Effect of voids on the reliability of BGA/CSP solder joints

Voids in solder joints have been considered as a defect in electronics assembly. The factors that affect void formation are complex and involve the interaction of many factors. There are no established standards for void size and void area in a solder joint for it to be deemed defective. Inspection criteria have been very subjective. The effect of voids on the reliability of solder joint may depend not only on the size, but also on frequency and location. This study is focussed on investigating the effect of voids on the reliability of solder joints. The size, location and frequency effects on the reliability were studied. Testing was done by mechanical deflection testing (torsion) system and air to air thermal cycling (−40 °C/125 °C). Failures were analyzed for the failure modes by cross sectional analysis. The results indicate that voids reduce the life of the solder joint. Voids which are greater than 50% of the solder joint area, decrease the mechanical robustness of the solder joints. Small voids also have an effect on the reliability, but it is dependent on the void frequency and location.