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.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
L.F. Miller: Controlled collapse reflow chip joining. IBM J. Res. Develop. 13, 239 (1969).
K.N. Tu and K. Zeng: Tin-lead (SnPb) solder reaction in flip chip technology. Mater. Sci. Eng. R 34, 1 (2001).
T.Y. Lee, K.N. Tu, S.M. Kuo and D.R. Fear: Electromigration of eutectic SnPb solder interconnects for flip chip technology. J. Appl. Phys. 89, 3189 (2001).
E.C.C. Yeh, W.J. Choi and K.N. Tu: Current-crowding-induced electromigration failure in flip chip solder joints. Appl. Phys. Lett. 80, 580 (2002).
Y.C. Hu, Y.H. Lin, C.R. Kao and K.N. Tu: Electromigration failure in flip chip solder joints due to rapid dissolution of copper. J. Mater. Res. 18, 2544 (2003).
C.Y. Liu, C. Chen, C.N. Liao and K.N. Tu: Microstructure-electromigration correlation in a thin stripe of eutectic SnPb solder stressed between Cu electrodes. Appl. Phys. Lett. 75, 58 (1999).
Q.T. Huynh, C.Y. Liu, C.i. Chen and K.N. Tu: Electromigration in eutectic SnPb solder lines. J. Appl. Phys. 89, 4332 (2001).
Y.H. Lin, Y.C. Hu, C.M. Tsai, C.R. Kao and K.N. Tu: In situ observation of the void formation-and-propagation mechanism in solder joints under current-stressing. Acta Mater. 53, 2029 (2005).
G.A. Rinne: Issues in acceleratedelectromigration of solder bumps. Microelectron. Reliab. 43, 1975 (2003).
D. Gupta, K. Vieregge and W. Gust: Interface diffusion in eutectic Pb–Sn solder. Acta Mater. 47, 5 (1999).
M.C. Flemings: Solidification Processing (McGraw-Hill, New York, 1974), p. 101.
P.D. Adams and J.S.L. Leach: Resistivity of liquid lead-tin alloys. Phys. Rev. 156, 178 (1967).
K.N. Tu, J.W. Mayer and L.C. Feldman: Electronic Thin Film Science (Macmillan, New York, 1992), pp. 355–367.
K.N. Tu, T.Y. Lee, J.W. Jang, L. Li, D.R. Frear, K. Zeng and J.K. Kivilahti: Wetting reaction versus solid state aging of eutectic SnPb on Cu. J. Appl. Phys. 89, 4843 (2001).
H.B. Huntington: Electromigration in metals, in Diffusion in Solids: Recent Developments, edited by A.S. Nowick and J.J. Burton (Academic, New York, 1975), p. 303.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Liao, CN., Chung, CP. & Chen, WT. Electromigration-induced Pb segregation in eutectic Sn–Pb molten solder. Journal of Materials Research 20, 3425–3430 (2005). https://doi.org/10.1557/jmr.2005.0420
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1557/jmr.2005.0420