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Microstructure evolution during electromigration in eutectic SnPb solder bumps

Published online by Cambridge University Press:  03 March 2011

C.M. Lu ,
T.L. Shao ,
C.J. Yang  and
Chih Chen
C.M. Lu
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
T.L. Shao
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
C.J. Yang
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
Chih Chen*
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 300 Taiwan, Republic of China
*
a)Address all correspondence to this author. e-mail: chih@cc.nctu.edu.tw
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Abstract

A technique has been developed to facilitate analysis of the microstructural evolution of solder bumps after current stressing. Eutectic SnPb solders were connected to under-bump metallization (UBM) of Ti/Cr-Cu/Cu and pad metallization of Cu/Ni/Au. It was found that the Cu6Sn5 compounds on the cathode/chip side dissolved after the current stressing by 5 × 103 A/cm2 at 150 °C for 218 h. However, on the anode/chip side, they were transformed into (Nix,Cu1-x)3Sn4 in the center region of the UBM, and they were converted into (Cuy,Ni1-y)6Sn5 on the periphery of the UBM. For both cathode/substrate and anode/substrate ends, (Cuy,Ni1-y)6Sn5 compounds were transformed into (Nix,Cu1-x)3Sn4. In addition, the bumps failed at cathode/chip end due to serious damage of the UBM and the Al pad. A failure mechanism induced by electromigration is proposed in this paper.

Keywords

Phase transformationPackagingElectromigration
Type
Articles
Information
Journal of Materials Research , Volume 19 , Issue 8 , August 2004 , pp. 2394 - 2401
Copyright
Copyright © Materials Research Society 2004

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References

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