Mechanical Reliability of Cu Electrode for Flexible Electronics under Asymmetric Bending Deformations

Recent advancements in portable electronic devices have driven a shift from rigid to flexible designs, leading to the commercialization of foldable smartphones and laptops. To realize such transformative form factors, it is essential to ensure not only the electrical performance of the devices but also their mechanical reliability under repetitive use. Enhancing the reliability of flexible electronic devices requires an in-depth understanding of the stress mechanisms and their effects during device operation. In this study, we investigated the changes in electrical resistance under repeated asymmetric bending stress applied to metal electrodes deposited on flexible substrates. Two distinct conditions were examined: (1) curvature asymmetry and (2) height asymmetry. Experimental results revealed that increased curvature asymmetry induced more extensive cracking in the electrodes, resulting in significant increases in electrical resistance. For height asymmetry, localized bending caused concentrated crack formation, which similarly led to resistance increases. We expect that this study will contribute to reducing defects in the manufacturing process of foldable electronic devices and support the improvement of hinge design and management to enhance reliability and performance.