Thermal Simulation for Reliability of Automotive Control System

When Valeo Electronics & Connective Systems Branch in France needed to ensure the reliability of the electronic motor control unit governing the speed of an engine-cooling fan, they turned immediately to the Flotherm thermal simulation software. The electronic motor control unit is a sealed aluminum and plastic box situated in an extremely harsh environment, close to the engine, and is subject to ambient temperatures of up to 120°C. Using thermal simulation combined with infra-red imaging, Valeo engineer Marc Iliozer was able to predict the temperature of the sensitive electronic devices inside the control unit quickly and accurately, and ensure that all components would operate inside their specified temperature limits – essential for their reliability. Detailed, board-level thermal simulations were carried out at the beginning of the design process, before fixing the locations of the key components on the board. Excellent correlation between IR measurements and thermal simulations were observed, even on such details as the copper tracks at the surface of the PCB (which are subject to a non-linear heating phenomenon known as “Joule heating”) and in the components themselves, where the thermal conductivity changes with temperature.