I am trying to find a formula for figuring minimum conductor width for foil thickness. I have found a reference of 2 times the conductor thickness is the undercut amount. I have also looked in the IPC Design Guide and only found a statement that does not give you a bases from which to work. "The actual design minimum conductor width will be governed by either the minimum width that can be successfully produced, based on fabrication yield considerations, of as required by controlled impedance considerations. In both instances, the impact of conductor (foil) thickness must be taken into account." Thanks Dee Stover National Optical Astronomy Observatories [log in to unmask]