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Home » CadSoft Support Forums » eagle.support.eng » How does one remove non-functional pads in vias?
How does one remove non-functional pads in vias? [message #160323] Sat, 11 April 2015 14:33 Go to next message
Bruce Mellen
Messages: 20
Registered: April 2015
Junior Member
How does one remove non-functional pads in vias?  I’m not finding the
requisite check box(es) or other settings. 
I need to minimize the discontinuities in at least the higher frequency
paths, want to somewhat shrink the resulting anti-pads on the ground and
supply layers to improve current return impedance, and it can often
contribute to better routing in the vicinity of vias.
I was hoping to even set it by layer and perhaps set the restring by
layer, having it depend upon whether there is a trace connected or not.
The only alternative seems labor-crazy intensive, effectively:
* Setting normal via restring values and applying the appropriate
teardrops to the various layers
* Minimize the restring values to the smallest NFP values wanted for the
board, and
* apply a circle to each and every capture pad where there is a trace to
be connected
* subsequently approving the circle overlap DRC errors
Please describe a better way…?

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Re: How does one remove non-functional pads in vias? [message #160324 is a reply to message #160323] Sat, 11 April 2015 16:27 Go to previous messageGo to next message
eaglecandies
Messages: 186
Registered: September 2011
Location: Cincinnati
Senior Member
what exactly is a: non-functional pads in vias?

I've never heard of such a thing.
Re: How does one remove non-functional pad s in vias? [message #160329 is a reply to message #160324] Sat, 11 April 2015 19:17 Go to previous messageGo to next message
Bruce Mellen
Messages: 20
Registered: April 2015
Junior Member
Also called a NFP, it is any via capture pad (most often thought of on
an inner layer) that does not have an attached trace.  They serve no
purpose (see contradictory note) but adversely affect high frequency
communications due to their capacitance/inductance, forming an unneeded
non-uniformity in the electrical path.  Note: they may serve some
purpose if the board gets drilled before lamination, and there is
discussion regarding their contribution toward barrel failures one way
or the other.  Here are a couple papers and a simple google will yield
others:
https://www.altera.com/en_US/pdfs/literature/an/an529.pdf
https://www.speedingedge.com/PDF-Files/anatomy%20of%20a%20plated%20hole.pdf
http://www.circuitinsight.com/programs/53503.html
http://www.ee-training.dk/announcement/high-speed-via.htm
...and many others...

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Re: How does one remove non-functional pads in vias? [message #160330 is a reply to message #160323] Sat, 11 April 2015 21:09 Go to previous messageGo to next message
warrenbrayshaw
Messages: 1767
Registered: January 2010
Location: New Zealand
Senior Member
On 12/04/2015 2:33 a.m., Bruce Mellen wrote:
> How does one remove non-functional pads in vias? I’m not finding the
> requisite check box(es) or other settings.
> I need to minimize the discontinuities in at least the higher frequency
> paths, want to somewhat shrink the resulting anti-pads on the ground and
> supply layers to improve current return impedance, and it can often
> contribute to better routing in the vicinity of vias.
> I was hoping to even set it by layer and perhaps set the restring by
> layer, having it depend upon whether there is a trace connected or not.
> The only alternative seems labor-crazy intensive, effectively:
> * Setting normal via restring values and applying the appropriate
> teardrops to the various layers
> * Minimize the restring values to the smallest NFP values wanted for the
> board, and
> * apply a circle to each and every capture pad where there is a trace to
> be connected
> * subsequently approving the circle overlap DRC errors
> Please describe a better way…?
>
> --
> To view any images and attachments in this post, visit:
> http://www.element14.com/community/message/146824
>


So you mean " How does one remove the unused restrings from the inner
layers"

This is all about 'pad stacks' and the ability to specify the restring
by layer or even pad/via. Historically this feature was requested many
times and has not been delivered by Cadsoft. Jorge did mention recently
that they were working on keep-outs for the inner layers so perhaps that
implies pad stacks are coming. As an aside; I note that many of the
power users who were vocal about their need for pad stacks either are
known to have moved away from eagle or are not heard from very often
these days suggesting they have voted with their feet.

You may care to investigate the following ideas:
(1) Edit/delete these unwanted restrings in your Gerber editor.
(2) Don't place the circle, that you subsequently have to approve in the
DRC, on the signal layer but rather on a user defined non signal layers
and merge the signal and non signal layer when you generate the Gerber
for that copper/signal layer.
(3) Create a ULP to automate the 'labor-crazy' part. Again, start as you
have with minimised inner restrings. Use the ULP to locate the inner
restrings that have traces connected. The ULP then adds a polygon
(circle) over that restring of the required size. The polygon is given
the same signal name as the trace so there are no DRC errors.

HTH
Warren
Re: How does one remove non-functional pad s in vias? [message #160332 is a reply to message #160330] Sun, 12 April 2015 01:30 Go to previous messageGo to next message
Bruce Mellen
Messages: 20
Registered: April 2015
Junior Member
Warren,
Thanks for the potential workarounds; I understand what you are
describing.  My knowledge of ULP and the data structures, however, is
non-existent. 

It appears that the product is not quite ready to do the serious work I
was hoping to occasionally do.

You gave me an idea….. What might be an even better workaround might be:
for the person that does the teardropsc URL (helpful in preventing
breakout with drill wander and providing a more secure connection to
vias), to also include an arc (of the same signal) that mostly surrounds
the hole, with each end of the arc at the teardrop intersections with
the capture pad.  After teardropsc is run as one of the last steps
before generating Gerbers, the inner restring value can then be
minimized.  The snippet below shows what might result in an inner layer
– being just my curved trace, two short traces, and three arcs, to cover
the area that needs to be occupied by the normal restring capture pad. 
The via hole is the circle in the center.

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Re: How does one remove non-functional pads in vias? [message #160357 is a reply to message #160323] Tue, 14 April 2015 07:55 Go to previous messageGo to next message
Morten Leikvoll
Messages: 1351
Registered: November 2007
Senior Member
On 11.04.2015 16:33, Bruce Mellen wrote:> How does one remove
non-functional pads in vias? I’m not finding the
> requisite check box(es) or other settings.
<stuff deleted>

This subject is non trivial. Some manufacturers need these rings to
prevent de-lamination of the stack and/or to make a proper via at all.
The ones that don't need it may or may not remove them wihtout asking.
The moral is to always specify what you want with them, wether or not
they are in your gerbers. The specification of the pcb manufacturing is
a process to be taken seriously, especially when you are talking about
high speed signals. Don't go easy on it.

On the other hand, if Eagle supported a way to remove them, it would
direct tell the manufacturer that you don't want them, and allow the
manufacturers DRC to notify if their process doesn't allow.
Re: How does one remove non-functional pad s in vias? [message #160483 is a reply to message #160357] Wed, 22 April 2015 14:55 Go to previous messageGo to next message
Bruce Mellen
Messages: 20
Registered: April 2015
Junior Member
I'm working on adding an enhancement to the teardrops URL within
downloads, to have it to draw connected via capture pads, so if restring
is subsequently set to zero, it will effectively remove the
non-functional pads.  This will be by layer.  Let me know if any
specific feature is desired, or what to watch out for, and I may be able
to incorporate.

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Re: How does one remove non-functional pads in vias? [message #170754 is a reply to message #160323] Thu, 15 June 2017 14:33 Go to previous messageGo to next message
Glenn Courtney
Messages: 5
Registered: June 2006
Junior Member
To your knowledge has this situation changed as far as the toll itself goes?
Did you get anywhere with a viable work around?

Thanks

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Re: How does one remove non-functional pads in vias? [message #170756 is a reply to message #170754] Thu, 15 June 2017 16:13 Go to previous message
Jorge Garcia
Messages: 1294
Registered: April 2010
Senior Member
On 6/15/2017 10:33 AM, Glenn Courtney wrote:
> To your knowledge has this situation changed as far as the toll itself goes?
> Did you get anywhere with a viable work around?
>
> Thanks
>
> --
> To view any images and attachments in this post, visit:
> https://www.element14.com/community/message/224125
>

Hi Glenn,

I hope you're doing well. The situation has not changed yet, as other on
this thread noted years ago the solution is padstacks which EAGLE does
not yet have.

Now under Autodesk are development resources have increased greatly, so
this is a feature that now has a chance of being developed in a timely
manner. At this time I don't have a timeline for when it will come into
EAGLE.

Sorry I don't have more information for you.

Please let me know if there's anything else I can do for you.

Best Regards,
Jorge Garcia
Autodesk Support

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