Effect of the mole ratios of silane-modified polyvinylimidazoles on adhesion promotion of the polyimide/ copper system

Abstract

Polyvinylimidazoles (PVIs) modified with vinyltrimethoxysilane (VTS) and y-methacryloxypropyltrimethoxysilane (γ-MPS) in different mole fractions were used as adhesion promoters (primers) for the polyimide (PI)/copper interface. The effects of the compositions of the silane-modified PVI copolymers on the lap shear strength between PI and copper were investigated at different bonding temperatures. Contact angle measurements and scanning electron microscopic (SEM) analysis were performed to characterize the interfacial phenomena between PI and the primer, and Fourier transform infrared (FTIR) spectroscopy was employed to investigate the thermo-oxidative degradation of PI at the different bonding temperatures and the locus of failure after the lap shear test. In the PI/γ-MPS-modified PVI/copper system, γ-MPS-modified PVI containing a lower γ-MPS content showed higher lap shear strengths, but the behavior was opposite in the PI/VTS-modified PVI/copper system. In particular, VTS-modified PVI with a 1: 1 silane/VI mole ratio showed the best performance for adhesion promotion of the PI/copper interface at all bonding temperatures. The interfacial adhesion strength between PI and the primer was a crucial factor for adhesion promotion of the PI/γ-MPS-modified PVI/copper system. In the PI/VTS-modified PVI/copper system, however, the primer's capability to suppress the thermal degradation of PI at the bonding temperature was the main factor in controlling the adhesion strength.