Advancing the Solidification of Sn–Bi Alloys for Electronic Packaging: Challenges, Progress, and Future Directions

Marcella Gaute Cavalcante Xavier; Bismarck Luiz Silva; José Eduardo Spinelli

doi:10.1002/metm.70015

journal article Open Access Aug 18, 2025

Advancing the Solidification of Sn–Bi Alloys for Electronic Packaging: Challenges, Progress, and Future Directions

Marcella Gaute Cavalcante Xavier Bismarck Luiz Silva José Eduardo Spinelli

MetalMat Vol. 2 No. 4 · Wiley

View at Publisher Save 10.1002/metm.70015

Abstract

ABSTRACT
In the early 2000s, the soldering industry faced a major shift due to regulations restricting Pb usage. As a result, four main alloy systems emerged as alternatives: Sn–Bi, Sn–In, Sn–Cu, and Sn–Ag. However, for reasons not initially evident, higher melting point alloys were the first to be widely developed, most notably the Sn–Ag–Cu (SAC) alloys, which became the industry standard due to their balanced performance in reliability, mechanical strength, and process compatibility. Over the past decade, increasing emphasis has been placed on low‐temperature soldering (LTS), requiring studies not only on defects such as warpage, interfacial pores, and joint strength but also on the fundamental melting and solidification behavior of these alloys. Sn–Bi alloys have emerged as a commercial alternative, particularly for consumer products such as clients and server computers, while maintaining compatibility with surface mount technology (SMT) technology for high‐volume manufacturing. The thermal fatigue reliability of Sn–Bi is also well‐recognized. This short review will provide an overview of various studies conducted on the solidification behavior of Sn–Bi based alloys. The solidification paths, eutectic formation, morphologies, and properties will be explored. Future research directions comprise microalloying insights to improve ductility, interaction between Sn–Bi solder balls and SAC (Sn–Ag–Cu) pastes to mitigate PCB warpage, and exploring advanced characterization techniques such as X‐ray microtomography (XMT) and nanohardness testing. These developments are essential for optimizing LTS alloys and ensuring their reliability in next‐generation electronic packaging.

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Details

Published: Aug 18, 2025
Vol/Issue: 2(4)
License: View

Authors

M

Marcella Gaute Cavalcante Xavier

Department of Materials Engineering Federal University of São Carlos São Carlos Sao Paulo Brazil

B

Bismarck Luiz Silva

Department of Materials Engineering Federal University of Rio Grande do Norte, UFRN Natal Rio Grando do Norte Brazil

J

José Eduardo Spinelli

Department of Materials Engineering Federal University of São Carlos São Carlos Sao Paulo Brazil

Funding

Fundação de Amparo a Pesquisa do Estado de São Paulo Award: 2023/06107

Cite This Article

Marcella Gaute Cavalcante Xavier, Bismarck Luiz Silva, José Eduardo Spinelli (2025). Advancing the Solidification of Sn–Bi Alloys for Electronic Packaging: Challenges, Progress, and Future Directions. MetalMat, 2(4). https://doi.org/10.1002/metm.70015

Advancing the Solidification of Sn–Bi Alloys for Electronic Packaging: Challenges, Progress, and Future Directions

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