Analysis of LED lighting heating and heat radiation coating application
In recent years, with the LED technology as a new generation of lighting technology has been a wide range of concerns, the increase in LED power, heat dissipation problem will be more and more attention. Chi Sheng Wei Hua thermal coatings of long-term observation, the researchers found. This is because led decay or life and its junction temperature is directly related to poor heat dissipation of the junction temperature is high, the service life is short.
Use of different traditional incandescent and fluorescent lamps, the energy loss is great, however, in addition to most of the energy of visible light energy consumption directly through the infrared radiation, reduce heat led, and other energy conversion becomes hot. In addition, due to the recent years, electronic products are gradually to high density, the development of highly integrated, LED products are no exception, so to solve the LED heat to become the main problem to improve the performance of LED, LED industry development.
LED cause of fever:
Because the addition of electric energy into the LED of light energy is not all, but some become heat. At present only 100lm / LED of the W light effect, the electro-optical conversion efficiency is only about 20% to 30%. This is about 70% of the electric energy is converted into heat energy.
Specifically, LED junction temperature is caused by two factors:
Internal quantum efficiency is not high, that is to say, when the electron and hole recombination, and can not produce 100% of all the photons, is commonly referred to as the "leakage current" to leave the PN area carrier recombination rate decreased. The leakage current is multiplied by the voltage, the voltage of the power supply, which is converted into thermal energy, but this part is not accounted for the main component, because the internal photon efficiency is close to 90%.
Internally generated photons emitted into the chip can not be completely converted into heat and the last one, which is the main part, due to the current is called external quantum efficiency only about 30% converted to thermal energy of the most.
As said earlier, although the incandescent light efficiency is very low, only 15LM / W, but almost all of the electricity can transformed into light and radiation out, because most of the radiation is the infrared, so the light efficiency is very low, but it eliminates the problems of heat dissipation.
LED cooling solution:
Solve the heat dissipation of LED is good, mainly from two aspects, before and after packaging, can be understood as LED lamp, LED chip cooling and cooling. The selection and process of the heat sink substrate and the circuit of LED chip is given priority to, this paper introduces the transient. This paper describes the heat lamp LED, because any LED light generated by the LED chip heat, so the last will always be scattered into the air through the lamp housing. If the heat is not good, because the heat capacity of LED chip is small, a little bit of heat accumulation make the chip junction temperature will increase rapidly, if the long time working at high temperature, it will soon be shortened its service life. However, these heat can really guide the chip to reach the outside air through a variety of ways to go. Specifically, the LED chip is generated by heat from its metal heat sink, which is the first solder of the printed circuit board of the aluminum plate, and through the hot bonding agent, only in the aluminum radiator. Therefore, in fact, the heat conduction and heat radiation of the LED lamp includes two parts.
However, LED lamp housing size and power consumption based on the use of places, there will be different options. Now the main cooling methods are the following:
Aluminum heat sink: This is the most common way of cooling, as part of the shell to increase the heat dissipation area of aluminum fins.
Hot plastic shell: plastic injection molding, filled with heat conductive materials, increase the thermal conductivity of the plastic shell, heat capacity.
The air fluid mechanics using shell shape, creating an air convection, this is the lowest cost way, in order to improve the cooling.
The fan shell inside, has the advantages of long service life, high efficiency fan, strengthen heat dissipation, low cost, good effect. But be sure to change the fan of the trouble, does not apply to the outdoors, this design is very rare.
The heat pipe technology of the heat pipe is used, and the heat conduction to the shell of the cooling heat sink of the LED chip is used. In large lamps, such as street lamps and so on, this is a common design.
Surface radiation heat treatment shell surface radiation heat treatment, the simple method is the thermal radiation Zhi Sheng Wei Hua paint, can remove heat from the surface of the radiation pattern shell.
The following describes a new different thermal coating: heat ZS-411 cooling coating, paint and coatings, with the heat dissipation of the high thermal conductivity and high surface area, and in a wide wavelength range (1-20 m) with high emission rate can be significantly improved, including conduction, convection and radiation heat of overall performance.
Using this paint Beijing Hua Weizhi Sheng Chemical Co., Ltd. is the independent research and development of high performance thermal solution and the solution with higher thermal visible light and near infrared reflectance, high thermal infrared emission rate and stability of the special properties, but also has good physical properties, chemical properties and good processability of various complex and cooling solution, its working principle is on inorganic colloidal particles (less than 100nm), to produce a combined force of the agglomerates. The addition of carbon nanotubes in solution with high thermal conductivity and emissivity of materials such as paint, that shows the morphology of the macro group and nanometer roughness of materials of coating surface is smooth, greatly increase the heat sink area of contact with the outside world, significantly improve the heat dissipation effect. Electronic transitions, while adding a large variety of infrared radiator as the spinel composite, both to increase the impurity content and improves the infrared radiation coefficient, while maintaining appropriate thermal stability and heat resistance.
Overall, the current LED luminous efficiency is still relatively low, resulting in increased junction temperature, life expectancy. In order to reduce the junction temperature, in order to improve the life of enterprises, we must attach great importance to the issue of heat.