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Effect of Substrate Composition on Whisker Growth in Sn Coatings

Jagtap, Piyush and Narayan, P Ramesh and Kumar, Praveen (2018) Effect of Substrate Composition on Whisker Growth in Sn Coatings. In: JOURNAL OF ELECTRONIC MATERIALS, 47 (7). pp. 4177-4189.

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Official URL: https://dx.doi.org/10.1007/s11664-018-6275-9


Whisker growth was studied in Sn coatings deposited on three different substrates, namely pure Cu, brass (Cu-35 wt.% Zn) and pure Ni. Additionally, the effect of a Ni under-layer (electro- or sputter-deposited and placed between the Sn coating and the substrate) on whisker growth was also studied. It was observed that the substrate composition and placement of under-layers significantly affected the whisker growth in Sn coating by altering the growth rate and the morphology of the interfacial intermetallic compounds (IMC). Whisker propensity was the highest when Sn coatings were deposited directly on the brass substrate, while it was completely inhibited for at least a year when the coatings were deposited on either pure Ni or brass with a Ni under-layer. Bulk and surface stress measurements revealed that the surface of the Sn coatings on Ni, irrespective of whether it was in bulk or under-layer form, remained more compressive as compared to the bulk, throughout the observation period. Therefore, a negative out-of-plane stress gradient, which is crucial for whisker growth, could never be established in these samples. Interestingly, a phenomenon of through-thickness columnar voiding (reverse of whiskering) was observed in the Sn coatings deposited on Ni. The origin of this phenomenon is discussed.

Item Type: Journal Article
Publisher: SPRINGER, 233 SPRING ST, NEW YORK, NY 10013 USA
Additional Information: Copy right of this article belong to SPRINGER, 233 SPRING ST, NEW YORK, NY 10013 USA
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 25 Jun 2018 15:53
Last Modified: 25 Jun 2018 15:53
URI: http://eprints.iisc.ac.in/id/eprint/60075

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