Role of the Intermediate Layer and Factors Determining Chemical Composition of the Film in the Electroless Ferrite-plating

Abstract

This paper describes electroless ferrite-plating on a Cu substrate whose surface is oxidized (the Cu-oxide layer works as an intermediate layer for the plating). Electron-diffraction and cathodic-reduction analyses showed that a Fe₃O₄ thin layer is formed on the intermediate layer during the initial reaction of the plating. This thin layer grows by the repetition of the adsorption of metal ions to the surface of the layer and the oxidation of the adsorbed Fe^II ions. Based on the adsorption-equilibrium of the metal ions on the surface of the film, the relationship between the composition of the metal ions adsorbed and that of the metal ions incorporated into the Co-ferrite film was formulated in terms of the concentrations of the metal ions in the reaction solution and the reaction pH. The analysis of the experimental data with this equation showed that the Co^II ions are more readily incorporated into the ferrite layer, as the mol ratio of the adsorbed Co^II ions to adsorbed iron ions (R_ads.) increases, but that a higher R_ads. becomes unfavorable for the incorporation.