Simulating package behavior under power dissipation using uniformthermal loading

The thermomechanical behavior of electronic packages under power dissipation is simulated using uniform thermal loading. Two packages are studied, a large periphery leaded plastic quad flat pack (PQFP) package and a more compact plastic ball grid array (PBCA) package, both mounted on a printed circuit board (PCB). Experimentally verified linear elastic finite element models are used to find the displacements at the predicted failure location during power dissipation, and then during uniform thermal loading. The results for the two cases are then analyzed to find correlations between power dissipation levels and equivalent heating temperatures. One use of the results could be to replace power cycling fatigue tests with thermal cycling tests, For the packages studied, the results revealed that very little uniform heating is required to simulate the thermomechanical effects at the failure location resulting from power dissipation. Due to the prestrained state of the packages at room temperature, power dissipation decreases the expansion mismatch while increasing the thermal mismatch between package and PCB