Adam, guarded or shielded traces can be very useful to prevent coupling into a sensitive trace or from a trace with very short rise time, even on a multilayer board. But make sure that you ground your ground trace every 1" or so. That way you keep the shield from becoming an antenna itself. Volkmar Hawes, Adam wrote: > I feel sure this is probably an issue for a lot of PCB > designers...... > > Recently, I have come across an increasing number of engineers who > wish to have certain tracks on multilayer PCB's shielded by ground traces > running adjacently. It seems to be a case of jumping on the bandwagon to me > because we never used to do this until about 12 months ago. > > I was under the impression that ground tracks only served a useful > purpose on 1or 2 layer boards and that on a multilayer they were essentially > a waste of space as most of the capacitive coupling would be straight to the > ground plane. > (cut) -- Volkmar Huß Dräger ProTech GmbH Engineering Electronic Circuit Boards Elektronikbaugruppen Phone +49 451 882-3998 Moislinger Allee 53/55 FAX -4365 23542 Lübeck / Germany mailto:[log in to unmask]