A Study on Activation and Acceleration by Mixed PdCl2 / SnCl2 Catalysts for Electroless Metal Deposition

Abstract

Five different compositions of mixed acidic catalysts for electroless plating were investigated mainly by electrochemical and x‐ray photoelectron spectroscopy measurements, and also by ultraviolet and visible photospectroscopy, transmission electron microscopy, and Auger electron spectroscopy. It is shown that the potential sweep technique using a catalyzed gold electrode in yields voltammograms which depend upon the catalyst activity, and that this technique is applicable for simple diagnosis of the activity of mixed catalyst systems. It was found by transmission electron microscopy that large colloidal particles are required for high catalytic activities. X‐ray photoelectron spectroscopy showed that these colloidal particles consist of a system in which Pd and Sn atoms have an interaction such as in Pd‐Sn intermediates or alloys. The ratio of Pd/Sn after acceleration is not constant but depends on the catalyst activity. The accelerator ( or 1:1 ) not only removes Sn(IV) ions from the substrate but also causes coagulation of small particles adsorbed on the substrate, and these actions result in a drastic increase in the activity of low activity catalysts.