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Whisker Formation on Electroplated Sn-Cu

Published

Author(s)

Maureen E. Williams, C E. Johnson, Kil-Won Moon, Gery R. Stafford, C A. Handwerker, William J. Boettinger

Abstract

The probability of whisker growth on as-deposited tin (Sn) electrodeposits has been measured as a function of copper (Cu superscript2+) addition to a commercial bright methanesulfonate electrolyte. Two substrate materials were used: free standing 250 um thick pyrophosphate Cu and 40 nm thick fine grain Cu evaporated on silicon (Si)(100) wafer. Deposits 3 um thick and 3 cm (superscript 2) in area with average composition between 0% and 1.6% mass fraction Cu were produced from Cu (superscript 2+) electrolyte concentrations between 0 and 25 x 10 (superscript 3) mol/L respectively at 60 mA/cm (superscrip 2) in a rotating disk geometry. Whisker defects were not observed on any of the pure Sn deposits regardless of substrate, nor were they present on Sn-Cu films deposited on the evaporated Cu on Si(100) substrate. However, whiskers started to grow after only 2 days on the Sn-Cu films deposited on the pyrophosphate Cu substrates. Detailed measurements over 12% of the deposit areas after one year of room temperature storage show a defect density of less than 5 /mm (superscript -2) for compositions below 0.25% mass fraction Cu, but a density of approximately 40 /mm(superscript 2) for compositions above 0.7% mass fraction Cu. The effect of Cu content and substrate material on the defect density is discussed.
Proceedings Title
SUR/FIN 2002 | | | The American Electroplaters and Surface Finishers Society, Inc.
Conference Dates
June 24-27, 2002
Conference Title
AESF SUR/FIN

Keywords

Cu concentration, defect density, electrodeposit, electrolyte concentrations, Sn whiskers, substrate

Citation

Williams, M. , Johnson, C. , Moon, K. , Stafford, G. , Handwerker, C. and Boettinger, W. (2002), Whisker Formation on Electroplated Sn-Cu, SUR/FIN 2002 | | | The American Electroplaters and Surface Finishers Society, Inc. (Accessed May 24, 2024)

Issues

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Created June 1, 2002, Updated February 17, 2017