Hostname: page-component-586b7cd67f-rcrh6 Total loading time: 0 Render date: 2024-11-23T10:48:08.925Z Has data issue: false hasContentIssue false
  • English
  • Français

Effect of electromigration on mechanical shear behavior of flip chip solder joints

Published online by Cambridge University Press:  01 March 2006

Jae-Woong Nah ,
Fei Ren ,
Kyung-Wook Paik  and
K.N. Tu
Jae-Woong Nah*
Affiliation:
Department of Materials Science and Engineering, University of California at Los Angeles, Los Angeles, California 90095-1595
Fei Ren
Affiliation:
Department of Materials Science and Engineering, University of California at Los Angeles, Los Angeles, California 90095-1595
Kyung-Wook Paik
Affiliation:
Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Taejon 305-701, Korea
K.N. Tu
Affiliation:
Department of Materials Science and Engineering, University of California at Los Angeles, Los Angeles, California 90095-1595
*
a) Address all correspondence to this author. e-mail: [email protected]
Get access

Abstract

Effect of electromigration on mechanical shear behavior of flip chip solder joints consisting of 97Pb3Sn and 37Pb63Sn composite solder joints was studied. The under bump metallurgy (UBM) on the chip side was TiW/Cu/electroplated Cu, and the bond pad on the board side was electroless Ni/Au. It was found that the mode of shear failure has changed after electromigration and the mode depends on the direction of electron flow during electromigration. The shear induced fracture occurs in the bulkof 97Pb3Sn solder without current stressing, however, after 10 h current stressing at 2.55 × 104 A/cm2 at 140 °C, it occurs alternately at the cathode interfaces between solder and intermetallic compounds (IMCs). In the downward electron flow, from the chip to substrate, the failure site was at the Cu–Sn IMC/solder interface near the Si chip. However, in the upward electron flow, from the substrate to chip, failure occurred at the Ni–Sn IMC/solder interface near the substrate. The failure mode has a strong correlation to microstructural change in the solder joint. During the electromigration, while Pb atoms moved to the anode side in the same direction as with the electron flow, Sn atoms diffused to the cathode side, opposite the electron flow. In addition, electromigration dissolves and drives Cu or Ni atoms from UBM or bond pad at the cathode side into the solder. These reactions resulted in the large growth of Sn-based IMC at the cathode sides. Therefore, mechanical shear failure occurs predominantly at the cathode interface.

Keywords

ElectromigrationPackaging
Type
Articles
Information
Journal of Materials Research , Volume 21 , Issue 3 , March 2006 , pp. 698 - 702
Copyright
Copyright © Materials Research Society 2006

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

REFERENCES

1.Lau, J.H., Pao, Y.H.: Solder Joint Reliability of BGA, CSP, Flip Chip, and Fine Pitch SMT Assembles (McGraw-Hill, New York, 1997), p. 47.Google Scholar
2.Tu, K.N.: Recent advances on electromigration in very-large-scale-integration of interconnects. J. Appl. Phys. 94, 5451 (2003).CrossRefGoogle Scholar
3.Lee, T.Y., Tu, K.N., Kuo, S.M., Frear, D.R.: Electromigration of eutectic SnPb solder interconnects for flip chip technology. J. Appl. Phys. 89, 3189 (2001).CrossRefGoogle Scholar
4.Lee, T.Y., Tu, K.N., Frear, D.R.: Electromigration of eutectic SnPb and SnAg3.8Cu0.7 flip chip solder bumps and under-bump metallization. J. Appl. Phys. 90, 4502 (2001).CrossRefGoogle Scholar
5.Choi, W.J., Yeh, E.C.C., Tu, K.N.: Mean-time-to-failure study of flip chip solder joints on Cu/Ni(V)/Al thin-film under-bump-metallization. J. Appl. Phys. 94, 5665 (2003).CrossRefGoogle Scholar
6.Nah, J.W., Paik, K.W., Suh, J.O., Tu, K.N.: Mechanism of electromigration-induced failure in the 97Pb–3Sn and 37Pb–63Sn composite solder joints. J. Appl. Phys. 94, 7560 (2003).CrossRefGoogle Scholar
7.Hsu, Y.C., Shao, T.L., Yang, C.J., Chen, C.: Electromigration study in SnAg3.8Cu0.7 solder joints on Ti/Cr–Cu/Cu under-bump metallization. J. Electron. Mater. 32, 1222 (2003).CrossRefGoogle Scholar
8.Shao, T.L., Lin, K.C., Chen, C.: Electromigration studies of flip chip Sn95/Sb5 solder bumps Cr/Cr–Cu/Cu under-bump metallization. J. Electron. Mater. 32, 1278 (2003).CrossRefGoogle Scholar
9.Shao, T.L., Chiu, S.H., Chen, C., Yao, D.J., Hsu, C.Y.: Thermal gradient in solder joints under electrical-current stressing. J. Electron. Mater. 33, 1350 (2004).CrossRefGoogle Scholar
10.Shao, T.L., Chen, Y.H., Chiu, S.H., Chen, C.: Electromigration failure mechanisms for SnAg3.5 solder bumps on Ti/Cr–Cu/Cu under-bump metallization pads. J. Appl. Phys. 96, 4518 (2004).CrossRefGoogle Scholar
11.Lin, Y.H., Tsai, C.M., Hu, Y.C., Lin, Y.L., Kao, C.R.: Electromigration-induced failure in flip-chip solder joints. J. Electron. Mater. 34, 27 (2005).CrossRefGoogle Scholar
12.Lin, Y.H., Hu, Y.C., Tsai, C.M., Kao, C.R., Tu, K.N.: In situ observation of the void formation-and-propagation mechanism in solder joints under current-stressing. Acta Mater. 53, 2029 (2005).CrossRefGoogle Scholar
13.Liu, Y.H., Lin, K.L.: Damages and microstructural variation of high-lead and eutectic SbPb composite flip chip solder bumps induced by electromigration. J. Mater. Res. 20, 2184 (2005).CrossRefGoogle Scholar
14.Nah, J.W., Suh, J.O., Tu, K.N.: Effect of current crowding and Joule heating on electromigration-induced failure in flip chip composite solder joints tested at room temperature. J. Appl. Phys. 98, 013715 (2005).CrossRefGoogle Scholar
15.Ren, F., Nah, J.W., Gan, H., Suh, J.O., Tu, K.N., Xiong, B., Xu, L., Pang, J. Effect of electromigration on mechanical behavior of solder joints, in Materials, Technology and Reliability of Advanced Interconnects—2005, edited by Besser, P.R., McKerrow, A.J., Iacopi, F., Wong, C.P., and Vlassak, J. (Mater. Res. Soc. Symp. Proc. 863 Warrendale, PA, 2005), B10.2.Google Scholar
16.Mercado, L.L., Sarihan, V., Guo, Y., Mawer, A.: Impact of solder pad size on solder joint reliability in flip chip PBGA packages. IEEE Trans. Adv. Packag. 23, 416 (2000).CrossRefGoogle Scholar
17.Pang, J.H.L., Chong, D.Y.R., Low, T.H.: Thermal cycling analysis of flip-chip solder joint reliability. IEEE Trans. Compon. Packag. Technol. 24, 705 (2001).CrossRefGoogle Scholar
18.Kariya, Y., Hosoi, T., Terashima, S., Tanaka, M., Otsuka, M.: Effect of silver content on the shear fatigue properties of Sn–Ag–Cu flip-chip interconnects. J. Electron. Mater. 33, 321 (2004).CrossRefGoogle Scholar
19.Nagesh, V.K., Peddada, R., Ramalingam, S., Sur, B., Tai, A. Challenges of flip chip on organic substrate assembly technology, in Proc. 49th Electronic Components and Technology Conference (IEEE, Piscataway, NJ, 1999), p. 975.Google Scholar
20.Shukla, R., Murali, V., Bhansali, A. Flip chip CPU package technology at Intel: A technology and manufacturing overview, in Proc. 49th Electronic Components and Technology Conference (IEEE, Piscataway, NJ, 1999), p. 945.Google Scholar
21.Guo, Y., Kuo, S.M., Zhang, C.: Reliability evaluations of under bump metallurgy in two solder systems. IEEE Trans. Compon. Packag. Technol. 24, 655 (2001).CrossRefGoogle Scholar
22.Yeh, E.C.C., Choi, W.J., Tu, K.N., Elenius, P., Balkan, H.: Current-crowding-induced electromigration failure in flip chip solder joints. Appl. Phys. Lett. 80, 580 (2002).CrossRefGoogle Scholar