pressure planarization method is proposed. The changes of material removal rate and surface roughness of sapphire wafer with processing time under different variable gap conditions are studied, and the magnetorheological variable gap dynamic pressure planarization finishing mechanism is analyzed. The results show that the axial low-frequency extrusion vibration is applied to the magnetorheological polishing fluid through the sapphire wafer, the polishing pressure changes dynamically, and the magnetorheological fluid produces extrusion strengthening effect, which significantly improves the polishing efficiency and polishing effect. Under the conditions of workpiece pressing speed of 1.0 mm/s, lifting speed of 3.5 mm/s and extrusion vibration amplitude of 1 mm, the surface roughness Ra of sapphire wafer decreased from 6.22 nm to 0.31 nm and the material removal rate was 5.52 nm/min. Compared with constant gap magnetorheological polishing, the surface roughness decreased by 66% and the material removal rate increased by 55%. Changing the moving speed of variable gap can regulate the flow field characteristics of magnetorheological fluid, and the appropriate workpiece pressing speed and workpiece lifting speed are conducive to improve the polishing efficiency and surface quality of workpiece.

Keywords

• magnetorheological polishing
• variable gap dynamic pressure
• planarization finishing
• surface roughness
• material removal rate