Free Space Dielectric Techniques for Diamond Composite Characterization

Compact millimeter-wave arrays demand novel packaging solutions that feature low-cost dielectric materials with significant thermal conductivity ( $\sim$ 100 W/m ⋅ K). To characterize the permittivity and loss tangent of the dielectric materials above 100 GHz, free-space characterization is proposed to avoid de-embedding conductor losses. We review current approaches for characterization to investigate the properties of ultradense diamond composite materials at D-band. We compare free-space calibration multiple methods to extract the permittivity and loss tangent. Time-domain gating is employed to reduce the uncertainty in the free space characterization. Material characterizations of the dielectric constant and loss tangent include pure polymer TMPTA, PDMS, TMPTA-based, PDMS-based diamond composites as well as quartz and sapphire wafers for calibration from 120–160 GHz. To the author's knowledge, this is the first characterization of diamond composites for thermally conductive dielectric packaging requirements at D-band.