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Electromigration-induced Pb segregation in eutectic Sn–Pb molten solder

Published online by Cambridge University Press:  01 December 2005

Chien-Neng Liao*
Affiliation:
Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan, Republic of China
Chien-Ping Chung
Affiliation:
Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan, Republic of China
Wen-Tai Chen
Affiliation:
Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan, Republic of China
*
a)Address all correspondence to this author. e-mail: cnliao@mx.nthu.edu.tw
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Abstract

Preferential Pb electromigration (EM) in eutectic Sn–Pb molten solder was characterized by examining Pb segregation at the anode of the solder on a thin stripe of Cu metallization. The eutectic Sn–Pb molten solder stressed at current densities of 103−104 A/cm2 was found to form columnar Pb-rich phase (α) at the anode side and Pb deficiency at the cathode side. The columnar α-phase grew in the direction parallel to the electron flow, and its growth rate increased proportionally with the current density applied through the molten solder. By measuring the growth rate of the columnar α-phase, we calculated the Pb effective charge number of EM in the eutectic Sn–Pb molten solder to be 2.7, which is one order of magnitude lower than the reported value of 47 for self-electromigration in bulk Pb. The mechanism for the EM-induced Pb segregation in Sn–Pb solder was also explored.

Type
Articles
Copyright
Copyright © Materials Research Society 2005

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References

REFERENCES

1.Miller, L.F.: Controlled collapse reflow chip joining. IBM J. Res. Develop. 13, 239 (1969).CrossRefGoogle Scholar
2.Tu, K.N. and Zeng, K.: Tin-lead (SnPb) solder reaction in flip chip technology. Mater. Sci. Eng. R 34, 1 (2001).CrossRefGoogle Scholar
3.Lee, T.Y., Tu, K.N., Kuo, S.M. and Fear, D.R.: Electromigration of eutectic SnPb solder interconnects for flip chip technology. J. Appl. Phys. 89, 3189 (2001).CrossRefGoogle Scholar
4.Yeh, E.C.C., Choi, W.J. and Tu, K.N.: Current-crowding-induced electromigration failure in flip chip solder joints. Appl. Phys. Lett. 80, 580 (2002).CrossRefGoogle Scholar
5.Hu, Y.C., Lin, Y.H., Kao, C.R. and Tu, K.N.: Electromigration failure in flip chip solder joints due to rapid dissolution of copper. J. Mater. Res. 18, 2544 (2003).CrossRefGoogle Scholar
6.Liu, C.Y., Chen, C., Liao, C.N. and Tu, K.N.: Microstructure-electromigration correlation in a thin stripe of eutectic SnPb solder stressed between Cu electrodes. Appl. Phys. Lett. 75, 58 (1999).CrossRefGoogle Scholar
7.Huynh, Q.T., Liu, C.Y., Chen, Chih and Tu, K.N.: Electromigration in eutectic SnPb solder lines. J. Appl. Phys. 89, 4332 (2001).CrossRefGoogle Scholar
8.Lin, Y.H., Hu, Y.C., Tsai, C.M., Kao, C.R. and Tu, K.N.: In situ observation of the void formation-and-propagation mechanism in solder joints under current-stressing. Acta Mater. 53, 2029 (2005).CrossRefGoogle Scholar
9.Rinne, G.A.: Issues in acceleratedelectromigration of solder bumps. Microelectron. Reliab. 43, 1975 (2003).CrossRefGoogle Scholar
10.Gupta, D., Vieregge, K. and Gust, W.: Interface diffusion in eutectic Pb–Sn solder. Acta Mater. 47, 5 (1999).CrossRefGoogle Scholar
11.Flemings, M.C.: Solidification Processing (McGraw-Hill, New York, 1974), p. 101.Google Scholar
12.Adams, P.D. and Leach, J.S.L.: Resistivity of liquid lead-tin alloys. Phys. Rev. 156, 178 (1967).CrossRefGoogle Scholar
13.Tu, K.N., Mayer, J.W. and Feldman, L.C.: Electronic Thin Film Science (Macmillan, New York, 1992), pp. 355367.Google Scholar
14.Tu, K.N., Lee, T.Y., Jang, J.W., Li, L., Frear, D.R., Zeng, K. and Kivilahti, J.K.: Wetting reaction versus solid state aging of eutectic SnPb on Cu. J. Appl. Phys. 89, 4843 (2001).CrossRefGoogle Scholar
15.Huntington, H.B.: Electromigration in metals, in Diffusion in Solids: Recent Developments, edited by Nowick, A.S. and Burton, J.J. (Academic, New York, 1975), p. 303.CrossRefGoogle Scholar