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Microstructural evolution and interfacial reactions of fluxless-bonded Au-20Sn/Cu solder joint during reflow and aging

  • Jeong-Won Yoon (a1), Hyun-Suk Chun (a1), Hoo-Jeong Lee (a1) and Seung-Boo Jung (a1)


The microstructural evolution and interfacial reactions of fluxless-bonded, Au-20wt%Sn/Cu solder joint were investigated during reflow and aging. After reflowing at 310 °C, only one thick and irregularly shaped ζ(Cu) layer was formed at the interface. After the prolonged reflow reaction, the AuCu layer was formed between the ζ(Cu) layer and the Cu substrate. During reflowing, the Cu substrate reacted primarily with the ζ-phase in the solder matrix. The solid-state interfacial reaction was much faster at 250 °C than at 150 °C. After aging at 250 °C for 100 h, thick ζ(Cu), AuCu and AuCu3 IMC layers were formed at the interface. The formation of the AuCu3 intermetallic compound (IMC) was caused by Cu enrichment at the AuCu/Cu layer interface. After aging for 500 h, cracks were observed inside the interfacial AuCu layer. The study results clearly demonstrate the need for an alternative surface finish on Cu, to ensure the high temperature reliability of the Au-20Sn/Cu solder joint.


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1Matijasevic, G.S., Wang, C.Y.Lee, C.C.: Void free bonding of large silicon dice using gold-tin alloys. IEEE Trans. Comp., Hybrids. Manuf. Technol. 13, 1128 1990
2Tsai, J.Y., Chang, C.W., Shieh, Y.C., Hu, Y.C.Kao, C.R.: Controlling the microstructures from the gold-tin reaction. J. Electron. Mater. 34, 182 2005
3Katz, A., Wang, K.W., Baiocchi, F.A., Dautremont-Smith, W.C., Lane, E., Luftman, H.S., Varma, R.R.Curnan, H.: Ti/Pt/Au-Sn metallization scheme for bonding of InP-based laser diodes to chemical vapor deposited diamond submounts. Mater. Chem. Phys. 33, 281 1993
4Pittroff, W., Barnikow, J., Klein, A., Kurpas, P., Merkel, U., Vogel, K., Würfl, J.Kuhmann, J.: Flip chip mounting of laser diodes with Au/Sn solder bumps: Bumping, self-alignment and laser behavior. IEEE 1997 Electronic Components and Technology Conference 1235 (1997)
5Doesburg, J.Ivey, D.G.: Microstructure and preferred orientation of Au-Sn alloy plated deposits. Mater. Sci. Eng., B 78, 44 2000
6Djurfors, B.Ivey, D.G.: Microstructural characterization of pulsed electrodeposited Au/Sn alloy thin films. Mater. Sci. Eng., B 90, 309 2002
7Yoon, J.W., Chun, H.S.Jung, S.B.: Reliability analysis of Au-Sn flip-chip solder bump fabricated by co-electroplating. J. Mater. Res. 22(5), 1219 2007
8Djurfors, B.Ivey, D.G.: Pulsed electrodeposition of the eutectic Au/Sn solder for optoelectronic packaging. J. Electron. Mater. 30, 1249 2001
9Tsai, J.Y., Chang, C.W., Ho, C.E., Lin, Y.L.Kao, C.R.: Microstructure evolution of gold-tin eutectic solder on Cu and Ni substrates. J. Electron. Mater. 35, 65 2006
10Kim, D.Lee, C.C.: Fluxless flip-chip Sn-Au solder interconnect on thin Si wafers and Cu laminated polyimide films. Mater. Sci. Eng., A 416, 74 2006
11Lee, C.H., Wong, Y.M., Doherty, C., Tai, K.L., Lane, E., Bacon, D.D., Baiocchi, F.Katz, A.: Study of Ni as a barrier metal in AuSn soldering application for laser chip/submount assembly. J. Appl. Phys. 72, 3808 1992
12Chromik, R.R., Wang, D-N., Shugar, A., Limata, L., Notis, M.R.Vinci, R.P.: Mechanical properties of intermetallic compounds in the Au-Sn system. J. Mater. Res. 20, 2161 2005
13Massalski, T.B.: Binary Alloy Phase Diagrams ASM International Materials Park, OH 1990 433
14Yoon, J.W., Chun, H.S., Koo, J.M., Lee, H.J.Jung, S.B.: Microstructural evolution of Sn-rich Au-Sn/Ni flip-chip solder joints under high temperature storage testing conditions. Scripta Mater. 56, 661 2007
15Yoon, J.W.Jung, S.B.: (unpublished paper)
16Kuang, J.H., Sheen, M.T., Chang, C.F.H., Chen, C.C., Wang, G.L.Cheng, W.H.: Effect of temperature cycling on joint strength of PbSn and AuSn solders in laser packages. IEEE Trans. Advan. Packag. 24, 563 2001
17Kim, J., Kim, D.Lee, C.C.: Fluxless flip-chip solder joint fabrication using electroplated Sn-rich Sn-Au structures. IEEE Trans. Advan. Packag. 29, 473 2006
18Kim, J.Lee, C.C.: Fluxless wafer bonding with Sn-rich Sn-Au dual-layer structure. Mater. Sci. Eng., A 417, 143 2006
19Song, H.G., Morris, J.W. Jr.McCormack, M.T.: The microstructure of ultrafine eutectic Au-Sn solder joints on Cu. J. Electron. Mater. 29, 1038 2000
20Yoon, J.W.Jung, S.B.: Interfacial reactions and shear strength on Cu and electrolytic Au/Ni metallization with Sn-Zn solder. J. Mater. Res. 21, 1590 2006
21Zakel, E.Reichl, H.: Au-Sn bonding metallurgy of TAB contacts and its influence on the kirkendall effect in the ternary Cu-Au-Sn. IEEE Trans. Comp., Hybrids. Manuf. Technol. 16, 323 1993
22Kallmayer, C., Jung, E., Kasulke, P., Azadeh, R., Azdasht, G., Zakel, E.Reichl, H.: A new approach to chip size package using meniscus soldering and FPC-bonding. IEEE Trans. Comp., Packag. Manuf. Technol. Part C 21, 51 1998
23Baggerman, A.F.J.Batenburg, M.J.: Reliable Au-Sn flip-chip bonding on flexible prints. IEEE Trans. Comp., Packag. Manuf. Technol. Part B 18, 257 1995
24Song, H.G., Ahn, J.P., Morris, J.W. Jr.: The microstructure of eutectic Au-Sn solder bumps on Cu/electroless Ni/Au. J. Electron. Mater. 30, 1083 2001
25Zakel, E.: Ph.D. Thesis, Technical University, Berlin, Germany, 1994
26Massalski, T.B.: Binary Alloy Phase Diagrams ASM International Materials Park, OH 1990 358



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