SUBSTRATE-CATALYZED ELECTROLESS GOLD PLATING

Hydrazine is used as a reducing agent in a novel electroless gold plating formulation. Anodic polarization curves have shown that excess free cyanide, used to stabilize the gold cyanide complex, poisons hydrazine oxidation on gold but not on transition metals such as nickel and cobalt. This allows a new type of plating, "substrate-catalyzed," which is neither immersion nor autocatalytic plating. This bath plates pure gold films at high initial rates up to 10-mu-m/h with exceptional bath stability and life.