  Thermal FEM (Finite Element Method) simulations can be used to predict the
thermal behavior of power semiconductors in application. Most power
semiconductors are made of silicon. Silicon thermal material properties are
significantly temperature dependent. In this paper, validity of a common
non-linear silicon material model is verified by transient non-linear thermal
FEM simulations of Smart Power Switches and measurements. For verification,
over-temperature protection behavior of Smart Power Switches is employed. This
protection turns off the switch at a pre-defined temperature which is used as a
temperature reference in the investigation. Power dissipation generated during
a thermal overload event of two Smart Power devices is measured and used as an
input stimulus to transient thermal FEM simulations. The duration time of the
event together with the temperature reference is confronted with simulation
results and thus the validity of the silicon model is proved. In addition, the
impact of non-linear thermal properties of silicon on the thermal impedance of
power semiconductors is shown.
