Reduction of Residual Stresses in Sapphire Cover Glass Induced by Mechanical Polishing and Laser Chamfering Through Etching
Keywords:picosecond laser, laser curvature method, residual stress, stress relief, wet etching, sapphire
AbstractSapphire is a hard and anti-scratch material commonly used as cover glass of mobile devices such as watches and mobile phones. A mechanical polishing using diamond slurry is usually necessary to create mirror surface. Additional chamfering at the edge is sometimes needed by mechanical grinding. These processes induce residual stresses and the mechanical strength of the sapphire work piece is impaired. In this study wet etching by phosphate acid process is applied to relief the induced stress in a 1” diameter sapphire cover glass. The sapphire is polished before the edge is chamfered by a picosecond laser. Residual stresses are measured by laser curvature method at different stages of machining. The results show that the wet etching process effectively relief the stress and the laser machining does not incur serious residual stress.
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