Thermal Influence Coefficients-Based Electrothermal Modeling Approach for Power Electronics

Abstract

An inverter or converter achieves the desired dc-ac or dc-dc conversion as required by electric and hybrid electric vehicles. This conversion is typically performed using semiconductor switches such as Insulated Gate Bipolar Transistors (IGBTs) modules consisting of transistors and diodes. Multiple transistors-diode pairs are integrated under a common copper base plate (also referred to as case). As power density increases, the heat dissipation of each device is influenced by other devices. The heat loss from semiconductor devices needs to be effectively dissipated to the ambient to maintain the temperature of IGBTs and diodes within acceptable limits (mentioned by the component manufacturer or based on the desired thermal margin in design). The over-temperature of the IGBT junction causes reliability issues resulting in solder fatigue and bond wire wear-out. The current work comprises predicting the temperature-dependent heat loss (electrothermal modeling) and thermal management techniques to dissipate these losses effectively to the ambient. An influence coefficient matrix is defined for liquid-cooled IGBT modules and used to estimate the die-to-die thermal influence. The IGBT module's heat distribution and its effect on the die temperature are studied for dc-dc and dc-three phase ac conversion.