Journal of Electronic Materials

, Volume 45, Issue 1, pp 21–29 | Cite as

Quantifying the Rates of Sn Whisker Growth and Plastic Strain Relaxation Using Thermally-Induced Stress



Whiskers and hillocks that grow out of Sn-based coatings are a critical reliability issue in Pb-free electronics. Although their growth is widely regarded as a stress-relaxation mechanism, quantitative understanding of the relationship between the stress, growth kinetics, and strain relaxation is still lacking. In this work, the well-controlled strain induced by thermal-expansion mismatch was used to study the whiskering behavior of electroplated Sn films. Stress was quantified by monitoring wafer-curvature and the density of whiskers and hillocks was measured simultaneously by use of optical microscopy. Evolution of the volume of individual features was also measured by scanning electron microscopy after different periods of heating. The measurements were used to develop a model for temperature-dependent and stress-dependent growth kinetics of whiskers and hillocks and to determine the amount of strain relaxation which occurs as a result of their formation.


Tin whiskering thermal cycling stress relaxation grain boundary diffusion 


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Copyright information

© The Minerals, Metals & Materials Society 2015

Authors and Affiliations

  1. 1.School of EngineeringBrown UniversityProvidenceUSA

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