Al Horn, Associate Research Fellow, Rogers Corporation
John W. Reynolds, Rogers Corporation
Patricia A. LaFrance, Rogers Corporation
James C. Rautio, Sonnet Software

It has been long known that conductor surface roughness can increase the conductor loss as frequency increases to the extent that the signal skin depth is comparable or smaller than the scale of the conductor roughness. In the present work, we experimentally show that the increase in conductor loss is larger than the factor of two predicted by the most widely used roughness factor correction correlation. This is consistent with the findings of a more recent theoretical paper on the effect of random roughness on conductor loss.

We also experimentally show that increasing the conductor roughness alone increases the propagation constant or effective dielectric constant, in thin circuitry by up to 30% and substantially increases dispersion. Conductor profile is clearly a major variable in the performance of thin high frequency circuits.