CHARACTERIZATION OF A PDCL2 SNCL2 ELECTROLESS PLATING CATALYST SYSTEMABSORBED ON BARIUM TITANATE-BASED ELECTROACTIVE CERAMICS/

A PdCl2/SnCl2 metallisation catalyst system, of the type used to activ ate non-conducting surfaces for electroless metal deposition, has been characterised by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The substrate is a barium titanate (BaTiO3) -based electroactive ceramic of the type used in the fabrication of mu ltilayer ceramic capacitors (MLCC). The treatment of the substrate sur face with the PdCl2/SnCl2 ''sensitiser'' solution leads to the adsorpt ion of catalytically inactive compounds of palladium and tin. Subseque nt treatment of this surface with an ''accelerator'' solution removes excess oxides, hydroxides and salts of tin thereby leaving the active catalyst species, Pd(x)Sn(y), on the surface. Such sites, on exposure to the appropriate electroless plating bath, are then responsible for the metal deposition. In this study, the chemical state and relative q uantities of the various surface species present after each of the pro cessing stages have been determined by XPS. The surface roughness of t he substrate results in less of the tin compounds present thereon bein g removed on washing the catalysed surface in the accelerator solution than normally reported for such systems, thereby affecting the measur ed Pd:Sn ratio. SEM studies show that the accelerator solution treatme nt generates crystalline areas, which may be a result of coagulation o f the Pd(x)Sn(y) particles present, in the otherwise amorphous catalys t coating.