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March 2011

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Subject:
From:
Pradeep M <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Pradeep M <[log in to unmask]>
Date:
Mon, 14 Mar 2011 14:54:40 +0530
Content-Type:
text/plain
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text/plain (54 lines)
Dear technetters,

We are from a PCB mfg organization. One of our customers has made an
observation on one of the boards that we had supplied to them earlier. This
is a 6 layer card which we had manufactured in July 2007. This board does
not have solder mask and has normal HASL as the surface finish. The customer
had taken this up for manual assembly with hand soldering after some time.
Typically with this customer, the whole assembly usually takes nothing less
than 6-8 months for completion.  They had completed the assembly and had
subjected the assembled board for thermal cycling ( a procedure which they
follow). Thermal cycling is being done at 60 deg C for 2.5 Hrs then at 13
degC for 2.5 Hrs for five cycles.  After this the assembled board has been
coated with conformal coating.  Some more functional tests were conducted
and this card is integrated together with other boards. Then a hot and cold
storage test as part of test and evaluation (T&E) of the package was done.
Storage test (passive ) is at the same extremes but active at 40 deg C. The
customer had opened the package for correcting an anomaly observed, when
they found some 'delamination' on the board.  The customer has sent a
photograph and wants us to respond with our comments. Customer says the
board was looking fine after assembly as well as after the first thermal
cycling. 

We are quite surprised on how a delamination can happen at max of 60 deg C.
We do a microsection analysis of every processed panel and also does a
thermal stress as per IPC TM 650 prior to the dispatch. We have asked for
the actual board to ascertain the delamination, but this might take some
time. The conformal coating material removed by peel off manually by the
customer. We had used Nelco 4000-6 170 Tg FR4 material.  

Can anybody provide us some inputs. The photograph may be shared directly.

Rgds

Pradeep

 



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