A Study on Electro-deposited Multi-layered Diamond Tool for Grinding Sapphire Wafers

Recently sapphire wafer has expected as smart phone cover material, however, brittle nature of sapphire needed edge grinding processes to prevent early initiation of cracks. Electro-deposited multi-layered groove tools with $35{\mu}m$ diamond particles were studied for sapphire wafer grinding. Solid particle flow behaviors in agitated electrolyte was studied using PIV(Particle Image Velocimetry), and uniform particle distribution in Ni bond were obtained when agitating impeller was located lower part of electrolyte. Hardness values of $400{\pm}50Hv$ were maintained for retention of diamond particles in electro-deposited bond layer. Sapphire wafer edge grinding test was carried out and multi-layered $160{\mu}m$ thick diamond tool showed much greater grinding capabilities up to 2000 sapphire wafers than single-layered $50{\mu}m$ thick diamond electro-deposited tools of 420 wafers. The reason why 3 times thicker multi-layered tools than single-layered tools showed 5 times longer tool lives in grinding processes was attributed to self-dressed new diamond particles in multi-layered tools, and multi-layered diamond tools could be promising for sapphire grinding.

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