Thermal performance of lead-free microelectronic BGA package with defects

In this study, the detection and evaluation of defects at Pb-free BGA solder joints (SAC387, 95.5wt%Sn/ 3.8wt%Ag/ 0.7wt%Cu) in Printed Circuit Boards (PCB) placed under different thermal cycle conditions are investigated. By using digital radiography X-ray technique, the soldering defects in the packages including bridges, voids, ball missing, poor wetting, and tilted balls are identified. Subsequently, the thermal mechanical behaviours of the selected defective BGA packages are investigated by high temperature Moiré method. Based on the shear strain values obtained from Moiré tests, the fatigue life of defective and non-defective BGA packages subjected to thermal cycling tests is predicted and compared. It shows that various defect will have different influences on the thermal mechanical behaviours and reliability of a BGA package. The decrease in lifetime of defective packages depends on temperature and the defect classification. The experimental results achieved will provide valuable data for further optimization of Pb-free BGA design.