Metallization on polymer by catalyzation in supercritical CO 2 and electroless plating in dense CO 2 emulsion

Abstract

In this study we propose a novel technique for electroless plating on polymer substrates using a dense CO 2 beyond the critical point. Ni–P thin films were fabricated by a novel, hybrid technique consisting of two processes: catalyzation in supercritical CO 2 with Pd bis-acetylacetonate and electroless plating in emulsion with dense carbon dioxide. These catalyzation processes were discussed by atomic force microscopic images and the roughness of the surface. Catalyzation in supercritical CO 2 enabled the nucleation of a large number of Pd nuclei on a polyimide substrate without chemical pretreatment, and 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 deposition behavior of Pd nuclei in supercritical CO 2 was different from that in conventional catalyzation. When a polyimide was catalyzed in supercritical CO 2 and plated by conventional electroless plating in electrolyte solution, the plated film was pocked with small, peeled sections formed via the hydrogen bubbles of the sub-reaction and nodules formed via crystal growth of Ni–P. In contrast, the electroless plating in emulsion with dense CO 2 produced a uniformly plated film without peeling or nodules. The improved uniformity was attained by the solubility and diffusivity of the dense CO 2 beyond the critical point in the emulsion.