A simple analytic method for converting standardized IC-package thermal resistances (theta(ja), theta(jc)), into a two-resistor model (theta(jb), theta(jt))

A typical data-sheets of an IC package supplied by a manufacturer, include two standardized thermal resistances, junction-to-ambient resistance theta (ja) and junction-to-case resistance theta (jc). It is well known that thes e two parameters are not applicable in thermal analysis of practical system s. Large errors can be encountered in predicting die temperature. In recent years, the concept of "compact model" was introduced. It predicts die temp eratures to a higher level of accuracy. The simplest is a two-resistor mode l with junction-to-board and junction-to-top as thermal resistors (theta (j b) and theta (jt) respectively). There are number of methods for the creati on of this model. Unfortunately, it requires information that is considered proprietary by the manufacturer. In this paper, we propose a novel approach that overcomes this difficulty. The two resistors are evaluated based solely on the manufacturer data-sheet . The method, named PERIMA, is a simple analytic algorithm, which is easy-t o-use. The standard test methods for measuring the thermal resistances thet a (ja) and theta (jc) are analytically re-constructed and the unknown resis tors theta (jc) and theta (jt) are derived. PERIMA was applied successfully for representative types of IC packages. The results compare very well wit h available data found in the literature, theta (jb) with less than 20% and theta (jt) in a range of 10% to 40%.