Lattice Boltzmann method study of bga bump arrangements on void formation

• This paper study the factors leading up to voids formation on three different BGA orientations
• Three dimensional multi-phase setup of encapsulation process according to San-Chen formulation
• Middle empty orientation has the highest potential of void formation typically towards the end of mold flow.
• High bond number and highly viscous material could reduce probability of air voids formation during the encapsulation process

This paper studies effects of different bump orientations on the void formation using Lattice Boltzmann method (LBM) based software. Prediction of air void is vital typically at the onset of reflow soldering which could reduce the reliability of the mold cavity. The effect of variations in pressure and velocity of the mold during flow on the formation of air voids are investigated for three different ball grid array (BGA) orientations namely perimeter, middle empty and full. The findings identified the predicted locations of void formation during the underfill encapsulation process. It was shown that middle empty orientation has the highest potential of void formation typically towards the end of mold flow as a result of low pressure and high velocity flow. In addition, using high bond number and high viscosity material could further reduce the air void formation.