Nicholas Cobb wrote:

> Everyone,
>         I am making a board that has internal power and ground planes and I would
> like to make an island that is isolated from all layers on my board. I have
> made a split plane of both the power and ground to have the isolated +5, and
> isolated gnd.  I just don't know how to keep the gnd and +5 plane from
> invading.

If you place a split plane border around the area you want isolated, that takes
care of it.

> I have outlined my "island" with traces on the keepout layer. I
> put one around the border and then I made an identical trace that was
> separated from the first by 5mm.  If anyone can help I would appreciate it.

You don't need the keepout layer.  The border of the split plane does the
isolating by physically cutting the sheet of copper with a band of 'no-copper'.
These inner regions need to be assigned to a specific net name, so you
need to assign different net names in the schematic for these nets.
You need to pour 4 polygons, for the normal gnd and power, and then
for the isolated gnd and power.  The Protel algorithm has problems with
one split plane region that totally encloses another.  So, the outer split planes
need to 'wrap' around the inner ones, but leave a little gap where the wrapped
around ends meet.

Jon

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