Experimental study on the processing of sapphire with a free-abrasive assisted fixed-abrasive lapping plate

To improve the lapping efficiency of the self-made fixed-abrasive lapping plate for sapphire, free-abrasives were added to the lapping solution to improve the plate's self-dressing performance to realise high-efficiency and high-quality processing for sapphire wafers. The effects of free-abrasive types, size and concentration on processing sapphire wafers were studied, and the processing mechanism of free-abrasive assisted fixed-abrasive lapping was also revealed. The results show that the material removal rate (MRR) of the sapphire wafer increases with increasing the free-abrasive hardness and the size, and first increases and then decreases with increasing concentration; the surface roughness Ra first decreases and then increases with increasing the free-abrasive hardness, increases with increasing the size and continually decrease with increasing the concentration; the lapping plate wear ratio first increases and then decreases with increasing the free-abrasive hardness and concentration and increases with increasing the size. When the free-abrasive, abrasive size and concentration are SiO2, 20 μm, and 3 wt. %, a processed surface with Ra of 0.141 μm and MRR of 4.24 μm/min could be obtained. Compared with the lapping without free-abrasive, the MRR increased by 103.94%, the surface quality improved by 14.45%, and the plate wear ratio increased by 152.15%.