Electrochemical deposition mechanism of copper-zinc-tin alloy and structural characterization

Abstract The electrodeposition of Cu-Sn-Zn coating (CZT) was investigated. The bath consisted of aqueous solution of Cu, Sn and Zn sulphate in the presence of sodium citrate (NaC6H5Na3O7) as complexing agent. The pH was set between 4 and 5.5 to stabilize the bath. Cyclic voltammetry exhibited four peaks during cathodic scan corresponding to the reductions of metal ions and adsorbed hydrogen. Impedance measurements were made at each potential peak. The effect of the metal salts concentration and the potential scan rate were studied. The deposit mechanism is controlled by mass transfer in parallel with a faradaic reaction. For the deposition of Cu-Sn and Cu-Sn-Zn alloys, the average diffusion coefficients of Cu2+ and Sn2+ ions and Cu2+, Sn2+ and Zn2+ ions were calculated. At E = -1.5 V, a Cu-Sn-Zn deposit is obtained with 55 at% copper, 25 at% tin and 20 at% zinc. The X-ray diffraction pattern shows the characteristic peaks of Cu, Cu6Sn5 and Cu3Zn2 phases. The deposit morphology was characterized by SEM.