ELECTROLESS GOLD PLATING BY DISULFITEAURATE COMPLEX

Non-cyanide electroless gold plating, using a disulfiteaurate complex, is unsatisfactory because the complex is unstable and easily decomposes. Bath stability was improved by using Na2SO3,Na2S2O3 and nitrilotriacetic acid as complexing agents; the disproportionation reaction of gold(I) ions was suppressed by the addition of cupferron, bipyridine or Ni(CN)(2) . 2KCN. The plating rate ranged from 0.7 to 1.0 mu m/hr with sodium ascorbate as a reducing agent. The rate was increased to about 1.5 to 2.0 mu m/hr with the addition of sodium ascorbate and hydrazine sulfate. Based on these results, gold wire bondability was evaluated. Gold crystal orientation was influenced by the wire bonding, and high bonding strength was obtained with (220) and (311) preferred orientation gold films.