I believe you should tie the external ground plane at one point only.
The return current path often completes a loop antenna - a highly directional
radiation source - and if, by connecting the components to the outer shield,
you make the outer plane a part of the current return path you have turned
your shield into a radiation source.

Don Walker
[log in to unmask]

> We design high speed line scan cameras and use internal and
> external ground planes (external for shielding) on our PCB's.
> My question is this-
>
> Should the internal and external planes be tied throughout the board (at
> vias, etc.) or should the external planes be tied back only at a single
> soure (power connector) and leave the internal plane(s) for all component
> connections?  I am wondering if there are advantages of one over the other.
>
> VIP Lab
> University of Arkansas

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