Analysis of thermal transient data with synthesized dynamic models for semiconductor devices

A technique for synthesizing dynamic models comprised of discrete thermal resistances and capacitances directly from thermal step-response data on packaged semiconductor devices has been developed. Such models reveal the effective internal-package thermal resistances which comprise the overall junction-to-ambient or junction-to-case thermal resistance. These models can discriminate lumped internal constituent resistances including die/die-attachment spreading, internal package spreading, and case-to-air dissipation. The thermal step-response has been experimentally and analytically studied using the electrical method of junction temperature measurement. The interpretation and accuracy of these synthetic models have been investigated on a collection of test-case devices. Overshoot anomalies exhibited by junction-to-case thermal step responses have been examined experimentally and explained with synthetic model analysis. The application of synthetic models to computing thermal impedance for nonconstant or cyclic device-powering conditions is also presented.>