Thermal sub-modeling of the wirebonded plastic ball grid array package

Abstract

Numerical simulation of the steady-state thermal behavior of the plastic ball grid array (PBGA) package can be greatly eased through the use of appropriate thermal sub-models. Detailed heat conduction models are used to characterize the thermal constriction effects of the solder sphere array connecting the PBGA to the printed wiring board (PWB) and the thermal vias in the PBGA substrate. The results of the sub-models allow the use of more accurate, yet geometrically-simpler entities in a finite-element (FE) or control-volume simulation, thereby shortening the overall cycle time required for a given analysis. Thermal performance of a PBGA mounted on a standard thermal test board is simulated through FE and computational fluid dynamics (CFD) methods and compared to experimental data from 225- and 357-lead PBGAs.