On April 17 2005, the Millstone nuclear generating plant in Connecticut shut down when a circuit board monitoring a steam pressure line short-circuited. In 2006, a huge batch of Swatch watches, made by the eponymous Swiss company, were recalled at an estimated cost of $1bn (£500m). In both cases, “tin whiskers” - microscopic growths of the metal from soldering points on a circuit board - were blamed.

It’s not the first time these mysterious growths have been blamed for electronics failures. In fact, they’ve been known about since the 1940s.

The solution to “whiskering”? Mix lead into the solder, as was done from the 1950s. But since 2006, lead has been banned from solder in the European Union. While environmental groups applauded the move, without lead to tame it, tin behaves oddly on circuit boards. Left alone, tin plating spontaneously generates microscopic shreds of metal - less than one-tenth as wide as a human hair - which push up from the base. If they grow far enough to touch another current-carrying location, they’ll cause a short that can wreck the equipment while leaving barely any trace.

Critics cite reports that solder substitutes - pure tin,  tin-silver-copper - simply cannot match the lead mixture for reliability, coverage and cost. Therefore, the US military, Nasa and medical and high-level research equipment are exempt from what authorities view as untrustworthy commercial components.

Double standards

This means the unwitting consumer bears the cost of the experimental burden.  

The question is, are the products we are using now being affected by tin whiskers? When your computer stops working, could that be the cause? I rang eight manufacturers to enquire about encounters with whiskers. Apple was the only manufacturer to respond, stating that the company “has been using lead-free solders since 2004 without issue”.

Overall, was it sensible to go lead-free? “I would say no,” says Bob Willis, an opponent of the EU directive and technical director for the SMART Group in the UK. In fact, critics argue that substitutes are more toxic and energy-wasteful than the lead they replace.

The National Electronics Manufacturing Centre for Excellence, sponsored by the US Navy, did find that modifying the temperatures at which soldered items are bathed and stored diminished whiskering, but still recommends the “use of lead in conflict with future industrial practice.”

Perhaps a reliable lead-free process will be conjured up soon. But this debate among professionals looks like it needs to come out in the open.