Automotive grade IGBT power module heat dissipation substrate technology

The main reason for the failure of the GBT power module is the thermal stress caused by excessive temperature. Good thermal management is extremely important for the stability and reliability of the IGBT power module. 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 IGBT power module in the motor controller will generate a lot of heat due to long-term operation and frequent switching. 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 vehicle 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.

1. The function and type of heat dissipation substrate of IGBT module

The heat dissipation substrate is the core heat dissipation function structure and channel of the IGBT power module, and it is also an important component with a relatively high value in the module. Features such as matching thermal expansion coefficient, sufficient hardness and durability.

1. Copper needle heat sink substrate

The copper pin-type heat dissipation substrate has a pin-fin structure, which greatly increases the heat dissipation surface area, allowing the power module to form a pin-fin direct cooling structure, effectively improving the heat dissipation performance of the module, and promoting the miniaturization of the power semiconductor module. Since power semiconductor modules for motor controllers of new energy vehicles have high requirements for heat dissipation efficiency and miniaturization, they have been widely used in the field of new energy vehicles.

The process flow of the copper needle heat dissipation substrate is shown in the figure above. The main steps of production include: mold design, development and manufacturing, cold precision forging, shaping punching, CNC machining, cleaning, annealing, sandblasting, bending arc, electroplating, resistance Soldering/engraving traceability code, inspection test, etc.

2. Copper flat base heat sink

The copper flat bottom heat dissipation substrate is a common heat dissipation structure for power semiconductor modules in the traditional field. Its main function is to transfer the heat of the module to the outside and provide mechanical support for the module. This product is traditionally used in industrial control and other fields, and is currently also used in emerging fields such as new energy power generation and energy storage.

The process flow of the copper flat-bottom heat dissipation substrate is shown in the figure above. The main production steps include: shearing, punching and blanking, CNC machining, punching/flattening the boss, sandblasting, electroplating, bending arc, solder mask, inspection test etc.

2. Heat dissipation method of automotive grade IGBT power module

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.