1. Observed Whisker Growth Statistics
28 Days of Incubation
Observations:
Large whisker densities are observed for both compressive and tensile net stress states. This is in agreement with earlier work in our laboratory with “imposed” stress states formed by deliberate coupon curvature.
There are whiskers observed for the “zero” stress state, but the density is relatively lower.
As incubation time increases, the largest whisker density is observed for the compressive stress state.
Whisker observations here agree with the very early experiments in our laboratory which established the validity of the Hoffman approach to the whisker growth issue.
Sn Film State
Whisker Density
(cm-2)
Average Whisker Length (µm)
Comp
4,585
4.3
None
786
2.3
Tensile
7,991
16.5
96 Days of Incubation
Longest whisker from tensile stressed film: 338 µm.
Sn Film State
Whisker Density
(cm-2)
Average Whisker Length (µm)
Comp
15,850
5.3
None
4,061
3.4
Tensile
12,051
26.8
Large average whisker length

2. Whisker Micrographs Compressive None Tensile 9380x 16900x 3260x 5910x