Liquid waxless fixturing of microsize wafers

Abrasive tool making process – material – or composition – Impregnating or coating an abrasive tool

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Details

51237R, 51283R, 511313, B24B 3704

Patent

active

045191689

ABSTRACT:
The disclosure teaches an improved manner of firmly holding a thin brittle wafer, such as a 0.01" thick silicon disc 3" in diameter, so as to allow the wafer to be brought into abrading contact with a moving lap wheel. The fixturing provides a pedestal ground flat and a pad of resilient but firm cellular material bonded on the pedestal and ground flat also. The pedestal and pad are each sized only slightly larger than the wafer to be lapped. A guide ring surrounds the pedestal and pad, leaving only a slight clearance gap therebetween, and further projects away from the pad a distance less than the thickness of the wafer as it will be after lapping. A special liquid is applied as a thin uniform film over the face of the pad, and the wafer is biased against the pad face with a uniform force sufficient to squeeze the film to near zero thickness and into the open cells or pores of the pad. By using liquid that is water soluble, is hygroscopic, and has high surface tension, such as carbo wax polyethylene glycol or an equivalent from the glycol or glycerine family, the liquid squeezed into the cells of the pad create an adhesion to the wafer for holding the same firmly in place even after the biasing force is removed. The pad preferably is formed of polyurethane, but could be from the family including cellular urethane, Pellon perforated pad K, some hard styrofoam materials, or even polystyrene to provide the needed characteristics of good porosity, firmness and resiliency.

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patent: 4258508 (1981-03-01), Wilson et al.

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