Characterisation of the interfacial morphology of explosive welded tin and copper plates under isothermal ageing

After the ban on toxic lead (Pb) in solder alloys, Pb-free solder alloys are extensively used in the applications of electronic packaging, with tin (Sn) comprising over 90% of the composition. The formation of an intermetallic layer at the solder/substrate interface due to chemical bonding is a common phenomenon. However, during continuous service conditions, the growth of the intermetallic (IMC) layer may affect the electrical and thermal properties. In real conditions, the IMC thickness associated with ageing is very important because the reliability of the joint is allied to the growth of the IMC layer. Therefore, investigating the formation of intermetallic layers during joining and ageing is challenging. In the current research, Sn/Cu plates were welded using controlled underwater shock waves without the formation of intermetallic phases. Further, studies on the evolution of interfacial morphology in isothermally heat-treated tin/copper joints over extended periods were also assessed. Pure Sn and Cu plates were bonded by adopting the underwater shock waves method at water distances from 30 mm to 60 mm. Fused Sn/Cu plates were isothermally aged at 150 °C from 1 day to 4 days. The findings indicated the evolution of interfacial morphology and the growth rate of intermetallic compounds being thermally activated.