Application of the Ultrasonic Vibration in Lapping of Sapphire
Date Issued
2015
Date
2015
Author(s)
Chang, Shu-Ling
Abstract
LED products have been used widely in daily life. Sapphire is the main material of substrate of LED because of its well lattice matching with GaN. However, the planarization process of sapphire wafer takes lots of time due to its excellent mechanical and chemical properties. In the planarization process of sapphire, double-side lapping not only gets the flatness of sapphire substrate, reducing the surface roughness, but also remove the surface damage causing by slicing. In industrial process, although sapphire wafer can be flattened quickly by using large grain size Boron Carbide as the abrasive of double-side lapping, it might cause severe damage that need more time to remove in next processing. To solve the problem, this study uses smaller diamond abrasive to reduce the damage caused by the hard abrasive on the surface of sapphire. This study also adds silicon dioxide as soft abrasive and uses 304 stainless steel as lapping tool to get better lapping efficiency by the mechanism of mechano-chemical lapping. Based on aforementioned abrasive mixed by diamond and silicon dioxide, this study applies a self-designed ultrasonic vibration assistant device to the lapping machine. This study also discusses the lapping efficiency and the surface roughness lapping with single diamond abrasive, mixed abrasive, and self-designed ultrasonic vibration assistant mixed abrasive. The result of study shows that although the mixed abrasive system can maintain the material removal rate during experiment, the performance on surface roughness is worse than single diamond system. Full-time ultrasonic vibration assistant mixed abrasive system can get better surface roughness after lapping, but the material removal rate is poor. Multiple steps ultrasonic vibration assistant mixed abrasive system can get the best material removal rate and surface roughness, and the material removal rate increases 75% compared with single diamond abrasive system.
Subjects
ultrasonic
mixed abrasive
sapphire
Type
thesis
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