Validity and limits of the junction temperature concept for integrated power devices

he paper makes an attempt to define rigorously the junction temperature concept for large active area power devices. It is first shown that, from a mathematical point of view, the junction temperature must be defined as the average temperature in the active area. Then two criteria based on electrical and thermal considerations are set in order to check the validity of the junction temperature concept. Examples are given and discussed for components exhibiting stable and unstable electrothermal behaviours.