Abstract: A process and an apparatus are described for regenerating an electroless copper plating bath containing a complexing agent, preferably ethylenediamine tetraacetic acid. From the bath solution to be regenerated, the copper content is reduced by electrolysis to a value below 20 mg/l and the complexing agent subsequently precipitated by acidification and recovered. After dissolution in an alkaline electrolytic solution, the solution thus obtained is fed back to the electroless copper plating bath. A particularly pure ethylenediamine tetraacetic acid free from by-products is obtained if the pH value is kept constant during electrolysis, an anodic current density i.sub.+ of 100 A/m.sup.2 is not exceeded, and the anodic current density during electrolysis is reduced according to the electrolysis characteristic or in steps.

Abstract: The invention concerns a process for automatically regenerating copper chloride etch solutions, wherein regeneration is effected by means of hydrogen peroxide and hydrochloric acid in a regeneration unit separated from the etch chamber. The addition of hydrogen peroxide is controlled by a redox electrode, while hydrochloric acid and water are added in computed quantities. Hydrogen peroxide and hydrochloric acid are converted in an oxidation reactor into hypochlorous acid and immediately afterwards are combined with the copper (I) chloride etch solution which contains at least the quantity of hydrochloric acid required for oxidizing the copper (I) ions. In the regeneration unit a salt basket with solid sodium chloride is arranged or adjacent to said unit a salt tank with an overflow to said regeneration unit is provided, both of which permit the sodium chloride concentration of the etch solution being kept constant.