Effect of nano-Fe₂O₃ additions on wettability and interfacial intermetallic growth of low-Ag content Sn-Ag-Cu solders on Cu substrates

In the present study, Fe₂O₃ nanoparticles were synthesized and smelted with pure Sn, Ag, and Cu to prepare Sn-1.0Ag-0.7Cu-xFe₂O₃ nano-composite solders. The content of Fe₂O₃ nanoparticles ranged from 0 to 1 wt.% in the solders. The influences of Fe₂O₃ nanoparticles on the wettability and the morphology of interfacial intermetallics compounds (IMCs) of low-Ag Sn-Ag-Cu solders on Cu substrate were investigated. Results show that added Fe₂O₃ nanoparticles can remarkably improve the wettability of Sn-1.0Ag-0.7Cu solder alloys and inhibit the formation and the growth of the interfacial IMCs between the nano-composite solders and Cu substrate. Meanwhile, not only the wettability of the nano-composite solders but also the formation and the growth of the interfacial IMCs, during reflow and aging, are identically relied on Fe₂O₃ weight percent in nano-composite solders. The enhancement of wettability improvement and interfacial IMC inhibition caused by nano-Fe₂O₃ addition increased with the addition amount under small concentration. However, excessive addition of Fe₂O₃ nanoparticles in the Sn-1.0Ag-0.7Cu solder alloys will degrade the wettability and the inhibition effect on the interfacial IMCs. There is an optimum amount of Fe₂O₃ nanoparticles in Sn-1.0Ag-0.7Cu solder alloys, which is 0.4 wt.%, and Sn-1.0Ag-0.7Cu-0.4Fe₂O₃ solders possess the best wettability and the inhibition effect on the interfacial IMCs formation and growth. The reason for improving wettability and simultaneously inhibiting IMCs formation and growth due to Fe₂O₃ nanoparticles addition is explained.