THERMAL INSTABILITY IN POWER BJT's: RADIOMETRIC DETECTION OF TRANSIENT TEMPERATURE MAPS AND ELECTRO-THERMAL SIMULATION

摘要

The hot spot onset in power bipolar transistors is examined, both from the experimental and simulation viewpoint. A simple three-dimensional electro-thermal model is proposed, based on an extraction tool of the layout structure, a fitting of the experimental dependence of input and output characteristics from the temperature, and packaging and heatsink thermal modelling. Experimental detection of transient temperature maps, by means of infrared detection technique, is presented and discussed about its validity. It allows to show the hot spot onset and location for two commercial power BJT. Collector current crowding is also described by the model in the hot spot mode. Finally, a detailed analysis of the hot spot onset locus in the I_c-V_(ce) plane is performed, showing a good agreement between experimental and simulation data.