Effects of thermal cycling parameters on lifetimes and failure mechanism of solder interconnections

The work presented in this paper focuses on a) clarifying the underlying physical failure mechanism of Sn-rich solder interconnections under thermomechanical loading and b) identifying the means to accelerate the failure mechanism by optimizing the dwell-times and ramp-rates of thermal cycling test. The statistical results showed that as the dwell-times were decreased the number of cycles to failure increased but the shortest testing time was achieved with 10-minute dwell-times. Increase of ramp-rate did not affect the number of cycles to failure but the time to failure was significantly reduced. Investigations of the nucleation of cracks in solder interconnections revealed that nucleation is much more dependent on the number of thermal cycles than on the studied test parameters and that the nucleation took place within about the first quarter of the average lifetimes. Furthermore, cracking of the SnAgCu interconnections under all thermal cycling conditions studied took place through the bulk of the solder interconnections along the continuous network of grain boundaries produced by recrystallization. An approach to further accelerate thermal cycling tests is proposed based on the formed understanding of the failure mechanism.