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February 1998

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Subject:
From:
Matthew Park <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 26 Feb 1998 12:25:17 -0800
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Try to isolate where popcorn noise is coming from,

1. bake bare boards at a low temp (80-100'c) to drive out
moisure for about 30min to 1hr, and stuff boards and reflow.
And see whether this produce same popcorn noise?
2. bake suspected plastic pkg components  at 80 -100'c for
about 30min, and stuff them in prebaked boards. And see
whether you get same popcorn noise?

It could be that components and boards are complaining "I can't
stand too much heat!   Get me outa here!"

re
Matthew Park
NII Norsat International Inc.



>>> Koushik ATD Banerjee
<[log in to unmask]> February 26,
1998  11:41 am >>>
I would like to request for input / feedback on an interesting
problem
that we are seeing sporadically in our SMT line.

Some of the PCBs, post component attach, when they are either
in or
are coming out of the reflow oven are making a "crackling" noise
!  We
have not identified any defects in the boards or the components
yet
and we are unsure what is causing the noise.  Sometimes, we
are also
hearing this noise when we take a board in our hands post SMT
and try
to warp it a little !  The boards are approx 5" x 12", have
components
on both sides (passives and some actives) and is not very
densely
populated.  Any suggestions on what could be the reason would
be
greatly appreciated !

Thanks,-Koushik Banerjee-

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