Large circuit boards that stand the heat Flexible printed circuit boards (PCBs) with high operating temperatures could replace bulky cabling in high-temperature zones of aircraft engines. The weight and space savings should help achieve reductions in fuel consumption and emissions. Industrial Technologies Energy © amgun, Thinkstock The Clean Sky initiative is a unique and ambitious public-private partnership between the European Commission and industry to bring about a step change in the environmental impact of aviation. Many innovative design concepts are focused on minimising fuel consumption and associated emissions. The EU funded the project LHTFPCB (Demonstration of a large, high temperature, flexible printed circuit board) to support the advancement of electronics that will help meet related goals. Flexible PCBs were originally designed as a replacement for traditional wire harnesses. Scientists developed materials and processes that led to the delivery of full-size PCBs integrated and tested at engine level at a technology readiness level of 6. Using existing and novel polymers, researchers achieved an increase in operating temperature from the current state-of-the-art maximum of 200 °C. The target was a range from minimum 260 °C to a maximum of 400 °C. Further, the materials and processes were designed to facilitate this high-temperature performance in a large-area format with required overall length of 5 m in a single-piece multilayer PCB without joints. Scientists subjected the sample PCBs to thermal cycling tests over the range of 260 to 330 °C and also conducted random vibration tests. Microsection analysis following the test campaign allowed researchers to draw important conclusions regarding polymer degradation. In particular, they determined the rate of propagation of polymer degradation from the PCB edge, aiding in delineation of PCB design rules. In addition, having identified oxidation as the major source of polymer degradation, the team focused on improving the robustness of the oxygen barrier for PCB performance optimisation. LHTFPCB demonstrated that long, multilayer flex PCB technology is viable and supports the Clean Sky initiative for the aerospace industry, providing a lightweight alternative to current cabling. The technology is likely to attract interest from other sectors as well, including the oil and gas industry. Keywords Printed circuit boards, high-temperature, aircraft engines, LHTFPCB, polymer degradation
