Engineers at Agere Systems (Allentown, PA) have developed an effective packaging "mix" that improves the long-term reliability of lead-free semiconductor devices. The company's tin-nickel formula eliminates hazardous lead from the packaging process and avoids a potentially devastating flaw in bringing to market lead-free packages.
The European Union (EU) has pushed for lead-free semiconductor packaging within approximately the next year, but such packaging will also be required for nearly every global semiconductor market (an approximate $166 billion industry). Most current semiconductor packages consist of a layer of tin and lead over copper. Lead-free alternatives use a combination of just tin over copper but are processed at temperatures significantly hotter than packages containing lead. While experimenting with tin-over-copper solutions, Agere's engineers have learned that many commercial tin-over-copper packaging solutions form "whiskers" that can create electrical shorts or break off and cause other system failures. Three tests have been proposed by the JEDEC Solid State Technology Association with guidance from the National Electronics Manufacturing Initiative (NEMI) to more effectively screen for the susceptibility to tin whiskers. Of the three tests, two display no discernable difference between matte-tin on copper and nickel undercoated matte-tin on copper. Agere has demonstrated that a layer of nickel between the copper and the layer of tin provides dramatic improvements in the third test using the real-world customer environment.
According to Dr. Melissa Grupen-Shemansky, Agere's director of packaging and interconnect technology, "we are unveiling these findings in hopes that the electronics industry will adopt our approach to avoid the problems Agere observed in currently accepted copper and tin packages." She added that "we evaluated multiple options being used by other semiconductor companies in a scientifically valid study over a prolonged timeframe and found that Agere's tin-nickel-copper combination resolved the tin whisker problem seen after high-temperature, high-humidity storage." Findings of the company's research are available in a white paper for free download from the company's web site.