Study of Tin Electroplating Process Using Electrochemical Impedance and Noise Techniques

The tin electroplating process was studied by means of electrochemical impedance and noise (EN) technique. Scanning electron microscopy (SEM) was used to investigate the morphology of tin electrodeposits. Electrochemical impedance results reveal that charge transfer resistance of tin electroplating decreases with the potential bias η exponentially at this experimental condition. It is found that the EN generated at high current density has large potential oscillation amplitude and positive potential drift, while the EN show small noise amplitude at low current density. With the decrease of current density, the corresponding deposit changes from large conglomerate particles to compact. New parameters are proposed to cultivate the relationship between the EN feature and the structure of tin deposits. The variation trend of Parameter n 2 was found to be in accordance with the crystallite size. For different Sn 2+ concentrations, the oscillation amplitude of the potential noise at low concentrations are much larger than that of high concentrations, which may be correlated with that tin electroplating process is coupled with hydrogen evolution at low Sn 2+ concentrations.