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

A PdCl2/SnCl2 metallisation catalyst system, of the type used to activate 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 multilayer ceramic capacitors (MLCC). The treatment of the substrate surface with the PdCl2/SnCl2 ''sensitiser'' solution leads to the adsorption of catalytically inactive compounds of palladium and tin. Subsequent 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 quantities of the various surface species present after each of the processing stages have been determined by XPS. The surface roughness of the substrate results in less of the tin compounds present thereon being removed on washing the catalysed surface in the accelerator solution than normally reported for such systems, thereby affecting the measured Pd:Sn ratio. SEM studies show that the accelerator solution treatment generates crystalline areas, which may be a result of coagulation of the Pd(x)Sn(y) particles present, in the otherwise amorphous catalyst coating.