Effect of CF4 plasma treatment on the interfacial fracture energy between inkjet-printed Ag and flexible polyimide films

The effects of a CF4 plasma treatment on the interfacial fracture energy of an inkjet-printed Ag/polyimide system were investigated for inkjet printing metallization techniques in flexible printed circuit board applications. The interfacial fracture energy was evaluated by using a 180° peel test and by calculating the plastic deformation energy of the peeled metal and polyimide films from an energy balance relationship during the steady-state peeling process. The interfacial fracture energy between the Ag and the polyimide increased after the CF4 plasma treatment to the polyimide surface. This was caused by an increase in the surface roughness as well as changes to the surface functional groups of the polyimide film. Therefore, both the mechanical interlocking effect and the chemical bonding effect were responsible for the improvement in the interfacial adhesion in inkjet-printed Ag/polyimide systems.