I'm not sure, in one case (floating) you have two series capacitors. In the case of a single via connecting a short leg of some copper to ground you have a capacitor then (inductor || capacitor) to your lines. Probably the former is worse since the later has much lower impedance. Either way the best solution is to lose the copper island. James
On 6/2/06, Hans Nieuwenhuis <[EMAIL PROTECTED]> wrote:
On Fri, 2 Jun 2006 18:46:07 -0500 "James Cotton" <[EMAIL PROTECTED]> wrote: > I think the problem with such an automatic approach would be that > right now there isn't a good way to clear off unused copper islands > from polygons, so that would reconnect them and make lots of little > antennas all over your board. > Leaving them floating as it is now would cause more problems IMHO. If you have an unconnected copper island next to a high frequency switching trace it would cause a capacitive coupling between the trace and the floating island. If that island has a natural resonance that lies near the switching frequency of the trace beneath it, then I have no idea what is going to happen. If that island is connected to ground I can treat it as a transmission line and calculate how big the gap between them needs to be to not being affected by the capacitive coupling. Please correct me if I am wrong... Regards, Hans
