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Reliability analysis of Au–Sn flip-chip solder bump fabricated by co-electroplating

Published online by Cambridge University Press:  03 March 2011

Jeong-Won Yoon ,
Hyun-Suk Chun  and
Seung-Boo Jung
Jeong-Won Yoon
Affiliation:
School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Korea
Hyun-Suk Chun
Affiliation:
School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Korea
Seung-Boo Jung*
Affiliation:
School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Korea
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

In this study, we fabricated eutectic Au–Sn (Au–20 wt% Sn) flip-chip solder bumps from a single electroplating bath. After reflowing, the average diameter of the solder bump was approximately 80 μm. The (Ni,Au)3Sn2 phase was initially formed when the liquid Au–Sn solder reacted with the Ni UBM (under bump metallization). After aging at 150 °C, the (Ni,Au)3Sn2 intermetallic compound (IMC), which formed at the interface during reflow, was fully transformed into the (Au,Ni)Sn IMC due to the restricted supply of Ni atoms from the UBM to the interface. On the other hand, after aging at 250 °C for 1000 h, two IMC layers, (Au,Ni)Sn and (Ni,Au)3Sn2, were formed at the interface. The lower (Ni,Au)3Sn2 phase was formed when the (Au,Ni)Sn phase reacted with the Ni UBM. The interfacial (Au,Ni)Sn IMC grew with the preferential consumption of the available δ-phase in the solder matrix. Eventually, the ζ-phase covered most of the interfacial layer. In the bump shear tests, the Au–Sn/Ni joint aged at 150 °C fractured through the bulk of the solder, confirming the mechanical reliability of the interface. In contrast, the Au–Sn/Ni joint aged at 250 °C fractured along the interface, thereby demonstrating brittle failure, possibly a result of the brittle IMC layer at the interface.

Keywords

JoiningMicroelectronicsPackaging
Type
Articles
Information
Journal of Materials Research , Volume 22 , Issue 5 , May 2007 , pp. 1219 - 1229
Copyright
Copyright © Materials Research Society 2007

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