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LED Lamp Heat Dissipation Coating Application

Aug 12, 2020

As LED technology has received widespread attention as a new generation of lighting technology in recent years, LED power has increased, and heat dissipation has become more and more important. Researchers of Zhisheng Weihua heat dissipation coating have long-term observation and found that this is because the light decay of LED or its life is directly related to its junction temperature. If the heat dissipation is not good, the junction temperature will be high and the life will be short. Unlike the incandescent lamps and fluorescent lamps used in the past, their energy loss is large, but most of the energy is directly radiated through infrared rays, and the light source generates less heat; while LEDs, except for the energy consumed as visible light, other energy is converted Became hot. In addition, in recent years, electronic products have gradually developed toward high density and high integration, and LED products are no exception. Therefore, solving the problem of LED heat dissipation has become a major problem in improving LED performance and developing the LED industry.

The reason why the LED heats up is because the added electric 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%. In other words, about 70% of the electrical energy is turned into heat. Specifically, the junction temperature of the LED is caused by two factors: the internal quantum efficiency is not high, that is, when electrons and holes are recombined, 100% of photons cannot be produced, which is usually called "current leakage". 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 internally cannot be emitted to the outside of the chip and finally converted into heat. This part is the main one, because at present, the so-called external quantum efficiency is only about 30%, and most of them are converted into heat.

As mentioned above, although the luminous efficiency of incandescent lamps is very low, only about 15lm/W, it almost converts all electrical energy into light energy and radiates it out. Because most of the radiant energy is infrared, the light efficiency is very low. , But it avoids the problem of heat dissipation. LED heat dissipation solution: to solve the LED heat dissipation, we mainly start from two aspects. Before and after packaging, it can be understood as LED chip heat dissipation and LED lamp heat dissipation. Led chip heat dissipation is mainly related to the choice of substrate and circuit and process, so this article will not elaborate. 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 will always be dissipated 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, the accumulation of a little heat will make the junction temperature of the chip increase rapidly. If it is operated at a high temperature for a long time, its life will be shortened quickly.

However, there are many ways for this heat to actually guide the chip to the outside air. Specifically, the heat generated by the LED chip comes out of its metal heat sink, first passes through the solder to the aluminum substrate PCB, and then passes through the thermal conductive glue to the aluminum heat sink. Therefore, the heat dissipation of LED lamps actually includes two parts: heat conduction and heat dissipation. However, the heat dissipation of the LED lamp housing will have different options depending on the power and the place of use. Now there are mainly the following heat dissipation methods: Aluminum fins: This is the most common way to dissipate heat. Aluminum fins are used as part of the housing to increase the heat dissipation area. Thermally conductive plastic shell: Fill the plastic shell with thermally conductive material during injection molding to increase the thermal conductivity and heat dissipation capacity of the plastic shell. Aerodynamics uses the shape of the lamp housing to create convective air, which is the lowest-cost way to enhance heat dissipation.

In addition, the inside of the fan lamp housing uses a long-life and high-efficiency fan to enhance heat dissipation, which has low cost and good effect. However, it is more troublesome to change the fan, and it is not suitable for outdoor use. This design is relatively rare. The heat pipe uses heat pipe technology to conduct heat from the LED chip to the heat dissipation fins of the housing. This is a common design in large lamps, such as street lamps. Surface radiation heat treatment The surface of the lamp housing is treated with radiation heat. Simply apply the Zhisheng Weihua radiation heat dissipation paint to take the heat away from the surface of the lamp housing by radiation. The following new type of heat-dissipating paint: ZS-411 radiant heat-dissipating cooling paint. The paint coating has high thermal conductivity and large heat dissipation surface area, and at the same time has high emissivity in a relatively wide wavelength range (1-20μm), which can be displayed To improve the comprehensive performance of heat dissipation including conduction, convection and radiation.

This coating adopts a high-performance heat dissipation solution developed by a Beijing company. The heat dissipation solution has high visible light and near-infrared light reflectivity, high thermal infrared emissivity and stability, and other special properties. It also has good physical properties. Performance, chemical performance, and good workability have a variety of composite properties. The working principle of this heat dissipation solution is to rely on the aggregation of inorganic colloidal particles (less than 100 nanometers) to produce binding force. Adding carbon nanotubes and other materials with high thermal conductivity and emissivity to the coating solution can make the surface of the coating present a macroscopically smooth and microscopically rough nanomaterial component, which can greatly increase the contact area of the heat sink with the outside world. Significantly improve the heat dissipation effect. At the same time, a large number of various spinels that have been electronically transitioned are added as a composite infrared radiator, which not only increases the impurity energy level, improves the infrared radiation coefficient, but also maintains the corresponding thermal stability and heat resistance. Generally speaking, the luminous efficiency of the current LED is still relatively low, which causes the junction temperature to rise and the lifetime to decrease. In order to reduce the junction temperature and improve the life, it is necessary to attach great importance to heat dissipation.