The Elastic Impact of Polishing Pad for Sapphire Polishing

NITTA HAAS INCORPORATED, Katsumasa Kawabata, Keiichiro Fujimoto, Kazutaka Miyamoto

Sapphire substrate's application such as LED and cover glass
will be expanded year by year. After lapping, polishing is needed to
get smooth surface. In recent years, high throughput at polishing
became to be required for expansion of demand. Polishing pads
were classified to fiber type, urethane and suede one. Fiber type
made from polyurethane, polyether fiber has been used and it
performed moderate removal rate from contact area caused by
fiber. On the other hand, polishing conditions such as down force,
shear one became to be heavier recently to increase removal rate.
In case of utilizing that environment by designing with dynamic
pad’s feature, the pad should reveal higher removal rate. This
study sought a new key factor which can achieve high removal rate
under the environment. Firstly, pad's elastic feature was focused by
using nylon fiber for new design and it was confirmed that there
was correlation between the content and removal rate was. Then it
was found out that Young's modulus was the key factor and it
seemed to increase contact area at dynamic environment. Finally,
urethane type designed on low Young's modulus was evaluated. As
result, it was found out that this approach was efficient both for
fiber type and urethane one to achieve high removal rate.

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