Abstract: An aqueous solution for sensitizing the surface of a substrate to facilit the metallization of such surface. The solution comprises a stannous salt, a precious metal salt and a source of chloride ions. The stannous salt may be stannous chloride, the precious metal salt may be a salt of palladium, platinum, iridium, silver or gold and the source of the chloride ion may be a salt such as sodium chloride or potassium chloride or mixtures thereof.

Abstract: A process for metallizing a surface of a substrate. Preferably, the substrate is composed of a dielectric material such as a circuit board which has copper cladding on at least one face and at least one through-hole to provide a site for electrical connection to an adjacent circuit board. After cleaning the surface, it is sensitized by contacting such surface with an aqueous solution comprising a stannous salt, a precious metal salt and a source of chloride ions.

Abstract: There is disclosed a process for electroless plating of a conductive metal layer onto the surface of a non-conductive substrate, in which the substrate surface is prepared for receiving a coating of activator using conventional methods, and the coating of activator is applied by contacting the substrate surface with a stabilized sensitizing solution comprising ions of at least one Group VIII and IB transition metal, preferably palladium chloride, stannous ions in a molar concentration in excess of that of the transition metal ions, an acid, and a buffering salt; followed by contacting the sensitized substrate surface with a noble metal activating solution to catalyze the substrate surface for subsequent electroless plating. The sensitized and activated substrate is then contacted with an aqueous dry film photoresist, which is then imaged and developed to form a predetermined electrical circuit pattern, using conventional methods.