Thermal management and thermal resistance of high power LEDs

Summary form given only. The junction temperature of Light Emitting Diodes (LEDs) is a primary reliability parameter. Exceeding the maximum rated junction temperature could lead to accelerated light output degradation and sometimes even to catastrophic failures. Besides that junction temperature influences the desired LED properties in applications like light output efficiency, dominant wavelength and forward voltage. Therefore thermal management and proper thermal characterisation of high power LEDs is very important for a reliable product with good performance. By measuring the thermal resistance of a high power LED it has to take into account that the power applied to the device is converted into heat and light (-20-40% efficiency). This means that the thermal resistance of a LED can not be determined without knowing the energy flux emitted as light. Therefore in general the interpretation of a given thermal resistance of an optoelectronic device is not well defined. Establishing of a standard on how to do thermal resistance measurement for light emitting devices is necessary.