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40 PCB007 MAGAZINE I APRIL 2024 In my last column, I reviewed some relatively simple ways to reduce water usage in existing etch systems: cutting down cooling coil water flow, adding chillers to replace plant water for cooling, lowering flow rate nozzles for rinses, etc. is month, I'll continue with more ways to control water usage in your etcher. Most of these are not easily retrofittable to existing equipment but should be given serious consid- eration when new equipment is contemplated. With the right combination of add-ons, it is possible to bring the amount of water used in an etch system to almost zero. One of the best ways to reduce rinse water volume is the use of counter-current cascade rinses in place of single rinses to drain. is technology has been around for a long time and consists of several short stages, each with its own sump (usually nine to 10 gallons each), pump, and a single spray tube. Water is fed to the last stage, which then overflows into the preceding stage and so on down the line to the first stage immediately aer the etcher. In this way, the water is used (n)times, with n being the number of stages in the rinse, instead of just once and down the drain. Also, most of the contaminants dragged into the rinse end up in the first stage of the rinse with each stage hav- ing fewer contaminants as the board passes through until the board sees fresh water in the final stage. is concentration of contamination in the first stage also has waste treatment benefits. It is far more efficient and cost-effective to remove Reducing Etch System Water Usage, Part 2 The Chemical Connection by Don Ball, CHEMCUT