Thermal issues in microsystems packaging

Miniaturization of electronic/mechanical systems is achieved by packing dif ferent functional components into tight space, The heat transfer analysis f or such systems has to deal with geometrically complex heat transfer paths, and it needs to be done quickly in response to every design alteration. Th is paper proposes a concept that aims at reduction of analysis load on the packaging designer. The proposed scheme is composed of two major steps, Fir st, a computer program "configuration generator" is used to generate possib le geometric configurations of heat transfer paths in a systematic manner, Second, temperature solutions for these configurations are compressed into "fast estimate" formulas that free the packaging designer from the need to perform involved heat transfer analysis. This approach is illustrated using a topic of heat spreading on the planar substrate as an example, Miniaturization of systems also raises another issue for the thermal design ; that is the coupling between the system configuration and the overall hea t dissipation to the environment. A model situation is considered where hea t diffuses from a zone on the system shell and to the environment by natura l convection and radiation. In the parametric domain spanned by the thermal conductivity of shell material and the system's characteristic length ther e is a zone where the system-level heat transfer is sensitive to the system 's configuration, Such characteristic length is around 1 cm for systems enc apsulated in plastics, 3-10 cm for those in ceramic and alloy shells, and 1 0-40 cm in copper or aluminum clad systems.