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October 2000

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 17 Oct 2000 14:01:39 -0400
Content-Type:
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text/plain (67 lines)
Brad,
What is inexpensive? All relative, I suppose.  When I was still with Nortel
Networks, I carried out a couple of studies in this area using a four figure
analytical balance.  I was able to produce very good, smooth curves of the
moisture absorption/adsorption and the corresponding moisture loses with
different heating regimes.  However, a four figure balance is  a precision
piece of equipment, not something you put in the hands of just anybody.  It
also must be in a draft-free, vibration-free, dust-free zone.

As far as Jim's statement of always baking out BGA's before use, we (Nortel)
did not find this necessary if they were used directly out of the moisture
resistant bag right after they came in the door or if they were stored in
dry storage cabinets after arriving as just described.  If either of these
two conditions were not in play, then, yes, I agree with Jim regarding
baking.  Some conditions that might cause this to be necessary would be rips
in the incoming "sealed" bag, forgetting to put into dry storage, too much
time on a board before second side reflow or wave soldering.

Bev Christian
Director of Electronics Manufacturing
XLTEK

-----Original Message-----
From: Brad L. Matthies [mailto:[log in to unmask]]
Sent: Tuesday, October 17, 2000 12:34 PM
To: [log in to unmask]
Subject: [TN] Measuring Moisture in BGA Packages.


TN,

Does anyone know of a simple (i.e., inexpensive) way to measure the
moisture content in a BGA package?  We have thought about measure the
weight of parts, baking them out and remeasuring the weight to determine
if it dropped.  We have also considered using infrared imaging to look
at the parts after applying some heat to them.  Both of these seem
problematic though.  What we are trying to accomplish is to have our
receiving inspectors sample parts to determine if the parts have a
moisture contamination problem or not.  We would then use this
information to decide which parts need to be baked prior to being placed
into dry storage for use in production.  Any comments would be greatly
appreciated.

Regards,

Brad L. Matthies
SMT Process Engineer

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