Mitigation of whisker growth by improving the creep properties of Sn coating with bismuth

Bismuth has been proved a promising lead-free element that can mitigate whisker growth on Sn coatings. It is generally believed that the formation of the equiaxed crystal structure of Sn–Bi coating helps to relax the compressive stress uniformly. In this study, the Sn–xBi coatings with the columnar...

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Bibliographic Details
Published in:Journal of materials science 2021-10, Vol.56 (30), p.17131-17145
Main Authors: Tian, Shuang, Cao, Ruihua, Fan, Qizhou, Zhou, Xingxing, Jia, Yongqiang, Zhou, Jian, Xue, Feng, Sun, ZhengMing
Format: Article
Language:English
Subjects:
Alloys
Aluminum
Bismuth
Characterization and Evaluation of Materials
Chemistry and Materials Science
Classical Mechanics
Coatings
Columnar structure
Compressive properties
Creep strength
Crystal structure
Crystallography and Scattering Methods
Crystals
Density
Diffusion coating
Dislocation mobility
Electronic Materials
Humidity
Indium
Intermetallic compounds
Laboratories
Lead free
Materials Science
Morphology
Nanoindentation
Nucleation
Polymer Sciences
Solid Mechanics
Solution strengthening
Structure
Substrates
Thermal cycling
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Summary:Bismuth has been proved a promising lead-free element that can mitigate whisker growth on Sn coatings. It is generally believed that the formation of the equiaxed crystal structure of Sn–Bi coating helps to relax the compressive stress uniformly. In this study, the Sn–xBi coatings with the columnar structure were prepared on the Al substrate. The addition of Bi promoted the whisker nucleation on the coatings but effectively mitigated the growth of whiskers. The density of geometrically necessary dislocations increased with the increase in Bi content, resulting in a high whisker density on the coatings. The reason why Bi inhibited whisker growth was proposed from the perspective of creep properties of the Sn–xBi coatings. The solution strengthening of Bi in Sn improved the creep resistance of the coatings. The creep stress exponent measured by nanoindentation indicated that the creep mechanism of the Sn–xBi coatings is dislocation climbing. The improvement of creep resistance led to insufficient dislocations in the coating leading to the limitation of Sn atomic diffusion for whisker growth. Graphical abstract
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-021-06410-2