Effects of soldering temperatures and composition on the microstructures and shear properties of Sn58Bi-xSAC0307/ENIG solder joints

Abstract

Purpose

This paper aims to systematically study the effects of reflow temperature and SAC0307 (SAC) content on the micromorphology and mechanical properties of Sn58Bi-xSAC0307 composite solder joints to meet the requirements of high integration and low-temperature packaging of devices and provide references for the application of composite solder joints.

Design/methodology/approach

Sn58Bi and SAC0307 solder paste was mechanically mixed in different proportions to prepare Sn58Bi-xSAC0307/ENIG solder joints. The thermal properties, microstructure and mechanical properties of the composite solder joints were studied.

Findings

As SAC content in the solder increases, the balling temperature of SnBi-SAC solder gradually increases. The addition of SAC alloy reduces the grain size of large Bi-rich phase, and there are small-sized dispersed Bi and Ag3Sn particles in the bulk solder. The intermetallic compounds composition of the SnBi-xSAC/ENIG solder joint changes from Ni3Sn4 to (Ni, Cu)3Sn4 and (Cu, Ni)6Sn5 with SAC increasing. As the soldering temperature increases, the strength of all solder joints shows a rising trend. Among them, the shear strength of SnBi-20SAC solder joints at a reflow temperature of 150°C is approximately 37 MPa. As the reflow temperature increases to 250°C, the shear strength of solder joints increases to approximately 67 MPa.

Originality/value

This study provides a reference for the optimization of low-temperature solder composition and soldering process under different package designs.

Citation

Jiang, M., Liu, Y., Xue, Y., Shan, G., Lv, J. and Huang, M. (2024), "Effects of soldering temperatures and composition on the microstructures and shear properties of Sn58Bi-xSAC0307/ENIG solder joints", Soldering & Surface Mount Technology, Vol. 36 No. 4, pp. 239-251. https://doi.org/10.1108/SSMT-03-2024-0014