Broadband Material Parameter Characterization for Practical High-Speed Interconnects on Printed Circuit Board

Mainstream applications nowadays offer high-speed performance that until recently was only present in high-end applications. Special high-frequency materials and processing steps are, due to their inherent cost, not suited for high-volume applications. In this paper, a wideband material characterization technique to compare the behavior of different base materials is presented. The methodology can also be used for a quantitative analysis of the high-frequency limitations of traditional printed circuit board processing steps as thick copper plating and surface finish. It is based on the propagation constant extraction as part of the multiline through-reflect-line calibration. This powerful calibration technique makes it possible to directly compare different materials or processing steps, without the need for advanced modelling. From the extracted propagation constant, a more detailed analysis of the dielectric constant and the loss factor of the substrate material can be performed, based on known and tested formulas for microstrip transmission lines. Adaptations for a high track thickness to substrate height ratio and for the presence of a solder mask can be derived from the results. The practical material parameter extraction method proposed in this paper makes it possible for designers to overcome some of the high-frequency limitations associated with high-volume applications.