Study of SnAgCu Alloy Reliability

This work aims to understand the reliability ofSnAgCu solder interconnects used in PBGA packagesusing microstructure evolution laser moiréinterferometry and finite-element modeling. Aparticle coarsening based microstructure evolution ofthe solder joint material during thermal excursionswas studied for extended periods of time lasting forseveral months. The microstructure evolution andparticle coarsening was quantified and accelerationfactors were determined between benign field-useconditions and ATC conditions for PBGA packages withdifferent form factors and for two differentlead-free solder alloys. A new technique using lasermoiré interferometry was developed to assess thedeformation behavior of SnAgCu based solder jointsduring thermal excursions. This technique can used toestimate the fatigue life of solder joints quickly ina matter offew days instead of months. FEA in conjunction withexperimental data from the ATC for differentlead-free PBGA packages was used to develop a fatiguelife model that can be used to predict solder jointfatigue life for any PBGA package.