High-k and Low-Loss Dielectric Composite Feedstock Filaments Tailored for Additive Manufacturing of Microwave Devices

In this work, an improved methodology of making ceramic-thermoplastic composite feedstock filament with tailored dielectric properties is pursued. Prediction model-based approach is implemented for manufacturing a wide variety of thermoplastic composite filaments with varied ceramic filler volume ratios and ceramic filler surface conditions. A relative permittivity of 12 and a loss tangent of 0.003 have been demonstrated at frequencies up to 18 GHz for in-house prepared 3D printable composites loaded with 50% ceramic micro-particle fillers in volume. A comparison of dielectric properties of the 3D printed composite thin-sheet test specimens with and without surface treatment is performed. The composites with the chosen surface treatment exhibit an increment in measured permittivity values, while having insignificant change in measured dielectric loss tangents. The newly prepared filaments were used to print a Ku band dielectric waveguide (DWG), which has exhibited an impressive low loss of 0.017 dB/mm at 17.5 GHz