Metal films on polymer substrates stretched beyond 50%

When a freestanding plastically deformable metal film is stretched, it ruptures by strain localization, and the elongation is less than a few percent. When the film is deposited on a polymer substrate, however, strain localization may be retarded by the substrate. This paper reports Cu films deposited on Kapton substrates and stretched up to the rupture of the substrates (at an elongation between 50% and 60%). When Cr adhesion layers are introduced between Cu and Kapton, few microcracks in Cu may be found, and the measured electrical resistance agrees with a theoretical prediction. Micrographs show that the strain localization and debonding coevolve.