An increased demand for conformable, lightweight, and wireless devices has driven the development of Flexible Hybrid Electronics (FHE). Silver (Ag) inks are traditionally selected for FHE products due to their high conductivity. However, Copper (Cu) is emerging as a promising low-cost alternative. For this study, three commercially available Cu inks were chosen based on alignment with current Ag processing methods. Both Ag and Cu inks were printed using a fully automatic flat-bed screen printer and post-processed according to their relative material specifications. The study compared results of Cu inks against a baseline Ag ink and was completed in three phases: Print Related Evaluation (P.R.E.), printing/curing optimization and prototype fabrication. The P.R.E. process was conducted to assess adhesion, sheet resistivity and print definition. Design of Experiments (DOE) were developed and aimed to further optimize print parameters and drying/sintering of the Cu material. Finally, an end-user application specific scenario was fabricated with baseline Ag ink and replicated with Cu ink to test for functionality. The prototype demonstrates multi-layer circuitry, Bluetooth antenna, rigid passive/active component attachment, and an integrated heater on a flexible transparent substrate. The P.R.E. and DOE results as well as the details of the prototype will be presented in this study.
Authors: Samantha Stevens, Niraliben Patel, Nathaniel Richards, Ben Liesegang, Mark Sussman, Eric Tyson, Girish Wable, Jörg Richstein, Arnold Reta, Ed Collins, Sai Avuthu