Testing of microelectronic package dielectric material samples using direct capacitance measurements with impedance tester equipment is typically limited to frequencies helow 1 GHz. To overcome this limitation we explore the use of a general-purpose vector network analyzer (VNA) for obtaining S parameters of "in situ" test lines on test coupons fabricated utilizing the actnal process technology. Subsequent dam processing using full-wave inverse modeling yields the frequencydependent dielectric constant and loss tangent of the substrate simultaneously. This broadband approach has the additional advantage of comprehending possible changes of the dielectric properties due to processing conditions. It should ultimately allow a close correlation of design and experiment.