Real-time imaging of temperature distribution inside a power device under a power cycling test

The analysis of temperature distribution in a power device package is essential to increase the reliability of power devices, because the temperature swing during the operation creates mechanical stress at the interfaces between these materials. However, the temperature distribution is difficult to obtain under operating conditions because of the limitation in the use of non-destructive methods to measure the inside temperature of the device. In this paper, we propose a method of real-time imaging of temperature distribution inside a DUT. This method is based on a “real-time simulation”. The real-time simulation was realized by combining surface temperature monitoring and high-speed thermal simulation. The thermal simulator calculates temperature distribution inside the package by using the monitored surface temperature as a parameter. We demonstrate our system with a TO-220 package device under a power cycling test. The system indicated a temperature distribution change in the package with a frame rate of less than 1 s and the temperature difference at the Si chip was within 2 °C by a comparison with that estimated from forward voltage drop.