Electrodeposited tin-zinc alloys are considered promising as lead-free alternatives to solder coatings. Eutectic tin-zinc alloy film was deposited at 2∼3A/dm2, 25°C, and pH 4 using the following bath composition. 0.18M SnSO4, 002M ZnSO4, 05M sulfosuccinic acid, and 1g/L polyoxyethylenenonylohenol ether (POENPE). The presence of POENPE increased tin deposition polarization markedly over a wide potentials range, and an appreciable amount of zinc was codeposited. Tin and zinc ions in the elluent were separated in the form of hydroxide, and the residual concentration of tin and zinc ions were lowered to less than 0.1mg/L. On a copper substrate, zinc in the alloy film migrated rapidly to the copper substrate at below eutentic point. Plated nickel films were effective to preventing thermal zinc migration.
