Effect of Corrosion on Mechanical Reliability of Sn-Ag Flip-Chip Solder Joint

The shear strength and failure behaviors of the Sn-2.3 mass%Ag flip-chip solder joints before and after corrosion test were investigated. The relationships between the shear strength, corrosion amount, and fracture mode are elucidated in this study. The shear strength of the Sn-Ag solder bump joints decreased with increasing amount of corrosion, mainly due to the formation of brittle corrosion products. In addition, the shear strength was changed with corrosion site. After the shear test, the failure mode switched from a bulk-related ductile fracture to a corrosion-related brittle fracture, depending on the site and amount of corrosion. The top-side corroded bump did not affect the shear strength, whereas the shear strength was decreased for the partially corroded area at the side of the bump. After prolonged corrosion reactions, the joints had extremely low shear strength values and very brittle fracture surfaces. This result was discussed in terms of the relationship between the corrosion site, the shear height, and the resulting force-displacement (F-x) curves during the shear test.