Experimental and numerical analysis of cyclic ratchetting and low cycle fatigue behaviour in meander-shaped interconnects for stretchable electronics applications

Stretchable interconnect is a crucial component of a wearable device , responsible for establishing electrical connections throughout the system. Among various technologies, thin film-based interconnects provide superior electrical conductivity comparable to bulk metals, enabling high-quality signals in diverse wearable applications. Nevertheless, their relatively low mechanical fatigue life remains a significant challenge. Research has shown that flexible polymer-supported interconnects exhibit improved fatigue life compared to non-supported counterparts. Albeit widespread adoption of thin film-based stretchable tracks, underlying physical principles governing their fatigue life is not thoroughly studied. In this work, stretchable interconnects are fabricated and analysed using a cost-effective method suitable for mass fabrication. This study focuses on modelling of the stretchable interconnects using FEM under both static and dynamic loadings to discover the significant role of flexible polymer in increasing the cyclic fatigue life. Polyimide (PI)-supported interconnects show a major decrease (~ 20 %) in maximum strain under static load compared to non-supported interconnects. It has been demonstrated that under dynamic loading, non-supported interconnects fail mostly based on ratcheting strain , whereas low cycle fatigue (LCF) governs the failure mechanism of PI supported tracks. The latter happens due to the beneficial residual stress imposed by the flexible support layer. The findings are supported by characterizing the experimentally fabricated stretchable interconnects. • Polyimide significantly enhances cyclic fatigue life by altering failure mechanism. • PI shifts failure from ratcheting to low-cycle fatigue under dynamic loading. • PI-supported interconnects show 20 % strain reduction under static load. • Cost-effective fabrication of stretchable interconnects for mass production.