Micromechanics in solder materials used for microelectronic applications

In my previous articles I reported that, in solder materials subjected to mechanical fatigue under low-frequency conditions (f < 10(-3)/s) where intergranular failure occurs, there is some evidence that the grain, or colony, boundaries undergo sliding. To develop a better understanding of this phenomenon, the correlation between grain boundary orientation and intergranular cracking was investigated by examining cross sections of cracked grain boundaries in eutectic bulk solders subjected to tension-compression. A statistical picture of crack propagation was developed to provide evidence for the shear mechanism, which showing that there is a favored boundary orientation with respect to the surface of the specimen and the stress axis.