Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards general illumination. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the developments of LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 lumens/W, this is approximately 6 times the efficiency of a conventional incandescent tungsten bulb. Thermal management for the solid-state lighting applications is a key design parameter for both package and system level. Package and system level thermal management is discussed in separate sections. Effect of chip packages on junction to board thermal resistance was compared for both SiC and Sapphire chips. The higher thermal conductivity of the SiC chip provided about 2 times better thermal performance than the latter, while the under-filled Sapphire chip package can only catch the SiC chip performance. Later, system level thermal management was studied based on established numerical models for a conceptual solid-state lighting system. A conceptual LED illumination system was chosen and CFD models were created to determine the availability and limitations of passive air-cooling.

Thermal management of LEDs: Package to system

The use of ceramic substrates in high power LEDs is becoming increasingly common. However, the brittleness of ceramics makes them difficult to process and susceptible to cracking. This study used a CO2 laser with auxiliary gas to drill and cut Al2O3 and AlN ceramic substrates. The authors investigated the influences of parameters such as auxiliary gas pressure, laser power, repetition rate, and working speed on processing quality, in terms of pattern size, surface roughness, hole taper angle, and fracturing. The experiment results show that Al2O3 low-cost processing can be achieved with low laser power and high auxiliary gas pressure. In contrast, AlN has a high melting point and high thermal conductivity, for which lower auxiliary gas pressure is required to ensure high-quality processing.

CO2 Laser Processing On Ceramic Substrates Of Light Emitting Diode Assisted By Compressed Gas

Conference Name:2nd International Conference on Opto-Electronics Engineering and Materials Research, OEMR 2013. Conference Address: Zhengzhou, Henan, China. Time:October 19, 2013 - October 20, 2013.

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Heat Dissipation Simulation Research of LED Downlight and Optimization of Light Source Layout

In order to solve the heat dissipation problem of LED (light-emitting diode) downlight, CFD thermal simulation software was used to establish LED downlight dissipation model. Materials thermal conductivity, thermal resistance, thermal emissive values, heat load forms and other factors were all taken in considered, and then numerical simulation combined with laboratory measurement methods was used to analysis the lamps dissipation. Based on this method, focused on the dissipation effect with different LED quantities and LED ring distances, and then optimized light source layout of current LED downlight products. After experimental verification, LED working temperatures were more ideal after the light source layout optimized, and it can improve the LED lamp lifetime effectively, this result also has important practice significance in the future LED downlight design process.

Yang Xia Wang

Papers

Heat Dissipation Simulation Research of LED Downlight and Optimization of Light Source Layout

Heat Dissipation Simulation Research of LED Downlight and Optimization of Light Source Layout