Hostname: page-component-848d4c4894-jbqgn Total loading time: 0 Render date: 2024-06-23T00:44:50.587Z Has data issue: false hasContentIssue false

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
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
Get access

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.

Type
Research Article
Copyright
Copyright © Microscopy Society of America 2013 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Abtew, M. & Selvaduray, G. (2000). Lead-free solders in microelectronics. Mater Sci Eng 27, 95141.10.1016/S0927-796X(00)00010-3Google Scholar
Amagai, M., Watanabe, M., Omiya, M., Kishimoto, K. & Shibuya, Y. (2002). Mechanical characterization of Sn-Ag-based lead-free solders. Microelectron Reliab 42, 951966.10.1016/S0026-2714(02)00017-3Google Scholar
Bali, R., Fleury, E., Han, S.H. & Ahn, J.P. (2008). Interfacial intermetallic phases and nanoeutectic in rapidly quenched Sn-Ag-Cu on Au under bump metallization. J Alloys Compd 457, 113117.Google Scholar
Chinnam, R.K., Fauteux, C., Neuenschwander, J. & Janczak-Rusch, J. (2011). Evolution of the microstructure of Sn-Ag-Cu solder joints exposed to ultrasonic waves during solidification. Acta Mater 59, 14741481.10.1016/j.actamat.2010.11.011Google Scholar
Deng, X., Sidhu, R.S., Johnson, P. & Chawla, N. (2005). Influence of reflow and thermal aging on the shear strength and fracture behavior of Sn-3.5Ag solder/Cu joints. Metall Mater Trans A 36, 5564.Google Scholar
Ho, C.E., Yang, S.C. & Kao, C.R. (2007). Interfacial reaction issues for lead-free electronics solders. J Mater Sci: Mater Elec 18, 115174.Google Scholar
Kang, S.K., Choi, W.K., Yim, M.J. & Shih, D.Y. (2002). Studies of the mechanical and electrical properties of lead-free solder joints. J Electron Mater 31, 12921303.Google Scholar
Keller, J., Baither, D., Wilke, U. & Schmitz, G. (2011). Mechanical properties of Pb-free SnAg solder joints. Acta Mater 59, 27312741.Google Scholar
Kim, K.H. & Tu, K.N. (1996). Kinetic analysis of the soldering reaction between eutectic SnPb alloy and Cu accompanied by ripening. Phys Rev B 53, 1602716034.10.1103/PhysRevB.53.16027Google Scholar
Kim, K.S., Huh, S.H. & Suganuma, K. (2003). Effects of intermetallic compounds on properties of Sn-Ag-Cu lead-free soldered joints. J Alloys Compd 352, 226239.10.1016/S0925-8388(02)01166-0Google Scholar
Tang, W., He, A., Liu, Q. & Ivey, D.G. (2008). Fabrication and microstructures of sequentially electroplated Sn-rich Au-Sn alloy solders. J Electron Mater 37, 837844.10.1007/s11664-008-0401-zGoogle Scholar
Tu, K.N. & Zeng, K. (2001). Tin-lead (SnPb) solder reaction in flip chip technology. Mater Sci Eng R-Rep 34, 158.Google Scholar