In cases where forced convective cooling alone is inadequate, or where
the size of the housing limits the heat sink's dimensions, ICs can be
cooled using an active heat sink. Compared to a classical finned heat
sink, it can benefit from a substantial size reduction or from an imp
ortant enhancement of the heat transport from the IC to its surroundin
gs. The active heat sink's function is based upon a Peltier-effect coo
ling system. The active heat sink controls the IC's thermal resistance
to its surroundings. The Peltier-effect heat pump is a non-linear sys
tem. Therefore, surveys of the system's stability are far from evident
. Thermo-electric models for both the Peltier-effect heat pump and a N
TCR (Negative Temperature Coefficient Resistance) temperature sensor a
re presented. These are linked to thermal models for the IC packaging
and a finned heat sink on one hand and to electronic models for the co
ntrolling circuit on the other hand. Simulations show non-linear therm
al-behaviour and system instabilities according to the power load on t
he IC, to the forward amplification of the circuit, but also to the am
bient temperature change. The latter phenomenon occurs after power-on
of the whole device of which the IC is a part. The theoretical results
were confirmed by infrared thermographic measurements on a self const
ructed active heat sink. (C) 1997 Elsevier Science Ltd.