Heat Dissipation Method of IGBT Power Module
for New Energy Vehicles
The main cause of failure of IGBT power modules is thermal stress caused by excessive temperature. Good thermal management is extremely important for the stability and reliability of IGBT power modules. The new energy vehicle motor controller is a typical high power density component, and the power density is still increasing with the improvement of the performance requirements of new energy vehicles. The long-term operation and frequent switching of the IGBT power module in the motor controller will generate a lot of heat. As the temperature rises, the failure probability of the IGBT power module will also increase significantly, which will eventually affect the output performance of the motor and the reliability of the car drive system. . Therefore, in order to maintain the stable operation of the IGBT power module, a reliable heat dissipation design and a smooth heat dissipation channel are required to quickly and effectively reduce the internal heat of the module to meet the requirements of the module reliability index.
At present, automotive-grade IGBT power modules generally use liquid cooling for heat dissipation, and liquid cooling is divided into indirect liquid cooling and direct liquid cooling.
1. Indirect liquid cooling
Indirect liquid cooling uses a flat-bottomed heat-dissipating substrate. A layer of heat-conducting silicone grease is applied under the substrate, which is closely attached to the liquid-cooled plate. The cooling liquid is passed through the liquid-cooled plate. The heat-dissipating path is chip-DBC substrate-flat-bottomed heat-dissipating substrate-thermal silicon Grease-liquid cold plate-coolant. That is to say, the chip is the heat source, and the heat is mainly conducted to the liquid cooling plate through the DBC substrate, flat bottom heat dissipation substrate, and thermal conductive silicone grease, and the liquid cooling plate then discharges the heat through liquid cooling and convection.
In indirect liquid cooling, the IGBT power module does not directly contact the cooling liquid, and the heat dissipation efficiency is not high, which limits the power density of the power module.
2. Direct liquid cooling
Direct liquid cooling uses a pin-type heat dissipation substrate. The heat dissipation substrate located at the bottom of the power module adds a pin-fin heat dissipation structure, which can be directly added with a sealing ring to dissipate heat through the coolant. The heat dissipation path is chip-DBC substrate-pin heat dissipation substrate -Coolant, no need to use thermal grease. This method makes the IGBT power module directly contact with the coolant, the overall thermal resistance of the module can be reduced by about 30%, and the pin-fin structure greatly increases the heat dissipation surface area, so the heat dissipation efficiency is greatly improved, and the power density of the IGBT power module can also be designed more high. At present, direct liquid cooling has become the mainstream heat dissipation method for automotive-grade IGBT power modules.
