With the recent years LED technology as a new generation of lighting technology has been widely concerned, LED power increase, heat dissipation problem is more and more attention. The researchers of Chishen Wei Hua heat dissipation coating have observed for a long time that this is because the light decay of the LED or its life is directly related to its junction temperature, the heat dissipation is not good, the junction temperature is high, and the life is short.

Unlike incandescent and fluorescent lamps used in the past, although their energy loss is large, most of the energy is emitted directly through infrared light, and the heat of the light source is less; LED, in addition to the energy consumed as visible light, other energy is converted into heat. In recent years, electronic products have gradually developed to high density and high integration, and LED products are no exception, so solving the LED heat dissipation problem has become the main problem to improve the LED performance and develop the LED industry.

Causes of LED heat:

The reason why leds heat up is because the added electrical energy is not all converted into light energy, but part of it is converted into heat energy. The luminous efficiency of LED is currently only 100lm/W, and its electro-optical conversion efficiency is only about 20-30%. This means that about 70% of the electricity is turned into heat.

Specifically, the generation of LED junction temperature is caused by two factors:

The internal quantum efficiency is not high, that is, when electrons and holes are combined, photons cannot be generated 100%, which is usually called the "current leakage" and the recombination rate of carriers in the PN region is reduced. The leakage current multiplied by the voltage is the power of this part, which is converted into heat energy, but this part does not account for the main component, because the internal photon efficiency is now close to 90%.

The photons generated inside cannot all be ejected to the outside of the chip and eventually converted into heat, which is the main part, because the current so-called external quantum efficiency is only about 30%, most of which is converted into heat.

As mentioned earlier, although the light efficiency of incandescent lamps is very low, only about 15lm/W, but it almost all the electrical energy is converted into light energy and radiation out, because most of the radiant energy is infrared, so the light efficiency is very low, but it avoids the problem of heat dissipation.

LED heat dissipation solution:

To solve the heat dissipation of LED, mainly from two aspects, before and after packaging, it can be understood as LED chip heat dissipation and LED lamp heat dissipation. The heat dissipation of Led chip is mainly related to the selection and process of substrate and circuit, which is not elaborated in this paper. This article mainly introduces the heat dissipation of Led lamps, because any LED will be made into lamps, so the heat generated by the LED chip is always dispersed into the air through the shell of the lamp. If the heat dissipation is not good, because the heat capacity of the LED chip is very small, a little heat accumulation will make the junction temperature of the chip rapidly increase, if the long period of work in a high temperature state, its life will be quickly shortened. However, for this heat to be able to actually guide out of the chip to the outside air, there are many ways to go. Specifically, the heat generated by the LED chip, from its metal cooling block, first passes through the solder to the PCB of the aluminum substrate, and then through the thermal glue to the aluminum radiator. Therefore, the heat dissipation of LED lamps actually includes two parts: heat conduction and heat dissipation.