Skip to main content Accessibility help

Interfacial reactions of Sn–Cu and Sn–Pb–Ag solder with Au/Ni during extended time reflow in ball grid array packages

  • M.N. Islam (a1), Y.C. Chan (a1) and A. Sharif (a1)


Lead-free solders with high Sn content cause excessive interfacial reactions at the interface with under-bump metallization during reflow. The interface formed after reflow affects the reliability of the solder joint. For this paper, we investigated the interfacial reactions of Sn0.7Cu and Sn36Pb2Ag solder on electrolytic Ni layer for different reflow times. The traditionally used Sn36Pb2Ag solder was used as a reference. It was found that during as-reflowed, the formation of Cu-rich Sn–Cu–Ni ternary intermetallic compounds (TIMCs) at the interface of Sn0.7Cu solder with electrolytic Ni is much quicker, resulting in the entrapment of some Pb (which is present as impurity in the Sn–Cu solder) rich phase in the TIMCs. During extended time of reflow, high (>30 at.%), medium (30-15 at.%) and low (<15 at.%) Cu TIMCs formed at the interface. The amount of Cu determined the growth rate of TIMCs. Cu-rich TIMCs had higher growth rate and consumed more Ni layer. By contrast, the growth rate of the Ni–Sn binary intermetallic compounds (BIMCs) in the Sn36Pb2Ag solder joint was slower, and the Ni–Sn BIMC was more stable and adherent. The dissolution rate of electrolytic Ni layer for Sn0.7Cu solder joint was higher than the Sn36Pb2Ag solder joints. Less than 3 μm of the electrolytic Ni layer was consumed during molten reaction by the higher Sn containing Sn0.7Cu solder in 180 min at 250 °C. The shear strength of Sn–Pb–Ag solder joints decreased within 30 min of reflow time from 1.938 to 1.579 kgf due to rapid formation of ternary Ni–Sn–Au compounds on the Ni–Sn BIMCs. The shear strength of Sn0.7Cu solder joint is relatively stable from 1.982 to 1.861 kgf during extended time reflow. Cu prevents the resettlement of Au at the interface. The shear strength does not depend on the thickness of intermetallic compounds (IMCs) and reflow time. Ni/Sn–Cu solder system has higher strength and can be used during prolonged reflow.


Corresponding author

a) Address all correspondence to this author.e-mail:


Hide All
1Tummala, R.R.: Fundamentals of Microsystems Packaging (McGraw-Hill, New York, 2001)
2Ho, C.E., Chen, Y.M. and Kao, C.R.: Reaction kinetics of solder-balls with pads in BGA packages during reflow soldering. J. Electron. Mater. 28, 1231 (1999).
3Chan, Y.C., So, A.C.K. and Lai, J.K.L.Growth kinetics studies of Cu–Sn intermetallic compound and its effect on shear strength of LCCC SMT solder joints. Mater. Sci. Eng. B 55, 5 (1998)
4So, A.C.K., Chan, Y.C. and Lai, J.K.L.Effect of intermetallic compounds on the shear fatigue of Cu/63Sn–37Pb solder joints. IEEE Trans. CMPT, Part B, 20, 463 (1997)
5Tu, P.L., Chan, Y.C., Hang, K.C. and Lai, J.K.L.: Growth kinetics of intermetallic compounds in chip scale package solder joint. Scripta Mater . 44, 317 (2001).
6Kay, P. and McKay, C.A.Barrier layer against diffusion. Trans. Inst. Met. Finish. 57, 169 (1997)
7Kang, S.K., Choi, W.K., Shih, D.Y., Lauro, P., Henderson, D.W., Gosselin, T. and Leonard, D.N.Interfacial reactions, microstructure and mechanical properties of Pb–free solder joints in PBGA laminate. ECTC paper (2002), pp. 146153
8Kim, P.G., Jang, J.W., Lee, T.Y. and Tu, K.N.Interfacial reaction and wetting behavior in eutectic Sn–Pb solder on Ni/Ti thin films and Ni foils. J. Appl. Phys. 86, 6746 (1999)
9Tu, K.N. and Zeng, K.: Tin-lead (Sn–Pb) solder reaction in flip chip technology. Mater. Sci. Eng. R 34, 1 (2001).
10Zhang, C., Lin, J-K. and Li, L.I.Thermal fatigue properties of lead-free solders on Cu and NiP under bump metallurgies. ECTC paper (2001), pp. 463470
11Chen, W.T., Ho, C.E. and Kao, C.R.: Effect of Cu concentration on the interfacial reactions between Ni and Sn–Cu solders. J. Mater. Res. 17,263 (2002).
12Abtew, M. and Selvaduray, G.: Lead-free solders in microelectronics reports: A Review. J. Mater. Sci. Eng. 27, 95 (2000).
13Lin, J-K., De Silva, A., Frear, D., Yifan, G., Jin-Wook, J., Li, L., Mitchell, D., Yeung, B. and Zhang, C.Characterization of lead-free solders and under bump metallurgies for flip-chip package. ECTC paper (2001), pp. 455462
14Ho, C.E., Lin, Y.L., and Kao, C.R.: Strong effect of Cu concentration on the reaction between lead–free microelectronic solders and Ni. Chem. Mater. 14, 949 (2002).
15Kim, K.S., Huh, S.H., Suganuma, K.: Effects of intermetallic compounds on properties of Sn–Ag–Cu lead-free soldered joints. J. Alloys Compd. 352, 226 (2003).
16Alam, M.O., Chan, Y.C. and Hung, K.C.: Reliability study of the electroless Ni–P layer against solder alloy. J. Microelectron. Reliability 42, 1065 (2002).
17Jang, J.W., Kim, P.G., Tu, K.N., Frear, D.R. and Thompson, P.: Solder reaction-assisted crystallization of electroless Ni–P under-bump-metallization in low cost flip chip technology. J. Appl. Phys. 85, 8456 (1999).
18Zeng, K. and Tu, K.N.: Six cases of reliability study of Pb–free solder joints in electronic packaging technology. Mater. Sci. Eng. R 38, 55 (2002)
19Ho, C.E., Zheng, R., Luo, G.L., Lin, A.H. and Kao, C.R.Formation and resettlement of AuxNi1-xSn4 in solder joints of ball-grid-array packages with the Au/Ni surface finish. J. Electron. Mater. 29, 1175 (2000)
20Ho, C.E., Chen, W.T. and Kao, C.R.: Interactions between solder and metallization during long-term aging of advanced microelectronic packages. J. Electron. Mater. 30, 379 (2001)
21Islam, M.N., Chan, Y.C., Sharif, A. and Alam, M.O.: Comparative study of the dissolution kinetics of electrolytic Ni and electroless NiP by the molten Sn3.5Ag0.5Cu solder alloy. Microelectron. Reliability 43, 2031 (2003).
22Korhonen, T.M., Su, P., Hong, S.J., Korhonen, M.A. and Li, C.Y.Reactions of lead-free solders with CuNi metallizations. J. Electron. Mater. 29, 1194 (2000)
23Kulojärvi, K., Vuorinen, V. and Kivilahti, J.Effect of dissolution and intermetallic formation on the reliability of FC joints. Microelectron. Int. 15, 20 (1998)
24Park, J.Y., Yang, C.W., Ha, J.S. and Kim, C.U.Investigation of interfacial reaction between Sn–Ag eutectic solder and Au/Ni/Cu/Ti thin film metallization. J. Electron. Mater. 30, 1165 (2001)
25Islam, M.N. and Chan, Y.C.: Comparative study of lead free solder with electrolytic Ni and electroless NiP layer during long time reflow on BGA Packages. In Int. Conf. Electron. Packaging (IMAPS Japan, 2004), pp. 446451.


Interfacial reactions of Sn–Cu and Sn–Pb–Ag solder with Au/Ni during extended time reflow in ball grid array packages

  • M.N. Islam (a1), Y.C. Chan (a1) and A. Sharif (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed