The adhesion of plated metals on top of chemically treated epoxy layers for build-up purposes was examined. Specifically, the influence of wet chemical pretreatments on the adhesion of plated copper to epoxy polymer is investigated. This adhesion is related to the surface roughness of the polymer and the chemical composition of its surface. The chemical composition of the surface was examined by X-ray photoelectron spectrscopy and placed in the context of the development of the interface during the wet chemical pretreatments and related to the theory developed in previous publications. Various combinations of pretreatments were followed by an identical electrochemical Cu deposition and peel strength measurement sequence. This allowed interpretation of the changes of the peel strength with pretreatments. Using this interpretation, the peel strength of build-up layers was maximized. We propose that the surface of the polymer layer develops into a fractal surface during wet chemical oxidation. Using this proposition, in combination with pore diffusion for the oxidizer, the evolution of peel strengths with chemical pretreatment times can be qualitatively understood. The peel strength of electrochemically deposited copper can be quantitatively related to the atomic force microscopy measurements for limited oxidation treatment times. © 2005 The Electrochemical Society. All rights reserved.