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June 2007

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Subject:
From:
Dwight Mattix <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Dwight Mattix <[log in to unmask]>
Date:
Tue, 5 Jun 2007 09:10:26 -0700
Content-Type:
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text/plain (109 lines)
At 08:38 AM 6/5/2007, Kerry McMullen wrote:
>Hi Tom,
>Check the plating spec on the fab.   The plating thickness in the via's
>should be specified at 0.001" absolute minimum if you are going with LF
>processes, regardless of the board material.
>  (That is what I am told).

Class 2, 0.0008" minimum on PTH has been fine in our IST Pb-free qual 
work.  Quality of drill/roughness, hole prep, electroless Cu 
grain/porosity, and electrolytic Cu ductility is much more important.

>  I
>have made this change on my large 18+ layer boards, and my quality/yields
>have increased, and my opens have practically diappeared.
>
>Kerry McMullen
>Principal New Product Mfg. Engineer
>LTX Corporation
>825 University Avenue
>Norwood, MA 02062-2643
>(T) 781-467-5468
>(C) 508-631-1832
>(F) 781-461-0993
>
>
>
>Tom Parkinson <[log in to unmask]>
>Sent by: TechNet <[log in to unmask]>
>06/05/2007 10:13 AM
>Please respond to
>TechNet E-Mail Forum <[log in to unmask]>; Please respond to
>Tom Parkinson <[log in to unmask]>
>
>
>To
>[log in to unmask]
>cc
>
>Subject
>[TN] Via Open
>
>
>
>
>
>
>Tech Net & Designer Net
>
>Greetings. We are running into a situation on Lead Free processed PCBs.
>Failure mode is finding open vias during unit testing (fully populated).
>
>Boards are Tg170, Material type EM320, 0.063" thick boards.
>6 layers of 1 oz copper. ENIG 3~5u"
>
>Suspect vias go from top layer to bottom layer only.
>
>After running through reflow, we have found vias open. No visual signs of
>delamination, however when ohming out the via, if we press on the via we
>get
>continuity - thus we suspect the vias are opening during the process.
>
>Anyone out there having these problems, or information concerning this
>failure mode?  Z-expansion failure?
>
>
>Tom Parkinson
>Quality System Manager - CIT
>WinTronics, Inc.
>Phone: 724-981-5770 - extension 235
>
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