Evolution of microstructure and failure mechanism of lead-free solder interconnections in power cycling and thermal shock tests

Failure mechanisms of lead-free solder interconnections in power cycling and thermal shock tests have been investigated in this work. Even though there are some characteristic differences between the two tests, the failures in both cases were induced by recrystallization-assisted crack nucleation and propagation. The three major differences between the tests were: (i) minimum temperature during power cycling was considerably higher in comparison to thermal shock, (ii) the current flow in the power cycling test resulted in electromigration, and (iii) in the power cycling test heat originates locally from components themselves. These differences were also reflected in the test results in the following way: firstly, in the power cycling test the recrystallization occurred earlier than in the thermal shock test, mainly owing to the higher average temperature and secondly, the enhanced growth of intermetallic compound layer at the anode side due to the electromigration was observed during power cycling.