Initial Stage of Electroless Cu Deposition on Epoxy Substrate Catalyzed with Ag Nanoparticles

Ag nanoparticle catalysts having a Ag@SnO2 core/shell structure were adsorbed from their colloidal solution on the smooth epoxy substrates conditioned with poly(diallyldimethylammonium chloride). The amounts and morphology of the adsorbed catalysts suggest the uniform monolayer adsorption and the formation of the agglomerated two-dimensional domains comprising several nanoparticles. Citrate acceleration of the adsorbed catalysts dissolved the SnO2 shell of the catalysts, and somewhat increased the size of the agglomerated domains and the surface roughness of the substrate with adsorbed nanoparticles. Electroless Cu deposition rate on the substrates with adsorbed catalysts went through a maximum at the initial stage, and then decreased to its constant value. Isolated Cu particles were deposited at the initial stage, and they coalesced to form the continuous films after the deposition rates reached the constant value. On the substrates without the citrate acceleration, Cu particles were deposited only at the beginning, due to the desorption of catalysts into the plating bath. The citrate acceleration prevented the desorption, and hence increased the catalyst availability. This led to the higher deposition rate and the faster morphology development at the initial stage because of the rapid and progressive deposition of Cu particles. (C) 2014 The Electrochemical Society. All rights reserved.