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88 PCB007 MAGAZINE I MARCH 2020 Acid copper plating in most shops is done in vertical plating tanks. Acid copper solutions are not dumped but are continuously used with occasional carbon treatment to remove organic build-up from the additives and from dry film leaching. Anodes used are commonly copper balls in titanium baskets. The copper metal at the anode is continuously oxidized to the copper ion and goes into solution. The cop- per ion is then reduced to copper metal at the cathode (the panel): • At the anode: Cu 0 ¨ Cu ++ + 2e – • At the cathode: Cu ++ + 2e ¨ Cu 0 The plating reaction requires vigorous solu- tion movement to maintain the replenishment of copper ions at the plating interface. This is normally done by strong uniform air agitation. Air is a mild oxidant and would help the an- odic oxidation and the dissolution of copper. Over time, the copper content of the electro- lytes will continue to rise to the point where it would violate the upper specification limit for copper concentration to meet the throwing power and integrity of the plated copper. When this occurs, the bath is diluted down by a partial dump and remake to reduce the copper concen- tration. The dumped electrolyte is then waste- treated by the use of alkaline precipitation. The copper falls out of solution as copper hydroxide. Then, the precipitate is filtered out using a fil- ter press, bagged, and disposed of by a certified waste disposal company. This is labor-intensive and costly; it also does not help the environment. The use of air sparging creates an acidic mist that pollutes ambient air in the plating area and is hazardous if not properly removed. This is accomplished by an exhaust system above the tank. Exhaust systems are costly to build and maintain. Eliminating Waste From Electrolytic Acid Copper Plating The Plating Forum Feature Column by George Milad, UYEMURA

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