FREGEN – Electrochemical Regeneration of Ferric Chloride and Cupric Chloride Etch Solutions

September 2020

Darron Brackenbury, Dr. Brian Dougherty, and Dr. Samaresh Mohanta Electrochemical Design Associates (EDA), Inc.

EDA has developed an electrochemical system for regeneration of common etch solutions and simultaneous removal of tramp metal. Labora­tory work on spent etch solutions has shovm that their petformance is related to the ratio of concentration of the oxidized to reduced state of the active agent. This is measured and monitor­ed electrically and is known to analysts as the Oxygen Redox Potential (ORP). Electro­chemical oxidation of the etchant solution and simultaneous removal of dissolved etched materials can be used to fully recover working solutions. Combining these two techniques, monitoring of the etchant strength and controlling the degree of electrochemical treatment can be used to maintain consistent performances in the etch bath hour after hour. Our equipment has been run for several months at a nameplate manufacturing plant, demon­strating that Oxygen Redox Potential can be maintained at a high levels while extending the etch solution life by at least 6 times. Metal etched into solution from the workpiece is broadly in balance with plated tramp metal, which is removed from solution as dendritic, high-surface-area metal. The ability to maintain a more consistent, potent and long-lived etch is beneficial to the consistency, quality, perform­ance and economics of the etching process.

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