Danger to lead-free electronics: tin whiskers

Whisker-related malfunctions
Failures blamed on tin whiskers have run the gamut of devices and manufacturers.

In the 1980s, the U.S. Food and Drug Administration recalled some pacemakers because of a high failure rate caused by tin whiskers.

In 1998, PanAmSat Corp.'s $250 million Galaxy IV communications satellite, which provided service to tens of millions of pagers across North America and thousands of pay-at-the-pump gas station machines, was deemed a total loss after two processors failed. The main spacecraft control processor, which governs the satellite's positioning and other functions, failed for an unknown reason, and the backup couldn't be used because tin whiskers had shorted it out a year before.

At least 10 other satellite failures have been blamed on tin whiskers, according to the NASA database.

Over the past two decades, also according to the NASA database, nuclear power plants have been temporarily shut down at least seven times after tin whiskers in the alarm system circuit boards triggered false alarms, alerting managers to threats that didn't exist. There have been no reported injuries.

SOME TIN-WHISKERS FAILURES Some recent failures caused by tin whiskers: 1986: Malfunctions in radar equipment for U.S. Air Force F-15 fighter jets. Culprit found to be tin whiskers that had detached and fallen into active circuitry, causing intermittent performance problems for the radar. Problem would suddenly disappear when vibration from the aircraft caused the whiskers to shift position again. 1987 to present: At least seven nuclear power plant shutdowns. Whiskers were growing within the alarm system circuitry, not the reactors themselves, and falsely alerted managers that certain critical systems weren't working properly. 1989: Tin whiskers reported on Phoenix air-to-air missiles used by the U.S. Navy. The whiskers were discovered in a tin-lined box enclosing the missiles' target-detection system. 1998 to present: At least 11 problems on commercial satellites in orbit. Failures occurred in processors that control the satellites' position, among other functions. Four satellites have been deemed total losses, including PanAmSat Corp.'s $250 million Galaxy IV communications satellite, which provided service to tens of millions of pagers across North America. 2006: During a test, malfunctioning electronics inaccurately pointed the space shuttle Endeavour's engine, knocking the rocket's trajectory off-kilter. NASA engineers later found millions of tin whiskers, some measuring up to 25 millimeters. The pure-tin parts causing the problems had been approved by NASA before the space agency began requiring a small amount of lead in tin coatings. Sources: Published reports in technical journals and a database of publicly disclosed failures kept by researchers at NASA's Goddard Space Flight Center in Greenbelt, Md.

"There's a real loss of money because the plant is shut down and stays down, and it also presents a situation where workers are taught not to believe the alarms," Leidecker said. "Are you comfortable with that? I am not."

Searching for a solution
The military also isn't immune. Whisker-related malfunctions have been reported in the radar used aboard fighter jets, in the target-detection system of certain missiles, along with various unspecified problems in other parts of the U.S. military's missile programs.

Little is known about those failures, other than the part that failed and the cause. Most involve military secrets and are only known because they're revealed in technical forums by defense contractors, who incur heavy repair expenses for malfunctioning tin-whisker-infested equipment and are active in scientific circles looking for a fix that doesn't involve lead.

Tin whisker experts said the industry is working fast to come up with a lead-free solution. So far, other materials have shown to be effective in preventing tin whiskers, but not as powerfully as lead.

One promising remedy is tin-silver-copper solders, said George Galyon, a senior technical staff member at IBM Corp. However, Galyon noted that lead-free solders often require much higher temperatures, which can warp circuit boards and cause materials to degrade.

Despite the setbacks, he said the major players realize anti-lead laws give them no choice.

"It's whistling in the wind if you think we're turning this back," he said. "China's full-bent on it, the major markets are into it. The world flipped over in one fell swoop."

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