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Local solidification thermal parameters affecting the eutectic extent in Sn-Cu and Sn-Bi solder alloys

Rafael Kakitani (Department of Manufacturing and Materials Engineering, University of Campinas, UNICAMP, Campinas, Brazil)
Cassio Augusto Pinto da Silva (Department of Manufacturing and Materials Engineering, University of Campinas, UNICAMP, Campinas, Brazil)
Bismarck Silva (Department of Materials Engineering, Federal University of Rio Grande do Norte, UFRN, Natal, Brazil)
Amauri Garcia (Department of Manufacturing and Materials Engineering, University of Campinas, UNICAMP, SP, Brazil)
Noé Cheung (Department of Manufacturing and Materials Engineering, University of Campinas, UNICAMP, SP, Brazil)
José Eduardo Spinelli (Department of Materials Engineering, Federal University of São Carlos, UFSCar, São Carlos, Brazil)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 24 June 2021

Issue publication date: 3 January 2022

176

Abstract

Purpose

Overall, selection maps about the extent of the eutectic growth projects the solidification velocities leading to given microstructures. This is because of limitations of most of the set of results when obtained for single thermal gradients within the experimental spectrum. In these cases, associations only with the solidification velocity could give the false impression that reaching a given velocity would be enough to reproduce a result. However, that velocity must necessarily be accompanied by a specific thermal gradient during transient solidification. Therefore, the purpose of this paper is to not only project velocity but also include the gradients acting for each velocity.

Design/methodology/approach

Compilation of solidification velocity, v, thermal gradient, G, and cooling rate, Ṫ, data for Sn-Cu and Sn-Bi solder alloys of interest is presented. These data are placed in the form of coupled growth zones according to the correlated microstructures in the literature. In addition, results generated in this work for Sn-(0.5, 0.7, 2.0, 2.8)% Cu and Sn-(34, 52, 58)% Bi alloys solidified under non-stationary conditions are added.

Findings

When analyzing the cooling rate (Ṫ = G.v) and velocity separately, in or around the eutectic composition, a consensus cannot be reached on the resulting microstructure. The (v vs. G) + cooling rate diagrams allow comprehensive analyzes of the combined v and G effects on the subsequent microstructure of the Sn-Cu and Sn-Bi alloys.

Originality/value

The present paper is devoted to the establishment of (v vs. G) + cooling rate diagrams. These plots may allow comprehensive analyses of the combined v and G effects on the subsequent microstructure of the Sn-Cu and Sn-Bi alloys. This microstructure-processing mapping approach is promising to predict phase competition and resulting microstructures in soldering of Sn-Cu and Sn-Bi alloys. These two classes of alloys are of interest to the soldering industry, whereas manipulation of their microstructures is considered of utmost importance for the metallurgical quality of the product.

Keywords

Acknowledgements

The authors thank the support provided by FAPESP – São Paulo Research Foundation, Brazil, (grants 2019/23673–7, 2017/12741–6 and 2017/15158–0); CNPq – National Council for Scientific and Technological Development, Brazil, and CAPES – Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil, (Finance Code 001).

Conflicts of interest: The authors declare no conflict of interest.

Availability of data: The data presented in this study are available on request from the corresponding author. The data are not publicly available because pertain to a research still in development.

Citation

Kakitani, R., Pinto da Silva, C.A., Silva, B., Garcia, A., Cheung, N. and Spinelli, J.E. (2022), "Local solidification thermal parameters affecting the eutectic extent in Sn-Cu and Sn-Bi solder alloys", Soldering & Surface Mount Technology, Vol. 34 No. 1, pp. 24-30. https://doi.org/10.1108/SSMT-01-2021-0003

Publisher

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Emerald Publishing Limited

Copyright © 2021, Emerald Publishing Limited

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