A UNIQUE TIN WHISKER GROWTH STUDY OF NINE LEAD FREE ALLOYS

摘要

Tin whiskers are of great concern for long term reliability of lead free assemblies. Many theories and tests have been established to filter out potential whisker growth and to include similar growth environments for tin whisker, while also concentrating on tin plating and not alloys. Several groups and organizations including iNEMI and NASA have in depth studies of tin whiskers. The International Electronics Manufacturing Initiative (iNEMI) states that they (iNEMI) have "found it possible to get conflicting data on the same finishes and also on the same mitigation practices from different users". This is very typical of tin whiskers. Conformal coating, annealing (reflowing tin) at 150°C have all been suggested to mitigate tin whisker growth. One point that is not tested in all the studies reviewed has been mechanically stressing the finish coat. In prior studies reviewed, there was similar testing running thermal cycling -40 or -55 to +85, ambient soak 30c 60 Rh, and high temperature soak 60°C 87 RH. All the studies tests were on as processed finishes, or in an annealed state. Some tests have been conformal coated to mitigate whisker growth. Additionally, all tests have looked at surface finishes for lead coatings.