Screen-printing paste for use as a barrier layer on a substrate during maskless cladding

摘要

Disclosed is a screening paste for covering a selected portion of a metallurgical pattern on a substrate while leaving other metallurgy uncovered. The paste is free of polymers and consists, in one example, of 75-80% of a ceramic particulate (such as alumina), 2-8% amorphous fumed silica and 15-20% of linear alcohol. The linear alcohol serves as a vehicle to deliver the solid particles in the paste. In use, after covering the selected portion of the metallurgical pattern with the paste, the alcohol content therein is expelled by subjecting to vacuum treatment at room temperature or heating to a low temperature below about 275° C. thereby obtaining an inert, dry and crack-free protective coating. Upon evaporation of a new metal layer onto the substrate and removal of the protective coating and new metal layer from everywhere except the uncovered metallurgy, the metallurgical pattern is selectively coated with the new metal.