Thermal Consideration of LED Array for Rear Lamp by Simulation and Measurement

LEDs have been used for rear lamp applications over the past several years. Though multiple LEDs contribute to an aesthetic appearance, a meticulous arrangement of LEDs should be needed to avoid thermal damage to substrates of LED. This paper presents a thermal consideration of an LED array, which includes LEDs, metal plates as electrodes and a plastic base for rear lamp application.

Firstly, we discussed fundamental component related to thermal management and challenges to evaluate temperatures of LED array with a practical model by a thermal simulation. According to this study, the cathode side metal plate has a significant role to manage the temperature of LED array as a heatsink. Secondly, parametric evaluations were carried out for each design parameter of metal plate such as surface area, material and thickness using simplified LED array, which has three LEDs. Also, we considered the effect of mounting direction of LED array on temperatures, when that array was placed in a plastic box whose volume is adjustable. The effect of each parameter was evaluated with a thermal resistance from lead frame to ambient air. We found that most sensitive parameter of the thermal resistance is surface area, which is flexible and inexpensive parameter to manage the temperatures of LED array. The thermal simulation for each parametric model was also executed to indicate validity of the calculation. Thirdly, we measured the junction temperature that is a decisive criterion of cooling system and estimated the thermal resistance from junction to ambient air for a simple model having an LED with the thermal resistance test system. Additionally, we examined that the methodology is beneficial to improve the accuracy of numerical LED model.