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Microstructural evolution in lead-free solder alloys: Part I. Cast Sn–Ag–Cu eutectic

Published online by Cambridge University Press:  03 March 2011

Sarah L. Allen ,
Michael R. Notis ,
Richard R. Chromik  and
Richard P. Vinci
Sarah L. Allen
Affiliation:
Department of Materials Science and Engineering, Lehigh University, Whitaker Laboratory,5 East Packer Avenue, Bethlehem, Pennsylvania 18015
Michael R. Notis
Affiliation:
Department of Materials Science and Engineering, Lehigh University, Whitaker Laboratory,5 East Packer Avenue, Bethlehem, Pennsylvania 18015
Richard R. Chromik
Affiliation:
Department of Materials Science and Engineering, Lehigh University, Whitaker Laboratory,5 East Packer Avenue, Bethlehem, Pennsylvania 18015
Richard P. Vinci
Affiliation:
Department of Materials Science and Engineering, Lehigh University, Whitaker Laboratory,5 East Packer Avenue, Bethlehem, Pennsylvania 18015
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Abstract

Coarsening of the ternary eutectic in cast Sn–Ag–Cu lead-free solder alloys was investigated. The process was found to follow r3 ∝ t kinetics where r is the rod radius of the dispersed phase and t is time. The effective activation energy for the process is 69 ± 5 kJmol-1. The two types of intermetallic rods, Cu6Sn5 and Ag3Sn, in the eutectic structure coarsen at different rates, with each having a different rate-controlling mechanism. The overall coarsening kinetics for the Sn–Ag–Cu ternary eutectic is significantly slower than that found for the Pb-Sn eutectic, which has implications for long-term reliability of Sn–Ag–Cu solder joints.

Keywords

AgingKineticsJoining

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Type
Articles
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Journal of Materials Research , Volume 19 , Issue 5 , May 2004 , pp. 1417 - 1424
Copyright
Copyright © Materials Research Society 2004

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References

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