D-band Free Space Dielectric Characterization of a Low-Cost Ultradense Microdiamond Composite for Heat Spreading

Abstract

Low-cost dielectric materials are needed above 100 GHz with low permittivity and loss tangent as well as significant thermal conductivity $(\sim 100W/m\cdot K)$. A free-space measurement setup is demonstrated to characterize a proposed ultradense diamond composite material at D-band. We leverage free-space calibration with the NIST iterative method to extract the permittivity and loss tangent and compare this approach with other methods. Time-domain gating is employed to reduce the uncertainty in the free space characterization. Our measurement indicates the diamond composite offers a relative permittivity of 3.5 and loss tangent of $3\times 10^{-2}$ from 110-140 GHz. To the author’s knowledge, this is the first report of diamond composite compatible with packaging requirements at D-band.