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Effects of Sn grain structure on the electromigration of Sn–Ag solder joints

Published online by Cambridge University Press:  17 February 2012

Yiwei Wang ,
Kuan H. Lu ,
Vikas Gupta ,
Leon Stiborek ,
Dwayne Shirley ,
Seung-Hyun Chae ,
Jay Im  and
Paul S. Ho
Yiwei Wang
Affiliation:
Microelectronics Research Center, University of Texas at Austin, Austin, Texas 78758
Kuan H. Lu
Affiliation:
Intel Corp., Chandler, AZ 85226
Vikas Gupta
Affiliation:
Texas Instruments Inc., Dallas, Texas 75243
Leon Stiborek
Affiliation:
Texas Instruments Inc., Dallas, Texas 75243
Dwayne Shirley
Affiliation:
Texas Instruments Inc., Dallas, Texas 75243
Seung-Hyun Chae
Affiliation:
Texas Instruments Inc., Dallas, Texas 75243
Jay Im
Affiliation:
Microelectronics Research Center, University of Texas at Austin, Austin, Texas 78758
Paul S. Ho*
Affiliation:
Microelectronics Research Center, University of Texas at Austin, Austin, Texas 78758
*
a)Address all correspondence to this author. e-mail: paulho@mail.utexas.edu
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Abstract

In this article, we investigated the effect of Sn grain structure on the electromigration (EM) reliability of Sn–2.5Ag (wt%) solder joints used in flip-chip packages. The electron backscattering diffraction technique was applied to characterize the Sn grain size and orientation of the solder joints. Failure analyses on Sn–2.5Ag solder joints after EM tests showed that the Sn grain structure was important in controlling the kinetics of the intermetallic compound growth and void formation under EM. Further microstructural analysis revealed that the grain sizes and orientations of the solder joints after multiple solder reflows were statistically different from those with a single solder reflow and resulted in an improved EM reliability. Thermal annealing effect was also investigated to separate the thermal effect from the EM-induced effect. Results obtained in this study demonstrated that EM reliability of Pb-free solder joints could be improved by optimization of the Sn grain structure.

Keywords

ElectromigrationSolderingPackaging
Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 8 , 28 April 2012 , pp. 1131 - 1141
Copyright
Copyright © Materials Research Society 2012

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References

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