Tin whiskers continue to be a mystery and a serious problem. Research continues on ways to reduce tin whisker impact, the following is the latest that we’ve picked up on the subject.
IPC Association Connecting Electronics Industries
IPC Tin Whiskers Conference in Schaumburg, Ill. Dec. 6-7
The conference theme is “Practical Perspectives,” which focuses attention on understanding what causes tin whiskers and ways to mitigate their impact when they do occur.
This project will provide data and materials measurements necessary to improve the reliability of solder interconnects degraded by the switch to lead-free technology. In particular, the state of compressive stress and the localized creep response (whisker growth) of tin-based lead-free electrodeposits are being measured. Industry will use these measurement methods and data to modify processing conditions to prevent the formation of tin-whiskers.
BY MELISSA GRUPEN-SHEMANSKY
Experimental findings indicate that current standard life testing may miss the issue. In evaluation, prospective lead-free finishes must be subjected to board-level reflow conditions as a preparatory step to accelerated life testing or reliability testing. To ensure backward compatibility, it is advised that reliability testing be conducted with both sets of solder preconditioning exposure. Thorough observations show that tin whiskers may grow, even in the Sn/Pb case under specific application conditions. Experimental evidence, however, indicates that a barrier metal such as nickel deposited between the copper lead frame and the matte-tin finish can significantly retard tin whisker formation — even eliminate it.
Tin whiskers spontaneously grow from electrodeposited Sn-containing films, but the growth mechanism is not well understood. The current tin whisker testing outlined in JEDEC22A121 fails to provide information on film properties necessary to predict the propensity of a film to whisker. Evaluating local grain structures, grain boundary mobility and grain orientations around whiskers and correlating these film properties to whisker growth provide valuable information regarding the propensity of a film to whisker.
Company’s research finds tin-nickel combination in semiconductor packaging mitigates ‘tin whisker’ problem; improves long-term reliability of lead-free devices.