Torsional and bending endurance analysis of screen-printed interconnects on various flexible substrates

Additive manufacturing is an economic and resource efficient route for development of flexible electronics for applications such as robotics, wearables, and real-time health monitoring systems. Although the 2-D and 3-D printing are mature technologies, their application in flexible electronics is still in early stage and comes with challenges such as poor reliability under repeated bending conditions. This is because the level of mechanical stresses that various components of a flexible electronic module must endure is substantially high. For example, the interconnects experience a large part of bending and twisting stresses, which can affect their conductivity and decrease the responsivity and reliability of the electronic module. In this paper, we assess the base resistance and endurance of screen-printed silver interconnects on commonly used soft and flexible substrates for up to 4000 bending and twisting cycles. It is observed that the base resistance and endurance of screen-printed silver interconnects are heavily dependent on the substrate. The endurance analysis present here will benefit applications such as smart tags, where screen printed interconnects or metal lines are extensively used.