Abstract
In these study, the effect of Bi content on shear strength of Sn-xBi (x=0, 2.5, 5, 15) solder balls were investigated. The Bi addition could improve the shear strength of solder balls, added 2.5wt.% Bi into pure Sn solder alloys had a greater increase in shear strength. The fracture mode always remained the same and the shear strength had no obvious changes with increasing the aging time. The Sn-2.5Bi solder balls had the highest fracture energy due to its large elongation properties and the high shear strength. The shear strength of Sn-5Bi and Sn-15Bi solder balls were bigger than pure Sn solder alloys, when aging time increased to 10 days, the shear strength reached maximum value. Due to the growth of IMCs and the change of fracture mode, the shear strength of Sn-5Bi and Sn-15Bi solder balls had a considerable change. The fracture mode of Sn-5Bi and Sn-15Bi solder balls changed from ductile solder mode to mixed solder/IMC mode, finally converted to brittle IMC mode. Sn-15Bi solder balls had the lowest fracture energy due to its poor elongation properties and lower shear strength.
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