Browsing by Author "Lin, Jie-An"

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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
;
Lin, Chung-Kuang
;
Liu, Chen-Min
;
Huang, Yi-Sa
;
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.
;
Chu, Yi-Cheng
;
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.