LED Thermal management of high-power

by / Monday, 12 May 2014 / Published in Company Blog

Thermal management of high power LEDs is a crucial area of research and development. It is highly necessary to keep the junction temperature below 120°C to run the LED’s for maximum lifetime.

In order to maintain a low junction temperature in order to maintain a good performance of a LED, any method for removing heat from LEDs should be considered. Conduction, convection and radiation are the three ways to transfer heat.
Typically, the LEDs are encapsulated in a transparent resin, which is a poor conductor of heat. Substantially all of the heat produced is conducted through the backside of the chip.
Heat is generated by the PN junction by the electric energy that was not converted into useful light, and leading to the outside atmosphere by a long way since the output of the welding point, point, and on board solder and the board of the heatsink atmosphere. A side view LED and thermal model type are shown in the figures.
Junction temperature will be lower when the thermal impedance is smaller, and even at a lower ambient temperature. In order to maximize the effective range of from room temperature to a given power dissipation, all of the heat resistance between the barrier layer and the surrounding temperature must be minimized.
The values ​​of the heat resistance is highly variable, depending on the material or the supplier. For example, JCR is between 2.6 ° C / W 18 ° C / W depending on LED manufacturers.
(TIM), the thermal resistance of the thermal interface material will also vary depending on the nature of the chosen material. TIM common are epoxy, thermal grease, pressure-sensitive adhesive and welding. Power LEDs are often metal core PCB (MCPCB), which is mounted with an LED heatsink mounted.
Heat is conducted from the LED MCPCB and heatsink is delivered by convection and radiation. In the package design, the surface flatness and quality of each component, applied increased pressure, the contact surface, the type of interface material, and its thickness are important parameters for the design of the thermal resistance.
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