Role of Additives in the Electrodeposition of Sn, Ag and Sn-Ag Films from Iodide-Pyrophosphate Solution

Abstract

Studies towards the understanding of the electrodeposition Sn-Ag alloys from KI-K4P2O7 solution and the effect of PEG 600 and Hydrazine Hydrochloride additives on their electrochemistry and material properties is presented. PEG acts as a complexing agent that reduces the difference in the reduction potentials of Sn+2 and Ag+ species. Hydrazine Hydrochloride acts as an anti-oxidant of Sn+2 species and also a reducing agent of Sn+4 species to Sn+2. Hydrazine Hydrochloride also prevents the formation of Sn dendrites during electrodeposition, as the presence of Sn+4 is being proposed as one of the main causes of the dendrite formation. The ideal deposition conditions included the bath composition of Ag at 0.0035 M and deposition current density of 40 mA/cm2. Stress measurements of the Sn-Ag films shows that it is Tensile. X-Ray analysis of the deposit showed the presence of pure Sn and Ag3Sn intermetallic in the deposit.