Influence of Cu column under-bump-metallizations on current crowding and Joule heating effects of electromigration in flip-chip solder joints

被引:22
作者
Liang, Y. C. [1 ]
Tsao, W. A. [1 ]
Chen, Chih [1 ]
Yao, Da-Jeng [2 ]
Huang, Annie T. [3 ]
Lai, Yi-Shao [4 ]
机构
[1] Natl Chiao Tung Univ, Dept Mat Sci & Engn, Hsinchu 30010, Taiwan
[2] Natl Tsing Hua Univ, Inst Microelectromech Syst, Hsinchu 30013, Taiwan
[3] Acad Sinica, Res Ctr Appl Sci, Taipei 11529, Taiwan
[4] Adv Semicond Engn Inc, Cent Labs, Kaohsiung 811, Taiwan
关键词
FAILURE;
D O I
10.1063/1.3682484
中图分类号
O59 [应用物理学];
学科分类号
摘要
The electromigration behavior of SnAg solder bumps with and without Cu column under-bump-metallizations (UBMs) has been investigated under a current density of 2.16 x 10(4) A/cm(2) at 150 degrees C. Different failure modes were observed for the two types of samples. In those without Cu column UBMs, when SnAg solder bumps that had implemented 2 mu m Ni UBMs were current stressed at 2.16 x 10(4) A/cm(2), open failure occurred in the bump that had an electron flow direction from the chip side to the substrate side. However, in those with Cu column UBMs, cracks formed along the interface of Cu6Sn5 intermetallic compounds and the solder on the substrate side in the Sn-3.0Ag-0.5Cu solder bump that had an electron flow direction from the substrate side to the chip side. A three-dimensional simulation of the current density distribution was performed in order to obtain a better understanding of the current crowding behavior in solder bumps. The current crowding effect was found to account for the void formation on both the chip and the substrate side for the two kinds of solder bumps. One more important finding, as confirmed by infrared microscopy, is that the alleviation of current crowding by Cu column UBMs also helped decrease the Joule heating effect in solder bumps during current stressing. Therefore, the measured failure time for the solder joints with Cu column UBMs appears to be much longer than that of the ones with the 2 mu m Ni UBMs. (C) 2012 American Institute of Physics. [doi:10.1063/1.3682484]
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页数:7
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