Intermetallic Formation between Sn-Ag(-Cu) Solder Bumps and Au/Ni/Ti UBM and It’s Effects on the Shear Force of the Solder Bumps


Article Preview

The shear force of Sn-3.5Ag and Sn-3.8Ag-0.7Cu solder bumps formed by the stencil printing method was measured and the effects of intermetallic formation on the shear force of solder bumps were investigated. The Sn-Ag(-Cu) solder paste was printed on the Au/Ni/Ti under bump metallurgy (UBM) and then reflowed repeatedly. The shear force of the solder bumps was measured as a function of the reflow times. The intermetallic formation in the Sn-Ag(-Cu) solder/UBM was characterized using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffractormeter. Ni3Sn4 phase was formed in the Sn-3.5Ag solder/UBM interface and (Cu,Ni)6Sn5 phase formed at the Sn-3.8Sg-0.7Cu solder/UBM interface. The shear force of solder bumps was sensitive to the depletion of Ni layer and the intermetallic thickness at the solder/Ni interface. The shear forces of Sn-3.5Ag solder bumps decreased rapidly after the fifth reflow due to the depletion of Ni layer in the UBM. The shear forces of Sn-3.8Ag-0.7Cu solder bumps decreased after the tenth reflow due to extensive growth of intermetallic layer in the solder/Ni interface.



Materials Science Forum (Volumes 475-479)

Main Theme:

Edited by:

Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie




S. H. Park and Y. H. Kim, "Intermetallic Formation between Sn-Ag(-Cu) Solder Bumps and Au/Ni/Ti UBM and It’s Effects on the Shear Force of the Solder Bumps", Materials Science Forum, Vols. 475-479, pp. 1881-1884, 2005

Online since:

January 2005




[1] J.H. Lau: Low Cost Flip Chip Technologies for DCA, WLCSP, and PBGA Assemblies (McGraw-Hill, New York 2000), pp.50-55.

[2] Y.D. Jeon, A. Ostmann, H. Reichl, and K.W. Paik: 53rd Electronic Components and Technology Conference (2003), pp.1203-1208.

[3] J.H. Lau: Chip on Board Technologies for Multichip Module (Kluwer Academic Publishers, Dordrecht 1994), pp.243-246.

[4] F. Zhang, M. Li, and C.C. Chum: J. Materials Research Society. Vol. 17 (2002), pp.2757-2760.

[5] S.T. Yang, Y. Chung, and Y.H. Kim: J. Microelectronics & Packaging Society. Vol. 9 (2002), pp.1-9.

[6] K. Suganuma: Current Opinion in Solid State & Materials Science. Vol. 5 (2001), pp.55-64.