Dear Nick,

Split planes, isolated areas, edge isolation, tracks on internal power planes. This is 
questions that pops up once in a while. To totally avoid these kind  problems I can 
only suggest what I with success have done many years: Avoid internal planes use a 
signal layer with a polygon plane instead. Doing this gives you totally control of the 
layer and it will be crystal clear what the layer *actual* looks like. If you want to 
produce a isolated island simply draw a thin line (in the correct layer) around the 
object you want to isolate and tick the option 'Remove dead copper'.

Many designers do not want to produce polygone planes for historical reasons - in the 
'old days' it simply was to time consuming to produce. These days it will only take a 
couple of seconds to produce this polygon plane !

With a background in EMC I can only emphasise the importance of a good ground layer. 
Also do place as much ground plane as you can on all the signal layers. It can even be 
a very good idea to have two ground layers in stead of usual Vcc/Gnd ! I know this 
controversial and many will disagree; but it is true.

RenÚ S°rensen

----- Original Message ----- 
From: Nicholas Cobb <[EMAIL PROTECTED]>
To: Protel EDA Forum <[EMAIL PROTECTED]>
Sent: Friday, August 31, 2001 1:16 AM
Subject: [PEDA] Isolated "Island" on PCB


> 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. 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.
> Nick Cobb
> 
> 

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