Thermal characterization of a PLCC-expanded Rjc methodology

It was previously proposed to extend the use of the junction-to-case thermal resistance to nonisothermal packages by defining an appropriately weighted, average surface temperature based on numerically derived thermal influence coefficients for each package surface (or segment) of interest. In the present study the authors apply the expanded R_c methodology to an actual PLCC package. Experimental data and the results of an extensive three-dimensional thermal simulation are used to establish the values of 11 sensitivity coefficients, which make it possible to determine the weighted-average case temperature. The variations in the sensitivity coefficients and the accuracy of the chip temperature predictions, with the number of data sets used to determine the coefficients, are also examined