Electronic waste poses a substantial threat to the environment as lead and other chemicals leach from computers, cell phones and other electronic devices being buried in landfills. From 1 July, the EU will strictly limit the amount of lead and other hazardous materials allowed in the circuitry of any electronic appliance sold. Given the global nature of the electronics industry, the European ban is in effect international in scope. The US Department of Energy’s Ames Laboratory has developed a lead-free solder which will help meet this challenge.
The circuit board of a computer only contains a tiny amount of lead solder holding components in place and linking circuitry. However, the massive amount of electronic equipment dumped daily means the total quantity is significant.
The challenge posed by developing a substitute to the traditional solder blend of 63 percent tin and 37 percent lead lies in delivering similar properties. It must melt and flow easily, set quickly, create a strong bond with good conductivity and be a eutectic alloy – one that acts like a pure metal with a single melting and solidification point.
The Ames Laboratory metallurgists settled on a tin-silver-copper alloy that offers a lower melting temperature and greater strength than other lead-free alternatives being considered. The solder technology was patented in 1996 and to date more than 60 companies worldwide have licensed Ames Lab’s lead-free solder, generating royalties in excess of $5 million.
The Ames Lab says that with the European directives pending and a similar commercial initiative in
One ongoing problem with lead-free alternatives now available is a tendency to get brittle over time after repeated or prolonged heating cycles. This becomes more of a factor as computer processor speeds increase, leading to a corresponding increase in the amount of heat they generate.
To combat this solder “aging” problem, the Ames Lab researchers have recently been experimenting with adding different substances to the formula, including silicon, titanium, chromium, manganese, nickel, zinc and germanium. So far, zinc has shown the best results in terms of retained ductility and strength after repeated heating and cooling.