Ball shear strength and fracture mode of lead-free solder joints prepared using nickel nanoparticle doped flux

The trend towards the miniaturization and the replacement of lead-based solders in microelectronic devices raise concerns over reliability in the recent year. Particularly, the rapid growth of interfacial intermetallic compound layers can lead to brittle fracture in solder joints. In the present study, a novel nanoparticle doped fluxing method was used to prepare ball grid array solder joints in between lead-free Sn-3.0Ag-0.5Cu solder balls and organic solderability preservative-Cu pads. In this method, nickel nanoparticles were mixed with a water soluble flux prior to its use. The shear strength and fracture modes of resulting solder joints were determined as a function of aging time The results showed that the average shear strength of solder joints prepared by using 0.1 wt.% Ni doped flux was only marginally higher than that of solder joints prepared with undoped flux. In case of undoped condition, the percentage of catastrophic brittle fracture mode increased with increasing the aging time. On the other hand, 0.1wt.% Ni doped flux solder joints showed excellent resistant against brittle fracture up to 30 days of aging.