The statistics of tin whisker diameters versus the underlying film grains

Abstract

We compare the statistics of tin whisker diameters to that of the underlying film grains. Both are well approximated by the lognormal distributions. However, the parameters of those distributions can be rather different, not confirming the assumption that each whisker grows from a single grain. We conclude that several adjacent grains with similar crystal orientations can contribute to a whisker development. Our observations are consistent with the recent theory of multi-filament whisker structure. A modification of the particle size log-normal distribution is developed clarifying the nature of its dispersion.