RoHS, WEE, Pb-Free, Lead-Free, all buzzwords in this era of ultra green sensitivities. Many obstacles have had to be overcome on the path to compliance, not the least of which was an entire new line of processing equipment and processes (reflow, assembly, rework, materials development, etc.) that is necessary to work with the higher temperatures required by lead-free solders. One problem looms as a potential major issue in years to come: Tin whiskers.

Tin whiskers are the crystalline tendrils that "grow" out of the relatively high concentrations of tin in the solder alloy. NASA experimented with tin-based solders back in the 1970s for weight savings over lead-based solders. Everyone was excited, until suddenly for no apparent reason, short circuits were being discovered. Failure analysis determined that what infamously became known as "tin whiskers" were developing and were actually growing between different nodes in electrical circuit boards and connectors, and even inside integrated circuit packages.

What was intended to be a panacea for the aerospace program circuit weight reduction efforts became a nightmare since a lot of equipment was deployed before the phenomenon was discovered.

Now, thirty years later, the electronics industry is re-visiting tin-based solders in order to comply with the RoHS directives. Materials sciences and metallurgy has advanced considerably since the early tin whiskers problems, so hopefully most - preferably all - of the problems have been solved. But, don't be too sure. Not that long ago articles and letters to editors were being written by old-timers who "were there" to remind the new crop of developers about their experiences. More than a few appeared to have been previously unaware of this lurking tin whiskers menace. Yikes.

Fortunately for most of the early adopter manufacturers, we do not expect our consumer devices to last more than two or three years anyway and are never surprised if they just stop working for no apparent reason - we simply go buy a newer model that we really wanted an excuse to buy anyway. In a perverse kind of way, tin whiskers are good for the consumer market.