Dielectric characterization of printed circuit substrates

Abstract

Presents a novel technique for measuring the dielectric properties of printed-circuit-board substrates based on the measured scattering (S) parameters of a transmission line. The S-parameters are measured with an automatic network analyzer. The measurement is de-embedded to remove connector and adaptor errors. The complex permittivity is then calculated by transforming the error-corrected S-parameters into impedance parameters and relating them to the transmission-line propagation constant. A discussion of techniques for characterizing the dielectric properties of printed circuit boards is also presented. It is found that the proposed parameter transformation technique has several advantages over other dielectric characterization methods. This technique is based on measurements with the same electric and magnetic field distributions as printed circuit trace. This attribute should lead to more accurate values for anisotropic, nonhomogeneous materials such as the composite substrates being explored for high-speed digital signal propagation. It is also noted that the proposed approach can be utilized with test coupons for the testing of novel dielectric composites or for quality assurance purposes.< >