Thermal Analysis of Packaging Solution for GaN Multi-Chip Power Micromodule

This paper presents the results of thermal analysis of a novel compact GaN Multi-Chip Power Micromodule mounted on a multilayer printed circuit board of a high-density DC-DC converter. GaN Multi-Chip Power Micromodule consisted of two chips of power E-mode GaN HEMTs (EPC2052), packaged Si gate driver (UCC27524) and passive components that were assembled on a ceramic AIN direct bonded copper substrate with castellations. The heat dissipation from the GaN Multi-Chip Power Micromodule is implemented through a metal baseplate mounted in the multilayer PCB window. Using the results of FEM modeling the temperature distribution throughout the volume of the GaN Multi-Chip Power Micromodule was obtained. The parameters of the equivalent thermal circuit were calculated from temperature distribution map. The proposed solution was found to have a junction-to-ambient equivalent thermal resistance of $43 \mathrm{~K} / \mathrm{W}$. This is more than $40 \%$ better than the conventional constructive solution recommended by manufacturer, when power GaN HEMTs are directly mounted on the PCB. The use of GaN Multi-Chip Power Micromodule with a reduced thermal resistance as part of a high-density DC-DC converter can contribute to an increase in its power density or reliability.