Closed-form and dispersive model considerations for relative permittivity extraction at millimetre-wave frequencies.

This study provides a simple broadband method for determining the dielectric properties of laminate substrate materials used in integration and packaging solutions for commercial millimetre-wave applications. Relative permittivity and loss tangent are extracted from coplanar lines using closed-form equations that account for as-fabricated transmission line dimensions. The method is applied to a low loss substrate alumina and further tested on glass impregnated epoxy resin materials with metals that have an appreciable metal surface roughness. The work expands existing material characterisation methods that are typically based on thin films. The dielectric substrates are thin, similar to integrated circuits, but the metal thicknesses remain on the order of packaging substrates. This study considers the critical parameters and manufacturing features for designs and millimetre-wave material measurements on these types of materials. The method has an accuracy of within 10% of known values, utilises off-the-shelf software solutions when available, and requires no fixturing beyond the sample material. Error analysis is provided with material information on Isola FR408 up to 110 GHz. [ABSTRACT FROM AUTHOR]