Highly Conductive, Flexible, Polyurethane‐Based Adhesives for Flexible and Printed Electronics

Abstract Flexible interconnects are one of the key elements in realizing next‐generation flexible electronics. While wire bonding interconnection materials are being deployed and discussed widely, adhesives to support flip‐chip and surface‐mount interconnections are less commonly used and reported. A polyurethane (PU)‐based electrically conductive adhesive (ECA) is developed to meet all the requirements of flexible interconnects, including an ultralow bulk resistivity of ≈1.0 × 10 −5 Ω cm that is maintained during bending, rolling, and compressing, good adhesion to various flexible substrates, and facile processing. The PU‐ECA enables various interconnection techniques in flexible and printed electronics: it can serve as a die‐attach material for flip‐chip, as vertical interconnect access (VIA)‐filling and polymer bump materials for 3D integration, and as a conductive paste for wearable radio‐frequency devices.