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January 1997

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Subject:
From:
"Max Bernhardt "<[log in to unmask]>
Date:
Tue, 14 Jan 1997 07:22:00 -0600
Content-Type:
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With TSOP packages, we have done this test for lack of anything more
scientific.  We have found that even after temperature cycling, ICT, and
functional testing that we still have problems with leads being loose on
the board.  Therefore, the only quick and dirty way of checking for bad
leads is to use a dental pick on the leads.   I hope this helps.
 ----------
From: [log in to unmask]
To: [log in to unmask]
Subject: ASSY: Fine Pitch Solder Joint Inspection Method?
Date: Monday, January 13, 1997 9:49PM


Hello all,

     I've got a question, how many of you out there check whether or not
a fine
pitch solder joint is good by dragging the tip of an exacto-knife blade
or a
steel pick across the foot of the leads?

     I have seen it done back in the past by a few inspectors maybe 4 or
5 years
ago, but not anytime recently...until I heard about it today. Is this
still a
common practice?

     I'm pretty sure it's not the smart thing to do, but when you have
someone
call and tell you that the fine pitch solder joints on the board you
built for
them are insufficient because the leads come loose when they check them
with an
exacto-knife...they sure don't want to hear you tell them that they
shouldn't be
dragging anything across the leads.

     I'm almost sure it's not one of the cases where sometimes a solder
joint
will become plastic during wave soldering and separate from the pad,
some of you
may have seen that before. You know, where the fillet stays attached to
the foot
of the lead with a nice wetting angle and all that stuff, but it's not
attached
to the pad...but I haven't actually seen the actual boards that
supposedly has
the insufficient solder yet, the customer has to bring them to me...

     Oh, another thing, these boards have all been through and passed
ICT, a
24-hour burn-in, and a functional test after burn-in. So it would seem
to me
that if I have a problem with my solder joints, it would have showed
itself for
sure in burn-in...

     But before they get here, I'd thought I'd ask and see if it's a
common
practice to rake fine pitch leads with a steel object...by the way,
we're
talking about .020" pitch QFP devices here...


(gimme' some ammo guys!) Thanks in advance!



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