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In Situ Heating Transmission Electron Microscopy Observation of Nanoeutectic Lamellar Structure in Sn–Ag–Cu Alloy on Au Under-Bump Metallization

Published online by Cambridge University Press:  06 August 2013

Jong-Hyun Seo ,
Sang-Won Yoon ,
Kyou-Hyun Kim ,
Hye-Jung Chang ,
Kon-Bae Lee ,
Tae-Yeon Seong ,
Eric Fleury  and
Jae-Pyoung Ahn
Jong-Hyun Seo
Affiliation:
Advanced Analysis Center, Korea Institute of Science & Technology (KIST), Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of Korea Department of Materials Science and Engineering, Korea University, Anam-dong 5-1, Seongbuk-gu, Seoul 136-701, Republic of Korea
Sang-Won Yoon
Affiliation:
Electronic Materials Lab, Samsung Corning Precision Materials 644-1, Jinpyeong-dong, Gumi-City, Gyeongsangbuk-do 730-735, Republic of Korea
Kyou-Hyun Kim
Affiliation:
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL 61801, USA
Hye-Jung Chang
Affiliation:
Advanced Analysis Center, Korea Institute of Science & Technology (KIST), Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of Korea
Kon-Bae Lee
Affiliation:
School of Advanced Materials Engineering, Kookmin University, Seoul 136-702, Republic of Korea
Tae-Yeon Seong
Affiliation:
Department of Materials Science and Engineering, Korea University, Anam-dong 5-1, Seongbuk-gu, Seoul 136-701, Republic of Korea
Eric Fleury
Affiliation:
High Temperature Energy Materials Center, Korea Institute of Science & Technology (KIST), Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of Korea
Jae-Pyoung Ahn*
Affiliation:
Advanced Analysis Center, Korea Institute of Science & Technology (KIST), Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of Korea
*
*Corresponding author. E-mail:jpahn@kist.re.kr
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Abstract

We investigated the microstructural evolution of Sn96.4Ag2.8Cu0.8 solder through in situ heating transmission electron microscopy observations. As-soldered bump consisted of seven layers, containing the nanoeutectic lamella structure of AuSn and Au5Sn phases, and the polygonal grains of AuSn2 and AuSn4, on Au-plated Cu bond pads. Here, we found that there are two nanoeutectic lamellar layers with lamella spacing of 40 and 250 nm. By in situ heating above 140°C, the nanoeutectic lamella of AuSn and Au5Sn was decomposed with structural degradation by sphering and coarsening processes of the lamellar interface. At the third layer neighboring to the lamella layer, on the other hand, Au5Sn particles with a zig-zag shape in AuSn matrix became spherical and were finally dissipated in order to minimize the interface energy between two phases. In the other layers except both lamella layers, polycrystal grains of AuSn2 and AuSn4 grew by normal grain growth during in situ heating. The high interface energy of nanoeutectic lamella and polygonal nanograins, which are formed by rapid solidification, acted as a principal driving force on the microstructural change during the in situ heating.

Keywords

in situ heatingSn–Ag–Cu solderUBMmicrostructureTEMSTEM
Type
Research Article
Information
Microscopy and Microanalysis , Volume 19 , Supplement S5: IUMAS , August 2013 , pp. 49 - 53
Copyright
Copyright © Microscopy Society of America 2013 

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