| Abstract Scope |
High entropy alloys (HEAs), unlike conventional alloys with one primary element, have an equimolar ratio of constituents and are stabilized by high mixing entropy. This allows them to form simple solid solutions with single crystal structures, such as BCC or FCC. HEAs are currently being explored for high-performance diffusion barrier layers in lead-free solder joints, with the FeCoNiCrMn alloy being particularly significant. This study examines the microstructural evolutions at the interfaces between FeCoNiCrMn HEA and Sn-based solders, including pure Sn and Sn-3wt.%Ag-0.5wt.%Cu, at temperatures from 250°C to 500°C. The dominant reaction phase, (Fe,Cr,Co)Sn2, exhibited two sublayers with different contrasts and microstructures, indicating varied reaction mechanisms. Additionally, oversaturated precipitation led to the formation of large chunky grains of (Co,Ni)Sn3, while the grain sizes of the faceted (Fe,Cr,Co)Sn2 grains significantly decreased. The reactions revealed acceptable wettability, sluggish growth of (Fe,Cr,Co)Sn2, and a stable interface without spalling of the reaction phases. |