Measurement and simulation of junction to board thermal resistance and its application in thermal modeling

The junction-to-board thermal resistance, /spl theta//sub JB/ or theta JB, is a figure of merit for the thermal performance of surface mount integrated circuit packages relative to the printed circuit board temperature. The determination of /spl theta//sub JB/ by measurement or simulation is described. Examples of the use of /spl theta//sub JB/ in thermal modeling are provided along with estimates of anticipated accuracy. This model provides substantial accuracy improvements over estimates of thermal performance based on junction-to-ambient thermal resistance.