THE EFFECT OF GOLD-NICKEL METALLIZATION MICROSTRUCTURE ON FLUXLESS SOLDERING

Gold plating is used in the microelectronics industry to maintain the wettability of metal substrates. The nature of wetting during soldering of gold plated metals is discussed, and the results of experiments on the fluxless wettability and oxidation of gold plated nickel are described. The results suggest that electrodeposition of a thin gold plate (0.14 mum) and the concurrent reduction of nickel oxide produce a gold-nickel system which will wet without flux. Oxidation of nickel was observed to occur via nickel out-diffusion and by direct exposure of the substrate through pinhole plating defects. Auger chemical analysis indicates that pinholes do not produce oxidation of the surrounding substrate area.