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Description / Abstract:
ABSTRACT
As most of the world converts to lead-free manufacturing, the
concern over tin whiskers as a reliability hazard has grown due to
the emergence of pure tin as a dominate component surface finish. A
significant amount of research on tin whisker formation and tin
whisker mitigating strategies has been performed in both commercial
and defense industries. David Pinsky [11] summarizes the concern
well:
Whiskers are elongated single crystals of pure tin that have
been reported to grow to more than 10 mm [0.250 in] in length
(though they are more typically 1 mm or less) and from 0.3 to 10 μm
[11.8 to 393.7 μin] in diameter (typically 1.0 –3.0 μm [39.4 – 118
μin] ). Whiskers grow spontaneously without an applied electric
field or moisture (unlike dendrites) and independent of atmospheric
pressure (they grow in vacuum). Whiskers may be straight, kinked,
hooked, or forked and some are reported to be hollow. Their outer
surfaces are usually striated. Whiskers can grow in nonfilament
types which are sometimes called lumps or flowers. Whisker growth
may begin soon after plating. However, initiation of growth may
also take years. The unpredictable nature of whisker incubation and
subsequent growth is of particular concern to systems requiring
long term, reliable operation.