IGBT Power Module thermal solution
IGBT, as a new type of power semiconductor device, plays an important role in emerging fields such as rail transit, new energy vehicles, and smart grids. The thermal stress caused by excessive temperature can lead to the failure of IGBT power modules. In this case, a reasonable heat dissipation design and unobstructed heat dissipation channels can effectively reduce the internal heat of the module, thereby meeting the performance requirements of the module. Therefore, the stability of IGBT power modules cannot be achieved without good thermal management.
Vehicle grade IGBT power modules usually use liquid cooling for heat dissipation, which is further divided into indirect liquid cooling and direct liquid cooling. Indirect liquid cooling adopts a flat bottom cooling substrate, with a layer of thermal conductive silicone grease coated on the substrate and tightly attached to the liquid cooling plate. Then, the cooling liquid is passed through the liquid cooling plate, and the cooling path is: chip DBC substrate flat bottom cooling substrate thermal conductive silicone grease liquid cooling plate cooling liquid. The chip serves as a heat source, and the heat is mainly transmitted to the liquid cooling plate through the DBC substrate, flat bottom heat dissipation substrate, and thermal conductive silicone grease. The liquid cooling plate then releases the heat through liquid cooling convection.
The direct liquid cooling cooling adopts a needle type heat dissipation substrate. The heat dissipation substrate located at the bottom of the power module adds a needle fin shaped heat dissipation structure, which can be directly sealed with a sealing ring to dissipate heat through the coolant. The heat dissipation path is from chip DBC substrate needle type heat dissipation substrate coolant, without the need for thermal conductive silicone grease. This method allows the IGBT power module to come into direct contact with the coolant, reducing the overall thermal resistance value of the module by about 30%. The needle fin structure greatly improves the heat dissipation surface area, greatly improving the heat dissipation efficiency. The power density of the IGBT power module can also be designed to be higher.
Thermal conductive grease is a thermal conductive material that reduces the interfacial contact thermal resistance, with a thickness of up to 100 microns (adhesive line thickness or BLT) and a thermal conductivity coefficient between 0.4 and 10W/m · K. It can reduce the contact thermal resistance between power devices and heat sinks caused by air gaps, and balance the temperature difference between interfaces. Reasonable selection of thermal interface material thermal conductive silicone grease can protect the safe and stable operation of IGBT modules.
