Developing a micro-thermography system for thermal characterization of LED packages

Abstract

LED system design is often limited by the thermal performance of the system. Increased temperatures can cause a decrease in optical performance and can lower the overall reliability of the system. Therefore, proper thermal management and design is crucial for the device performance. Accurately measuring the junction temperature of a LED die is a complicated task. This paper is focusing on the application of micro-thermography for measuring the resulting surface temperature of a bare die bonded on a PCB substrate. First, relevant literature about thermal management of LED systems and standard approaches for junction temperature measurements are given. Then, the thermography system is introduced, and the implementation of the measurement procedure is discussed. The emissivity correction is an important part of the calibration of the system and is described in detail. A thorough thermal analysis has been conducted using the novel micro-thermography approach and the results are used for determining the thermal resistance of the system under analysis. Furthermore, a thermal simulation has been conducted using Finite Element Modeling. The model and meshing are described, and initial simulation results are given. The experimental data is then used to modify the thermal simulation model to accurately represent the thermal behavior of the system.