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Ripening-assisted void formation in the matrix of lead-free solder joints during solid-state aging

Published online by Cambridge University Press:  03 March 2011

J.W. Jang ,
J.K. Lin ,
D.R. Frear ,
T.Y. Lee  and
K.N. Tu
J.W. Jang*
Affiliation:
Freescale Semiconductor, Inc., Tempe, Arizona 85284
J.K. Lin
Affiliation:
Freescale Semiconductor, Inc., Tempe, Arizona 85284
D.R. Frear
Affiliation:
Freescale Semiconductor, Inc., Tempe, Arizona 85284
T.Y. Lee
Affiliation:
Department of Materials Engineering, Hanbat National University, Daejeon, Republic of Korea
K.N. Tu
Affiliation:
Department of Materials Science and Engineering, University of California–Los Angeles, Los Angeles, California 90095-1595
*
a) Address all correspondence to this author. e-mail: j.jang@freescale.com
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Abstract

Void formation in lead-free solder joints, away from the joint interface, has been observed after solid-state aging. These voids are attached to intermetallic precipitates in the solder matrix, especially to those that are adjacent to the layered intermetallic at the joint interface. Two potential void formation mechanisms are discussed. The mechanism proposed to describe void formation is that a flux of vacancies is created due to volume contraction during solid-state reaction. The ripening process among the intermetallics also assists this process. Using the suggested mechanisms, the void size was estimated. This phenomenon differs from the classical Kirkendall void formation because it is a nonequilibrium state of void formation and stress generation.

Keywords

DiffusionPackagingSoldering
Type
Rapid Communications
Information
Journal of Materials Research , Volume 22 , Issue 4 , April 2007 , pp. 826 - 830
Copyright
Copyright © Materials Research Society 2007

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References

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