If you found ONE that barely reaches spec.   What is the probability that one with larger length has occurred on this same sample bard.
Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Tuesday, November 05, 2013 6:03 PM
To: [log in to unmask]
Subject: [TN] IPC-6012 Copper Wicking Defect in PTH

I know what the spec limits are for wicking and I have a coupon that just barely violates the maximum requirement for class 3A.

I was asked what kind of failure this would lead to if it were used and I could not answer the question.

I researched the TechNet archives and found an email from Paul Reid where he stated:

"The worst-case condition is a short between holes drilled on a tight grid.  The most insidious condition that wicking is a site for CAF (conductive anodic filament) growth."

There is no tight grid on this board so the short between holes is not going to happen.  CAF is always a concern but I would have thought that a failure would be related to some kind of stress point mechanism of failure based on how rough the hole looks.  I know a picture would make this a lot easier but I am not at liberty to release it.  The copper in the hole is very thick but the entire hole looks like it had a bad drill and overly aggressive desmear operation.  There is wicking all up and down the wall of the hole but only excessive in length in one spot.

So the question is:  How does excessive wicking cause a failure?  This was the kind of question that I used to send to Werner to get further education on.

Any and all comments are appreciated.

Phil

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