Interdiffusion analysis of the soldering reactions in Sn-3.5Ag/Cu couples |
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Authors: | K S Bae S J Kim |
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Affiliation: | (1) Department of Electronic Materials Engineering, University of Suwon, The P.O. Box 77, 440-600 Suwon, Kyunggi-do, Korea |
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Abstract: | Extensive microstructural and kinetic studies on the formation and growth of the intermetallics of Sn-rich solder/Cu couples
have been reported. However, experimental data on the interdiffusion mechanisms during soldering reactions are limited and
in conflict. The interdiffusion processes for soldering of Sn-3.5Ag alloy/Cu couples were investigated by using the Cr-evaporated
surface as a reference line. At the beginning of soldering, Cu was observed to outdiffuse to the molten Sn−3.5Ag alloy until
saturation, and the Sn−Ag solder dissolved with Cu collapsed below the reference line. As a result, the scallop-shaped Cu6Sn5 intermetallic compound was formed at the newly-formed Sn−Ag−Cu solder/Cu interface below the original Cu surface. When the
soldered joint was reflowed at the lower temperature to suppress the Cu dissolution, the Cu6Sn5/Cu interface moved into the Cu substrate. Therefore, Sn is the dominant diffusing species for the intermetallic formation
during the soldering process, although the extensive Cu dissolution occurs at the early stage of soldering. |
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Keywords: | Sn− 3 5Ag/Cu soldering intermetallic formation interdiffusion kinetics Cu dissolution |
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