Large circuit boards that stand the heat

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 is funding the 'Demonstration of a large, high temperature, flexible printed circuit board' (LHTFPCB) project to support the advancement of electronics that will help meet related goals.

Scientists are developing the materials and processes that will lead to delivery of full-size PCBs integrated and tested at engine level at a technology readiness level (TRL) of 6. Using existing and novel polymers, researchers are targeting an increase in operating temperature from the current state-of-the-art maximum of 200 degrees Celsius. The goal is a range from minimum 260 degrees Celsius to a maximum of 400 degrees Celsius. Further, the materials and processes must be able to facilitate this high-temperature performance in a large-area format with required overall length of 5 metres in a single-piece multilayer PCB without joints.

Within the first reporting period, a number of multilayer PCB samples were prepared from a variety of advanced polymers. Scientists subjected them to thermal cycling tests over the range of 260 to 330 degrees Celsius, 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 is focusing on improving the robustness of the oxygen barrier for PCB performance optimisation.

LHTFPCB investigators expect to deliver full-scale (5 metres long) single-piece multilayer flexible PCBs capable of withstanding at least 260 degrees Celsius and achieving a TRL of 6 in engine-level testing. The technology will support the Clean Sky initiative for the aerospace industry, providing a lightweight alternative to current cabling. It is likely to attract interest from other sectors as well, including the oil and gas industry.