Motorola Corporation

Russell Mallen

Prosanto K Mukerji

Harry Fuerhaupter

George N Demet

A method for producing a coating composed of an electroless metal plate, such as a copper plate, tightly bonded to a polyimide layer comprises a multi-step cure of the polyimide layer carried out in combination with a palladium-catalyzed electroless deposition process. A solution of a polyamic acid compound that is the precursor for the desired polyimide resin in a vaporizable solvent is applied to a substrate and heated preferably to temperature below 250.degree. C., to form a soft-cured polyimide film. The film is immersed in an aqueous palladium-tin colloidal suspension to deposit the colloidal particles thereon, which particles are then activated to form palladium nuclei dspersed on the surface. The soft-cured film is then heated, preferably above about 250.degree. C., to vaporize residual solvent and form a hard-cured polyimide layer having the palladium nuclei dispersed on the surface. The hard-cured layer is immersed in an electroless metal plating solution, whereupon the palladium nuclei catalyze deposition of the metal to form a continuous plate. In one aspect of the method, the metal-clad layer is further heated between about 350.degree. C. and 450.degree. C. to final cure the polyimide. It is found that the plate of the coating formed by this multi-cure method strongly adheres to the polymer layer to permit extended deposition and thereby form a relatively thicker plate without catastrophic separation from the polymer.

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Glen Ellyn, IL, United States of America

Russell Mallen