Robustness of Novel Anisotropic Conductive Epoxy for Stretchable Wearable Electronics

Stretchable, wearable, conformal electronics are emerging in many applications such as wearable medical monitoring systems, e-skin, and smart textiles, and other wearable sensor technology. Due to the nature of the stresses applied during their use, such stretchable devices are expected to be mechanically robust and sustain their electrical performance under high tensile strain. Most of these stretchable electronic devices are hybrid in nature, where they comprise both soft and rigid electronic components. Hence, the robust, and reliable interconnection between these soft and rigid components is a must to ensure proper functionality of the device. Interconnections between the electrically functional control systems and wearable e-textile materials have a variety of current, traditional methods, such as high pressure and temperature Anisotropic Conductive Adhesives (ACA), solder, snap/cinch connections, and isotropic epoxy adhesives. Each of these electrical connections pose issues with the necessary material sets for wearables/e-textile materials. There are significant drawbacks related to mechanical and/or thermal damage during the connection process; poor mechanical adhesion; inability to connect standard-pitch functional devices; and lack of robustness when connecting to nonplanar surfaces seen in wearable technology. ZTACH® ACE mitigates these issues, providing a superior connection method for manufacturing robust interconnects.

ZTACH® ACE, an Anisotropic Conductive Epoxy, has been developed by SunRay Scientific Inc. of Eatontown, NJ offering several advantages over conventional bonding materials. ZTACH® ACE offers a mechanically robust flexible-to flexible and flexible-to-rigid electrical connection. In addition, it allows for pressure-less assembly, low-temperature cure, excellent adhesion to various substrates, and fine pitch reliability without sacrificing contact resistance or mechanical bond integrity. Along with these benefits, the ZTACH® ACE technology integrates well into traditional Surface Mount Technology lines, with minimal added capital expenditures. Thus, making this a friendly technology to the existing manufacturing infrastructure in the printed electronics market. Herein, we conducted electromechanical and environmental characterization of ZTACH® ACE interconnections in four critical interfaces: e-textile to e-textile, e-textile to SMD resistor, Cu-Flex PCB/e-textile/SMD resistor to Polymerized Liquid Metal Network, and e-textile to electronic module board (rigid and flex). ZTACH® ACE demonstrated superior adhesion, low contact resistance, and mechanical robustness during electromechanical testing, proving ZTACH® ACE as a reliable, compliant medium between stretchable to stretchable/flex/rigid materials with high electrical conductivity.

Acknowledgment: This abstract is based on AFWERX Phase 2 Project FA864920C0048: ZTACH® ACE: Robust Interconnections for Military Wearable Sensors, in partnership with AFRL Material and Manufacturing Directorate, Binghamton University, GE Research, and Human Systems Integration.