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Waste Minimization Assessment for Multilayered Printed Circuit Board Manufacturing
Citation:
Kirsch, F. W. AND G. P. Looby. Waste Minimization Assessment for Multilayered Printed Circuit Board Manufacturing. U.S. Environmental Protection Agency, Washington, DC, EPA/600/M-91/021 (NTIS 91-234534), 1991.
Impact/Purpose:
to inform the public
Description:
The U.S. Environmental Protection Agency (EPA) has funded a pilot project to assist small- and medium- size manu facturers who want to minimize their generation of hazardous waste but lack the expertise to do so. Waste Minimization Assessment Centers (WMACs) were established at selected universities and procedures were adapted from the EPA Waste Minimization Opportunity Assessment Manual(EPA/625/7-88/003, July 1988). The WMAC team at Colorado State University inspected a plant manufacturing multilayered circuit boards. This complex operation has seven key elements: preparing individual layers of boards; transferring circuit patterns to these layers and forming copper oxide castings; bonding to form multiple layers; applying copper (electroless plating) to ensure electrical contact; applying photoresist to define the area on which copper circuits are to be plated; applying copper electrolytically to establish circuit patterns on outer board surfaces followed by tin or tin/lead plating to protect the circuits; and applying solder and final cleanup after selectively removing protective tin layers. All these elements of the manufacturing process generate hazardous waste, e.g., electrolytic application of copper generates sulfuric acid; propylene glycol methylether; copper-laden deionized water and rinse water; ethoxylated octylphenol; copper-free drag-out-laden water; and copper sulfate. The plant had already instituted waste minimization techniques; the team's report, detailing findings and recom- mendations, indicated that additional reductions and savings, although not as great, were still possible. The greatest reduction would come from separating liquid wastes into four streams containing differing amounts of waste. Copper-containing streams could be further treated and reused in process rinses and baths. Spent process solutions could be stored for recycling and reclaiming. This Research Brief was developed by the principal investigators and EPA's Risk Reduction Engineering Laboratory, Cincinnati, OH, to announce key findings of an ongoing research project that is fully documented in a separate report of the same title available from the authors.