This is a good idea.  Especially if you have high speed signals running
near the board edge.  The only problem I see is where you say to "...tie
the external planes and the internal ground plane together..." I think
you probably meant to say "...tie the external planes and the internal
GUARD RINGS together..."  This prevents any possibility of the shield
becoming a part of the return path.

Don Walker
[log in to unmask]

>    to run a guard ring of ground around the periphery of the board on all
>    layers and tie the external planes and the internal ground plane
>    together through closely spaced (.25 inch) vias only at the guard
>    ring.

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************