Is there any reason not to flood vias on PCBs?

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daqq
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Posted by daqq: Thu. Jan 24, 2013 - 03:46 PM
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Hi guys,

In some of the boards I check out the vias are flooded - completely connected to the surrounding copper pour. But on others, the vias are connected through a thermal relief patern and on one both methods were used.

See:

(warning: Gargantuan image)
http://bunniefoo.com/ntw/ntw_dec...
http://bunniefoo.com/ntw/ntw_dec...

Bottom of the picture.

Is there any reason one way or the other? Cause, I can't think of any reason not to flood them, when they aren't used for soldering.

Thanks,

David

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Learning and Information, General Electronics
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clawson
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Posted by clawson: Thu. Jan 24, 2013 - 06:01 PM
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David,

You must be psychic. Only this morning I was thinking "where do some of the 'regulars' like David Gustafik disappear to?" And then you go and post! Amazing.

Cliff

(I see I missed your previous posts - Jan 1st/2nd - I was on holiday).

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daqq
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Posted by daqq: Thu. Jan 24, 2013 - 06:11 PM
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Cliff, I thought I sensed a disturbance in the Force... thanks for the thought :-)

Actually, I'm lurking about and occasionally post something. My school is still keeping me busy as is my job. I still play with AVRs and electronics, but these days mostly for the job.

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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ka7ehk
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Posted by ka7ehk: Thu. Jan 24, 2013 - 06:47 PM
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I see no real reason to put thermal reliefs on vias.

Vias are usually too small to put any lead into, excepting maybe stripped wire-wrap wire. Not that I have not done that :)

I don't know about additive board fabrication or about special "issues" with multi-layer boards. Ignoramus is probably the expert, here.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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stevech
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Posted by stevech: Fri. Jan 25, 2013 - 03:47 AM
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beware super-subtle "copper islands" with flooding, where you assume the big hunk of copper is really ground but it isn't. And it doesn't show on the PC's screen. Under a magnifying glass, you see it, and go

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Chris-Mouse
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Posted by Chris-Mouse: Fri. Jan 25, 2013 - 09:40 PM
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The only reason I can see for filled or not filled vias would have to do with why the via is there. If it's just carrying a signal between layers, then not filling is just fine. If it's for connecting high current traces and/or RF shielding, then thermal reliefs would probably cause problems. If it's for connecting copper areas for heatsinking of PC mounted components, then thermal reliefs would defeat the purpose. Filling the vias wouldn't hurt RF and high current performance, but probably won't help much either. Filling the via will help thermal transfer significantly.

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daqq
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Posted by daqq: Fri. Jan 25, 2013 - 10:57 PM
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Thanks guys. I was starting to suspect some arcane reason they let you in only once you've been at it for 15 years, but no one I asked could come up with a reason to include a thermal relief for a via.

Then again... if it's really a secret... :-)

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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stevech
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Posted by stevech: Sat. Jan 26, 2013 - 10:48 PM
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thermal relief .. hard to hand solder without it.

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daqq
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Posted by daqq: Sat. Jan 26, 2013 - 11:26 PM
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steve: I know, I was refering to vias - layer to layer connections, not pads for soldering.

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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peret
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Posted by peret: Mon. Jan 28, 2013 - 07:43 PM
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I only use thermal relief for component leads. I explicitly turn it off for vias.

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stevech
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Posted by stevech: Wed. Jan 30, 2013 - 06:22 AM
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peret wrote:
I only use thermal relief for component leads. I explicitly turn it off for vias.
And connectors / sockets.

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