This paper provides guidelines and recommendations for material selection, stack-up optimization and trace routing.
Abstract—A novel method for practical prediction of
interconnect conductor surface roughness effect on multi-gigabit
digital signals is proposed. A differential impedance operator of a
conductor is constructed with Trefftz finite elements and locally
adjusted with a correction coefficient to account for the
roughness effect. Any correction coefficient derived for the
additional power loss due to roughness can be used with the
proposed method. Modified Hammerstad’s correction coefficient
is proposed and used here as an example. A test board is
manufactured and investigated up to 50 GHz. Parameters of the
conductor roughness model are identified with generalized
modal S-parameters. An increase of effective dielectric constant
due to conductor surface roughness is observed and explained by
capacitive effect of spikes on the surface of conductor. It is shown
that the constructed interconnect models are consistent with the
measured data.
Published: 12/14/2011