The risk of tin whiskers is typically greatest with electroplated pure tin deposits, which could be used on component leads. Soldering those leads with Sn/Pb is one way of reducing the risk, as Pb acts as a natural suppressant to tin whisker formation. There are cases of tin whiskers forming from Sn/Pb solder deposits, but the growth rate, length and number of whiskers may meet your customer's requirement.
I suggest mitigation of tin whiskers followed by running tin whisker tests based on available standards like GEIA-STD-0005-2, JESD201, JP201, and JESD22A121. There may be other, more current standard for tin whiskers.
Tony Lentz
Field Applications, FCT Assembly
Tony has worked in the electronics industry since 1994. He worked as a process engineer at a circuit board manufacturer for 5 years. Since 1999, Tony has worked for FCT Companies as a laboratory manager, facility manager, and most recently a field application engineer. He has extensive experience doing research and development, quality control, and technical service with products used to manufacture and assemble printed circuit boards. He holds B.S. and M.B.S. degrees in Chemistry.
There is not a lot known about tin whiskers other than they tend to occur under stress of an SNPB solder joint. How the solder joint is formed if by reflow oven, vapor phase, or hand soldering, I would not feel confident enough to say tin whiskers are less likely for any particular soldering technique. As long as you are using tin in the process, there is a risk for tin whiskers.
Brien Bush
Manufacturing Applications Specialist, Cirtronics Corp.
Mr. Bush has over 30 years of experience in electronics contract manufacturing. Major areas of expertise include through-hole, SMT, wave, and selective soldering.
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