Abstract: The ORP of the initial etchant solution is utilized as a set point. A predetermined change in the ORP triggers the removal of a predetermined volume of spent etchant. Fresh etchant addition steps and oxidation of the working etchant (addition of chlorine) are sequenced by the initial fixed volume withdrawal. The oxidation and fresh etchant addition steps proceed to conclusion independently. The oxidation step is terminated by a return of the ORP to the initial level.

Abstract: System and apparatus for the controlled etching of copper work pieces with ferric chloride etchants. The working solution is constantly monitored with regard to its oxidation reduction potential (ORP) by comparison with a standard solution or voltage. To reduce the build up of etched copper in the working solution, an ORP controller activates the removal of specific quantities of that solution which are then replaced in precise stoichiometric proportions with fresh etchant. Simultaneously, oxidant is injected into the fluid to reoxidize ferrous ions to ferric ions. The solution is constantly monitored and the ORP control means repeats the above procedure as often as necessary to maintain the ORP of the fluid within an acceptable range.

Abstract: System and apparatus for the controlled etching of copper work pieces with ferric chloride etchants. The working solution is constantly monitored with regard to its oxidation reduction potential (ORP) by comparison with a standard solution or voltage. To reduce the build up of etched copper in the working solution, an ORP controller activates the removal of specific quantities of that solution which are then replaced in precise stoichiometric proportions with fresh etchant. Simultaneously, oxidant is injected into the fluid to reoxidize ferrous ions to ferric ions. The solution is constantly monitored and the ORP control means repeats the above procedure as often as necessary to maintain the ORP of the fluid within an acceptable range.