Self-healing Interconnects with Nearly Plastic Stretching of Repairs

Abstract

Flexible electronic systems such as roll up displays, wearable devices etc. promise exciting possibilities that could change the way humans interact with the environment. However, they suffer from poor reliability of interconnects and devices. Interconnects on flex are prone to open circuit failures due to mechanical stress, electrostatic discharge and environmental degradation. Passive approaches such as the use of stretchable conductors and novel geometries improve their response to mechanical stress but cannot salvage the interconnect if a fault were to occur. Active approaches using self healing techniques can repair a fault and have been demonstrated using methods that either use relatively rare materials, change conventional interconnect fabrication processes, only address faults due to mechanical stress or do not permit stretching. In this work we discuss a self healing technique that overcomes these limitations and demonstrate heals having metallic conductivity and nearly plastic stretchability. This is achieved using a dispersion of conductive particles in an insulating fluid encapsulated over the interconnect. Healing is automatically triggered by the electric field appearing in the open gap of a failed interconnect, irrespective of the cause of failure. The field polarizes the conductive particles causing them aggregate and chain up to bridge the gap and repair the fault. Using copper-silicone oil dispersions, we show self healing interconnects with the stretchable heal having conductivity of about $5 \times 10^{5}$ Sm and allowing strains from 12 to 60. Previously, stretchable interconnects used materials other than copper. Here we effectively show self healing, stretchable copper. This work promises high speed, self healing and stretchable interconnects on flex thereby improving system reliability.