Disruption of crystalline structure of Sn3.5Ag induced by electric current

This study presented the disruption of the Sn and Ag₃Sn lattice structures of Sn3.5Ag solder induced by electric current at 5-7 × 10³ A/cm² with a high resolution transmission electron microscope investigation and electron diffraction analysis. The electric current stressing induced a high degree of strain on the alloy, as estimated from the X-ray diffraction (XRD) peak shift of the current stressed specimen. The XRD peak intensity of the Sn matrix and the Ag₃Sn intermetallic compound diminished to nearly undetectable after 2 h of current stressing. The electric current stressing gave rise to a high dislocation density of up to 10¹⁷/m². The grain morphology of the Sn matrix became invisible after prolonged current stressing as a result of the coalescence of dislocations.