Thanks for the info from everyone! We are a defense contractor which
makes the switch from HASL even more touchy. It is further complicated
by the fact that, for the time being anyway, lead is good, RoHS is bad
in our world. So, we have to move slowly. Everything was fine until we
started using more and more fine pitch parts on flex circuits. The
majority of the flex assemblies we do here are not rigid flex and only
have parts on one side of the flex. Our SMT manufacturing engineer is
very familiar with ENIG. I will have to talk to him about immersion
silver. I found a patent (US Patent 6656370 ) describing the technique.
Very interesting, so as I understand it, one immersion silver deposit
serves as both the etch resist and final finish. 
I think that because we tend to "stockpile" printed circuit boards
though, ENIG's longer shelf life would be a big plus over immersion
silver.
Best Regards and thanks to all that responded,
Dave Connitt
 
Dave Connitt CID+
Printed Circuit Designer
KDI Precision Products, Inc.
A Wholly Owned Subsidiary of:
L3 Communications
3975 McMann Road
Cincinnati, Ohio 45245
Ph. 513- 943-2010   Fax 513-943-2288

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