Transient thermal impedance of semiconductor devices

In this paper the thermal behavior of the semiconductor device is referred to the junction. Devices consisting of multiple parts which are non homogeneous and with varying outlines are subdivided into homogeneous elements with simple outlines which are successively related to the junction. Thermal impedance calculations of cylindrical and spherical sectors are given numerically. Stationary thermal impedances provide the framework to assemble a valid succession of transient thermal impedances. The analysis is expanded for long heating cycles by a simple lumped-component approach with limits of validity.