Flexible Hybrid Electronics via Near-Infrared Radiation-Assisted Soldering of Surface Mount Devices on Screen Printed Circuits

Abstract

The development of flexible hybrid electronics (FHEs) with high-throughput integration of electrical components onto digitally printed circuits has a wide range of applications, such as asset tracking, wearable electronics, and structural health monitoring. However, one of the major challenges with FHEs is the process of soldering the electrical components onto a printed circuit while having minimal thermal damage to the printed traces and their temperature-sensitive polymeric substrates. Here, the possibility of utilizing near-infrared (NIR) technology as a nondestructive photonic approach for rapid soldering and mounting electrical components onto printed circuits while keeping the polymer substrate at a relatively low temperature during the soldering process is investigated. Results of this systematic study show that FHEs prepared with the optimized NIR processing conditions produce the desired reflow of solder with effective electrical connection and metallic bonding of electrical components onto the conductive traces with excellent mechanical stability (no failure even after 1000 cycles of bending). Furthermore, using this technique and as a proof of concept, the fabrication of a wearable FHE device that provides a remote assessment of the wound exudate absorption in dressings and notifies caregivers of the appropriate time to change the dressing is demonstrated.