> -----Original Message----- > From: piclist-bounces@mit.edu On Behalf Of peiserma@ridgid.com > Sent: Thursday, January 18, 2007 1:13 PM > > > > The only reference that I was able to find indicated that > > the via drill size should be greater than the metal width/3. > > So for a 40mil wide metal the drill size should be greater > > than 14mils. > > got a reference? I'd be interested in this. I don't have a web reference but look at it this way. If you roll up a 40 mil trace to be like a via you will have a cylinder. The trace width equals the circumference so you calculate the diameter from the circumference (diameter = circumference / pi). I suspect the original source just used the handy single digit approximation of pi. Paul -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist