Parameter identification of micron-sized freestanding stretchable electronic interconnects using integrated digital height correlation

For the development of reliable stretchable electronic systems, it is essential to comprehend and predict their mechanical behavior. It is important to test and analyze original as-processed samples, as opposed to standard tests on bulk material. Dedicated analysis methods are necessary for obtaining the material properties from the tests, as complex 3D deformations complicate the use of existing methods. This paper presents an integrated digital height correlation (IDHC) method for the mechanical characterization of a recently developed ultra-stretchable freestanding interconnect. Height maps from an out-of-plane loading experiment are correlated to a numerical model, with the aim to identify the material parameters in the plastic regime. The IDHC method is tested on a virtual test case, where it is shown that the algorithm converges for the considered three plasticity parameters. For the real experiment, simultaneous correlation of all three parameters is not possible due to an inherently flat residual landscape with many local minima. However, the initial yield strength and hardening exponent were still identified and estimated at 225-300 MPa and 0.15-0.2 respectively. Despite the moderate accuracy of the identification, the potency of the IDHC method for this extremely challenging case of micron-sized delicate freestanding stretchable electronic interconnects is demonstrated.