Behavior of Evaporated Palladium Catalyst for Electroless Nickel-Phosphorus Film Formation

Vacuum-evaporated palladium was used as catalyst for electroless Ni-P deposition on polyimide and alumina substrates. The effect that varying amounts of Pd had on the early stages of electroless plating was investigated by means of Rutherford backscattering spectrometry and transmission electron microscopy. No significant diffusion of the catalyst into the Ni-P film was observed; in some cases, a small amount of Pd tended to diffuse into the deposited Ni-P film, particularly on polyimide substrates. The deposition rate of the Ni-P film on polyimide was always less than that on alumina. An increased amount of catalyst decreased the deposition rate significantly without altering the stoichiometry of the plated film. When less than 10^l6 Pd at./cm² were evaporated onto the substrate, the catalyst formed clusters of palladium particles on the surface, whereas larger amounts of Pd (e.g., 2 x 10¹⁶ at./cm²) settled as a continuous film at the substrate.