Tin Whiskers
For Release
September 14, 2004
Milpitas, CA
The world-wide environmental mandate to eliminate Pb in electronic assemblies
has resulted in Sn and Sn alloys becoming the replacement to Sn/Pb solder.
Pure tin possesses a high reliability risk due to migration of the tin, commonly
known as “tin whiskers”. Tin whiskers grow spontaneously within pure tin coatings
as single crystalline structures which are electrically conductive. Tin whiskers
can grow to several millimeters in length. Tin whiskers were first discovered in
electronic equipment in the early 1940’s.
Tin whiskers can cause two major reliability problems:
The commercial market place at large is typically not severely affected by tin
whiskers, since tin whiskers generally manifests itself outside of the usual product
reliability window. Tin whiskers can become a severe problem in high reliability
applications with long life cycle expectancies. Since 1988 several military weapons
systems have failed due to tin whiskers. Failures have also been documented in the
medical, aerospace, and energy fields. One of the most notable recent tin whisker
related failures has been dubbed “The Day the Pagers Died”. On May 19, 1998, the
$200,000,000 Galaxy IV communications satellite which serviced 90% of the pagers
in North America and several broadcast networks, became space junk.
Common mitigation practices such as nickel barrier, conformal coating, reflow,
etc., cannot effectively eliminate tin whiskers. The primary way to reduce the risk
of tin whisker induced failures is to avoid the use of tin plated components. Unfortunately,
many of today’s commercial of-the-shelf electronic components (COTS) already have
tin plated leads. For tin plated components which are to be used in a high reliability
and long life cycle applications, Six Sigma strongly recommends hot solder dipping
the component’s plated leads using tin-lead solder to completely reflow and alloy
the tin plating. Six Sigma has been hot solder dipping components for military and
aerospace contractors since 1989. Our reputation is second to none. Six Sigma will
take the guess work out of determining whether or not your procured COTS components
have the potential for tin whiskers. Six Sigma can analyze the lead finish in our
state-of-the art reliability lab and report our findings and recommendations to
you in a timely manner. For additional technical assistance or quotation, call us
at (408) 956-0100.
Photo Courtesy of Andre Pelham (Intern)
NASA Goddard Space Flight Center
Tin "Whisker" shown above growing between pure tin-plated hook terminals
of an electromagnetic relay similar to MIL-R-6106 (LDC 8913)
To learn more about Six Sigma's Lead Tinning Service, visit
http://www.sixsigmaservices.com/leadtinningservice.asp
For detailed scientific information on tin whiskers, visit
http://nepp.nasa.gov/whisker/background/index.htm
Contact:
Dale Albright
Sales and Marketing
SIX SIGMA
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