Impact Force Characteristics of Package-level Solder Joints Under Ball Impact Test

The ball impact test is developed as a package-level measure for the board-level drop reliability of solder joints in the sense that it leads to fracturing of solder joints around intermetallics, similar to that from a board-level drop test. We investigate numerically in this paper the effect of yield stress variations of solder alloy on transient structural responses of a single package-level solder joint subjected to ball impact test. This study focuses on the characteristics of the ascending part of the impact force profile. According to the piecewise linear stress-strain curve obtained for the Sn-4Ag-0.5Cu solder alloy, parametric studies are performed by varying either segmental moduli or characteristic stresses of the curve at fixed ratios, in regard to the lack of available rate-dependent material properties of solder alloys.