Fine line thin dielectric circuit board characterization

Abstract

The rough surface of the copper foil, introduced to enhance its interfacial adhesion to the dielectric medium, will increase the signal propagation time constant and reduce the characteristic impedance of a signal line. The influence increases as the dielectric thickness decreases. Two high resolution resonant measurement techniques will be presented for such studies. The additional delay term due to the internal inductance at the frequency of interest is proportional to the square root of the signal rise time in the transient measurement. The additional delay associated with the signal rise time degradation due to skin effect resistance loss is minimized by measuring the delay at 1% of the voltage swing. We will also compare the results of different measurement techniques in this paper.