Fine line thin dielectric circuit board characterization

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. A high resolution resonant measurement technique will be presented for such study. The internal inductance will increase both the propagation time constant and the characteristic impedance. It adds an additional delay term, proportional to the square root of the signal rise time in the transient measurement. We will compare the results of different measurement techniques in this paper