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Effect of direct current and pulse plating parameters on tin whisker growth from tin electrodeposits on copper and brass substrates

journal contribution
posted on 20.11.2013, 13:58 by Mark Ashworth, Geoffrey Wilcox, Rebecca Higginson, Richard Heath, Changqing Liu
Electroplated tin finishes are widely utilised in the electronics industry due to their advantageous properties such as excellent solderability, electrical conductivity and corrosion resistance. However, the spontaneous growth of tin whiskers during service can be highly deleterious, resulting in localised electrical shorting or other harmful effects. The formation of tin whiskers, widely accepted as resulting from the formation of compressive stresses within the electrodeposit, has been responsible for a wide range of equipment failures in consumer products, safety critical industrial and aerospace based applications. The numbers of failures associated with tin whiskers is likely to increase in the future following legislation banning the use of lead in electronics, the latter when alloyed with tin, being an acknowledged tin whisker mitigator. Using a bright tin electroplating bath, the effect of process parameters on the characteristic structure of the deposit has been evaluated for deposition onto both brass and copper substrates. The effect on whisker growth rate of process variables, such as current density and deposit thickness, has been evaluated. In addition, the effect of pulse plating on subsequent whisker growth rates has also been investigated, particularly by varying duty cycle and pulse frequency. Whisker growth has been investigated under both ambient conditions and also using elevated temperature and humidity to accelerate the growth of whiskers. Studies have shown that whisker formation is strongly influenced by pulse plating parameters. Furthermore, increasing both current density and thickness of the deposit reduce whisker growth rates. It is also observed that whisker formation is greatly accelerated on brass substrates compared with copper. The basis for this observation is explained.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Citation

ASHWORTH, M.A. ... et al., 2013. Effect of direct current and pulse plating parameters on tin whisker growth from tin electrodeposits on copper and brass substrates. Transactions of the Institute of Metal Finishing, 91 (5), pp. 261 - 268.

Publisher

© Institute of Materials Finishing. Published by Maney on behalf of the Institute

Version

AM (Accepted Manuscript)

Publication date

2013

Notes

This article was published in the Transactions of the Institute of Metal Finishing [© Institute of Materials Finishing] and the definitive version is available at: http://dx.doi.org/10.1179/0020296713Z.000000000116

ISSN

0020-2967

Language

en

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