Study of an alkaline bath for tin deposition in the presence of sorbitol and physical and morphological characterization of tin film

Effects of sorbitol concentration on the deposition of tin on to platinum were studied by cyclic voltammetry. It was observed that sorbitol affected the tin-plating rate and also the thermodynamics of the deposition process. Rotating disk electrode studies showed that the deposition rate is controlled by mass transport and that the diffusion coefficient of the Sn(II) complex decreases with increasing sorbitol concentration. The presence of sorbitol in the plating bath was beneficial since a plating current efficiency of ∼70% was obtained, while in its absence it was ∼19%. Scanning electron microscopy showed that sorbitol works as a brightener since tin crystallites were much smaller than those obtained from alkaline solution in the absence of sorbitol. Also, at 1.0 M, sorbitol produced a very smooth film. X-ray spectra showed that β-Sn was deposited.