Electroless plating of copper on polyimide films modified by surface grafting of tertiary and quaternary amines polymers

Abstract

Argon plasma-pretreated polyimide (PI, Kapton ® HN) films were subjected to UV-induced surface graft copolymerization with N, N′-(dimethylamino)ethyl methacrylate (DMAEMA) and 2-(trimethylammonium)ethyl methacrylate chloride (TMMAC). The DMAEMA graft-copolymerized PI (DMAEMA- g-PI) surfaces were also quaternized and amino-functionalized with 3-bromopropylamine hydrobromide (the Q-DMAEMA- g-PI surfaces). The surface composition and the degree of quaternization of the graft-modified PI films were determined by X-ray photoelectron spectroscopy. The DMAEMA- g-PI, Q-DMAEMA- g-PI and TMMAC graft-copolymerized PI (TMMAC- g-PI) surfaces can be activated directly by PdCl 2, in the absence of prior sensitization by SnCl 2 (the ‘Sn-free’ activation process), for the subsequent electroless plating of copper. A shorter induction time for the electroless deposition of copper was found for the palladium-activated Q-DMAEMA- g-PI and TMMAC- g-PI surfaces than for the palladium-activated DMAEMA- g-PI surface. The T-peel adhesion strength of the electrolessly deposited copper with the Q-DMAEMA- g-PI surface was enhanced to above 6 N/cm, in comparison to only about 4 N/cm for the DMAEMA- g-PI surface, about 2.5 N/cm for the TMMAC- g-PI surface, or about 0.5 N/cm for the PI surface with argon plasma treatment alone.