Impact of laminate cracks under solder pads on the fatigue lives of ball grid array solder joints

BGA Interconnection Reliability in Mirrored Module Configurations

“…In TCT clearly distinguishable characteristic lifetimes were achieved for each configuration, as presented in Table IV. Overall, the lifetimes are quite short compared with the studies reported on similar assemblies [26]- [28], as even the SS configuration had a rather low characteristic lifetime compared to the often used qualification target of 800 to 1000 failure-free cycles in -40 to +125 °C TCT [29]. However, this target may be excessively high, as is noted in the paper and discussed further in [30].…”

“…It can be observed in Figure 4 that in the places where rupturing of the PCB occurs, the solder ball is not cracked as much. The impact of PCB laminate cracks on TCT results have been studied by Tegehall and Wetter [26]. Concerning PCB laminate cracks they concluded that these cracks "increase the flexibility of the joints", and that "the larger the cracks, the more fatigue life will be improved".…”

“…Further, there are challenges in detecting cracks in the laminate without ultraviolet light inspection combined with the addition of a fluorescent agent to the molding resin during processing of a sample for OM. However, as the authors in [26] also mention, in a more benign environment the risk of laminate failures is reduced. The failure mode is expected to change in a field environment with the current test set, as well.…”