Tin whiskers and lead: how they relate

Recently, Yong Sun, a mechanical engineering doctoral student at the University of South Carolina’s College of Engineering and Computing, produced some interesting research on “tin whiskers” in electronics.

Sun used a process called digital image correlation to track the microscopic deformations – a material’s reaction to strain — on the surfaces of micro-electronic components.

Spontaneous deformations called “tin whiskers” grow outward from the surface and can cause short circuits in electronic equipment.

A Google image search provides many examples. This NASA page provides images, too.

Several decades ago, Bell Labs found the addition of lead to tin solder plays a role in controlling the growth of tin whiskers. A 2012 NASA presentation says:

“Whiskering is dramatically inhibited when 0.5% (or more) lead (Pb) is added to Tin coatings: the shorting rate then approaches zero.”

Lead, of course, can present health hazards. The presentation goes on to note:

“. . . Pb [lead] use is being restricted by international legislation”

Many of our customers who have soldering or de-soldering applications that utilize lead solder use HEPA filtration to capture fumes

If your application requires solder with lead

Lead in solder is not prohibited in theU.S., although prohibition does appear to be on the horizon. While the industry develops acceptable substitutes, you should take precautions.

Soldering fumes that contain lead can be moved away from a worker’s breathing zone and trapped by filtration.

Sentry Air offers a range of fume extraction units for soldering applications.

Here’s a composite image [not to scale]:

Fourteen styles of solder fume extraction devices from Sentry Air Systems (not to scale).

Our soldering fume extraction unit selection addresses requirements for one or multiple workers, static discharge concerns, floor space and wall space, and effective filtration that protect workers’ breathing zone.

Our varied styles of source-capture fume extractors are effective engineering controls for solder fumes, solder pots and wave soldering fumes.

They can be equipped with high-efficiency filtration media, including HEPA and/or Activated Carbon. We offer ESD-safe units for those concerned with electrostatic discharge.

For information on solder fume options for your application, give us a call at 1.800.799.4609, email us at sales@sentryair.com, fill out this online form, or use the Request for Information form below to have a Sentry Air Systems Applications Specialist contact you to discuss your process.

Resources

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1281311/

http://en.wikipedia.org/wiki/Deformation_(mechanics)

http://nepp.nasa.gov/whisker/reference/tech_papers/2011-kostic-pb-free.pdf

http://nepp.nasa.gov/whisker/reference/tech_papers/2012-Panashchenko-IPC-Art-of-Metal-Whisker-Appreciation.pdf

http://www.sentryair.com/solder-fumes.htm