Fatigue of metals at nanoscale: Metal thin films and conductive interconnects for flexible device application

As electrodes and electrical interconnects in flexible electronic devices, metal films are one of the weakest components in the system against mechanical deformation in daily use. Fatigue reliability at nanoscale becomes a practical concern for these flexible electronic devices. This review introduces state-of-the-art fatigue testing techniques and evaluation methods for thin metal films and conductive interconnect materials constrained by a substrate. Then, experimental results about fatigue damage behaviors, fatigue properties and fatigue life prediction are summarized. Furthermore, fundamental insights into fatigue mechanisms of metals at the nanoscale and the size effects on fatigue properties are elucidated. Finally, the perspectives of studies on fatigue of thin metal films constrained by a substrate are proposed. Keywords: Fatigue, Nanoscale, Metal film, Size effect