The effect of pitch on deformation behavior and the stretching-induced failure of a polymer-encapsulated stretchable circuit

The deformation behavior and failure mechanisms of parallel-aligned, horseshoe-patterned, stretchable conductors encapsulated in a polymer substrate were investigated by numerical and experimental analyses. A design guideline for the optimal pitch between the conductors was proposed through numerical analysis, and two extreme cases—fine and coarse pitches—were investigated by in situ experimental observations. The experimental results demonstrate that the stretchable conductors enable elongation up to 123 and 135% without metal rupture for the fine and coarse pitches, respectively. The difference between these numbers is much smaller (12%) than expected from the simulations. It is found and confirmed by a modified simulation model that the reason for this is interfacial delamination, the onset of which depends on the pitch of the conductors and occurs before metal rupture of the conductors. The definition of 'stretchability of the electronic interconnects' is discussed based on the facts that two different failure mechanisms occur: interfacial delamination and metal rupture.