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Microstructure evolution during electromigration between Sn–9Zn solder and Cu

Published online by Cambridge University Press:  03 March 2011

Shih-Ming Kuo*
Affiliation:
Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan 701, Republic of China
Kwang-Lung Lin
Affiliation:
Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan 701, Republic of China
*
a) Address all correspondence to this author. e-mail: smi@mail.mse.ncku.edu.tw
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Abstract

This study investigated the electromigration behavior between Cu and Sn–9Zn solder under a current density of 1.0 × 103 A/cm2 for up to 230 h. The experimental results indicated that Cu5Zn8 was formed at the interface between Cu and the cathode side of the Sn–9Zn solder as well as in the bulk near the anode. Consumption of Cu was also observed for the Cu plating on the cathode side and anodic side, but with less compound formation and Cu consumption at the anode. The intermetallic compound layer on the cathode side was always thicker than that on the anode side after the same current-stressing time. The effect of chemical potential overwhelms electromigration in inducing Zn diffusion when a counterflow of electrons and chemical potential gradient exists. Voids formed at the Cu5Zn8–solder interface inside the solder regardless of the direction of current flow.

Type
Articles
Copyright
Copyright © Materials Research Society 2007

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