Mechanical behavior of lead-free solder joints under high speed shear test at different pad metallization substrate

The most common cause of failure in portable electronic products is accidental drop. Therefore, the effect of impact on electronic package is very important. This study examines the mechanical behavior of lead-free solder joints under high speed shear. In this research we will set up the high rate ball shearing impact test, the maximum impact speed can up to 1.0 m/sec. The effects of differential solder alloy and pad metallization were also considered. Various Sn-Ag-Cu lead-free solder balls were investigated at room temperature and at a high speed shear rates of 1.0 m/s. Four failure modes were identified during the high speed shear test. In Mode M1, fractures occurred around the interface but not remain the solder on the pad. In Mode M2, fractures occurred around the interface and remain the solder on the pad. In Mode M3, fractures were noted across the solder ball. In Mode M4, fractures on the substrate lifted. The M3 failure rate of Ni/Au substrates increases over time. Meanwhile, M2 failure rate increases in shear tests of velocity increases from 0.3 up to 1.0 m/s. The M2 and M3 failures are the major failure modes in another kind of SAC solder alloy. However, for all shear test conditions, 100% of M3 is detected by using SnPb solder alloy. In the case of OSP, M2 is also the major failure mode for all shear test conditions. Comparing OSP with Ni/Au pad metallization substrate reveals that aging time does not significantly affect failure rate in shear test.