Thermal graft copolymerization of 4-vinyl pyridine on polyimide to improve adhesion to copper

The surface of poly[N,N′-(oxydiphenylene)pyromellitimide] film, Kapton® HN, was modified to improve its adhesion to copper metal. The polyimide surface was argon plasma activated and then exposed to air. A nitrogen-containing monomer, 4-vinyl pyridine, was then polymerized at elevated temperature under constant pressure between the argon plasma activated polyimide film and copper foil without any added photoinitiator. Optimization of the argon pretreatment time, curing temperature and curing duration resulted in almost doubling of the single lap shear strength. It is postulated that failure occurred mainly between the polyimide and the poly(4-vinyl pyridine).