The interfacial reactions between solders and under bump metallization (UBM) have been of great interest recently in flip chip technology. Intermetallic compounds (IMCs), i.e., (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4, usually formed between solders and UBM. To fully understand the interfacial reactions and phase transformation phenomenon, a suitable phase diagram concerning solders, IMCs, and UBM materials is required. In particular, a Sn-rich phase region in the Sn–Cu–Ni ternary diagram is very critical in determining the concentration tendency of x and y values in (Ni1−x,Cux)3Sn4 and (Cu1−y,Niy)6Sn5 compounds. In this study, ternary Sn–Cu–Ni alloys were prepared and annealed at 240 °C. Three equilibrium phases, Sn, Ni3Sn4, and Cu6Sn5, were identified by x-ray diffraction analysis and also showed in backscattered electron imaging. Using electron probe microanalysis quantitative analysis, three acme compositions of the ternary region in the Sn–Cu–Ni isotherm near the Sn-rich corner were determined as 98.5 at.% Sn, (Ni0.80, Cu0.20)3Sn4 and (Cu0.59,Ni0.41)6Sn5. In addition, the solubility of Cu and Ni in (Ni,Cu)3Sn4 and (Cu,Ni)6Sn5 compounds was evaluated. Finally, the isothermal section of the ternary Sn–Cu–Ni system at 240 °C was proposed on the basis of experimental results in this study.
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J.H. Lau: Flip Chip Technologies (McGraw-Hill, New York, 1996), pp. 26–30.
T.Y. Lee, W.J. Choi, K.N. Tu, J.W. Jang, S.M. Kuo, J.K. Lin, D.R. Frear, K. Zeng and J.K. Kivilahti: Morphology, kinetics, and thermodynamics of solid-state aging of eutectic SnPb and Pb-free solders (Sn–3.5Ag, Sn–3.8Ag–0.7Cu and Sn–0.7Cu) on Cu. J. Mater. Res. 17, 291 (2002).
C.S. Chang, A. Oscilowski and R.C. Bracken: Future challenges in electronics packaging. IEEE Circuits Dev. 14, 45 (1998).
M.E. Loomans, S. Vaynman, G. Ghosh and M.E. Fine: Investigation of multicomponent lead-free solder. J. Electron. Mater. 23, 741 (1994).
A.A. Liu, H.K. Kim, K.N. Tu and P.A. Totta: Spalling of Cu6Sn5 spheroids in the soldering reaction of eutectic SnPb on Cr/Cu/Au thin films. J. Appl. Phys. 80, 2774 (1996).
K.L. Lin and Y.C. Liu: Manufacturing of Cu/electroless nickel/Sn–Pb flip chip solder bumps. IEEE Trans. Adv. Packag. 22, 575 (1999).
H.K. Kim, K.N. Tu and P.A. Totta: Ripening-assisted asymmetric spalling of Cu–Sn compound spheroids in solder joints on Si wafers. Appl. Phys. Lett. 68, 2204 (1996).
C.A. Harper: Electronic Packaging and Interconnection Handbook, 3rd ed. (McGraw-Hill, New York, 2000), pp. 6.78–6.82.
M. Abtew and G. Selvaduray: Lead-free solders in microelectronics. Mater. Sci. Eng. R-Rep. 27, 95 (2001).
J.W. Morris, J.L.F. Goldstein and Z. Mei: Microstructure and mechanical-properties of Sn–In and Sn–Bi Solders. JOM 45, 25 (1993).
K. Zeng and K.N. Tu: Six cases of reliability study of Pb-free solder joints in electronic packaging technology. Mater. Sci. Eng. R-Rep. 38, 55 (2002).
C.C. Young, J.G. Duh and S.Y. Tsai: Microstructural evoluation in the Sn–Cu–Ni and Pb–Sn solder joints with Cu and Pt–Ag metallized Al2O3 substrate. J. Electron. Mater. 30, 1241 (2001).
Y.G. Lee and J.G. Duh: Interfacial morphology and concentration profile in the unleaded solder/Cu joint assembly. J. Mater. Sci. 10, 33 (1999).
Y.G. Lee and J.G. Duh: Phase analysis in the solder joint of Sn–Cu solder/IMC/Cu substrate. Mater. Charact. 42, 143 (1999).
K. Zeng, V. Vuorinen and J.K. Kivilahti: Interfacial reactions between lead-free SnAgCu solder and Ni(P) surface finish on printed circuit boards. IEEE Trans. Electron. Packag. Manuf. 25, 162 (2002).
J.Y. Tsai, Y.C. Hu, C.M. Tsai and C.R. Kao: A study on the reaction between cu and Sn3.5Ag solder doped with small amounts of Ni. J. Electron. Mater. 32, 1203 (2003).
G. Ghosh: Interfacial microstructure and the kinetics of interfacial reaction in diffusion couples between Sn–Pb solder and Cu/Ni/Pd metallization. Acta Mater. 48, 3719 (2000).
B.L. Young and J.G. Duh: Interfacial reaction and microstructural evolution for electroplated Ni and electroless Ni in the under bump metallurgy with 42Sn58Bi solder during annealing. J. Electron. Mater. 30, 878 (2001).
S.K. Kang, R.S. Rai and S. Purushothaman: Interfacial reactions during soldering with lead-tin eutectic and lead (Pb)-free, tin-rich solders. J. Electron. Mater. 25, 1113 (1996).
C.R. Lin, S.W. Chen and C.H. Wang: Phase equilibria and solidification properties of Sn–Cu–Ni alloys. J. Electron. Mater. 31, 907 (2002).
C.S. Huang, J.G. Duh, Y.M. Chen and J.H. Wang: Effects of Ni thickness and reflow times on interfacial reactions between Ni/Cu under-bump metallization and eutectic Sn–Pb solder in flip-chip technology. J. Electron. Mater. 32, 89 (2003).
C.S. Huang, J.H. Yeh, B.L. Young and J.G. Duh: Phenomena of electroless Ni–P and intermetallic-compound stripping and dissolving in Sn–Bi and Sn–Pb solder joints with Au/EN/Cu metallization. J. Electron. Mater. 31, 1230 (2002).
C.S. Huang and J.G. Duh: Interface reactions and phase equilibrium between Ni/Cu under-bump metallization and eutectic SnPb flip-chip solder bumps. J. Mater. Res. 18, 935 (2003).
G.Y. Jang, C.S. Huang, L.Y. Hsiao and J.G. Duh: Mechanism of interfacial reaction for Sn–Pb solder bump with Ni/Cu UBM in flip chip technology. J. Electron. Mater. 33, 1118 (2004).
J.I. Goldstein, D.E. Newbury, P. Echlin, D.C. Joy, C.E. Lyman, E. Lifshin, L. Sawyer and J.R. Michael: Scanning Electron Microscopy and X-ray Microanalysis, 3rd ed. (Plenum Press, New York, 2003), pp. 391–420.
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Li, CY., Duh, JG. Phase equilibria in the Sn-rich corner of the Sn–Cu–Ni ternary alloy system at 240 °C. Journal of Materials Research 20, 3118–3124 (2005). https://doi.org/10.1557/JMR.2005.0391