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Wettability, interfacial reactions, and impact strength of Sn–3.0Ag–0.5Cu solder/ENIG substrate used for fluxless soldering under formic acid atmosphere

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Abstract

Fluxes have a negative impact on the environment; as a result, fluxless soldering has become a promising method in electronic packaging. However, detailed studies on fluxless soldering are very rare, especially those involving the use of electroless nickel immersion gold (ENIG) substrate under formic acid (FA) atmosphere that can effectively reduce the majority of solders. In this work, the characteristic parameters of FA reflow soldering performed by combining Sn–3.5Ag–0.5Cu (SAC305) solder and ENIG substrate are compared with the soldering conducted using liquid rosin mildly activated (RMA) flux. It is found that the wettability of FA-exposed solder is greater than that of RMA-containing solder because the former spreads across the interfacial layer of intermetallic compounds (IMCs) produced before the melting of SAC305. Additionally, the interfacial reactions of FA-exposed solder resemble those of RMA solder before and after the thermal aging at 150 °C. Therefore, the impact strengths of these two solders are almost the same due to the similarity of their microstructures and close growth rates of (Cu,Ni)6Sn5 IMC layers during thermal aging. The findings of this study suggest that FA reflow soldering is a promising environmentally friendly technique for electronic packaging.

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Acknowledgements

The authors would like to acknowledge SANYOSEIKO, LTD (Japan) for the financial support of this study.

Funding

This study was funded by the Project to Create Research and Educational Hubs for Innovative Manufacturing in Asia, Osaka University under the Special Project of the Ministry of Education, Culture, Sports, Science and Technology (MEXT).

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Authors and Affiliations

  1. Graduate School of Engineering, Osaka University, Suita, Osaka, 565-0871, Japan

    Siliang He, Runhua Gao & Jiahui Li

  2. Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka, 565-0047, Japan

    Siliang He, Runhua Gao, Yu-An Shen, Jiahui Li & Hiroshi Nishikawa

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  1. Siliang He
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Correspondence to Siliang He.

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He, S., Gao, R., Shen, YA. et al. Wettability, interfacial reactions, and impact strength of Sn–3.0Ag–0.5Cu solder/ENIG substrate used for fluxless soldering under formic acid atmosphere. J Mater Sci 55, 3107–3117 (2020). https://doi.org/10.1007/s10853-019-04153-9

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  • DOI: https://doi.org/10.1007/s10853-019-04153-9

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