Appears to be damage to package from - areas has excessive crazing and
meales.

Jeffrey Bush

Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED 

           76 Technology Drive - POB 1890 

              Brattleboro, Vermont 05302

                Voice - 802.257.4571 ext 37 

                    Fax - 802.257.0011

                       <http://www.vtcircuits.com/> 
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of - Bogert
Sent: Thursday, January 11, 2007 6:26 PM
To: [log in to unmask]
Subject: [TN] Is this CAF?

January 11, 2007

This is an e-mail for all you CAF experts out there.

We have an OEM that manufactures a 10-layer VME backplane assembly that
has press-fit power studs installed in the backplane.  The manufacturer
has experienced system level test failures.  Some of these failures did
not occur during the initial testing but the assemblies failed at some
subsequent time during testing.  The failure mode was shorting of the
+12V layer 1 to the +5V layer 3 via the pressed-in power studs.  The OEM
had the backplane sent to an outside lab to determine the root cause of
the problem.  After looking at the pictures taken from the evaluation,
it appears to me that the problem could be due to CAF because of the
damage done to the glass fibers in the FR4 board material.  CAF is also
suspected since the test failures do not occur on initial testing of the
equipment.  We verified that the PWB conductor spacing meets IPC-2221
requirements.  Another factor is, we believe the OEM may have used some
Type H flux per J-STD-004.  Not sure this is an issue unless some of the
flux residue entered the PWB internally via the press-fit power studs.

Steve Gregory was kind enough to post 13 pictures on his web site.  They
are files GLB CAF # 1 through GLB CAF#13.

Can folks identify whether CAF could be the root cause of the problem?
Any help would be appreciated.  

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