This paper describes the development of a thermal flow simulation method for the design of electronic equipment. In the proposed sequence of analyses the first step is the estimation of heat generation rate from electric circuit. The method was applied to the thermal design of a new switch mode power supply (SMPS). The analysis was carried out using a computational fluid dynamics (CFD) code (Icepak: trademark of Fluent Inc.). In reducing the actual structural organizations of the printed circuit board (PCB) and the power semiconductor devices to simpler models the method of experimental design (MED) was employed. Following the prescription of MED the PCB was modeled as a simple plate having a thermal conductivity of epoxy resin. The power semiconductor devices were modeled by hexahedral resistance network. The heat sources are a field effect transistor (FET) and a diode, and computation of the power loss from them is described. The difference between measured and calculated temperatures on the power semiconductor devices was found to be within approximately 10 K.

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