Electroless gold plating using erythorbic acid as reducing agent

The purpose of this investigation was to study electroless Au plating from a sulfite/thiosulfate complex bath (0.015M Na-3[Au(SO3)(2)]+0.1M Na2S2O3+0.4M Na2SO3+0.05M C6H7O6Na+0.18M KOOCCH(OH)CH(OH)COONa) using erythorbic acid as the reducing agent. Deposition rates by autocatalytic reaction and displacement reaction were increased with increasing the concentration of erythorbic acid. The deposition rate by autocatalytic reaction was increased with increasing bath temperature. The deposition rate by displacement reaction was suppressed by the addition of benzotriazole (BTA), di-sodium ethylenediaminetetraacetate (EDTA) and ethylenediamine (en). Electroless Au film which shows a good characteristics in the solder joint strength was obtained from a bath containing BTA, EDTA and en.