The surface layer pH in the electroless copper plating process

Abstract

The pH at the surface of the coating (pH s) was measured using an ordinary glass electrode, the surface of which was in the zone of the reaction during the autocatalytic reduction of copper(II) ions by formaldehyde. The pH s value is significantly lower (by up to 1.3 units) than the pH bulk value in most tartrate and ethylenediamine tetraacetate (EDTA) solutions. The pH s value changes the dependence of the electroless copper plating rate on the alkalinity of the solution (the rate maximum shifts from 12.6 - 12.7 to 11.7 - 12.0). The pH changes at the surface depend mainly on the catalytic process rate and the buffering capacity of the solution; the evolution of H 2 also has a great influence at the medium rate of copper plating (1 - 3 μm h -1).