Investigating the physical, mechanical, and reliability study of high entropy alloy reinforced Sn–3.0Ag–0.5Cu solder using 1608 chip capacitor/ENIG joints

High entropy alloy (HEA) receives noticeable attention in the electronic industry, and one of the best ways to incorporate HEA with the existing assembly setup is to reinforce HEA particles in Pb-free solder. This paper investigates the properties of Sn3.5Ag0.5Cu (SAC 305) solder reinforced with HEA particles. FeCoCrNiCu particle was synthesized via ball milling and dispersed in SAC 305 paste by powder mixing technique. DSC analysis confirms a reduction in melting temperature and undercooling with the addition of HEA. The dispersion of HEA in the solder resulted in a significant refinement in β-Sn grain size, Ag₃Sn, and Cu₆Sn₅ IMC particle size. Also, SAC 305 with 0.2 wt% HEA noted a better spreading performance and lowest contact angle. 1608 chip capacitor/HEA reinforced solder joint was assembled, subjected to − 40 to + 125 °C thermal shock, and tested for the shear strength. The reliability analyzed through Weibull analysis showed a 30% increase in the 75% survival probability strength for HEA-added joints. Also, HEA addition till 0.1 wt% suppressed the growth of (Cu, Ni)₆Sn₅ IMC after thermal shock cycles. After 1000 thermal shock cycles, 0.1 wt% HEA-added solder retained the shear strength of 22.5 MPa, equivalent to the strength exhibited by the SAC 305 in the as-reflow condition.