A numerical study of the combined heat transfer by conduction, natural convection, and radiation in a sealed electronic package is reported. The goal of the study is to investigate the importance of the various heat transfer modes, the effectiveness of different heat transfer paths, and the impact of a number of design changes on the overall thermal performance of a typical electronic package. The package consists of an enclosure containing three printed circuit boards on which are mounted various heat-generating electronic components. Heat transfer processes at both small (i.e., inside a component) and large (i.e., the package) scales as well as all heat transfer modes are included simultaneously in the numerical model. Both one and two-dimensional radiation is considered. Results are presented in terms of streamline and isotherm plots and average temperatures and heat transfer rates. Overall, the numerical data show favorable agreement with available empirical data. One significant conclusion is that natural convection inside the enclosure has only a minor effect on the heat transfer in the present system.

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