Sn Bi solder alloys stand out as lead-free alternatives for low-temperature electronic applications; however, their use is still limited by the brittleness associated with Bi-rich phases and by challenges related to solderability. In this work, the influence of carbon nanotube (MWCNT) additions at different contents (0, 0.25, 0.50, and 1.00 wt%) on the microstructure, mechanical properties, and wetting behavior of Sn Bi alloys was systematically investigated. The samples were characterized by scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS). Mechanical properties were evaluated by nanoindentation, while wetting behavior was analyzed by wetting force tests using a wetting balance. The results indicated that the unreinforced Sn Bi alloy exhibited a Vickers hardness of 26.3 HV and an elastic modulus of 30.8 GPa. The addition of MWCNTs promoted a progressive increase in these properties, reaching values of 28.1 HV and 34.3 GPa for the composition containing 1.00 wt% MWCNTs, accompanied by a reduction in plasticity from 93.37% to 88.12%. Microstructural analyses revealed modifications in the distribution of Bi-rich phases. Wetting tests indicated that the presence of MWCNTs influences the interfacial reactivity of the molten solder. The correlation between microstructure, mechanical properties, and wetting behavior allowed the identification of a MWCNT content range capable of balancing mechanical reinforcement and processability. • MWCNT additions refined β-Sn dendrites and Bi-rich phase distribution in Sn–Bi solder. • Hardness and elastic modulus increased by up to 7% and 11%, respectively. • Moderate reinforcement preserved wetting, whereas excessive addition impaired solderability. • An optimal content balanced mechanical enhancement and interfacial processability.
Silva et al. (Thu,) studied this question.