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Date: Sun, 15 Feb 2015 10:01:34 -0500
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Subject: Re: [geda-user] Commonness of internal layer cutouts/cavities?
From: Bob Paddock <bob DOT paddock AT gmail DOT com>
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On Sun, Feb 15, 2015 at 9:08 AM, Jason White
<whitewaterssoftwareinfo AT gmail DOT com> wrote:
> How common are cavities (that is internal cutouts on a PCB specific to
> a single layer) in the electronics world?

Common, no.  Sometimes required, yes.

For example in some applications you don't want a plane under an
op-amp because of the stray capacitance to the plane causes
oscillations.

Sometimes you need a slot for isolation reasons, such as under an opto-coupler.

On the other hand it is best to avoid slots and cutouts because of the
increase in EMI they cause.

Always trade offs. :-(