The failure mechanism of recrystallization-assisted cracking of solder interconnections

Microstructures and mechanical properties of the near-eutectic SnAgCu solder interconnections undergo notable evolution during use of electronic products. Under the standardized accelerated thermal cycling conditions widely employed by the electronics industry, recrystallization has been observed to enhance cracking of the solder interconnections by providing favorable propagation sites along the network of newly formed high-angle boundaries. It is well known that the increased internal energy of deformed solder provides the driving force for the competing restoration processes of deformed microstructures: recovery and recrystallization. However, Sn being a high stacking fault material with efficient recovery, recrystallization is initiated under restricted loading conditions: dynamic loading where strain hardening is more effective than recovery. Recent investigations of the acceleration factors of different thermal cycling conditions have suggested that the standardized thermal cycling can create failure mechanisms that differ from those taking place under use conditions due to the interaction between the restoration processes. The reason for the change in failure mechanism is thus related to the balance of stored energy accumulation and release by the restoration processes in different operation environments.