Hi Jerry & Dave & All -

Another possibility:  If the lead frame on the devices you're dealing with was
PLATED and not reflowed promptly after, then that may be the answer to your
problem rather than any alloy combination.  Most of the tin/lead platings lose
their solderability rapidly after application unless reflowed and cleaned
immediately after plating.

One additional test that you might try, in addition to an alternate flux,
might be to try a "bright dip", then rinse, flux and solder the parts
immediately.  Most of the bright dips are a 1 to 3%  HCl solution which will
do a pretty quick job of deoxidizing the parts.  As above, this surface loses
its solderability rather quickly and isn't something you would want to do for
production.

I think most of us have seen some fairly significant variances in finish
alloys over the years, even on parts supplied from the same manufacturer.
Availability of improved fluxes has probably done more to ease concerns and
difficulties encountered in the military/government sector of the industry
than anything else in recent years.

Regards - Kelly

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