• Korean Journal of Optics and Photonics
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• v.24 no.6
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• pp.342-346
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• 2013

We present the thermal analysis result of die bonding for a high power LED package using a metal hybrid silicone adhesive structure. The simulation structure consists of an LED chip, silicone die adhesive, package substrate, silicone-phosphor encapsulation, Al PCB and a heat-sink. As a result, we demonstrate that the heat generated from the chip is easily dissipated through the metal structure. The thermal resistance of the metal hybrid structure was 1.662 K/W. And the thermal resistance of the total package was 5.91 K/W. This result is comparable to the thermal resistance of a eutectic bonded LED package.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.12
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• pp.920-923
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• 2013

In this paper, the characteristics of a carbon nanotube composite heat sink proposed to replace the advanced Al heat sinks for LED lighting devices were studied. Proposed CMP-PLA heat sink was made by mixing 20~70 wt% carbon nanotube, 20~70 wt% bio-degradable polymer of melt-blended PLA (poly lactic acid) and PBS (poly butylene succinate) and PLA nucleating agents composed of the mixture of soybean oil and biotites, at $150{\sim}220^{\circ}C$ with 1,000~1,500 rpm. Optical and electric characteristics of 7.5 W LED lighting devices using heat sinks with such prepared CMP-PLA were investigated. And, the properties of the heat, which was not released from the CMP-PLA type heat sinks, was also investigated. The color temperature of LED lighting devices using the CMP-PLA heat sinks was 5,956 K, which is x= 0.32 and y= 0.34 in the XY chromaticity, and the color rendering index was 75. The luminous flux and the luminous efficiency of LED lighting devices using the CMP-PLA heat sinks was 540.6 lm and 72.68 lm/W respectively. Measured initial temperature of the heat sinks was $27^{\circ}C$, and their temperature increased as time to be saturated at $52^{\circ}C$ after an hour.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.730-733
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• 2010

The Green Lamp Fixture (GLF) of LED prepared with thin panel structure was investigated for illumination of street lamps and other lighting system uses, which was also very useful to aquaculture and aquafarm lighting uses, or fish luring lights and marine aquanautics of aquamarinautics (aquamarine+aquanautics) uses, etc. In the case of fish luring lights, it was verified that the fish luring of Green Lamp Fixture of LED was very effective for phototaxis movement and ecological community promotion to the micro-living things of organisms and the small fries and fishes, like as 'crowding together'. For the aquaculture lightings, it was also very excellent in waterproof and heat-sink properties, photosynthetic growing of algae and micro-organisms, water-weeds and seaweeds living underwater.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.158-163
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• 2013

In this paper, thermal analysis of heatsink for 30 W class Chip-on-Board (COB) LED light source is performed by using SolidWorks Flow Simulation package. In order to increase the convection heat transfer, number of fin and shape of the heatsink is optimized. Furthermore, a copper spread is applied between the COB LED light source and the heatsink to mitigate the heat concentration on the heatsink. With the copper spread, the junction temperature between the COB LED light source and the heatsink is $50.9^{\circ}C$, which is $5.4^{\circ}C$ lower than the heatsink without the copper spread. Due to the improvement of the junction temperature, the light output is improved by 5.8% when the LED light source is stabilized. The temperature difference between the simulation and measured result of the heatsink with the copper spread is within $2^{\circ}C$, which verifies the validity of the thermal design method using a simulation package.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1167-1171
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• 2008

The flow and thermal performance of the skiving and louver fin type heat sinks for the cooling system of the small LED projector were experimentally evaluated. A small fan tester based on AMCA standards was used to control and measure the air flow rate into the heat sink. Three heat blocks were used to simulate the heat and light sources(red, green and blue) of the small LED projector. We measured the pressure drop, temperatures and input power at the specific air flow rate and discussed those results. As a result, it is found that the louver fin type heat sink has higher pressure drop and lower thermal resistance than the skiving type. From the comparison of the temperature of the heat block between skiving and louver fin type, the louver fin type heat sink was found to be more suitable for cooling the high power heat source than skiving type. The thermal performance of the fan-sink(louver fin type) system was discussed with the picture taken by a thermal video.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.830-836
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• 2012

An efficient cooling system is essential for the electronic packaging such as a high-luminance LED lighting. A special heat transport technology, Pulsating Heat Pipe (PHP), can be applied to the cooling of LED lighting. In this paper, the operational characteristics of the PHP in the imposed thermal boundary conditions of LED lighting were experimentally investigated. The experimental PHP was made of copper tubes of internal diameter of 2.1 mm. The working fluids of ethanol, FC-72, water, acetone and R-123 were chosen for comparison. The results showed that an optimum range of charging ratio exists for high cooling performance; 50% for most of the fluids. Among the five working fluids, water showed the highest heat transfer rate of 260 W. Two distinguished characteristics of pulsating direction were identified. It is also identified that high vapor pressure gradient is one of key parameters for better heat transfer performance.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.297-302
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• 2015

Nanocrystalline diamond(NCD) coated aluminium plates were prepared and applied as heat sinks for LED modules. NCD films were deposited on 1 mm thick Al plates for times of 2 - 10 h in a microwave plasma chemical vapor deposition reactor. Deposition parameters were the microwave power of 1.2 kW, the working pressure of 90 Torr, the $CH_4/Ar$ gas ratio of 2/200 sccm. In order to enhance diamond nucleation, DC bias voltage of -90 V was applied to the substrate during deposition without external heating. NCD film was identified by X-ray diffraction and Raman spectroscopy. The Al plates with about 300 nm thick NCD film were attached to LED modules and thermal analysis was carried out using Thermal Transient Tester (T3ster) in a still air box. Thermal resistance of the module with NCD/Al plate was 3.88 K/W while that with Al plate was 5.55 K/W. The smaller the thermal resistance, the better the heat emission. From structure function analysis, the differences between junction and ambient temperatures were $12.1^{\circ}C$ for NCD/Al plate and $15.5^{\circ}C$ for Al plate. The hot spot size of infrared images was larger on NCD/Al than Al plate for a given period of LED operation. In conclusion, NCD coated Al plate exhibited better thermal spreading performance than conventional Al heat sink.

• Korean Journal of Optics and Photonics
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• v.32 no.5
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• pp.230-234
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• 2021

Relief of thermal stress has received great attention, to improve the beam quality and stability of high-power laser diodes. In this paper, we investigate a microtrench structure engraved around a laser-diode chip-on-submount (CoS) to relieve the thermal stress on a laser-diode bar (LD-bar), using the SolidWorks® software. First, we systematically analyze the thermal stress on the LD-bar CoS with a metal heat-sink holder, and then derive an optimal design for thermal stress relief according to the change in microtrench depth. The thermal stress of the front part of the LD-bar CoS, which is the main cause of the "smile effect", is reduced to about 1/5 of that without the microtrench structure, while maintaining the thermal resistance.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1724-1725
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• 2011

본 논문에서는 LED 패키지의 방열문제를 해결하기 위해 FR4 PCB에 Via-hole을 형성함으로써 열전달 능력을 향상시키고자 하였다. 또한 FR4 PCB의 면적과 Via-hole 크기 및 수량을 변화를 주어 그에 따른 K-factor를 측정 하였으며 열 저항 특성을 분석하였다. 결과로서, Via-hole을 형성한 FR4 PCB의 경우 초기 면적이 증가함에 따라 열 저항 및 접합온도가 급격히 감소하는 특성을 보였으며 200 [mm2]에서 안정화 되는 특성을 보였다. 또한 PCB 면적 및 Via-hole을 형성함에 따라 광 출력이 최대 17% 향상 되었다. 따라서 접합온도 및 열 저항에 있어서 PCB면적의 증가 및 Via-hole을 구성함에 있어 열전달 능력을 향상시킬 수 있음을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.27-33
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• 2013

To ensure proper functioning of electrical and mechanical systems, cooling devices are of great importance. A heat sink is the most common cooling device used in many industries such as the semiconductor, electronic instrument, LED lighting, and automotive industries. To design an optimal heat sink, the required surface area for heat radiation should be calculated based on an accurate expectation of the heat flow rate in the target environment. In this study, the convective heat flow characteristics were numerically investigated for a vertically installed typical heat sink and a horizontally installed one in free convection using ANSYS CFX. Comparative experiments were carried out to reveal the quantitative effect of the installation direction on the cooling performance. Moreover, the result was analyzed using the dimensionless correlation with the Nusselt number and Rayleigh number and compared with well-known theories. Finally, it was observed that the cooling performance of the vertically installed heat sink is approximately 10~15% better than that of the one in natural convection.