Solution processed low-k dielectric core-shell nanoparticles for additive manufacturing of microwave devices

This study introduces a new core-shell structured polytetrafluoroethylene (PTFE)/polyimide (PI) nanoparticle for additive manufacturing of microwave substrates. Materials were synthesized using a solution processed method through the electrostatic interaction between PTFE with negative potential and poly(amic acid) salt (PAAS, a PI precursor) with positive potential followed by the thermal imidization of PAAS. Microscopic studies by transmission electron microscopy, scanning electron microscopy, and atomic force microscopy confirmed the formation of core-shell nanoparticles, a porous material network, and a reduction of surface roughness upon imidization. In addition to excellent high temperature stability (<0.4% weight loss at 500 degrees C), the synthesized materials showed improved particle-to-particle adhesion and particle-to-substrate adhesion compared to PTFE alone, and good dielectric properties measured at 7.2 GHz utilizing a cavity perturbation technique. The materials consisting of 5% to 35% of PI exhibited low relative permittivity (epsilon') of 2.14 to 2.38 and loss tangent (tan delta) of 0.001 to 0.0018, which make them well suited for use in additive manufacturing. (C) 2017 Wiley Periodicals, Inc.