Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-05T11:14:22.726Z Has data issue: false hasContentIssue false

Whisker Formation in Sn Coatings on Cu

Published online by Cambridge University Press:  01 February 2011

Eric Chason
Affiliation:
Division of Engineering, Brown University, Providence, RI 02912
Lucine Reinbold
Affiliation:
Division of Engineering, Brown University, Providence, RI 02912
Sharvan Kumar
Affiliation:
Division of Engineering, Brown University, Providence, RI 02912
Get access

Abstract

In the microelectronics industry, Sn is often electroplated as a protective layer on Cu conductors. Pure Sn layers on Cu develop whiskers that can cause component failures and have even been implicated in the loss of several satellites. Alloying Sn with Pb suppresses whisker formation, but the push towards Pb-free processing will make this unacceptable in the future. To understand the driving forces and mechanisms of whisker formation on pure Sn, we are measuring the kinetics of stress evolution and intermetallic formation in Sn/Cu layers. By using thin films of Sn and Cu, we can monitor the stress evolution in real time using wafer-curvature based techniques. Preliminary results of stress evolution in vapor-deposited films are presented showing the evolution of tensile stress in the Cu layers and compressive stress in the Sn layers.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

[1] Cobb, H.L., “Cadmium Whiskers”, Monthly Rev. Am. Electroplaters Soc., 33 (28): pp. 2830 (1946).Google Scholar
[2] Brusse, J., “Tin Whiskers: Revisiting an Old Problem”, NASA's EEE Links Newsletter, 4 (4), pp. 57 (December 1998).Google Scholar
[3] Silverstein, S., “Reasons for Failure Lost with Galaxy 4”, Space News, pp. 3, 20 (August 17–23, 1998).Google Scholar
[4] FDA Website: “Tin Whiskers”. www.fda.gov/ora/inspect_ref/itg/itg42.html Google Scholar
[5] NASA Goddard Space Flight Center Tin Whisker Experimentation Page, www.nepp.nasa.gov/whisker/experiment/index.html Google Scholar
[6] Sabbagh, N.A.J., McQueen, H.J., “Tin Whiskers: Causes and Remedies”, Metal Finishing, p. 27 (March 1975).Google Scholar
[7] Cheng, Y.T., Weiner, A.M., Wong, C.A., Balogh, M.P., and Lukitsch, M.J.. “Stress-Induced Growth of Bismuth Nanowires”, Applied Physics Letters, 8 (17), pp. 32483250 (October 2002).Google Scholar
[8] Fisher, R.M., Darken, L.S., and Carroll, K.G., “Accelerated Growth of Tin Whiskers”, Acta Metallurgica. 2 (3): pp. 368372 (May 1954).Google Scholar
[9] Lee, B.Z. and Lee, D.N., “Spontaneous Growth Mechanism of Tin Whiskers”, Acta Metallurgica, 46 (10): pp. 37013714 (1998).Google Scholar
[10] Tu, K.N., “Interdiffusion and Reaction in Bimetallic Cu-Sn Thin films”, Acta Metallurgica, 21 (4): pp. 347354 (1973).Google Scholar
[11] Tu, K.N., “Irreversible Processes of Spontaneous Whisker Growth in Bimetallic Cu-Sn Thin Film Reactions”, Phys. Rev. B, 49, 2030 (1994).Google Scholar
[12] Eshelby, J.D., “A Tentative Theory of Metallic Whisker Growth”, Phys. Rev., 91: pp. 755756 (1953).Google Scholar
[13] Barsoum, M.W., Hoffman, E.N., Doherty, R.D., Gupta, S., Zavaliangos, A., “Driving Force and Mechanism for Spontaneous Metal Whisker Formation”, Phys. Rev. Letters, 93 (20), (November 2004).Google Scholar
[14] UnpublishedGoogle Scholar
[15] Chason, E. and Floro, J.A., “Measurements of Stress Evolution during Thin Film Growth”, Mater. Res. Symp. Proc. 428, 499 (1996).Google Scholar
[16] Chason, E., Reinbold, L., Kumar, S., in preparation.Google Scholar