Atomic insight into the interfacial reactions in Ni-Sn-Cu systems: A TEM and molecular dynamic study

YH Du and XL Ji and YS Wang and AW Liu and F Guo, APPLIED SURFACE SCIENCE, 705, 163507 (2025).

DOI: 10.1016/j.apsusc.2025.163507

Interfacial reactions are crucial in composite studies because they significantly influence the composite material's properties. In microelectronic soldering, these reactions exhibit increased complexity. Over the past few decades, extensive research has demonstrated that incorporating foreign reinforcements into Sn-based lead-free solders can overcome the limitations of traditional Sn-based binary and ternary solders, leading to highly reliable solder joints. Many researchers chose Ni-coated carbon materials as the reinforcement due to their superior mechanical properties and better interfacial compatibility with Sn. However, research concerning the formation process of interfacial intermetallic compounds in the Ni-Sn-Cu system remains inconclusive. Here, we used Nicoated carbon fibers (Ni@CFs) as reinforcements within Sn-3.0Ag-0.5Cu solder. The interfacial reactions during the soldering of the Ni-Sn-Cu system were investigated at the atomic level, establishing a link between molecular dynamic processes and macroscopic experimental phenomena. It is found that incorporating Ni into the soldering system boosts the Cu-Sn interdiffusion, leading to the faster arrival of Cu atoms at the Ni/Sn interface. Therefore, although Ni3Sn4 nano-grains initially form at the Ni/Sn interface, the quick arrival of Cu atoms favors the formation of (Cu, Ni)6Sn5 over Ni3Sn4. The findings will contribute to a more comprehensive understanding of the interfacial reactions within composite solder materials.

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