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Date: | Wed, 17 Apr 96 08:11:00 CDT |
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We have processed millions of components which use Alloy 42 as a base
material. Solderability of these leads is fine under a variety of
applications. We had one situation concerning a large number of assemblies
where problems were experienced due to low joint strength even on
ANSI/J-STD-001A Class 3 joints.
Cracks were discovered along the Alloy 42 interface. Low pull strength was
correlated with certain manufacturers. During the course of the
investigation, it was learned that many of our off-shore suppliers
sub-contracted the plating of the leads which resulted in a range of pull
strengths from a single supplier. It was suspected, but never proved, the
process controls on the Alloy 42 PRIOR to plating played a major role in
this variation. It was also learned that some well respected component
manufacturers do less than you might expect to monitor the performance of
their packages in this respect; ie pull strength of a soldered lead.
Some of this problem can be mitigated by the strength of the flux and, to
some degree, the reflow profile. But your options are limited in the world
of no-clean. However, the most significant factor was shown to be not only
the supplier, but which sub-contractor the supplier used for lead plating.
Fortunately, this was only one situation. However, I suspect the problem
may be more prevelent as a number of board design, handling, and test
factors were involved which may have put stress on the joints to initiate
the cracks.
I would be interested to know if anyone else has seen similar performance
(low pull strength) with Alloy 42.
Bill Barthel
Electronic Assembly Corp.
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