Microstructure and preferred orientation of Au–Sn alloy plated deposits

In single metal electroplating, the microstructure produced is related to the current density or polarization. At low current densities, the growth of existing grains is favored, while at high current densities the formation of new grains is favored. The microstructures formed from alloy plating solutions have not been studied as thoroughly. In this study, pulsed current electrodeposits were formed using a gold–tin alloy plating solution based on ammonium citrate, KAuCl4, SnCl2-2H2O, sodium sulfite and l-ascorbic acid. A series of electroplating tests at average current densities ranging from 1.2 to 3.6 mA cm−2 were performed in order to study the effects of current density on the microstructure and preferred orientation. The types of microstructures produced from the plating solution described follow the trend of microstructures, which have been proposed for single metal electroplating. The preferred orientation in the deposits relates not only to the microstructure produced, but also to the phase or phases, which are present in the deposit.