The synergistic inhibition of the growth of intermetallic compounds at Sn-0.7Cu/Cu interface by Al and Pt

The construction of intermetallic compounds (IMCs) connection layers with special compositions by adding small amounts of alloying elements has been proven to be an effective strategy for improving the reliability of electronic component interconnect. However, the synergistic effect mechanism of multi-component alloy compositions on the growth behavior of IMCs is not clear. Herein, we successfully prepared a new quaternary alloy solder with a composition of Sn-0.7Cu-0.175Pt-0.025Al (wt%) using the high-throughput screening (HTS) method. The results showed that it possesses excellent welding performance with an inhibition rate over 40% on the growth of IMCs layers. For Cu₆Sn₅, the co-doping of Al and Pt not only greatly improves its thermodynamic stability, but also effectively suppresses the phase transition. Meanwhile, the co-doping of Al and Pt also significantly delays the generation time of Kirkendall defects. The substitution sites of Al and Pt in Cu₆Sn₅ have been explored using atomic resolution imaging and advanced data informatics, indicating that Al and Pt preferentially substitute Sn and Cu atoms, respectively, to generate (Cu, Pt)₆(Sn, Al)₅. A one-dimensional (1D) kinetic model of the IMCs layer growth at the Sn solder/Cu substrate interface was derived and validated, and the results showed that the error of the derived mathematical model is less than 5%. Finally, the synergistic mechanism of Al and Pt co-doping on the growth rate of Cu₆Sn₅ was further elucidated. This work provides a feasible route for the design and development of multi-component alloy solders.

Graphical abstract