Impact of Fe-NPs doped flux on electromigration in Sn-based solder joints of chip-sized SMD components at lower Joule heating

The influence of incorporating iron nanoparticles through flux doping (0-2wt.%) in lead-free SAC305 (Sn3.5Ag0.5Cu) solder joints of chip-sized surface-mounted (SMD) components on electromigration has been investigated. To ensure high current densities throughout the experiment, track-to-pad joining angles of 135° on the anode site and 90° on the cathode site were implemented. The temperature was kept relatively low to minimize material transport attributable to thermal effects. Microstructural changes were examined through cross-sectional analysis, and push-off shear tests were performed to assess the influence of current loading on mechanical reliability. After 2000 and 4000 h of loading the samples with 4 A, joints with 0402 resistors showed copper dissolution from the tracks at the cathode sites in samples prepared with undoped flux. However, among the NP doped samples, the joints produced with 0.5 wt.% Fe-NPs showed no copper dissolution. Shear performance of joints with 0402 components deteriorated in all cases after 4000 hours of current loading.