Study on the interfacial IMCs growth of nt-Cu/In solder joints

With the trend of miniaturization, high density, and high frequency of electronic products, system in packaging devices are increasingly widely used in electronic products. Multiple reflow soldering is required in the production process of complex electronic products, and solders with different temperature gradients are necessary to achieve assembly. Indium has good flexibility, especially in low temperature service environments, it can still guarantee good flexibility, so it has relatively excellent thermal fatigue resistance. At the same time, nanotwinned copper (nt-Cu) has attracted attention in the field of microelectronics due to its excellent properties of ultra-high conductivity and ultra-high strength. In this paper, the microstructure and reliability of nt-Cu/In/nt-Cu micro solder joints at different reflow temperatures and time were studied. It is found that the phase of the Cu-In intermetallic compound at the interface is Cu11In9. And the shear tests were performed on samples of solder joints obtained under various reflow conditions to obtain the best solder joints. Finally, the growth kinetic equation of Cu11In9 was calculated.