Electrodeposition of eutectic Sn96.5Ag3.5 films from iodide–pyrophosphate solution

Electrodeposition of SnAg alloy films and the effect of additives like PEG-600 and hydrazine hydrochloride on the same were studied in KI–K4P2O7 solutions. PEG-600 was found to adsorb on the electrode surface, resulting in strong reduction inhibition of tin pyrophosphate complex ions, but it does not affect the reduction of silver iodide complex. It was found that hydrazine hydrochloride acted as a reducing agent for Sn4+ species and greatly improved surface morphology and roughness of the films by preventing the formation of Sn dendrites during electrodeposition. Eutectic Sn96.5Ag3.5 was obtained from a plating solution that contained both PEG-600 and hydrazine hydrochloride as additives, at the deposition current density of 40 mA cm−2. Stress measurements of the SnAg films showed that it was tensile. X-ray analysis of the deposit showed the presence of β-Sn and ɛ-Ag3Sn phases in the eutectic SnAg film. The DSC profile of SnAg film gave the melting point as 222 °C.

► It was found that PEG shifts the reduction potential of SnP2O72− complex towards more negative potential. But, it does not, considerably, influence the reduction potential of AgI43− complex.
► Hydrazine hydrochloride acts as a reducing agent for Sn4+ species and greatly improves the morphology and also roughness of eutectic Sn96.5Ag3.5 film.
► The eutectic Sn96.5Ag3.5 alloy with melting point of 222 °C and tensile stress was obtained by electrodeposition from 2 M KI to 0.5 M K4P2O7 solution, in the presence of PEG and hydrazine additives.