Thermal analysis of high power LED subassemblies for automotive front light application

High power LEDs for front lighting have been introduced on the market during 2007 and cost effective solutions are still challenging due to the high operating temperature, long lifetime and harsh environmental condition. We present LED subassemblies based on ceramic LED packages which provide up to 250lum per package. The subassemblies are LED matrices designed for adaptive front lighting and modern light guide based day running light / turn indicator combination. The LED package has two electrical and one additional thermal pad. An Rth of 4°C/W / Rth_real=5°C/W is measured for the LED package by applying the JESD51-14 standard using special IMS boards for controlled variation of the thermal interface. Different board materials, i.e. Fr4, Al-IMS, Cu-IMS and special Cu-IMS, are evaluated. The advantages of special copper IMS with direct thermal contact between the LED package and the metal core are demonstrated.