Eutectic orientation relationships in Sn-Bi solder
File(s)
Published version
Author(s)
Shen, X
Zois, A
Douglas, JO
Gourlay, CM
Type
Journal Article
Abstract
The Sn-Bi eutectic is used increasingly as a low temperature solder (LTS) in electronics manufacturing. Here, we
measure eutectic orientation relationships (ORs) in Sn-58Bi and compare the ORs formed during solidification of
undercooled solder balls with those from unidirectional solidification. In both solidification conditions, three
ORs formed, each involving {0112} as the main interface planes in (Bi) with different interface planes in β-Sn. In
each OR, the eutectic bismuth was commonly twinned, with multiple (Bi) orientations related to each β-Sn
orientation which is explained in terms of the orientation variants of the ORs and the twin variants in (Bi). It is
found that the dominant eutectic OR changes as the nucleation undercooling becomes deeper in solder balls
which is discussed in terms of the effects of undercooling on the fraction of tin dendrites and the eutectic growth
velocity. The ability to change the dominant eutectic OR may provide a pathway to control interfaces between
the β-Sn and (Bi) phases which play an important role in the reliability of Sn-58Bi joints.
measure eutectic orientation relationships (ORs) in Sn-58Bi and compare the ORs formed during solidification of
undercooled solder balls with those from unidirectional solidification. In both solidification conditions, three
ORs formed, each involving {0112} as the main interface planes in (Bi) with different interface planes in β-Sn. In
each OR, the eutectic bismuth was commonly twinned, with multiple (Bi) orientations related to each β-Sn
orientation which is explained in terms of the orientation variants of the ORs and the twin variants in (Bi). It is
found that the dominant eutectic OR changes as the nucleation undercooling becomes deeper in solder balls
which is discussed in terms of the effects of undercooling on the fraction of tin dendrites and the eutectic growth
velocity. The ability to change the dominant eutectic OR may provide a pathway to control interfaces between
the β-Sn and (Bi) phases which play an important role in the reliability of Sn-58Bi joints.
Date Issued
2025-07-05
Date Acceptance
2025-05-31
Citation
Journal of Alloys and Compounds, 2025, 1035
ISSN
0925-8388
Publisher
Elsevier BV
Journal / Book Title
Journal of Alloys and Compounds
Volume
1035
Copyright Statement
© 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
10.1016/j.jallcom.2025.181339
Publication Status
Published
Article Number
181339
Date Publish Online
2025-06-02