Heat transfer and nonlinear thermal stress analysis of a convective surface mount package

Most prior heat transfer and thermal stress analyses of convective surface mount packages have relied on either an isothermal (constant temperature) model or a constant heat transfer coefficient model. This usually leads to a concern for the accurate estimation of the local temperature distributions and the induced stresses. To release this concern, this paper presents the use of the finite element analysis method in predicting the local temperature and stress distributions of a ceramic ball grid array (CBGA) package. The analysis has included a local heat transfer coefficient model with the thermal boundary condition that was obtained from a previous computational fluid dynamics (CFD) solution. The results are compared with that predicted by the isothermal model and the constant heat transfer coefficient model. Instances where the temperature dependent and elastic-plastic material behavior are significant to produce nonlinear stress response in some components of the modeled package are also examined.