Sapphire Lapping By SiC Particles Assisted Fixed Abrasives

With advantages such as higher utilization ratio of abrasive, better process stability, friendly to environment, sapphire machined by fixed abrasive pad(FAP) can cut more cost compared with traditional loose abrasive lapping. But the mater ial removal rate slows down fast, so FAP is limited to apply to sapphire manufacturing industry owning to its ' weak performance of self-conditioning. Inspired by slurry abrasion experiment, SiC particles were added to slurry to assist FAP to improve performance of self-conditioning in this paper, and new process of fixed abrasive lapping was carried out. The main works and achievements are as follows:(1) These factors influencing self-conditioning characteristic of FAP had been analyzed systematically. Process parameters and properties of FAP are the two key factors. Resins are gradually worn by chips created by lapping process, self-conditioning has been achieved if abrasives expose out of sub-surface easily. Due to its' high hardness, the tiny chips of sapphire lead to insufficient self-conditioning capability of FAP. Based on the result, sapphire machined by SiC assisted FAP lapping is put forward, and good manufacturing performance has been achieved. SiC slurry preparation was explored from sedimentate and dispersion aspects when particles are mixed with liquid. Besides, numerical s imulation had been carried out to evaluate the effects of eccentricity, ratio of transmission between wafers and FAP on lapping trajectories, which can support choice of lapping parameters.(2) The SiC particles' role on sapphire lapping process had been explored. Three group contrast experiments had been carried out, which contained FAP(without abrasives) and FAP lapping under the condition of SiC slurry, FAP lapping without SiC slurry. Differences were compared from material removal rate, roughness of wafers, topography of FAP(distribution of diamond abrasives, holes that abrasives drop out)after lapping. Results show that material removal rate of sapphire machined by SiC in slurry is lowest, followed by FAP lapping without SiC slurry. And Si C assisted FAP lapping is far more than the former two, which can maintain in a long run. Conclusion after analysis of data and topography has been that SiC particles mainly play a role in conditioning FAP.(3) Process optimization for SiC slurry assisted FAP lapping sapphire had been conducted. Four factors, including hardness of FAP, concentration of SiC particles, size of particles, lapping pressure, were selected. Two-factor experiments were carried out. Results indicate that material removal rate rises with the increase of concentration of particles, size of particles and lapping pressure. Roughness of wafers will present the tendency that fall first, then rise with the increase of concentration of particles. At the same time, it rises with the increase of size of particles and falls with the increase of pressure. The better process parameter is that sapphire is lapped by 4#FAP under conditions of 5psi pressure, with slurry containing W10 SiC particles whose concentration is 3%. The material removal rate can reach to 482.0nm/min and surface roughness is 0.139?m, so sapphire can be machined by FAP in high efficiency.