Ductility of copper films on sandblasting polyimide substrates

Different surface morphologies of polyimide(PI)foils widely applied in flexible electronics were obtained using the technique of sandblasting.Copper(Cu)films were subsequently deposited on the treated surface of PI substrates.Upon tensile loading, the critical strain,crack density and count of cracks were measured to examine the ductility of Cu films on PI substrates.Obtained results show that after sandblasting treatment,the critical strain of Cu film decreases from 8.0%to 6.9%and,in comparison with the case without sandblasting,its surface crack density decreases remarkably,with no saturation of the crack density.The reduced crack density is attributed to the increase of contact area and interfacial adhesion after sandblasting,and whether the crack density is saturated or not is dependent upon the morphology of the cracks formed as a function of tensile strain.