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

Abstract

ABSTRACTThis 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 °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 (ɛ′) of 2.14 to 2.38 and loss tangent (tan δ) of 0.001 to 0.0018, which make them well suited for use in additive manufacturing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45335.