Abstract: The current method and apparatus relate to treating a dispersion bath using an ion exchange resin and an optional pH adjustor and wherein the ion exchange resin and the optional pH adjustor maintain a pH of within +/?2 of the initial pH of the dispersion bath.

Abstract: Black- or brown-oxidised copper laminates that are to be integrated into an electrical multilayer laminate in a subsequent process step are electrochemically reduced in order to avoid the formation of so-called "pink rings". To that end, they are connected as the cathode of an electrolysis in a suitable electrolyte. The atomic hydrogen produced in statu nascendi during the electrolysis completely or partially reduces the copper oxide layer on the metallic regions of the copper laminates, whereby the resistance of the surfaces of the metallic regions of the copper laminates to subsequent acid attack is considerably improved. The electrochemical reduction may optionally be coupled with a chemical reduction or precede a chemical reduction.