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A method for making high density foam semiconductor polishing pads and belts with controlled, reproducible microcellular structure by mechanical frothing. The method involves agitating a liquid polymer resin at a controlled temperature and pressure in order to produce a stable froth. Next, the resin

A method for making high density foam semiconductor polishing pads and belts with controlled, reproducible microcellular structure by mechanical frothing. The method involves agitating a liquid polymer resin at a controlled temperature and pressure in order to produce a stable froth. Next, the resin froth is metered under pressure to a mix head where it is typically combined with a desired amount of curative before being injected or poured into a mold.

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1. A high density, microcellular polishing pad or belt with consistent cell structure and properties, produced by combining a thermosettable liquid polymer or prepolymer resin and a nucleation surfactant, agitating the resin mixture in the presence of a frothing agent at a controlled temperature and

1. A high density, microcellular polishing pad or belt with consistent cell structure and properties, produced by combining a thermosettable liquid polymer or prepolymer resin and a nucleation surfactant, agitating the resin mixture in the presence of a frothing agent at a controlled temperature and pressure in order to produce a stable resin froth, metering the resin froth under pressure to a mix head, optionally combining the resin froth with a curative, injecting or pouring the resin froth into a mold; said polishing pad or belt being free of hollow polymeric microelements or microballoons. 2. The product of claim 1, wherein the resin is a polyurethane. 3. The product of claim 1, wherein a catalyst and a blowing agent are combined with the resin to create an open-celled structure or to enlarge the cells after the mixture is injected or poured into the mold. 4. The product of claim 1, wherein the nucleation surfactant is a block copolymer containing at least one block comprising polydimethylsiloxane, and at least one other block comprising polyether, polyester, polyamide, or polycarbonate segments. 5. The product of claim 1, wherein the frothing agent is dry nitrogen or dry air. 6. The product of claim 5, wherein the frothing agent is used in the head space of a resin frothing vessel. 7. The product of claim 1, wherein the resin froth is produced at a temperature of ambient to 100° C., and at a pressure of ambient to 100 psig. 8. The product of either claim 1 or claim 7, wherein the resin froth is metered to the mix head under a pressure of ambient to 200 psig. 9. The product of claim 1, wherein resin froth is prepared in continuous or semi-continuous fashion, in-line between a resin holding tank and a dispensing mix head. 10. The product of claim 1, wherein the nucleation surfactant comprises a polyalkyleneoxidemethylsiloxane copolymer. 11. The product of any one of claims 1, 4 and 10, wherein the nucleation surfactant and the liquid polymer or prepolymer resin are present in a ratio of about 5 parts by weight of the nucleation surfactant to about 100 parts by weight of the liquid polymer or prepolymer resin. 12. The product of any one of claims 1, 4 and 10, wherein the nucleation surfactant and the liquid polymer or prepolymer resin are present in a ratio of about 0.5 parts by weight of the nucleation surfactant to about 100 parts by weight of the liquid polymer or prepolymer resin. 13. The product of claim 1, wherein a curative is used, and the curative is a diamine. 14. The product of claim 1, wherein a curative is used, and the resultant microcellular foam has approximately 0.68 specific gravity. 15. The product of claim 1, wherein a curative is used, and the resultant microcellular foam has approximately 0.92 specific gravity. 16. The product of claim 1, wherein a curative is not used, and the resultant microcellular foam has approximately 0.41 specific gravity.