[SI-LIST] Re: Non-Functional Pads
- From: "Nash, Timothy J" <timothy.j.nash@xxxxxxxx>
- To: cherrick@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Fri, 27 Apr 2007 14:38:41 -0600
Hi Chris,
Board manufacturers prefer to remove the non-functional pads because it
simplifies the artwork, and ultimately, it's that much more copper they
have to drill through. However, many designers of hi-rel boards (i.e.
space applications) insist that the pads are kept to maintain the
physical integrity of the via. The catch is that if the unused pads are
kept, then the drill can wear out faster and is more susceptible to
wander on thicker stackups. Depending on the size of your annular ring,
this may or may not be a problem. So, keeping the pads can reduce
overall yield and drive up the cost of fabricating the PWB. Removing
them can weaken the via. It's a trade off.
Regards,
Tim
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Chris Herrick
Sent: Friday, April 27, 2007 2:26 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Non-Functional Pads
Hello all, it's my understanding that non-functional pads degrade
performance of signal vias however most PCB manufactures do not remove
them by default. I do a lot of via modeling and am curious about what
the most common practice is. Do people generally request to remove
non-functional pads or do they leave them in the design? How common are
the manufacturing issues that prohibit removal of the NFPs.
Thanks,
Chris
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