Fixed Abrasive Mechanical Chemical Polishing Of Single Crystal Sapphire Substrate

Single crystal sapphire (α-A12O3) has excellent optical and electrical properties, chemical stability, high wear resistance, high melting point and high hardness and other characteristics. It is widely used in optoelectronics, communications, defense and other fields. These applications have a very high demand for the processing quality of the sapphire. As a typical hard and brittle materials, sapphire is difficult to achieve a high efficiency and low damage ultra-precision machining, which becomes the main obstacle that hinders its application. There are chipping, scratches and other damages produced by traditional hard abrasive machining method, and a further chemical mechanical polishing processing is necessary to improve quality. Therefore, the efficient and low damage sapphire processing methods are urgently needed to be researched and developed.The paper proposes an innovative high efficiency and low damage sapphire substrate polishing method with a fixed abrasive mechanical chemical polishing (FA-MCP) disk. The structure of FA-MCP polishing disk is designed and the manufacturing process of it was also developed on the basis of analyzing the sapphire solid-phase chemical reaction. In addition, four soft abrasives, including magnesia,silica,ceria,a-alumina, which can have a solid-phase chemical reaction with sapphire under a certain conditions, are picked out,and the manufacturing process of the resin bond and the magnesium oxychloride bond FA-MCP polishing disk is developped. Then some polishing experiments are conducted by using these FA-MCP polishing disk in UNIPOL-1260constant pressure polishing tool. The surface roughness, damage, three-dimensional morphology of the sapphire are measured by using optical microscopy, three-dimensional surface profiler and other instruments. At the same time, the material removal rate sapphire is measured by using ultra-precision electronic balance and precision measuring machine. Based on the results of experiments, the formula of the FA-MCP grinding disk is optimized. The processing performance of FA-MCP polishing disk and diamond grinding disk was compared. Experimental results show that the surface roughness of sapphire is Ra0.3nm and the material removal rate is0.22μm/min after polishing withthe new FA-MCP polishing disk.