Microstructural Features and Crystallographic Texture of Sn3.5Ag Solder Joints Produced with Fe-Nanoparticle Doped Flux*

This study concerns the effect of Fe nanoparticles (NPs) addition on the structure and performance of Sn3.5Ag solder joints. Alternative to the commonly used strategy of mixing nanoparticles with the solder, various amounts (0.0-2wt%) of Fe-NPs were added to the flux. Solder joints were then prepared by placing the NP-doped flux between the Sn-based solder foils and Cu substrates to achieve a proportionally high concentration of the NPs at the interface. The effect of Fe-nanoparticle additions on the formation and growth of interfacial intermetallic compounds (IMCs) and the microstructure of the bulk solder was investigated in as-reflow condition and after thermal aging up to 180°C and 480h. The results showed a reduced growth rate of the interfacial intermetallic phases (IMCs) of the solder joints prepared with NP-doped flux. Detailed structural and chemical analyses revealed the encountered interfacial reactions and dominancy of strong textural components for the Fe-NP-doped Sn-based solder joints.