Abstract
In this study, a self-adjusting concentration of graphene thermal grease was developed to reduce the contact surface thermal resistance of 50 W light-emitting diodes (LEDs). The purpose was to identify an important type of heat conduction material with a high thermal conductivity coefficient, which can be applied to the contact surface of various high-heat sources or concentrated heat sources to achieve seamless heat transfer with an extremely low thermal resistance state. The contact heat conduction material conductivity reached the highest K value of 13.4 W/m·K with a 15 wt.% self-adjusting concentration of graphene grease. This material could continuously achieve a completely uniform and rapid thermal diffusion of heat energy. Therefore, we performed an analysis of chip-on-board light-emitting diodes (LEDs) with a highly concentrated heat source, which showed excellent heat dissipation under natural convection heat transfer. As such, this study achieved the natural convection mechanism and a heat sink volume thermal performance capacity of 473,750 mm3 for LEDs under 50 W, but those over 50 W require an enhanced forced convection solution and a heat sink volume thermal performance capacity between 473,750 mm3 and 947,500 mm3. If the heat source dissipation reaches 100 W, the volume capacity must be at least 947,500 mm3 for lighting equipment applications. In the experimental study, we also verified and analyzed the research data, including an analysis of the measured data, grease component wt.%, heat sink material selection, increase in heat sink volume, heat transfer path, and contact surface, a discrimination analysis of infrared thermal images, and an analysis of flow visualization, which were conducted to ensure quantitative and qualitative improvement, provide a mechanism for judging the technical performance, and provide research results to enable discussion.
Highlights
A chip-on-board light-emitting diodes (LEDs) of 50–100 W was tested under natural convection a wind speed of less than 0.3 m/s
The ambient temperature was initially set at 15 ◦ C, specification design temperature value (Tcase < 75 °C spec.), as well as avoid chip-bonding the relative humidity was 60% RH, and the average ambient air velocity was less than temperature damage (Tj < 125 °C spec.), and immediately turn off the chip-on-board LED, 0.3 m/s
To further test whether the 50–100 W chip-on-board LED can operate as the surface contact conductivity material, and the chip-on-board LED operated 600 s for a long time under natural convection, we gradually reduced◦ the temperature of the after start-up
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Light-emitting diode (LED) devices are an important energy-efficient, energy-saving, and safe light sources in use in the 21st century. The light source changes from blue to white light through phosphor, breaking through the conversion efficiency of traditional low-efficiency light sources and turning into low-energy, low-pollution, long-life, green energy, and diverse light sources. The importance and effectiveness of the thermal conductivity property of graphene grease stem from its suitability for the preparation of synthetic thermal interface materials (TIMs), as it increases heat transfer and reduces contact thermal resistance. The development of thermal interface materials with high thermal conductivity is very important for the thermal management and packaging of electronic equipment
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