Development and Evaluation of a Belt Drive Fatigue Tester for Accelerated Thermo-mechanical Stress Testing of Thin Metallic Films on Flexible Substrates

This paper presents a novel approach to assess the fatigue performance of thin films on flexible polymer substrates, integral to applications such as flexible electronics. Existing fatigue tests, unsuitable for such substrates, prompted the development of an accelerated stress testing setup, resembling a belt drive. Through simulations and an analytical formula, the influence of design parameters like bending radius, tensile force, and material properties was analyzed. A belt-drive fatigue tester was constructed and successfully subjected thin metal layers to various stress conditions. Notably, fatigue crack growth and surface roughening was observed. An in-situ optical inspection method detected cracks, highlighting the advantages of the new approach.