THERMAL CHARACTERISATION OF PACKAGES BY INVERSE HEATING

摘要

Packages are normally characterised by heating the chip and measuring the chip temperature as a function of time. From the recorded junction temperature, an equivalent thermal RC network can be found. This approach not only describes the thermal behaviour of the package but includes the ambient as well. Needless to stress that the ambient is not always well defined. To improve the method two additional experiments have been carried out. First of all the surface temperature of the package itself is monitored using infrared thermography. A second experiment makes use of sudden change of the ambient temperature without any chip heating but still measuring the chip temperature. This inverse heating provides us quite different thermal time constants. The main purpose of these experiments is to gain a better knowledge of the heat transfer inside the package. All the experiments are fitted or compared with the originally found equivalent thermal RC network.