Effects of Sn Concentration and Current Density on SnBi Electrodeposition in Additive Free Plating Bath

Ying Heong Chiew,  A.S.M.A. Haseeb,  Yingxin Goh,  Seen Fang Lee
University of Malaya


Abstract

SnBi alloys were electroplated from sulphuric acid based additive free plating baths containing tin sulfate (SnSO4) and bismuth nitrate (Bi(NO3)3). The electrochemical behaviors of the plating baths were investigated by electrochemical studies. Potentiodynamic polarization curves of the plating bath revealed the large potential gap of 400mV between the two elements. The effects of SnSO4 concentration and current density on the composition and morphology of the SnBi electrodeposition were investigated. The surface morphology and composition of the SnBi alloys electrodeposited were investigated by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). The Sn content in the deposits increased with increasing Sn content in the bath. Bi content was found to decrease with increasing current density because of the more noble deposition potential of Bi. The microstructure and surface morphology of the SnBi electrodeposits become finer and smoother with increasing Sn content in bath but rougher and less compact when current density is increased. Sn-11.16 wt.% Bi alloy was fabricated from this additive free plating bath.