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84 PCB007 MAGAZINE I MAY 2022 Figure 4 shows a typical industrial mixer- separator drawing used for etchant regener- ation. Six separate mixer-separators are con- tained in this one unit. Many times, more than one unit is used for the extraction stage and for the stripping stage, as seen in Figure 1. Figure 5 shows an actual copper recovery unit installed in a printed circuit fabrication facility. 5 Conclusion When the LLE extraction and recovery unit was first designed in 1974 by Hewlett-Pack- ard's PCB Group for its alkaline etching sys- tem in Palo Alto, California, no others were in use. Today, more than 100 units have been installed around the world recovering copper and regenerating their PCB etchants. One of the most recent, installed at Whelen's Green- Source Fabrication in New Hampshire, recov- ers over $375,000 in copper every year. is puts the chemical and water recovery system into a profit generator for the facility. eir daily water use for the 100-panel per hour facility is less than what is used by their toilets. PCB007 References 1. "Improved Inner Layer Etching by Simultaneous Cupric Regeneration and Copper Recovery System," by Paul Watson, ILS Conference, Leeds, UK, 1999. 2. CEMCO Etchant Regeneration Brochure for Cupric Chloride, 2 Relay Rd. Waterlooville, Hamp- shire UK, 1999. 3. Liquid Ion Exchange in Metal Recovery and Recycling, by Lawrence V. Gallacher, 1980. 4. "New Horizons in Metal Removal And Recov- ery," by W. Daniel Ernt, P.E., American Institute of Chemical Engineers Annual Technical Meeting, April 17, 1990. 5. The Mecer TM System Brochure for PCB etchant recycling and copper recovery, Sigmametallextrak- ton AB, Datavagen 51, Sweden. Happy Holden has worked in printed circuit technology since 1970 with Hewlett- Packard, NanYa Westwood, Merix, Foxconn, and Gentex. He is currently a contrib- uting technical editor with I-Connect007, and the author of Automation and Advanced Procedures in PCB Fabrication, and 24 Essential Skills for Engineers. To read past columns or contact Holden, click here. Figure 4: Diagram of multiple mixer-separators used for extracting copper from PCB etchants. (Source: Sigma Engineering) Figure 5: An actual LLE mixer-separator in operation at a working PCB fabricator. (Source: Sigma Engineering)