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A tin whisker
is a single crystal that emerges from tin-finished surfaces.
It can take hours or years for them to grow, and they can
grow up to 9 millimeters in length. Tin whiskers have been
blamed for dangerous failures in heart pacemakers, satellites,
and nuclear power plants. The NASA
Tin Whisker Website provides a wealth of information
regarding the nature of tin whiskers and their ability to
cause:
- Short circuits
- Low pressure arcing
- Debris and contamination
Any of these issues is a showstopper
in electronic assembly. Unfortunately, much of the available
electronic component supply is assembled with some degree
of pure tin finish, especially on component leads. These
leads are extremely vulnerable to tin whiskers and their
associated failure mechanisms.
What can be done to eliminate the risk
of tin whiskering? Right now, the simplest, most cost-effective
way to mitigate the danger of tin whiskering is to remove
the tin finish - all of it. It has been clearly demonstrated
that partial removal of pure tin during the soldering process
is not enough. The terminations should then be refinished
with a SnPb solder, proven effective over 60 years of service
in high reliability applications. Other solutions remain
unproven.
Removal of tin and replacement with tin-lead
sounds simple, but can it be done reliably and repeatedly?
In 2004 the United States Navy, Raytheon,
University of Maryland, and Corfin Industries teamed up
for the three-year, $1,250,000, Transformational Manufacturing
Technology Initiative (TMTI) project to determine if tin
mitigation (the removal of pure tin and replacement with
tin-lead solder) could be reliably accomplished using Corfin’s
precisely-controlled Robotic Hot Solder Dipping process.
Click
here or on the photos at left to see a video demonstrating
the equipment’s precision.
The team designed an exacting process
of computer-controlled times and temperatures and precise
robotic component positioning to accomplish this task. In
short, Corfin’s Robotic Hot Solder Dip process successfully
removed the problematic tin finish from a wide variety of
components and replaced that finish with non-whiskering
tin-lead. It did so reliably, and repeatedly all of this
was accomplished without damaging sensitive components.
To learn more, please read the
final study report or Corfin’s
Tin Whisker brochure.
If pure tin-finished components are in
your inventory and tin whiskers are a concern, please give
us a call and talk to us about your lead-free control and
whisker mitigation needs.
For more information, please click
here to download our Tin Whisker Brochure.
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