Fabrication of low dielectric constant composite filaments for use in fused filament fabrication 3D printing

Abstract

In this paper we describe a method for creating flexible composite filaments with dielectric constants below 2.0 over a wide frequency band (i.e. 18–40 GHz). We demonstrate that a low dielectric constant composite filament, useful for FFF printing, can be manufactured by combining a base thermoplastic polymer with hollow microspheres and a plasticizer. Experimental results are provided for filaments made from two different base polymers (i.e. ABS and HDPE) and varying volume fractions of hollow microspheres. We also describe an effective media model to predict the dielectric properties of the composite filaments as a function of the properties of the constituent materials (e.g. base polymer, hollow microspheres) and their relative volume fractions within the composite filament. Experimental test samples were printed using the new low-K filaments and experimental characterization results are provided that validate this approach.