The WMAC team at Colorado State University performed an assessment at a plant manufacturing devices for converting alternating current into direct current (silicon-controlled rectifiers and Schottky rectifiers) -- approximately 2.5 million units per year. Rectifier manufacture is a two step process: wafer fabrication and assembly. Silicon wafers are doped, spin coated, cleaned, and rinsed. Next, the wafers are etched and the resist is stripped to produce a final groove pattern. Layers of polysilicate and silicon nitride are deposited via chemical vapor deposition, silicon glass is fused to the surface ground, and then the wafer is cut into chips or dice. The dice are tested, sorted, and evaluated and then transferred to assembly. The team's report, detailing findings and recommendatios, indicated that the majority of waste was generated by the stack scrubbers used to remove contaminants from exhausted plant air and that the greatest savings could be obtained by redirecting reject water from the reverse osmosis unit to the stack scrubbers to eliminate the wastewater stream from the reverse osmosis unit.

"EPA/600-S-92-036." "Sept. 1992." Shipping list no.: 92-0605-P.