Metallization on polymer via quantitatively controlled catalyzation in Sc-CO2 and electroless plating with Sc-CO2 emulsion for micro and nano-device

This study was conducted to examine how catalyzation in supercritical CO"2 with Pd-bis(acetylacetonate) influences electroless plating on polymer substrates. Catalyzation in supercritical CO"2 enabled the nucleation of abundant Pd nuclei on a polyimide substrate without chemical pretreatment, ultimately leading to the deposition of a uniform Ni-P metal film. Conventional catalyzation without chemical pretreatment led to the deposition of only a few nuclei in sparse, island-like formations. The area of the substrate occupied by the catalyst particles in Sc-CO"2 catalyzation was estimated by visual point counting. The low density and poor uniformity of the catalysts on the polyimide substrate in the electroless plating procedure reduced the coverage of the Ni-P film. A catalyzation time of more than 20min was essential to induce a conventional catalyzation reaction adequate for complete Ni-P coverage, whereas catalyst nuclei induced by Sc-CO"2 catalyzation of only 5min were well deposited on all parts of the substrate. The period from 1 to 3min is thought to be the induction period in Sc-CO"2 for polyimide metallization. The size of the catalyst and the area of the polymer substrate occupied by the catalyst are the chief factors required for a completely continuous coverage of Ni-P film on polymer substrate.