| This work consists of two parts: temperature variation effects on bipolar power devices and thermal modelling of power module stacks. The switching characteristics of the non-complementary MOS-Controlled Thyristor (i.e. an MCT that is gated with respect to the cathode as opposed to the anode) are examined over a temperature range of {dollar}-{dollar}180 to 195{dollar}spcirc{dollar}C. The forward conduction drop and dynamic performance of these MCTs are discussed and compared to the behavior of similar complementary MCTs, IGBTs, and normally-off Bipolar Mode FETs (BMFETs) over the same temperature range. Additionally, the turn-off characteristics and forward conduction drop of Gate Turn-off Thyristors (GTOs) are examined over a temperature range of {dollar}-{dollar}125 to 125{dollar}spcirc{dollar}C. The forward conduction drop and dynamic performance of these GTOs are discussed and compared to the behavior of other types of thyristors, such as SCRs and MCTs. An analytical description of the forward conduction voltage drop is developed. Packaging of power devices in modules at elevated temperatures is presented in the second half of the work. A highly descriptive method for displaying heat flow in power modules is used to analyze three different transistor stack types: Direct Bond Copper (DBC), Thick Film Printed Substrate, and Insulated Metal Substrate (IMS). In addition to analyzing the highest performance configurations of each technology, the effects of variable substrate and baseplate thermal conductivity are shown. Variable baseplate-to-heat-sink grease conductivity is shown to greatly affect heat flow. The effects of solder voiding (both fatigue induced and manufacturing defects) on thermal resistance and flux are described for the DBC technology. Based on the results of these studies, design flaws are identified and remedies proposed. |
