Effect of cooling mechanism and powering configurations on thermal impedances in an electronic enclosure

An experimental investigation of the dependence of thermal impedance on a variety of typical design parameters including component arrangement, powering configuration, board placement, system orientation, and cooling mode is described. Some concepts of board and regional thermal impedances are introduced and the utility of these measures for performance comparison, data analysis, modeling, and design extrapolation is illustrated. A component-level energy balance is proposed to predict measured changes in peak component temperatures as a function of power level and location of neighboring components. Neighboring-component effects can increase effective junction to ambient thermal impedance by more than 25%. Measured heat transfer coefficients are compared to previously published values. The design issues of correcting for neighboring-component effects and utilizing the concept of regional thermal impedances are explored. A standardized portable database suitable for numerical model validation is described