Environmentally friendly method for regeneration of copper chloride acidic solutions used in etching of printed circuits

Abstract

Etching of copper with acidic CuCl2 solution is a widely used chemical method in printed circuits production. During the process, the solution is enriched in Cu(I) ions, resulting in reduction and then loss of etching bath capacity. In order to ensure the required etching kinetics, the solution is regenerated by oxidation of Cu(I) to Cu(II). The industrially applied Cu(I) oxidants are, e.g.: Cl2, chlorates. Their application is expensive and associated with drawbacks related to health, safety and environmental hazards (e.g. Cl2 emission). In the result of long-standing cooperation between the IMN and MATUSEWICZ Budowa Maszyn, an innovative, original and environmentally friendly method of acidic solutions regeneration used during printed circuits etching was developed. A new-type reactor equipped with oxidation monitoring-control systems using oxygen or oxygen-enriched air was applied. The reactor construction enables to run the process with oxygen circulation in the reactor, ensures full oxygen utilisation in the regeneration process, achievement of the required performance and process rate, and eliminates expensive, hazardous and often toxic reagents. This is an innovative method, and since there are no analogous technologies currently known and used in Europe and worldwide, the presented method is technologically, economically and ecologically unrivalled.