Effect of Boron on Microstructure and Properties of Sn-1.0Ag-0.5Cu Low-Silver Lead-Free Solder

Abstract:

In this work, B (boron) was added into Sn-1.0Ag-0.5Cu (SAC105) solder alloy using mechanical alloying method in order to develop a new low-silver lead-free solder, Sn-1.0Ag-0.5Cu-xB, where B ranges from 0wt% to 0.2wt%. The melting characteristics, wettability, mechanical properties of welded joints, and microstructure of this solder were studied. The results showed that with adding B into SAC105 alloy, the melting point and melting range was not obviously changed. Although the wettability decreases with the B content increasing, the solder joints exhibited higher shear strength. As a result, the shear strength was the highest at the B content of 0.2wt%. For example, the shear strength of the Sn-1.0Ag-0.5Cu-0.2B solder was 35.12MPa, while that of the B free SAC105 solder was only 28.94MPa. Furthermore, adding B had a significant effect on grain refinement on the SAC105 solder . Observations on solder matrix and weld joints by SEM showed that the IMC thickness of solder joints with the addition of B was less than the SAC105 lead-free solder. Moreover, with the addition of B, the solder grains were refined obviously which had the effect of refining straitening, and the growing rate of brittle IMC in solder joint could be effectively reduced during soldering and aging process. Thus solder joint performance can be improved significantly.

• Periodical: Materials Science Forum (Volume 898)
• Pages: 908-916
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.898.908
• Online since: June 2017
• Authors: Ruo Da Wang, Shao Ming Zhang, Qiang Hu*, Fu Wen Zhang
• Keywords: Boron, Intermetallic Compound (IMC), Low-Silver Lead-Free Solder, Sn-Ag-Cu, Solder Joint Performance

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