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Investigation of dynamic thermal performance is a key to improve the heat management of high-power (HP) vertical light-emitting diodes (VLEDs). Specifically, the thermal time constant is a crucial parameter for optimizing the design and reliability of HP LEDs. Herein, the dynamic thermal behavior of seven HP ThinGaN VLEDs with different constructions was demonstrated. The LEDs' thermal parameters were measured through the thermal transient tester system by a forward voltage technique. A three-stage of multiexponential function model was applied to divide the transient response curve into three regions with different thermal properties. This study focused on analyzing the first region that involved the chip region (epitaxial layer, wafer bonding layer, and submount) and chip bonding layer. The submounts of the LEDs under consideration include silicon carbide (SiC), silicon (Si), sapphire (Al2O3), and germanium (Ge). The results revealed that with a qualified wafer bonding layer, the LED packages with SiC, Si, and Al2O3 submount presented the optimum thermal time constant, which was 85, 69, 75, and 81 ms, respectively. [ABSTRACT FROM AUTHOR]

Purpose Thermal behavior of light-emitting diode (LED) device under different operating conditions must be known to enhance its reliability and efficiency in various applications. The purpose of this study is to report the influence of input current and ambient temperature on thermal resistance of InGaAlP low-power surface-mount device (SMD) LED.Design/methodology/approach Thermal parameters of the LED were measured using thermal transient measurement via Thermal Transient Tester (T3Ster). The experimental results were validated using computational fluid dynamics (CFD) software.Findings As input current increases from 50 to 90 mA at 25°C, the relative increase in LED package (ΔRthJS) and total thermal resistance (ΔRthJA) is about 10 and 4 per cent, respectively. In addition, at 50 mA and ambient temperature from 25 to 65°C, the ΔRthJS and ΔRthJA are roughly 28 and 22 per cent, respectively. A good agreement between simulation and experiment results of junction temperature.Originality/value Most of previous studies have focused on thermal management of high-power LEDs. There were no studies on thermal analysis of low-power SMD LED so far. This work will help in predicting the thermal performance of low-power LEDs in solid-state lighting applications. [ABSTRACT FROM AUTHOR]

Analysis of thermal properties plays an important role in the thermal management of high-power (HP) lighting-emitting diodes (LEDs). Thermal resistance, thermal capacitance, and thermal time constant are essential parameters for the optimal design of the LED device and system, particularly for dynamic performance study. In this paper, thermal characterization and thermal time constant of ThinGaN HP LEDs are investigated. Three HP cool-white ThinGaN LEDs from different manufacturers are used in this study. A forward-voltage method using thermal transient tester (T3Ster) system is employed to determine the LEDs' thermal parameters at various operating conditions. The junction temperature transient response is described by a multi-exponential function model to extract thermal time constants. The transient response curve is divided into three layers and expressed by three exponential functions. Each layer is associated with a particular thermal time constant, thermal resistance, and thermal capacitance. It is found that the thermal time constant of LED package is on the order of 22 to 100 ms. Comparison between the experimental results is carried out to show the design effects on thermal performance of the LED package. [ABSTRACT FROM AUTHOR]