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Microstructural Evolution During Electromigration in Eutectic SnAg Solder Bumps

Published online by Cambridge University Press:  03 March 2011

Y.H. Chen ,
T.L. Shao ,
P.C. Liu ,
Chih Chen  and
T. Chou
Y.H. Chen
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 30050, Taiwan
T.L. Shao
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 30050, Taiwan
P.C. Liu
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 30050, Taiwan
Chih Chen*
Affiliation:
National Chiao Tung University, Department of Material Science & Engineering, Hsin-chu 30050, Taiwan
T. Chou
Affiliation:
Macronix International Corporation, Ltd., Hsin-chu, 30078, Taiwan
*
a) Address correspondence to this author. e-mail: chih@cc.nctu.edu.tw
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Abstract

Microstructural changes induced by electromigration were studied in eutectic SnAg solder bumps jointed to under-bump metallization (UBM) of Ti/Cr–Cu/Cu and pad metallization of Cu/Ni/Au. Intermetallic compounds (IMCs) and phase transformations were observed during a current stress of 1 × 104 A/cm2 at 150 °C. On the cathode/substrate side, some of the (Cuy,Ni1−y)6Sn5 transformed into (Nix,Cu1−x)3Sn4 due to depletion of Cu atoms caused by the electron flow. It is found that both the cathode/chip and anode/chip ends could be failure sites. On the cathode/chip side, the UBM dissolved after current stressing for 22 h, and failure may occur due to depletion of solder. On the anode/chip side, a large amount of (Cuy,Ni1−y)6Sn5 or (Nix,Cu1−x)3Sn4 IMCs grew at the low-current-density area due to the migration of Ni and Cu atoms from the substrate side, which may be responsible for the electromigration failure at this end.

Keywords

DiffusionElectromigrationPackaging
Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 9 , September 2005 , pp. 2432 - 2442
Copyright
Copyright © Materials Research Society 2005

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