Creep behavior of BGA solder joints during thermal cycling by Moire Interferometry

The study of solder joint reliability and integrity is a significant issue in electronic packaging. Solder joints are subjected to cyclic strain due to thermal expansion mismatch between the bonded layers, as a result they undergo elastic and inelastic deformations, and finally experience microcracking and damage. There is very little test data available in the literature about thermomechanical response of actual micron scale solder joints in BGA products. In this study, thermal cycling of a Ball Grid Array (BGA) package between -55°C and 125°C is conducted by using a large capacity Super AGREE thermal chamber. High sensitivity Moiré Interferometry is used for measuring the irreversible strain after certain number of cycles. A novel specimen preparation technique allowed us to measure irreversible strain accumulation up to 20 cycles. The technique used casts a new look in the application of Moiré Interferometry method. Previously reported similar studies in the literature included one thermal cycle only. This new technique allows recording plastic deformations up to twenty cycles.