Rapid Thermal Modelling of Power MOSFET Using Bump Test Method to Evaluate Performance of Low Cost Heatsink

Abstract

Heat dissipator or heatsink is crucial for the reliability of MOSFET-based converters and inverters. Currently, products such as To-220 are low cost passive aluminium heatsink that fit to a single discrete MOSFET package did not followed by proper documentation about its thermal model and performance. Thermal modelling has been used widely for thermal studies, but the methods were often time consuming, complex setup, and require sophisticated equipments. This study proposed a different method in thermal modelling that is specifically applied to evaluate the performance of low cost heatsink through the Bump Test experiment. It emphasizes on rapid, simple setup and calculations. The experiment were finished in less than 1000 s in order to obtain dataset that were used to develop case to ambient thermal model of IRF840 n-channel MOSFET that was constructed by third order transfer function. Also, it was converted to Cauer equivalent RCs circuit to obtain physical meaning of heatsink block layers. The conducted experiments were applied to two different low cost heatsinks shapes; heatsink A resulted in a dissipation of MOSFET’s power limit to 4.21 W, while the attached heatsink B produced 5.38 W. In other words, heatsink B has 27.79% higher dissipated power handling, or 13.06% higher continuous Drain current utilization, than heatsink A. These values represented quantitative measure of heatsink performance. This study can be used as a technical reference for MOSFET based electronic circuit board fabricator in order to obtain rapid measure of low cost heatsink performance.