Browsing by Author "Chu, David T."

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Communication-Formation of Porous Cu3Sn by High-Temperature Current Stressing
(2016)
Lin, C. K.
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Chen, Chih
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Chu, David T.
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Tu, K. N.
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材料科學與工程學系
Cu3Sn is a compound commonly formed in solder joints on Cu. In this study, two different Cu3Sn structures were observed at different stages of current stressing. A normal layer-type and pore-less Cu3Sn structure was obtained at the current density of 2.27 x 10(4) A/cm(2) at 222 degrees C after 12 h. However, a porous Cu3Sn structure was formed under the same current stressing conditions after 22 h. The formation of porous Cu3Sn is explained by the mechanisms of phase transformation and reaction. The porous Cu3Sn structure is frequently observed in Cu/solder/Cu microbumps with a reduced solder height after electromigration tests. (C) 2016 The Electrochemical Society. All rights reserved.
Formation Mechanism of Porous Cu3Sn Intermetallic Compounds by High Current Stressing at High Temperatures in Low-Bump-Height Solder Joints
(2016-01-01)
Lin, Jie-An
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Lin, Chung-Kuang
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Liu, Chen-Min
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Huang, Yi-Sa
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Chen, Chih
Electromigration tests of SnAg solder bump samples with 15 m bump height and Cu under-bump-metallization (UBM) were performed. The test conditions were 1.45 x 10(4) A/cm(2) at 185 degrees C and 1.20 x 10(4) A/cm(2) at 0 degrees C. A porous Cu3Sn intermetallic compound (IMC) structure was observed to form within the bumps after several hundred hours of current stressing. In direct comparison, annealing alone at 185 degrees C will take more than 1000 h for porous Cu3Sn to form, and it will not form at 170 degrees C even after 2000 h. Here we propose a mechanism to explain the formation of this porous structure assisted by electromigration. The results show that the SnAg bump with low bump height will become porous-type Cu3Sn when stressing with high current density and high temperature. Polarity effects on porous Cu3Sn formation is discussed.
Growth competition between layer-type and porous-type Cu3Sn in microbumps
(2017-12-01)
Chu, David T.
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Chu, Yi-Cheng
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Lin, Jie-An
;
Chen, Yi-Ting
;
Wang, Chun-Chieh
Experimental study of growth competition between the co-existing layer-type and porous-type Cu3Sn in solder microbumps of Cu/SnAg/Cu is reported. The thickness of the SnAg solder is about 14 pm and the Cu column on both sides is 20 pm. Upon wetting-reflow, the solder is reacted completely to form Cu Sn iptermetallic compounds in a multi-layered structure of Cu/Cu3Sn/Cu6Sn5/Cu3Sn/Cu. Upon further annealing at 220 degrees C and 260 C, we obtain Cu/Cu3Sn/porous Cu3Sn/Cu3Sn/Cu, in which both types of Cu3Sn co-exist and form an interface. In the layer-type growth, we assume Cu to be the dominant diffusing species, coming from the Cu column. The Cu reacts with Cu6Sn5 to grow the Cu3Sn layer. In the porous-type growth, we assume Sn to be the dominant diffusing species, coming from the depletion of Sn in Cu6Sn5. The depleted Cu6Sn5 transforms to the porous-type Cu3Sn. At the same time, the Sn diffuses to the side-wall of Cu column to form a coating of Cu3Sn. Experimental observations of 3-dimensional distribution of voids in the porous-type Cu3Sn are performed by synchrotron radiation tomography; the voids are interconnected for the out-diffusion of Sn. The competing growth between the layer-type and the porous-type Cu3Sn is analyzed. (C) 2017 Elsevier Ltd. All rights reserved.