boji

Via bridges for increasing pour coverage
« on: December 30, 2018, 01:07:48 AM »
Would using via's to bridge pour areas that would otherwise be left open or orphaned be a bad idea?

The only time I've seen cards peppered with trace-less via's is for thermal reasons or multi-layer pcb's, so I'm fully prepared to be told it's a no no.
I'd like your input nonetheless, thank you!


« Last Edit: December 30, 2018, 04:08:58 AM by boji »


boji

Re: Via bridges for increasing pour coverage
« Reply #1 on: December 31, 2018, 03:07:09 PM »
Oops, I learned this is called 'via stitching' and searches say it's ok to do, but doesn't have much benefit at audio frequencies.

JohnRoberts

Re: Via bridges for increasing pour coverage
« Reply #2 on: December 31, 2018, 04:04:26 PM »
Oops, I learned this is called 'via stitching' and searches say it's ok to do, but doesn't have much benefit at audio frequencies.
It can help or maybe not, depends on the circumstance.  Generalities are only true in "general". YMMV

I am not a fan of trying to use brute force (like slightly lower impedance ground path) to insure signal integrity (I prefer using differential forward/back referencing).

I have used vias before to improve thermal transfer for SMD chips with heatsinks on the bottom.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

boji

Re: Via bridges for increasing pour coverage
« Reply #3 on: December 31, 2018, 05:29:42 PM »
Thanks John. Seeing as this card is passing balanced signal too, worrying over stitching is probably not the best use of time. :D

Anyways, happy new year to you and everyone else!

john12ax7

Re: Via bridges for increasing pour coverage
« Reply #4 on: December 31, 2018, 08:00:53 PM »
Having a copper pour not tied to anything is very detrimental for high frequency applications, proper stitching is crucial. I would still lean against it at audio frequencies, but that is in part due to habit,  never directly tested it.

boji

Re: Via bridges for increasing pour coverage
« Reply #5 on: January 02, 2019, 04:48:49 PM »
Quote
is in part due to habit,  never directly tested it.

Thanks 12ax,

Not to belabor the subject, but is the other part your concern it might negatively affect signal?
I guess I'm asking if there's any chance it could work against me. If so, I'll just remove them.

Edit: I should mention this is for shielding only; no audio signals directly reference 0v from this board.
« Last Edit: January 02, 2019, 05:08:35 PM by boji »

john12ax7

Re: Via bridges for increasing pour coverage
« Reply #6 on: January 02, 2019, 10:30:06 PM »
It could negatively affect things if the copper pour is left floating,  not electrically connected. You mention shielding,  what is it connected to?

Generally you pour copper on the top layer,  then stitch with vias to the bottom ground plane. Or you can omit the top layer pour altogether. Both ways tend to work fine.

The issues arise if you pour copper on the top layer but then don't properly stitch. This caused me problems in the past,  but it was for a very high frequency application. It may be a non-issue at audio frequencies, but can't say for sure since have never directly done it.
« Last Edit: January 02, 2019, 10:42:56 PM by john12ax7 »

boji

Re: Via bridges for increasing pour coverage New
« Reply #7 on: January 02, 2019, 11:35:14 PM »
Thanks for getting back to me on this.

Quote
Or you can omit the top layer pour altogether.
That's how I've done things so far. In this case, a single pcb is needed but they will be oriented horizontally,  four across, two high.

Quote
You mention shielding,  what is it connected to?
Pours are split. DC side, chassis, balanced signal side, acom.  Both will tie to respective bus bars shared with the group aca's in this bucket.

« Last Edit: January 03, 2019, 12:09:36 AM by boji »


 

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