Modelling of IC-Packages Based on Thermal Characteristics

Abstract

When modelling the thermal behaviour of electronic systems with Computational-Fluid-Dynamics (CFD), the problem usually occurs of how to treat IC-packages. Especially with finite-difference-type codes it is found that a detailed modelling of all interesting components, e.g. on a printed circuit board, is not feasible with regard to the number of grid cells, whereas crude block-models are unable to yield the desired results.

This paper describes a method of building compact models of IC-packages which meet the demands of an economical grid and at the same time show a thermal behaviour almost identical to the detailed model. It is further shown that such a compact model can be deduced directly from the data-sheet values of the thermal resistances R_th,JA and R_th,JC, vided the available data are well specified and based on meaningful test methods. From this point of view the often-criticized thermal resistance values appear quite useful, which adds an aspect to the current debate about thermal characterization of IC-packages.