Effects of Ag and melt undercooling on the microstructure of Sn–Ag solder balls
File(s)
Published version
Author(s)
Sun, Sihan
Li, Ao
Cheng, Chao
Gourlay, Christopher M
Type
Journal Article
Abstract
The microstructure of electronic solder joints is created by solidification in an undercooled melt. Here, we apply the framework of solidification microstructure selection maps (SMSMs) to Sn-Ag solder balls with compositions from 0.5 to 5.0 wt.% Ag and bulk undercoolings in the range 10–70 K. The effects of Ag and melt undercooling on the transition from single-grain to cyclic-twinned microstructures and the extent of interlacing are revealed. Controlled by the Ag content and the competitive nucleation between the β-Sn and Ag3Sn phases, a competition between tin dendrite and eutectic growth is observed that decides the microstructure of solder balls. The solidification microstructure selection map, modified to account for whether Ag3Sn or β-Sn nucleate first in competitive nucleation, is in reasonable agreement with coupled zone theory. The map provides a guide for tailoring desired solder microstructures for mechanical performance through controlling the nucleation undercooling of β-Sn and Ag3Sn during solidification.
Date Issued
2025-06-01
Date Acceptance
2025-05-14
Citation
Journal of Materials Science: Materials in Electronics, 2025, 36 (16)
ISSN
0957-4522
Publisher
Springer
Journal / Book Title
Journal of Materials Science: Materials in Electronics
Volume
36
Issue
16
Copyright Statement
© The Author(s), 2025 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
License URL
Publication Status
Published
Article Number
942
Date Publish Online
2025-06-02