Robustness and Reliability of Novel Anisotropic Conductive Epoxy for Stretchable Wearable Electronics

Stretchable electronic devices are hybrid in nature, comprised of soft and rigid electronic components. Robust and reliable electrical interconnections that accommodate rigid semiconductors, communications, and sensor components on an otherwise flexible circuit are necessary to ensure the proper functionality of the device. Magnetically aligned anisotropic conductive epoxy (ACE) takes advantage of magnetically induced self-assembly of Z-axis wires in a flexible and durable matrix is optimized to suit flexible hybrid electronic applications. ACE interconnect technology was chosen for this study because it allows for pressure-less assembly and provides adhesion to an unusually wide range of materials. Of equal importance, the technology integrates well into traditional Surface Mount Technology (SMT) lines. Presented here is a subset of our ongoing evaluation of this ACE technology using various test vehicles and rigorous electromechanical testing. Herein, the ACE is used to fabricate bonds between e-textile to e-textile, e-textile to SMD resistor, and e-textile to electronic module board. The conductors on the e-textile consist of either silver-plated or laminated screen-printed multilayers of silver and carbon on thermoplastic polyurethane. The electrical resistance of the test vehicle is monitored while exposing the test samples to various mechanical stressing including tensile tests, fatigue cycling, and shear test.Magnetically aligned anisotropic conductive epoxy has shown to offer mechanically robust flex-to-flex and flex-to-rigid electrical connections. As a demonstration, the ACE is used to create connections between e-textile and wearable electronic module. In addition, the durability before and after repeated washing in commercial home clothes washing machine is demonstrated.