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April 1997

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Tue, 15 Apr 1997 07:11:28 -0400 (EDT)
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Hi Doreen,
What you likely have are not "rubber" solder joints, but no solder joints at
all. That is, no metallurgical bond ever existed for these joints. If you
take these joints apart, you are likely to find that there is no sign of tin
on the lead surfaces that were surrounded by the solder. This can happen when
the leads are not solderable for whatever reason (there is Alloy 42
presumably from a mill in South Korea that is not solderable), but are
covered with a thin flash of solderable metal (Au, Ag, Cu, Pd) that promotes
the coverage of these leads with solder. Of course, this kind of "sliding" of
the lead foot out of the surrounding solder joint "sock" can only happen with
gullwing leads.

Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ  07945  USA
Phone & Fax: 201-543-2747
E-mail: [log in to unmask]

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