Tin solders with whiskers ý changes in environmental compliance

PCB design engineers have been widely affected by new environmental compliance laws that, among other things, govern the use of lead in the manufacture of printed circuit boards. Engineers have had no choice but to switch from traditional tin-lead to lead-free solders � with often disastrous results.

Those who write the environmental compliance rulebooks say the switch can only be a good thing. It eliminates the risk of toxic lead components poisoning the environment by entering landfill sites, certainly � but there�s a pay-off. And the pay-off is this: there is a very good reason why lead is put into solder. Without it, you get a curious physical anomaly called tin whiskers �, which is lethal to PCB designs.

Tin whiskers are an FPGA designer�s nightmare. They form in a totally unpredictable fashion, leading to shorting and failure of electronic systems. Component manufacturers have been forced to put perfectly reliable semiconductors on the scrap heap, installing �same as� products, which, some say, are anything but. Lead-free solders could compromise the reputation of every engineering company involved with the manufacture and supply of commercial electronic components and systems.

The irony of the situation is that while environmental compliance legislation such as the RoHS and REACH laws were laid down to protect the public, they could actually pose a threat. A large number of the components affected are installed on machines with a long lifespan, such as aircraft, weaponry, medical equipment, shipping and oil rigs. Replace a dependable FPGA design on an airliner with one that may suddenly begin shorting out at 30,000 feet, and the implications are obvious.

The move from leaded to lead-free solders came about as a result of the EU RoHS (Reduction of Hazardous Substances) ruling which became law in 2006. Although it applied only to electronic products sold in the EU, it had enormous implications for the US � a major exporter of electronic components to Europe. Even companies restricting their sales to the home market were not exempt; North American states began implementing environmental compliance laws of their own, such as California�s Electronic Waste Recycling Act (EWRA), which came into force in January 2007. This closely followed the EU directive, but with narrower margins on the products affected, and covering only the four heavy metals banned by the EU, rather than, for example, fire-repellents. However, this still means leaded solders are banned. Several other states have implemented laws along RoHS lines � or are considering doing so.

One light on the horizon was that certain products � for example military and hospital equipment - were exempt from the EU ruling. However, this has recently been given a shake-up, and most companies producing PCB designs for the European market are playing safe and exclusively employing lead-free solders in order to attract business. This is worrying for American military establishments, who are dependent on commercial companies to produce fail-safe PCB designs for their mission-critical systems. US generals are already seeing the problems that sprouting tin whiskers can cause � so perhaps the White House will intervene.

If environmental compliance and PCB design is giving you problems, we at Enventure Technologies have a full range of solutions to help.

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