Effect of the specimen size in predicting the mechanical properties of PbSn solder alloys

Abstract

The data obtained from bulk test specimens are often used in deformation models to predict the mechanical responses of parts that are very different in size and shape, such as solder joints in VLSI surface mount components. Such predictions are valid only if the size of the solder joints exceeds the representative deformation volume of the bulk specimens. In the present study, the measurement of the representative volume was performed for a single-phase solder alloy (98Pb-2Sn wt.%) deformed in both tension and cyclic loading. Deformation of 98Pb-2Sn alloy at room temperature was shown to be extremely inhomogeneous in both tensile and cyclic loading, and strain localization was observed at the grain boundaries. Strain distribution is more inhomogeneous in the specimen tested in fatigue than the specimen tested in uniaxial tension. This may be due to fatigue inhomogeneity in strain distribution or a small degree of buckling. The number of grains required for a representative volume of the 98Pb-2Sn alloy specimens tested is quite large.<>