Design of surface grooves on a polishing pad based on slurry uniform flow

Slurry uniform flow can ensure uniform slurry distribution, temperature distribution, mechanical and chemical reactions, and timely residue removal, which is conducive to the stability of the machining process. Surface pattern of a polishing pad is one of the main factors to control the flow of slurry. To achieve the slurry uniform flow, the hydrodynamics of the slurry were calculated to design the surface grooves on polishing pad. Finite element technology was adopted to simulate the flow field distribution of the designed polishing pad. Particle image velocimetry experiments were conducted to verify the uniformity of slurry flow on the designed pad surface. The polishing experiments with designed and groove-diffused pads were conducted to obtain the high surface quality in the same polishing conditions. The results show that the spiral surface pattern established by a curve equation with 2-mm-width and 1.5-mm-depth grooves was obtained for the slurry uniform flow. The experiments reveal that the new surface pattern retards the slurry flow, causing the radial velocity of slurry to be uniform. Surface roughness Sa of CaF2 crystal polished by the designed pad is 0.251 nm, which is much better than that by the groove-diffused pad. Therefore, the slurry uniform flow is conducive to obtain a better surface quality.