I believe you are looking at a barrel crack in the middle of a plated
through via (PTV).  This is a typical failure mode from "Z" axis expansion
of the material due to thermal excursions.  The thermal excursions of
assembly/rework could induce this failure mode.  Fabrication variables like
copper thickness/quality or the type of material used in fabrication could
be contributing factors.  It is possible that a couple of those dark lines
on the right side (middle and bottom) of the PTV in your picture are of
material delamination.

Paul Reid
PWB Interconnect Solutions Inc.

-----Original Message-----
From: Al Onderick [mailto:[log in to unmask]]
Sent: Thursday, November 04, 2004 5:55 PM
To: [log in to unmask]
Subject: [TN] Via hole failures (with pictures)


I have a couple of boards that have failed at a customer site. After
testing, a via was identified as open. The following link is a picture of
the cross section.

http://www.tier1gear.com/temp/via_crack.jpg

The board was .062, the via .010 and the surface finish immersion white
tin.

I would appreciate any insight into what may cause a failure like this.

Al Onderick
National Instruments

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