Evaluation of substrate (Ni)-catalyzed electroless gold plating process

The substrate (Ni)-catalyzed electroless gold plating process invented by I acovangelo and Zarnoch has been investigated for plating gold on electroles s nickel substrates for application to bonding of electronic devices. The p rocess was found to yield uniform and adherent gold films on Ni-B substrate s, whereas on Ni-P substrates acceptable gold films were obtained only when the P content was low and a pretreatment procedure was introduced to preve nt the formation of surface oxide or to remove it completely. Unlike the co nventional galvanic displacement process, the substrate-catalyzed process d oes not attack the nickel substrates and yields gold films with a very low porosity. Compared with autocatalytic electroless gold plating baths, the s ubstrate-catalyzed bath is inherently more stable, although the maximum gol d thickness obtainable is naturally limited. Results of these evaluations a re presented in detail. (C) 2000 The Electrochemical Society. S0013-4651(99 )106-062-0. All rights reserved.