To my knowledge it is a myth, that SN62 alloy (with 2% silver) is effective
in reducing silver metallization leaching during reflow. Solder has such high
solubility in tin and silver/tin intermetallics rapidly disperse throughout
the solder joint that a 2% silver content is not likely to any effect in the
leaching--actually dissolution-- process of the silver into tin. That is
really the reason why the nickel barriers came into widespread use. 

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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