Electroless Deposition of Copper on Surface Modified Poly(tetrafluoroethylene) Films from Graft Copolymerization and Silanization

To improve the adhesion of electrolessly deposited copper on poly(tetrafluoroethylene) (PTFE) film surface, Ar plasma treatment, graft copolymerization, and silanization of PTFE film surface were carried out. The surface of PTFE film was first treated with Ar plasma, followed by UV-induced graft copolymerization with 2-hydroxyethyl acrylate (HEA) (the HEA-g-PTFE surface), or N-(hydroxymethyl)methacrylamide (HMMAAm) (the HMMAAm-g-PTFE surface). The surface-hydroxylated PTFE film was then reactively silanized with N-[3-(trimethoxysilyl)propyl]diethylenetriamine The surface-modified PTFE films were subsequently activated for the electroless deposition of copper via sensitization with SnCl2 and immobilization of the palladium catalyst. The surface compositions of the PTFE films at various stages of surface modification were studied by X-ray photoelectron spectroscopy. The adhesion strength of the electrolessly deposited copper on the silanized PTFE film was affected by the concentration of the grafted HEA and HMMAAm polymers. The T-peel adhesion strength of the electrolessly deposited copper on graft-copolymerized and silanized PTFE surface could reach about 7 N/cm. This adhesion strength involving the additional silanization step represented a more than 10-fold and 6-fold increase, respectively, over those obtained when the PTFE films were modified by Ar plasma treatment and by graft copolymerization. The mechanism of the adhesion strength enhancement and the cohesive failure of the polymer-metal interface were also investigated.