Mechanism of direct copper plating on nonconducting substrates

The mechanism of direct copper plating on nonconducting resin substrates wa s investigated by high resolution transmission electron microscopy and scan ning electron microscopy observation and surface analysis techniques. The s ubstrates were catalyzed by Pd/Sn mixed catalyst and accelerated in an alka line solution containing copper ions and a reductant before the direct plat ing. After the acceleration, copper crystalline particles measuring approxi mately 300 nm were found to be dispersed at the population density of 1.4 X 10(11) m(-2) in addition to adsorbed palladium colloids. The colloids form ed clusters measuring 20 to 50 nm which consist of individual particles mea suring approximately 2 nm. The addition of copper ions in the acceleration solution exerted a remarkable promotion effect on the speed of lateral prop agation of direct plating. This effect can be explained by a modified stepw ise propagation mechanism in which dispersed copper particles formed in the Cu(II) containing accelerating solution play a critical role in determinin g the propagation speed. The copper particles also play an important role i n determining the uniformity of the propagation of copper plating. (C) 1999 The Electrochemical Society. S0013-4651(98)01-058-1. All rights reserved.