Is the environment variable acon_no_impedance width unset? This would let the tool adjust line width to compensaye for impedances on each layer. I set it because I don't agree with the Allegro methodology for calculating impedance. Correct impedance calculations are easy enough to do (or you can resort to Method Of Moments 2D tools) Either will give more satisfactory results. Another reason for not letting the tool decide is if you want to identify controlled impedance routes by layer to the fab shop. Just make sure that your plane fill aperture is different from the controlled line width or the fab shop will have a harder time of it! Best Regards David Greig _________________________________________ Director GigaDyne Ltd Buchan House Carnegie Campus Dunfermline KY11 8PL United Kingdom Tel. +44 (0) 1383 62 49 75 _________________________________________ _____ From: westfeldt [mailto:westfeldt_nbcd@xxxxxxxxx] Sent: 09 September 2004 16:27 To: icu-pcb-forum@xxxxxxxxxxxxx Subject: [PCB_FORUM] linewidth change Still getting used to v15.1. Sometimes tracewidth goes from my current width to minimum drc value when I drop a via; didn't do that in my v14.2. How do I fix this? Patrick Westfeldt, Jr. North Boulder Circuit Design westfeldt_nbcd@xxxxxxxxx 720-406-0887 c 720-272-5822 -- Virus scanned by Lumison.