TEM STUDY OF THE EFFECT OF ACCELERATORS ON Pd-Sn COLLOIDAL CATALYSTS AND ON THE INITIATION OF ELECTROLESS Cu DEPOSITION ON EPOXY.

Abstract

The first step in the formation of the Cu metallurgy on a circuit board generally entails the electroless deposition of Cu on an epoxy surface. In order to initiate the process, the epoxy must be made catalytic for the electroless Cu reaction. One frequency used catalyst consists of Pd-Sn particles deposited from a colloidal suspension (1). The particles have a catalytic core containing metallic Pd (and also some Sn), but the core is surrounded by a largely inactive layer of ionic tin. It is common, before Cu plating, to remove some of this tin with an accelerator, a solution that dissolves tin ions. Thin epoxy films were prepared as substrates for TEM. These substrates were used to examine the effects of various accelerating solutions on the Pd-Sn colloidal catalyst and on the initial stages of electroless Cu plating.