Doctoral student unravels 'tin whisker' mystery

Doctoral student unravels ‘tin whisker’ mystery
Tin whiskers growing on an electronic circuit.

(—Americans love their electronics, and millions will undoubtedly receive everything from flat-screen TVs and e-readers to video games and coffee makers this holiday season. Over time, even the best of these devices inexplicably stop working. Often it's not worth the time and money to have them repaired, but the nagging question of "why" still lingers long after they're thrown in the trash.

Yong Sun, a mechanical engineering doctoral student at the University of South Carolina's College of Engineering and Computing, has solved part of the puzzle.

Little-known culprits of this electronic destruction, tiny killers that leave no evidence the can detect, are microscopic strands known as "whiskers." These hair-like fibers of metal grow out of the tin used as solder and coating on many . The presence of these whiskers can cause short-circuits since they act as bridges to conduct electricity to closely-spaced parts, a problem expected to become more prevalent as devices are designed smaller and smaller.

The whisker phenomena have been known within scientific circles since the 1940s, but just how these form and grow was largely a mystery. He used a process called digital image correlation to track the deformation of the surfaces and was able to prove the growth of whiskers are caused by high-strain gradient built up inside the device.

Sun's findings were published in the Scripta Materialia, a journal. This fall he won the prestigious Acta Student Award, one of only six to receive the honor. A team of editors from Acta Materials, Scripta Materialia and Acta Biomaterials evaluated the applications and Sun beat out students from the world's top universities, including MIT.

"This shows that our research in is reaching an international audience," Sun said. "It is nice to be recognized for our work."

The importance of that work goes well beyond extending the operating life of consumer electronics. NASA has verified multiple commercial satellite failures it attributes to tin whiskers. Missile systems, nuclear power stations and heart pacemakers also have fallen victim to tin whiskers over the past several decades and they are also considered a suspect in reported brake failures in Toyota vehicles.

While manufactures had been able to control some whiskers by mixing small amounts of lead into tin solder, the 2006 European Union ban on lead in most electronic equipment had ignited a debate among scientists about whether whiskers would remain a perpetual problem. Some observers even predict that it's only a matter of time before miniature devices built after the ban start failing en masse.

Xiaodong Li, a professor in USC's Department of Mechanical Engineering who served as an adviser on the research, said Yong's work likely will prompt manufacturer to design lead-free products that diffuse stress.

"This (research) is a very big deal. As we move toward nano-scale devices, this is a problem that needs to be solved," Li said.

Explore further

Researchers Seeking Cure for Electronics-Killing Whiskers

Journal information: Scripta Materialia

Citation: Doctoral student unravels 'tin whisker' mystery (2012, December 5) retrieved 22 October 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Dec 05, 2012
RoHS (Removal of Hazardous Substances) put a ban on lead in solder. It's interesting because it was known that the tin whiskers would become a huge issue. Most electronics manufacturers really worry about this. But for the most part it is lost on the public of why lead needs to be in solder. I wonder if a risk analysis was ever performed to compare the potential for lead entering the waste stream vs. modern critical devices abruptly ceasing to function (like the brakes, pacemakers, etc noted in the article)

Dec 05, 2012
Tin whiskers are a problem even with leaded solder, but not nearly as much.

I spend a good deal of time repairing antique instruments like Hammond Organs and you run in to the whiskers fairly often.

That said the organs took decades to develop these whiskers and the lead went a long way towards preventing them. Removing lead from solder was a knee-jerk decision and it doesn't appreciably reduce the amount of lead in the environment.

I still use lead solder in my custom amplifiers. Shhhh don't tell anyone.

Dec 05, 2012
RoHS (Removal of Hazardous Substances) put a ban on lead in solder. It's interesting because it was known that the tin whiskers would become a huge issue. Most electronics manufacturers really worry about this. But for the most part it is lost on the public of why lead needs to be in solder. I wonder if a risk analysis was ever performed to compare the potential for lead entering the waste stream vs. modern critical devices abruptly ceasing to function (like the brakes, pacemakers, etc noted in the article)

The U.S. had leaded gasoline for several decades, in spite of science knowing it was dangerous. It was finally banned in the 1990's. The scientists have discovered that the average I.Q. in the nation has been rising ever since. I suspect that various diseases in the U.S. are caused by some form of lead poisoning; autism, cancers, birth defects, general malaise and other issues that seem unnatural.

Banning lead from casual, consumer electronics is the right move.

Dec 05, 2012
Sorry but when your flash, new, high end device fails on you for want of a few mg of abundant metal, when you've had to repeatedly clean and reflow circuit boards to fix a problem a mere trace of lead would've obviated, when you've lain awake at night wondering how to electroplate solder tracks or improvise a tough conformal coating.. THEN come and gloat over your airy fairy dolphin-friendly solder.

It's crazy, when we're so dependent on electronics, to pass legislation that leaves us more vulnerable to a well known and little understood hazard. Engineers strive to eliminate such single points of failure, and we had a solution... till the elf'n'safety gestapo marched in and put us back a century! It was already known to be exacerbated by strain, but also by pulsed DC - ie. digital electronics. Yet with clock speeds higher than ever and track widths narrower than ever, they just blithely chuck a big spanner in the works, with no workaround in the offing.

Typical EU busybodies..

Dec 05, 2012

Are you for forced population decrease or something?

Why would you value the convenience of a consumer electronics device above human life and health?

Losing I.Q. points sets people back more than a century.

Dec 05, 2012
Mr Vib. You have it absolutely right. Billions of gallons of Leaded gasoline burning and thus vaporizing tetraethyl lead has NOTHING to do with 3 mg of lead in tiny bits of wire per TV. Think of the wastage of electronics- then Americans go and buy new crap from China..

Dec 05, 2012
Lurker: the path for (tetra ethyl) lead in gasoline to get into the general environment is very obvious and inevitible. Gasoline is intended to be burned with air and all reaction products get dumped right into the atmosphere. Air circulation and rain take care of the rest.

How a small amount of lead in the solder for electronic gets into the environment is another story. If the electronics are recycled we can capture the lead and re-use it. If they are disposed of in a proper land fill, then it won't leach into the water. If they are thrown out and are exposed to environmental moisture (rain) then it will start to leach into the environment. Burn them and you are guaranteeing that you will spread the lead as much as possible.

A lot of electronics are being recycled due to the gold content anyways these days. It would make more sense to put the lead back into the solder to maintain long life and recycle than to build equipment we know will fail sooner.

Dec 05, 2012
Stability of metallic lead Vs lead oxides or lead salts are very different.
The eviro-lunatics that are always screaming the sky is falling are seemingly devoid of the mental capacity to differentiate between the relatively stable metallic lead and it's chemical cousins. If it's lead then it's bad, and it's got to go, no matter the cost. Which seems to prove the point, that a little bit of knowledge is a dangerous thing.
I hope they will someday learn the foolishness of their ways but it would seem that isn't going to be the case. It seems most have such a religious bent toward this new religion, of "Public Safety" over all other things, that they willingly sacrifice any rational abilities to think for themselves, nor can they learn from scientific methods and are bound by group think for whatever opinions they harbor as factual. Disagree with them and you get called names, it doesn't mater that you might actually have science on your side.

Dec 06, 2012
The reduction of of lead in solder from 50% to 0% is approximately correct. The coming increase of lead in solder from 0% to less than 1% will be even more approximately correct.

Dec 06, 2012
I wonder if adding silver is a solution. It is used in electronic contacts ib place of gold because silver oxide is a good conductor after it tarnishes.

Dec 06, 2012
Ah the EU is great at making up legislation but not so good at thinking through the consequences.

Dec 06, 2012
All we need is a tin shaver and we'll be a-okay!

Dec 06, 2012
It would be an interesting Hazard Risk Analysis, to compare lead deaths (deformities, IQ reductions) caused by SOLDER entering the environment vs. deaths caused by sudden failure of pacemakers, respirators, braking systems, etc. It just doesn't seem that this analysis was done and a presumed "fix" was implemented. If it has been done, please point it out, I couldn't find it.

Dec 06, 2012
Clarification...failures of those critical life systems due to tin whiskers.

Dec 06, 2012
Just about any metal you can think of is harmfull at some level of concentration so perhaps we should stop using any metal at all and live in a cave, That is where parnoia will take you. There are vast areas of the world including the USA that have naturaly occurring lead in the soil and people drink the water ,eat food grown there with no harmful effects as they have for centurys.Too much of anything including food and water is harmful so instead of mindless fear ,education and reasonable caution will prove to be what is practical.

Dec 08, 2012
We need to take matters into our own hands people. I just grabbed my cat and cut off both sides of all her whiskers. She looks weird as hell and is giving me this very displeased look but what she doesn't understand is this act alone will probably double to quadruple the lifespan of all my electronics. It needed to be done.

Dec 09, 2012
Lead in solder and electronics wouldn't be a problem if we had sense enough to realize that, now more than ever, we need to get as close to 100% recycling as possible, especially with electronics.

Dec 09, 2012
I don't think it's going to be much of a future problem when iPads become obsolete after 6 months I'm pretty sure that they'll be thrown away long before 20 years has passed.

Dec 09, 2012
Would anybody here bet that engineers simply cannot find a way around the problem of tin whiskers without using lead?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more