Integrated Microchannel Cooling for Power Electronic Modules

The power electronic module plays a key role in the power system by providing the needed physical support, electrical contact and insulation, and thermal pathway for power devices. Using wide bandgap power semiconductors in the power modules enables high-frequency and low-loss switching at relatively high temperatures for efficient power conversion. These advantages could lead to an increase in power-density for the power module as well as a reduction of cost, weight, and volume at the system level. However, the highly integrated power module requires advanced thermal management solutions for effective heat removal from the active chips to achieve high reliability. The evaluation of thermal performance for the power module is critical for its packaging design, because most of the heat generated by the semiconductors is dissipated through the module package. It is even more critical for the gallium nitride (GaN)-based power modules due to the lower thermal conductivity of the GaN material compared with that of silicon and silicon carbide. This paper provides a brief introduction of power modules in conventional packaging design and a review of several new packaging structures with advanced thermal management solutions. The direct-bonded-copper (DBC) substrate with integrated microchannel cooling designed for a new packaging structure is proposed for highly integrated power modules. In this design, the cooling microchannels are embedded inside the aluminum nitride (AlN) layer of the DBC substrate. In finite element analysis (FEA) simulation model of the new package, six high-voltage GaN transistors are arranged on the top surface of the DBC substrate to realize a three-phase inverter circuit. Three straight embedded microchannels with a cross-sectional area of 0.3 mm × 5 mm are located underneath the GaN devices. The average maximum temperature of the GaN devices in the new package is around 72 °C (50 W power loss applied on each die), which is about 16 °C lower than that in the traditional power module package. A thermal transfer coefficient of 2000 W/m2 K, which is equivalent to the liquid cooling condition, is applied on the bottom surface of the baseplate in the traditional package. Enhanced heat dissipation capability is demonstrated using this integrated microchannel cooling method. Further study will focus on the fabrication of a prototype and experimental testing.