SBIR-STTR Award

The proposal concerns development of an electrolytic process for the on-line regeneration of acid cupric chloride etching baths. Chemical regeneration on a batch basis is generally practiced today, utilizing chlorine and/or hydrogen peroxide to re-oxidize the Cu+, formed by the etching process, back to Cul+. These processes suffer the disadvantage of resulting in a net increase in solution inventory which must be disposed. Strong environmental and cost incentives exist for development of an efficient electrolytic regeneration process. Phase I will comprise the construction and operation of a flow loop to demonstrate continuous etchant regeneration, maintaining steady state concentrations of CuC@ ' , CuCl and HCI, with avoidance of the parasitic electrochemical reactions of chlorine and hydrogen evolution. At the same time, cathodicauy generated copper metal will be extracted from the system, balancing that consumed in the etching process.

Strong environmental and cost incentives exist for development of an efficient on-line electrolytic process for the regeneration of acid cupric chloride etchant, used in printed circuit board spray etchers. In the Phase I research, continuous etchant regeneration was demonstrated. Steady state concentrations of CuCl2, CuCl, and Hcl are maintained, while avoiding the parasitic electrochemical reactions of chlorine and hydrogen evolution. Cathodically generated copper metal is recovered from the system, balancing that consumed in the etching process. This is accomplished while the Cu+ ion concentration is held at the low levels required to achieve acceptable and consistent board etching rates. In Phase II, the process will be scaled up by about two orders of magnitude in terms of copper removal rate. Also, an auxiliary device will be developed to provide on-line electrochemical compensation for the chemical imbalance caused by the finite rate of oxygen ingress at the spray etcher.