Active Thermal Control of Distributed Parameter Systems Excited at MultipleFrequencies

Abstract

In testing packaged high-power integrated circuits, active thermal control is useful in providing die-level temperature stability. A time-varying heat load is applied to the surface of the package to compensate for the time-varying test power sequence applied to the die. An earlier study determined the proper control heat load for a single-frequency sinusoidal variation in die power subject to a finite allowed temperature variation on the die. Actual test power sequences contain many frequencies at various phase angles, each contributing to the temperature variation of the die. In the present study, we develop a method of controlling multiple frequency test sequences subject to a finite temperature tolerance. It is shown that the total control power may be minimized assigning temperature tolerances to the highest frequencies in the test power sequence.