Loss Performance of Planar Interconnects on FR-4 Up to 67 GHz

This paper shows the performance of planar transmission lines (TLs) on a multilayer stack-up with a flame resistant-4 (FR-4)-based core up to 67 GHz. These lines will be used as interconnects to integrate a CMOS circuit with an antenna fabricated on FR-4 for a low-cost system-in-package solution. The attenuation characteristics of coplanar waveguide (CPW), grounded coplanar waveguide (GCPW), and microstrip lines with different configurations are investigated. The peak attenuation varies from 0.15 to 0.45 dB/mm at 60 GHz, depending on the line type and geometry. In addition, the effective permittivity and loss tangent of the multilayer stack-up are determined using CPW TLs. The overall results show that FR-4-based materials are viable candidates for packaging at the millimeter-wave frequency range if suitable line lengths are utilized.