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1 – 10 of over 1000This study investigates the impact of three parameters such as: number of LED chips, pitch and LED power on the junction temperature of LEDs using a best heat sink configuration…
Abstract
Purpose
This study investigates the impact of three parameters such as: number of LED chips, pitch and LED power on the junction temperature of LEDs using a best heat sink configuration selected according to a lower temperature. This study provides valuable insights into how to design LED arrays with lower junction temperatures.
Design/methodology/approach
To determine the best configuration of a heat sink, a numerical study was conducted in Comsol Multiphysics on 10 different configurations. The configuration with the lowest junction temperature was selected for further analysis. The number of LED chips, pitch and LED power were then varied to determine the optimal configuration for this heat sink. A general equation for the average LED temperature as a function of these three factors was derived using Minitab software.
Findings
Among 10 configurations of the rectangular heat sink, we deduce that the best configuration corresponds to the first design having 1 mm of width, 0.5 mm of height and 45 mm of length. The average temperature for this design is 50.5 C. For the power of LED equal to 50 W–200 W, the average temperature of this LED drops when the number of LED chips reduces and the pitch size decreases. Indeed, the best array-LED corresponds to 64 LED chips and a pitch size of 0.5 mm. In addition, a generalization equation for average temperature is determined as a function of the number of LED chips, pitch and power of LED which are key factors for reducing the Junction temperature.
Originality/value
The study is original in its focus on three factors that have not been studied together in previous research. A numerical simulation method is used to investigate the impact of the three factors, which is more accurate and reliable than experimental methods. The study considers a wide range of values for the three factors, which allows for a more comprehensive understanding of their impact. It derives a general equation for the average temperature of the LED, which can be used to design LED arrays with desired junction temperatures.
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Jin Taek Kim, Cheul Ro Lee, Daesuk Kim and Byung Joon Baek
Thermal management under high heat flux is crucial to developing high‐power light‐emitting diode (LED) applications. The purpose of this paper is to propose an efficient thermal…
Abstract
Purpose
Thermal management under high heat flux is crucial to developing high‐power light‐emitting diode (LED) applications. The purpose of this paper is to propose an efficient thermal dissipation technique for an LED back light unit (BLU) system.
Design/methodology/approach
A typical BLU system includes an LED package (GaN on sapphire, cathode/anode, silicone encapsulant, resin plus phosphor) on a printed circuit board (PCB), a light guide panel, and an aluminum cover frame. The temperature distribution of this system has been simulated and the thermal behavior within a 3D model has been investigated using a commercial computational fluid dynamic code (FLUENT 6.3).
Findings
The authors examined the heat‐spreading effect of cover lengths ranging from 6 to 300 mm and also observed the effect of back cover thickness on the junction temperature and cover frame temperature and investigated the influence of the air gap between the package and the cover frame. Removing the air gap lowers the maximum temperature by about 6 percent. It was found that the addition of a copper layer covering the external surfaces of the LED chip enhanced the cooling efficiency. Finally, the maximum junction temperature can be decreased by more than 21 percent in the range of parameters considered by removing the air gap, adding a heat spreader, and using a thick cover frame.
Originality/value
In this paper, thermal management for efficient heat spreading through a typical BLU system without using any additional devices is investigated. Several parameters that increase the system's temperature are examined, and a combination of design features that attenuate the junction temperature is proposed.
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Chang Keun Lee, Jung Keun Ahn, Cheul Ro Lee, Daesuk Kim and Byung Joon Baek
The purpose of this paper is to investigate the thermal behaviors of high power LED packages to enhance the thermal performances of low temperature co‐fired ceramic chip on board…
Abstract
Purpose
The purpose of this paper is to investigate the thermal behaviors of high power LED packages to enhance the thermal performances of low temperature co‐fired ceramic chip on board (LTCC‐COB) package. Thermal analysis demonstrated an improved LTCC‐COB package design that is comparable to a metal lead frame package with low thermal resistance.
Design/methodology/approach
The LED device developed in this study is a LTCC package mounted directly on the metal PCB. A numerical simulation was performed to investigate the thermal characteristics of the LED module using the finite volume method, which is embedded in commercial software (Fluent V.6.3). Thermal resistance and temperature measurement validate the simulated results.
Findings
The effect of the thickness of the die attach material on the thermal resistance was dominant due to low thermal conductivity, and the junction temperature decreased significantly with slight increases in thermal conductivity, especially when the value was less than 5 W/mK. The results reveal that the thermal resistance of MCPCB is about 49 per cent‐58 per cent of the junction to board thermal resistance. The thermal model results showed good agreement with experimental results.
Originality/value
The developed model overcomes the large thermal resistance of a conventional LTCC package for high power LED module. The extensive results have demonstrated an improved thermal design, optimal dimensions of each component and boundary conditions for high power LTCC‐COB type package.
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Muna E. Raypah, Dheepan M.K., Mutharasu Devarajan, Shanmugan Subramani and Fauziah Sulaiman
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…
Abstract
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.
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GENERALLY speaking, the demand for thermo‐electric pyrometer equipment is such that individual calibration of each instrument and its couple is possible. For the measurement of…
Abstract
GENERALLY speaking, the demand for thermo‐electric pyrometer equipment is such that individual calibration of each instrument and its couple is possible. For the measurement of aircraft temperatures thermo‐electric pyrometers are employed but the following conditions render individual calibration impracticable:
Kaiçar Ammous, Slim Abid and Anis Ammous
The paper aims to focus on the semiconductor temperature prediction in the multichip modules by using a simplified 1D model, easy to implement in the electronic simulation tools.
Abstract
Purpose
The paper aims to focus on the semiconductor temperature prediction in the multichip modules by using a simplified 1D model, easy to implement in the electronic simulation tools.
Design/methodology/approach
Accurate prediction of temperature variation of power semiconductor devices in power electronic circuits is important for obtaining optimum designs and estimating reliability levels. Temperature estimation of power electronic devices has generally been performed using transient thermal equivalent circuits. This paper has studied the thermal behaviour of the power modules. The study leads to correcting the junction temperature values estimated from the transient thermal impedance of each component operating alone. The corrections depend on multidimensional thermal phenomena in the structure.
Findings
The classic analysis of thermal phenomena in the multichip structures, independently of powers’ dissipated magnitude and boundary conditions, is not correct. An advanced 1D thermal model based on the finite element method is proposed. It takes into account the effect of the heat‐spreading angle of the different devices in the module.
Originality/value
The paper focuses on mathematical model of the thermal behaviour in the power module. The study leads to a correction of the junction temperature values estimated from the transient thermal impedance of each component given by manufacturers. The proposed model gives a good trade‐off between accuracy, efficiency and simulation cost.
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IN research or development work on aero engines there are many occasions when it is desirable, or sometimes essential, to obtain temperature readings under somewhat difficult…
Abstract
IN research or development work on aero engines there are many occasions when it is desirable, or sometimes essential, to obtain temperature readings under somewhat difficult conditions. In many cases it is possible for serious errors to arise, under conditions which make their detection difficult, and the writer, therefore, thinks that the information he has gained in dealing with these problems may be of value to others.
N. Aizar Abdul Karim, P.A. Aswatha Narayana and K.N. Seetharamu
To demonstrate thermal modeling technique for a through hole light emitting diode (LED) package using a commercial computational fluid dynamic (CFD) code and to improve its…
Abstract
Purpose
To demonstrate thermal modeling technique for a through hole light emitting diode (LED) package using a commercial computational fluid dynamic (CFD) code and to improve its thermal performance through a series of sensitivity analyses.
Design/methodology/approach
Thermal resistance of the standard through hole LED is calculated using the simulation result. The result is then compared with actual measurement to establish the correct model. Using the validated model, series of sensitivity analyses are carried out through simulation. Taking the most optimum design, a prototype of the improved LED is fabricated and the thermal resistance performance is compared with the simulation result.
Findings
The simulation result of the standard LED is close to actual measurement with 5 percent difference. The thermal resistance of the through hole LED is reduced by changing the leadframe material from mild steel to copper alloy and increasing the leadframe width. Combination of both design changes resulted in thermal resistance reduction of 51 percent.
Originality/value
This paper identified the practicality of using CFD codes in achieving fast and accurate result in thermal modeling of LED package and also offers solutions on reducing the LED thermal resistance.
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Muna E. Raypah, Mutharasu Devarajan and Fauziah Sulaiman
Thermal management of high-power (HP) light-emitting diodes (LEDs) is an essential issue. Junction temperature (TJ) and thermal resistance (Rth) are critical parameters in…
Abstract
Purpose
Thermal management of high-power (HP) light-emitting diodes (LEDs) is an essential issue. Junction temperature (TJ) and thermal resistance (Rth) are critical parameters in evaluating LEDs thermal management and reliability. The purpose of this paper is to study thermal and optical characteristics of ThinGaN (UX:3) white LED mounted on SinkPAD by three types of solder paste (SP): No-Clean SAC305 (SP1), Water-Washable SAC305 (SP2) and No-Clean Sn42/Bi57.6/Ag0.4 (SP3).
Design/methodology/approach
Thermal transient tester (T3Ster) machine is used to determine TJ and total thermal resistance (Rth–JA). In addition, the LED’s optical properties are measured via thermal and radiometric characterization of power LEDs (TeraLED) system. The LED is mounted on SinkPAD using SP1, SP2 and SP3 by stencil printing to control a thickness of SP and reflow soldering oven to minimize the number of voids. The LED with SP1, SP2 and SP3 is tested at various input currents and ambient temperatures.
Findings
The results indicate that at high input current, which equals to 1,200 mA, Rth–JA and TJ, respectively, are reduced by 30 and 17 per cent between SP1 and SP2. At same current value, Rth–JA and TJ are minimized by 42 and 25 per cent between SP1 and SP3, respectively. In addition, at an ambient temperature of 85°C, Rth–JA and TJ are decreased by 34 and 7 per cent between SP1 and SP2, respectively. Similarly, the reduction in Rth–JA and TJ between SP1 and SP3 is 44 and 10 per cent, respectively. Luminous flux, luminous efficacy and color shift of the LED with the three types of SPs are compared and discussed. It is found that the SP1 improves the chromatic properties of the LED by increasing the overall light efficiency and decreasing the color shift.
Originality/value
Thermal and optical performance of ThinGaN LEDs mounted on SinkPAD via three types of SPs is compared. This investigation can assist the research on thermal management of HP ThinGaN-based LEDs.
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The purpose of this paper is to discuss the temperature failure effect on electronic components and their electrical parameters variation.
Abstract
Purpose
The purpose of this paper is to discuss the temperature failure effect on electronic components and their electrical parameters variation.
Design/methodology/approach
The MOSFET device parameters analysis was done by numerical analysis based on a double exponential model using the integrated pn junction.
Findings
The temperature dependence of these parameters is investigated; their evolution allows the evaluation of device's operation reliability in high‐temperature environments.
Originality/value
The paper demonstrates how the temperature affect the normal operation of the electronic device and the model accuracy is investigated at high temperature.
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