Abstract
The effects of the bath composition and the plating conditions of gold plating using 5,5-dimethylhydantoin-gold complex on deposition were investigated.
High current efficiency and bright films were obtained from the bath containing phosphate buffer in a wide range of current density in comparison with the citrate bath. In terms of the plating conditions, the plating temperature should be 60ºC to deposit with high current efficiency. The optimum pH value was 8.0 to increase the current efficiency to almost 100% in a wide range of current density. The optimum composition to obtain a bright yellow deposit film was 0.04mol/L of gold ion and 6 times that concentration of 5,5-dimethylhydantoin, even though the gold complex has four ligands in its molecular structure.
Addition of thallium ion shifted the deposition potential to positive direction and increased current density, and accelerated depositing. Thallium played an important role to make deposited grains uniform, refine and dense. As a result, the appearances of the deposited films were bright yellow.
