Failure mechanism of Pb-bearing and Pb-free solder joints under high-speed shear loading

Abstract

The failure behaviors of ball grid array (BGA) solder ball joints under the various loading speeds of the high-speed shear test were investigated both experimentally and with non-linear, 3-dimensional finite element modeling. Conventional Sn-37Pb and Pb-free, Sn-3.5Ag solder alloys were used to compare the failure behaviors. Far greater shear forces were measured by the high-speed shear test than by the low-speed shear test. The shear force further increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloys. Brittle interfacial fractures were more easily achieved by the high-speed shear test in the Sn-3.5Ag solder joints, especially at higher shear speed. This result was discussed in terms of the relationship between the strain-rate of the solder alloy, the work-hardening effect, and the resulting stress concentration in the interfacial regions. However, no transition of the failure mode was observed in the high-speed shear test of the Sn-37Pb solder joints.

Mechanical strength and fracture mode transition of Sn-58Bi epoxy solder joints under high-speed shear test

“…5, the shear force increased with increasing shear speed to a maximum at the highest shear speed. The shear forces measured by the high-speed shear loading (1,000 mm/s) were much higher than those of the lowspeed shear loading (10 mm/s), indicating that the increase in shear force with increasing shear speed was a direct consequence of the material properties, including both the time-independent plastic hardening and time-dependent strain-rate sensitivity [14]. In other words, the shear force increased with increasing shear speed, indicating that the resistance to plastic deformation was increased with increasing shear ram displacement rate.…”

“…It is generally known that the solder joint sheared at a lower loading speed was deformed more than that of a higher loading speed [14]. The smaller strains at faster loading speeds were caused by the so-called work-hardening of the solder during deformation, whereby a higher strain-rate increases the dislocation density.…”

A novel high-speed shear test for lead-free flip chip packages

“…Several studies [1][2][3] have been conducted on the reliability of board-level solder joints. The ball shear and pull tests are the most widely adopted methods of assessing the mechanical strength of solder ball bonds in BGA packaging (JESD22-B117).…”

Influence of small Sb nanoparticles additions on the microstructure, hardness and tensile properties of Sn–9Zn binary eutectic solder alloy

“…Intensive research on finding the suitable Pb-free solder replacement for the conventional Lead-Tin (Sn) eutectic alloy have sped up in the recent years owing to the realization of a harmful influence of the Pb [2]. The development of new lead-free solders and composites has been the focus of attention for many researchers, around the world.…”