Thermo-mechanical stress analysis of PBGA

The solder joint reliability is the biggest disadvantage the plastic ball grid array (PBGA) has as compared with other conventional packages. A 2D steady state stress analysis based on the FE method has been carried out to study the most critical item, the solder joint. The parametric studies have been carried out to study the effect of chip length and substrate thickness on the magnitude of the stress in the solder joints. The results indicate that the ball nearest to the die has the highest magnitude of stress and hence is the most critical. These results are expected to act as a database for reliable PBGA design.