Patent ID: 7435364
Filing Date: 2008-10-14
Classification: B24D,B29B,B29C

Abstract:
1. A method of forming a chemical mechanical polishing pad, comprising: providing a tank with polymeric materials; providing a storage silo with unexpanded microspheres; providing an isocyanate storage tank with isocyanates; providing a premix prep tank for forming a pre-mixture of the polymeric materials and the unexpanded microspheres; providing a recirculation loop on the premix prep tank for controlling a bulk density of the pre-mixture in the premix prep tank; providing an in-line densitometer in the recirculation loop for measuring the bulk density of the pre-mixture; providing a premix run tank for storing the pre-mixture; providing a mixer for forming a mixture of the pre-mixture and the isocyanates; providing a closed mold for molding the mixture; delivering the polymeric materials and the unexpanded microspheres to the premix prep tank forming a pre-mixture of the polymeric materials and the unexpanded microspheres; recirculating the pre-mixture through the recirculation loop on the premix tank and adding polymeric materials or unexpanded microspheres to obtain a desired bulk density; delivering the pre-mixture having the desired bulk density to the premix run tank; delivering the pre-mixture having the desired bulk density and the isocyanates to the mixer forming a mixture of the pre-mixture and the isocyanates; injecting the mixture into the closed mold; curing the mixture to form a molded product; and expanding the unexpanded microspheres in the molded product to form a polishing pad.