Microstructural Variation and Phase Evolution in the Reaction
of Sn-<Emphasis Type="Italic">x</Emphasis>Ag-Cu Solders and Cu-<Emphasis Type="Italic">y</Emphasis>Zn Substrates During Reflow |
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Authors: | Chi-Yang Yu Jenq-Gong Duh |
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Affiliation: | (1) College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing, China; |
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Abstract: | This study aims to investigate the reaction of Sn-xAg-0.5Cu (x = 1.0 wt.% and 3.0 wt.%) solders on Cu-yZn (y = 0 wt.%, 15 wt.%, and 30 wt.%) substrates at 250°C for 0.5 min, 2 min, and 10 min, respectively. Cu and Zn atoms dissolve
from the Cu-yZn substrates into the molten solders during reflow, leading to variation of the solder composition. It was revealed that
such composition variation altered the microstructure of the solders. The coarsening of the eutectic region and the decrease
of large-sized Cu6Sn5 compounds inside the Sn-1.0Ag-0.5Cu solder on both Cu-15Zn and Cu-30Zn substrates were correlated with this elemental redistribution.
In addition to the solder matrix, the interfacial reaction was also affected by Zn dissolution. For a Zn concentration of
15 wt.% to 30 wt.% in the Cu-Zn substrate, formation of Cu3Sn was suppressed. An increase of the Zn content in Cu6(Sn,Zn)5 at the solder/Cu-30Zn interface resulted in the formation of a new Cu(Zn,Sn) phase. It was demonstrated that the microstructural
variation and the phase evolution in the solder joints were controlled by the reflow time and the Zn concentration in the
Cu-yZn substrate. |
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Keywords: | |
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