LED thermal management of an automotive electronic control module with display

Abstract

In automobiles, an ECM (Electronic Control Module) is used for controlling internal ambient temperature of vehicles to enhance comfort level of passengers. It typically contains a display module to show various operational modes such as cooling air temperature, ON/OFF for blower, AC, de-fogger etc. The display module uses LEDs as source of illumination. Adequate illumination requires packaging of several LEDs m a compact/constrained space. Also LEDs must operate at very high ambient temperature of 85°C that leads to significant thermal management challenges. This paper describes parametric studies using various thermal management techniques such as heat spreader, increased PCB copper layer thickness, increased copper pad size for LED, high conductive plastic back cover along with pedestals, thermal via for LEDs and vent holes for the enclosure; to bring down LED temperatures within its safe operating limit. LEDs are modeled in detail (using contact resistance between the die and lead frame) in order to improve the accuracy of junction temperature prediction. A combination of thermal management solutions/techniques are used to mitigate heat from LEDs with significant bearing on cost competitiveness.