Ground pour questiion

Started by Perrow, March 21, 2012, 08:57:34 AM

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Perrow

I've begun filling my boards with as much ground as possible lately, because 1) I've heard that that's generally a good thing and 2) I'm cheap and want to save on etchant.

On the latest board design (quite large SS amp) the filling has resulted in the ground pour encircling parts of the design, like in this lower left corner:



Are such ground pour circles a problem?

I've searched some for this but the best I could find was how to do a ground pour on a circular board and that wasn't quite what I was looking for  :icon_rolleyes:
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Fender3D

#1
That's the so called "thermal relief" in PCB CAD software. It will help soldering 'cause solder heat doesn't spread around.
Your lower left shouldn't be an issue since there's no long ground loop, but messing with thermal relief parameters you might fix it.

Edit:
looking at the picture you might have a ground loop
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Perrow

The thermal reliefs I know are good, it was the larger loops I wondered about. Should I break them?
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Perrow

And, this was done in diylc so any messing with thermal relief settings are just messing with my head :D
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merlinb

Quote from: Perrow on March 21, 2012, 09:33:55 AM
The thermal reliefs I know are good, it was the larger loops I wondered about. Should I break them?
I wouldn't sweat it. The loop area is tiny, and it's probably going into a metal enclosure, right? Little loops like that won't be a problem.

Perrow

Hopefully I'll find a way to build a metal enclosure around it, but it's just about a minutes work to make two small breaks in the ground pour and have no loops, so I'll probably do that. It's not like two small breaks will ruin my etchant budget.
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Fender3D

Quote from: Perrow on March 21, 2012, 09:33:55 AM
... it was the larger loops I wondered about. Should I break them?

The larger loop I meant above is the big loop from the pot GND running under caps and resistors then returning to pot GND.
As merlin stated the loop around the pot pad is tiny and won't cause any issue
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Perrow

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merlinb

Quote from: Fender3D on March 21, 2012, 11:13:08 AM
The larger loop I meant above is the big loop from the pot GND running under caps and resistors then returning to pot GND.
As merlin stated the loop around the pot pad is tiny and won't cause any issue

Actually I was talking about the larger loop- it's too is puny to be any kind of problem below the gigahertz range.

Perrow

Quote from: merlinb on March 21, 2012, 12:41:50 PM
Actually I was talking about the larger loop- it's too is puny to be any kind of problem below the gigahertz range.

Oh, OK, so how large is large enough to bother with in the audio range? Is there any risk on say a 10x15 cm (4x6 inches) PCB?
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boogietone

Excellent question. I have wondered about this myself and have actually put broken loops similar but larger by adding a "Route Keepout" area that blocks the pour. I use DipTrace and don't know if it is as option in diylc. Does it have the ability to draw circles or rectangles? If possible, add a white colored shape with no outline over a section of the loop. Or, use or create a component which PCB pattern would be a large hole with no copper.

It would be nice to know if this is at all necessary, in any case.
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Perrow

Quote from: boogietone on March 22, 2012, 05:09:50 PM
Excellent question. I have wondered about this myself and have actually put broken loops similar but larger by adding a "Route Keepout" area that blocks the pour. I use DipTrace and don't know if it is as option in diylc.

The short answer is no, DIYLC doesn't have that option. On the other hand, it doesn't have a ground pour either, this is just me adding traces and black areas to make a ground pour.
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