Non-cyanide electroless gold plating using polyphenols as reducing agents

Polyphenol compounds were investigated as reducing agents for non-cyanide electroless gold plating for electronics assembly applications. The pH value and temperature were optimized to determine the conditions that lead to a high deposition rate without precipitation. The surface morphology was evaluated by scanning electron microscopy. Catechol, pyrogallol, and gallic acid yielded deposited films with good appearance and solderability under the optimized conditions. Among the tested reducing agents, catechol is the most suitable for use as a stable plating bath with a long life. It has a moderate reducing ability to stabilize the bath and deposit the film. The calculated values of the heat of formation and the highest occupied molecular orbital levels of the reducing agents supported the experimental results.