The affect of device level modeling on system-level thermal predictions

Thermal management is important for the performance and reliability of today´s high power and high density electronics systems. The thermal architecture between the device and heat sink can quickly become very complex when designing for ideal operating temperatures. In order to predict the temperature rise, it is desirable to have a simple modeling technique which reduces the amount of time and effort required to obtain accurate results. Often, the heat flux of the device is based on either the die area or the case area. Complication occurs when simplifying the contact area of a given component. Detailed analyses have been performed for two different cases that show the importance of die-level modeling. In the first case, models of an insulated gate bipolar transistor (IGBT) attached to a cold plate are compared to determine the cold plate temperatures when assuming uniform heat flux, and when modeling from the device level. The different analyses results in a heat sink ΔT that differs by 33%. In the second case, a heat spreader is used to cool several high power components. The heat generation areas of the components are significantly smaller than the case footprint. A detailed look at the device level spreading reveals a difference in maximum temperature of 14.5°C between the results of the different modeling techniques used.