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Author Topic: Benefits or detriments to use of Orphans in Polygon fills  (Read 823 times)

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Offline rbm

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Benefits or detriments to use of Orphans in Polygon fills
« on: September 29, 2016, 07:36:09 AM »
I've been trying to gather pros and cons to the use of the "orphans" option in polygons (islands of unconnected copper fill).  I generally have only used polygons to create a ground plane on both sides of a 2-layer board.  Up to now, I've turned on orphans because I like the aesthetics of the resulting layout.  I read a post recently warning of the dire consequences of using orphans because they created inadvertent antennas that could couple noise into the adjacent traces.  Some have said that orphans help to reduce the consumption of etchant.  I can't find a definite answer and am seeking help.

What are the consequences of turning on or off orphans?  When should I consider the use of orphans in a polygon fill that is acting as a ground plane?
« Last Edit: September 29, 2016, 09:39:34 AM by rbm »
- Robert
 

Offline vzoole

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Re: Benefits or detriments to use of Orphans in Polygon fills
« Reply #1 on: September 29, 2016, 04:55:17 PM »
Do not use unconnected polygon orphans, because it electro magnetic behavior is unpredictable.

Yes, you have to etching less copper, but it is not a real benefit.
 

Offline jgarc063

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Re: Benefits or detriments to use of Orphans in Polygon fills
« Reply #2 on: September 30, 2016, 08:59:31 AM »
Hi rbm,

I hope you're doing well. Orphans have a few advantages, for one you are removing less copper from the board. In situations of high mechanical and thermal stress this can avoid warping in the substrate because the copper is more uniformly spread on the surfaces of the board. Having the extra copper can give a slight advantage for heat dissipation, again because of copper uniformity on the surfaces.

With that said, vzoole is correct. Unconnected copper pours can behave like unintended antennas so it's best to avoid them if you have high frequency circuitry. For your basic arduino project it doesn't matter much either way. These things become problematic when you are working with high frequencies or high power.

hth,

Jorge Garcia
Autodesk Support
 

Offline rbm

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Re: Benefits or detriments to use of Orphans in Polygon fills
« Reply #3 on: September 30, 2016, 09:15:34 PM »
Hi jorge,

Doing very well, thank you.

That answers my question about orphans.  They do have their uses.  Since the circuits I've built to date are low frequency, my use of orphans has not been detrimental to the operation of the circuits.  I'll now know when and when not to click this option.  Much appreciated.
- Robert
 


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