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

Published online by Cambridge University Press:  01 October 2004

M.N. Islam ,
Y.C. Chan  and
A. Sharif
M.N. Islam
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong
Y.C. Chan*
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong
A. Sharif
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong
*
a) Address all correspondence to this author.e-mail: eeycchan@cityu.edu.hk
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Abstract

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.

Keywords

Mechanical propertiesMicrostructurePackaging
Type
Articles
Information
Journal of Materials Research , Volume 19 , Issue 10 , October 2004 , pp. 2897 - 2904
Copyright
Copyright © Materials Research Society 2004

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References

REFERENCES

1Tummala, R.R.: Fundamentals of Microsystems Packaging (McGraw-Hill, New York, 2001)Google Scholar
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).Google Scholar
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)Google Scholar
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)Google Scholar
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).CrossRefGoogle Scholar
6Kay, P. and McKay, C.A.Barrier layer against diffusion. Trans. Inst. Met. Finish. 57, 169 (1997)Google Scholar
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. 146–153Google Scholar
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)Google Scholar
9Tu, K.N. and Zeng, K.: Tin-lead (Sn–Pb) solder reaction in flip chip technology. Mater. Sci. Eng. R 34, 1 (2001).CrossRefGoogle Scholar
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. 463–470Google Scholar
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).Google Scholar
12Abtew, M. and Selvaduray, G.: Lead-free solders in microelectronics reports: A Review. J. Mater. Sci. Eng. 27, 95 (2000).CrossRefGoogle Scholar
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. 455–462Google Scholar
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).Google Scholar
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).Google Scholar
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).Google Scholar
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).Google Scholar
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)Google Scholar
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)CrossRefGoogle Scholar
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)Google Scholar
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).Google Scholar
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)Google Scholar
23Kulojärvi, K., Vuorinen, V. and Kivilahti, J.Effect of dissolution and intermetallic formation on the reliability of FC joints. Microelectron. Int. 15, 20 (1998)Google Scholar
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)Google Scholar
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. 446–451.Google Scholar