The mechanical behaviour of polyimide-copper laminates

Abstract

The peel energies of flexible laminates consisting of polyimide films bonded to copper foil with a polymeric adhesive have been measured and the peel mechanisms investigated by conducting peel tests inside a scanning electron microscope. These laminates were prepared from polyimide films that had been subjected to either a “high-thermal history” or “low-thermal history” treatment during the production of the film. The laminates prepared from the “high-thermal history” polyimide films had higher recorded peel energies and the locus of failure during the peel test was mainly by cohesive fracture through the adhesive layer. The laminates prepared from the “low-thermal history” polyimide films tended to fail in a weak boundary layer of the polyimide film. The peel energies were lower and displayed a greater scatter. Thein situ peel tests have also identified various failure mechanisms which account for the different features observed on the peeled surfaces and the various types of peel energy traces which were recorded.