Comparing Microchannel Technologies to Minimize the Thermal Stack and Improve Thermal Performance in Hybrid Electric Vehicles

Hybrid electric vehicles for military applications require advanced cooling to ensure peak power electronics performance and reliability. Two methods of reducing overall thermal resistivity by integrating microchannel coolers into the power electronics thermal stack are explored. The first approach involves silicon manifold microchannel coolers with direct fluid impingement on the semiconductor die. The second involves fabricating standard, parallel microchannels into a standard aluminum nitride substrate. Both designs are evaluated for flow and thermal performance in cooling a 4 mm silicon carbide diode. Both designs are found to be of comparable performance, primarily due to non-optimum microchannel dimensions for operating pressures below 35 kPa. For both types of devices, typical flow rates ranged from 40-60 mL/min with thermal resistivities on the order of 0.13-0.19degC-m²/W. Potential for future improvement of each design is discussed.