Technology

Tin Whiskers Are The Metallic Quirks That Spoil Everything From Televisions To Space Travel

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Sometimes, electronics just stop working. There doesn't seem to be any rhyme or reason to it—one day they're just fine, and the next day they're dead. The culprit may have been something you could never see with the naked eye. They're commonly called "tin whiskers," but they can happen to a number of different metals, not just tin.

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What Exactly Are They?

They may sound like the Tin Man's five o'clock shadow, but tin whiskers are actually pretty insidious. They're microscopic, crystalline structures that sprout out of the tin that's used to solder and coat many electronic circuits, though whiskers can also grow from metals like zinc, cadmium, and silver. Whiskers generally happen due to stress in the metal. Any bending, compression, stretching, or even scratches and nicks can be enough to sprout them. We've known about them since the 1940s, but they've actually gotten worse in recent years because of an unrelated safety guideline: the elimination of lead in electronics, which has been great for human health, but bad for electronics, since lead can keep whiskers from forming. Tin whiskers can extend several millimeters—sometimes even longer than 10 millimeters, according to NASA—but they don't need to be very big to wreak havoc on electronics.

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That's because they only need to be long enough to form a "bridge" between two different electronic parts. That bridge can cause problems as minor as intermittent short circuits and as damaging as metal vapor arcs. The latter occur when high current and voltage vaporize the whisker, turning it into a plasma of metal ions that can carry hundreds of amps, wreaking catastrophic destruction in its wake.

Silver Sulfide Whiskers growing out of surface-mount resistors from a Moog DS2000 servodrive.

Real-World Consequences

Here on Earth, whiskers can cause problems in everything from your TV remote to medical devices. In 1986, the FDA recalled several models of a pacemaker because tin whiskers were causing circuit problems. More recently in 2005, a nuclear reactor in Connecticut was suddenly shut down due to a computer malfunction caused by—you guessed it—a single tin whisker.

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Whiskers can cause even more damage above the ground. That's because higher altitudes help whiskers form even faster. The microscopic growths have been enough to shut down satellites, destroy airplane communication equipment, and ruin space shuttle components. The problem is especially risky for space travel, where any glitch could mean the difference between life or death. Luckily, experts are aware of the problem, and are hard at work figuring out solutions to fight it.

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