Thermal characterization of a PLCC-expanded Rjc methodology

In a previous study, it was proposed to extend the use of the junction-to-case thermal resistance, R_jc, 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. This expanded R_jc methodology is applied here to an actual plastic-leaded chip carrier (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