A New Digitally Driven Process for the Fabrication of Integrated Flex-Rigid Electronics

Conventionally, flexible and rigid electronics are produced separately using mask-based lithography techniques thus requiring connectors to join circuits together introducing potential failure modes and additional assembly. This work demonstrates a new manufacturing approach which overcomes this limitation by allowing the co-fabrication of both flex and rigid electronic circuitry within the same part. This is achieved by hybridizing polyetherimide fused filament fabrication with selective photosynthesis of silver nanoparticles and copper electroless plating. The performance and reliability of this approach has been experimentally validated via manufacturing and testing positional sensors. By printing thin layers (< 50 µm), polyetherimide exhibits a high flexibility with minimal degradation from fatigue. Where part thicknesses exceed 180 µm, components start to exhibit rigid properties. A combination of various layer thicknesses allows rigid-flex substrates to be produced, with secondary processing to deposit the circuitry. Positional sensors with metalized feature sizes down to 300 µm have been fabricated that when deflected demonstrate a repeatable 1.4 Ω resistance change for 43,500

cycles.