Thermal Management of High Power GaN MMIC on Silicon with Microjet Impingement Cooling

A high power GaN monolithic microwave integrated circuit (MMIC) power amplifier (PA) integrated on a silicon interposer with microjet impingement cooling is presented in this work. A Si interposer and a test cube for coolant supply were designed using computational fluid dynamics (CFD) method. The GaN MMIC is a 3-stage PA, and it was integrated on the interposer then assembled in the test cube. The microjets were arranged beneath the $3^{\mathrm{r}\mathrm{d}}$ stage transistors of PA to increase the heat transfer efficiency. The fluidic parameters of deionized (DI) water circulation, electrical and thermal characteristics of the chip were monitored in a cooling test platform. The hotspot power density at the junctions achieved 416.5 $\mathrm{W}/\mathrm{m}\mathrm{m}^{2}$ and the average heat flux of the chip was up to $53\mathrm{S}.9\mathrm{W}/\mathrm{c}\mathrm{m}^{2}$. The maximum junction temperature of GaN PA maintained at 158. $2^{\circ}\mathrm{C}$ at $70^{\circ}\mathrm{C}$ atmosphere temperature with the pressure drop of $\sim$270kPa at the flow rate of $\sim 500\displaystyle \mathrm{m}\mathrm{L}/\min$. The implementation results have demonstrated that microjet impingement cooling is an effective and practical solution for high power hetero-integration on silicon substrate.