Innovative thermal testing and evaluation methods for double-sided cooling automotive IGBT devices

IGBT (Insulated Gate Bipolar Transistor), an insulated gate bipolar transistor, is a composite fully controlled voltage drive composed of a (Bipolar Junction Transistor, BJT) bipolar transistor and an insulated gate field effect transistor (Metal Oxide Semiconductor, MOS). It is a power semiconductor device that has the advantages of both the high input impedance of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) and the low conduction voltage drop of a power transistor (Giant Transistor, GTR). The GTR saturation voltage is reduced, the current carrying density is large, but the driving current is large; the MOSFET driving power is small, the switching speed is fast, but the conduction voltage drop is large, and the current carrying density is small. IGBT combines the advantages of the above two devices, with low driving power and reduced saturation voltage. It is very suitable for use in converter systems with DC voltages of 600V and above, such as AC motors, frequency converters, switching power supplies, lighting circuits, traction drives and other fields.

IGBT is a power semiconductor device, which can be said to be one of the core technologies of electric vehicles. The quality of IGBT directly affects the release speed of electric vehicle power. Tesla Model

For another example, in the application of charging piles, when 220V AC mains power is used to charge the battery, the AC power needs to be converted into DC power to charge the battery through the power conversion circuit designed by IGBT. At the same time, the 220V voltage must be converted to an appropriate voltage or above. The battery pack is charged.

The innovation in the packaging structure of the IGBT module enables the double-sided cooling (DSC) power module to have stronger heat dissipation capabilities and lower parasitic parameters than the traditional single-sided cooling (SSC) power module. The successful mass application of double-sided cooling automotive IGBT devices in manufacturers such as Toyota (Denso), General Motors (Delphi), Tesla (ST), etc. has made thermal testing of double-sided cooling automotive IGBT devices more and more important.

IGBT is widely used in high-speed rail, rail transit, smart grid, aerospace, electric vehicles and new energy equipment and other fields. The IGBT packaging structure mainly consists of IGBT chips, DBC thermally conductive substrates, packaging materials, electrical connection terminals, etc. The chips are mainly Si, SiC, GaN, etc. The ceramic materials of the DBC copper-clad ceramic thermally conductive substrates mainly include Si3N4, AL2O3, ALN, etc. With the development of power electronic devices towards high density, high power and miniaturization, the large-scale use of electronic devices brings convenience to our lives. At the same time, higher and higher power makes the heat dissipation problem of electronic devices more and more serious.

Traditional power modules use a single-sided cooling structure, which mainly includes power chips, bonding wires, power terminals, outer frames, insulating substrates (DBC), base plates, and internal potting glue. The base plate is fixed on the surface of the cooler, and the power chip The heat generated by the loss is conducted to the radiator in one direction through the insulating substrate and bottom plate. However, for some small-sized and high-power modules, the traditional single-sided cooling structure cannot be used to meet their heat dissipation needs, and double-sided heat dissipation is becoming more and more important.

In this context, double-sided cooling automotive IGBT modules conduct heat to both the front and back sides at the same time, and their thermal test and evaluation methods need to be reconsidered. Many researchers have studied the one-dimensional heat transfer model of double-sided cooling power modules.

Luo Zhexiong, Zhou Wangjun, Lu Jinhui, and Dong Guozhong from Zhuzhou CRRC Times Semiconductor Co., Ltd. and the State Key Laboratory of New Power Semiconductor Devices published a paper in the 12th issue of "Electrical Technology" in 2022, "Double-sided cooling automotive IGBT module thermal test method "Research" provides a very good reference for the innovation of thermal test and evaluation methods for double-sided cooling automotive IGBT devices.

This paper focuses on the thermal testing method of double-sided cooling automotive IGBT modules. First, a new dual-interface thermal test idea is proposed, and then a thermal test tool is designed and developed based on the packaging structure of a double-sided cooling automobile X module, and the research and selection of thermal interface materials are completed. Through comparative research, a single-sided thermal impedance test method suitable for double-sided cooling automotive IGBT modules was developed, and the double-sided and single-sided thermal resistance tests of the X module were successfully implemented. Finally, the single-sided and double-sided thermal resistance values ​​and actual measurements were compared. The difference between the value and the simulation value is discussed, and the reasons for the difference and correction methods are discussed.

In the paper, a dual-interface cooling structure thermal testing method suitable for double-sided cooling automotive IGBT modules is proposed, which can realize single-sided thermal resistance testing and compare the differences between single-sided and double-sided thermal resistance values, measured values ​​and simulated values. ;For detailed details, you can refer to the paper.