At 03:01 AM 1/15/2004, Edi Im Hof wrote:
[I had written:]

By the way, it appears you have vias thermally relieved. That is probably not the best practice, it is better to set a design rule so that all vias are direct-connect. Vias do not generally need thermal relief, and direct connection has the lowest impedance.

And also reduces problems with the non existent power plane continuity check.

In fact, if you have vias direct-connect, and you have placed no blowout primitives on the plane, it is much less likely to happen that there is a continuity problem on an inner plane. The thermal reliefs from vias can pretty well chew up a plane; if they are direct connect, the fact that the vias have some clearance from each other guarantees that they can't interrupt continuity. I think that the use of direct-connect vias on inner planes could make a measureable noise difference over thermally-relieved vias, not only because of the lower impedance from the individual connections, but also because of better performance of the plane, which has more copper remaining.





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