Led technology in recent years has attracted widespread attention as a new generation of lighting technology, LED power increase, cooling problems will increasingly great importance. The researchers long observed, this led emergency lighting light failure, or life is directly related to the junction temperature and junction temperature heat is not good, and the short-lived.
 
         Unlike incandescent and fluorescent lamps used in the past, their energy loss is great, but the majority of the energy is directly radiated out via infrared, the heat generation of the light source; LED, in addition to visible light energy consumed, the other energy converter into heat. In recent years, electronic products gradually to the high-density, highly integrated development, Led products are no exception, so resolve led thermal issues become improve Led performance, the main problems of the development Led industry.
LED heat reasons:
The LED heat because not all because the added energy into light energy, but part is transformed into heat. LED light efficiency is only 100lm / W optical conversion efficiency of only about 20 to 30%. Means that about 70% of the energy into heat.
Specifically, the generation of the LED junction temperature is caused due to two factors:
1. The internal quantum efficiency is not high, that is, when the electron and hole recombination and not 100% of the resulting photon, often referred to as the carrier recombination rate by the current leakage in the PN area to reduce. The leakage current is multiplied by the voltage is this part of the power that is converted into heat, but this portion does not occupy a main component, because now has close to 90% efficiency of internal photon.
2. All internally generated photons can not emitted to the outside of the chip, while the last is converted into heat and this part is the main, because the current such as the external quantum efficiency of only about 30%, most are converted into heat.
As said before, although incandescent light efficiency is very low, only about 15lm / W, but it is almost all energy into light energy and radiated out, because most of the radiation is infrared light efficiency is very low , but it eliminates the problem of heat dissipation.
LED thermal solution:
Solve the heat of Led mainly from two aspects, pre-packaged and packaged, can be understood as the led chip cooling led lamps heat. Led chip cooling is mainly associated with the choice of substrate and circuit and process, this article is temporarily elaborate. This paper describes the led the heat lamp, because any LED will be made lamps, so the heat generated by the LED chip always end up through the lamp housing scattered into the air to go. If the heat is not good, because the heat capacity of the LED chip is very small, a little bit of heat accumulation will make the chip junction temperature is rapidly increasing, if a long time working in the high-temperature state, will soon shorten its life. However, this heat can really guide the chip to reach the outside air to go through a lot of ways. Specifically, the heat generated by the LED chip, from its metal heat sink block, the first pass through the solder to the aluminum substrate PCB, and then through the thermally conductive glue only to the aluminum radiator. Therefore, the heat dissipation of emergency flashlight lamps is actually composed of two parts of the thermal conductivity and heat dissipation.
However, LED lamp shell heat based on the power of the size and use of places, there will be a different choice. Following cooling method:
1 aluminum fin: This is the most common heat as part of the enclosure, aluminum cooling fins to increase the heat dissipation area.
Thermally conductive plastic case: plastic shell injection filled with thermally conductive materials, increase the plastic shell thermal conductivity, heat capacity.
The air fluid mechanics lamp shell shape, to create a convection air, which enhance the cooling mode is the lowest cost.
4 fan inside the lamp housing with longevity efficient fan to enhance heat dissipation, low cost, good effect. Want to change the fan is more trouble, does not apply to outdoor, this design is more rare.
The heat pipe heat pipe technology, the heat generated by the LED chip guide to shell fin. In large lights, street lamps is a common design.
Surface radiation heat treatment lamp shell surface to do radiation heat processing, the simple smear Zhi Sheng Weihua radiation heat paint, heat radiation, can be taken away from the surface of the lamp housing.
Overall LED luminous efficiency is still relatively low, causing the junction temperature rise, lower life expectancy. In order to reduce junction temperature and increased life expectancy must attach great importance to the problem of heat dissipation.