Growth kinetics of interfacial intermetallic compounds formed in SnPbInBiSb high entropy alloy soldered joints on Cu substrates

The growth behavior of the complex intermetallic compounds (IMCs) formed at the interface of Cu/SnPbInBiSb high entropy alloy solder joints was explored. The growth inhibition mechanism of the IMCs at the Cu/SnPbInBiSb solid-liquid reaction interface was revealed. The results showed that the growth rate of the complex IMCs obviously decreased at the Cu/SnPbInBiSb solid-liquid reaction interface. The maximum average thickness of IMCs only reached up to 1.66 μm after reflowing at 200 °C for 10 min. The mechanism for the slow growth of the complex IMCs was analyzed into three aspects. Firstly, the high entropy of the liquid SnPbInBiSb alloy reduced the growth rate of the complex IMCs. Secondly, the distorted lattice of complex IMCs restrained the diffusion of Cu atoms. Lastly, the higher activation energy (40.9 kJ/mol) of Cu/SnPbInBiSb solid-liquid interfacial reaction essentially impeded the growth of the complex IMCs.