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Title: An investigation into zinc diffusion and tin whisker growth for electroplated tin deposits on brass
Authors: Ashworth, Mark A.
Wilcox, G.D.
Higginson, Rebecca L.
Heath, Richard J.
Liu, Changqing
Keywords: Tin
Whisker growth
Issue Date: 2014
Publisher: Springer / © The Minerals, Metals & Materials Society
Citation: ASHWORTH, M.A. ... et al, 2014. An investigation into zinc diffusion and tin whisker growth for electroplated tin deposits on brass. Journal of Electronic Materials, 43 (4), pp. 1005 - 1016.
Abstract: It is widely documented that whisker growth is more rapid for tin deposits on brass compared with deposits produced on other substrate materials, such as copper. As a result, studies investigating the effect of process variables on tin whisker formation are often conducted on brass substrates to take advantage of the increased whisker growth rates. Although it has been understood since the 1960s that the increased whisker growth results from zinc diffusion, to date there has not been any detailed analysis of the zinc/zinc oxide distribution at the surface of the tin deposit. Using a commercial bright tin electroplating bath, the formation of zinc oxide at the surface of tin deposits on brass has been investigated. Analyses show that zinc oxide is present on the surface of the deposit within 1 day of electroplating. During storage at room temperature, a network of zinc oxide is formed at the surface grain boundaries, the extent of which increases with time. The critical role that zinc surface diffusion plays in whisker growth for tin deposits on brass has been demonstrated by electrochemical oxidation of the tin shortly after electroplating. This develops a tin oxide film that is thicker than the native air-formed oxide and subsequently serves as a diffusion barrier to zinc surface diffusion, thereby mitigating whisker growth.
Description: This article is published in the serial Journal of Electronic Materials [Springer / © The Minerals, Metals & Materials Society]. The final publication is available at Springer via http://dx.doi.org/10.1007/s11664-014-2983-y.
Sponsor: The authors would like to thank the UK EPSRC Innovative Electronics Manufacturing Research Centre for funding this research through the WHISKERMIT programme at Loughborough University. We would also like to acknowledge the contribution to the programme from our industrial collaborators; MacDermid plc, Rolls-Royce plc, Aero Engine Controls, NPL, MBDA UK Ltd., Park Air Systems Ltd. and Gen3 Systems.
Version: Accepted for publication
DOI: 10.1007/s11664-014-2983-y
URI: https://dspace.lboro.ac.uk/2134/16991
Publisher Link: http://dx.doi.org/10.1007/s11664-014-2983-y
ISSN: 1543-186X
Appears in Collections:Published Articles (Materials)

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