Failure site transition in PB-free solder joints caused by manufacturing variabilities in BGA and MLF components in low cycle fatigue analysis

This paper presents a comprehensive 3 level design of experiment that is applied on the manufacturing process to compare the effect of variability in printing and reflow processes on quality and durability of (Micro Lead Frame) MLF and BGA (Ball Grid Array) components. The quality of the BGA and MLF components produced under different runs of DOE (Design of Experiment) was studied very closely and a thermal cycling test was conducted to investigate and compare the thermo-mechanical durability. Different populations of failures were observed in both BGA and MLF components and failure analysis was conducted to determine the failure mechanisms and failure sites in both components. The levels of sensitivity of these two types of components to the process variability were compared. A Finite Element Analysis was conducted to determine the failure site for good quality joints and to correlate the experimental results. MLFs and BGAs show different levels of sensitivity to the process Variabilities. Conflictions were observed when a parameter variation caused durability improvement in one type and durability degradation in the other. Recommendations are made to the manufacturers for reduction of defects in production processes that involve both of these components.