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LED Heat Dissipation Technology/LED Heat Dissipation Material

　　 Heat dissipation is a major factor affecting the lighting intensity of LED lamps. The heat sink can solve the heat dissipation problem of low-illuminance LED lamps. A heat sink cannot solve the heat dissipation problem of 75W or 100W LED lamps.

　　In order to achieve the ideal lighting intensity, active cooling technology must be used to resolve the heat released by the LED lighting components. Some active cooling solutions such as fans have less lifespan than LED lamps. In order to provide a practical active cooling solution for high-brightness LED lamps, the heat dissipation technology must be low energy consumption; and can be applied to small lamps; its life span should be similar to or higher than the lamp source.

　　 Heat dissipation method

　　 Generally speaking, according to the way the heat is taken away from the radiator, the radiator can be divided into active heat dissipation and passive heat dissipation. The so-called passive heat dissipation means that the heat of the heat source LED light source is naturally dissipated into the air through the heat sink. The heat dissipation effect is proportional to the size of the heat sink, but because the heat is naturally dissipated, the effect is of course greatly compromised. In equipment that is not required, or used to dissipate heat for components that do not generate much heat. For example, some popular motherboards also adopt passive heat dissipation on the north bridge. Most of them adopt active heat dissipation. Active heat dissipation is forced by cooling devices such as fans. It is characterized by high heat dissipation efficiency and small size of the equipment.

　　 Active heat dissipation, subdivided in terms of heat dissipation, can be divided into air cooling, liquid cooling, heat pipe cooling, semiconductor cooling, chemical cooling, and so on.

　　 Air-cooled air-cooled heat dissipation is the most common way to dissipate heat. In comparison, it is also a cheaper way. Air cooling is essentially the use of a fan to take away the heat absorbed by the radiator. It has the advantages of relatively low price and convenient installation. However, it is highly dependent on the environment. For example, the heat dissipation performance will be greatly affected when the temperature rises and overclocking.

　　 Liquid cooling

　　 Liquid cooling heat dissipation is the forced circulation of the liquid under the drive of the pump to take away the heat of the radiator. Compared with air cooling, it has the advantages of quietness, stable cooling, and less dependence on the environment. The price of liquid cooling is relatively high, and installation is relatively troublesome. At the same time, try to install in accordance with the instructions in the manual to get the best heat dissipation effect. For cost and ease of use considerations, liquid-cooled heat dissipation usually uses water as the heat-conducting liquid, so liquid-cooled radiators are often referred to as water-cooled radiators.

     Heat pipe

    The heat pipe is a kind of heat transfer element. It makes full use of the principle of heat conduction and the fast heat transfer properties of the refrigerant. It transfers heat through the evaporation and condensation of the liquid in the fully enclosed vacuum tube. It has extremely high thermal conductivity and good isothermal properties. The heat transfer area on both sides of the cold and heat can be changed arbitrarily, heat can be transferred over a long distance, temperature can be controlled, and a series of advantages, and the heat exchanger composed of heat pipes has high heat transfer efficiency, compact structure, small fluid resistance, etc. advantage. Its thermal conductivity has far exceeded the thermal conductivity of any known metal.

　　 Semiconductor refrigeration

　　 Semiconductor refrigeration is to use a special type of semiconductor refrigeration chip to produce a temperature difference when it is energized. As long as the heat of the high temperature end can be effectively dissipated, the low temperature end will be continuously cooled. A temperature difference is generated on each semiconductor particle, and a refrigeration sheet is formed by connecting dozens of such particles in series, thereby forming a temperature difference on the two surfaces of the refrigeration sheet. Using this temperature difference phenomenon, combined with air cooling/water cooling to cool the high temperature end, excellent heat dissipation effect can be obtained. Semiconductor refrigeration has the advantages of low cooling temperature and high reliability. The cold surface temperature can reach below minus 10℃, but the cost is too high, and it may cause short circuits due to low temperature, and the current semiconductor refrigeration technology is not mature and insufficient practical.

　　Chemical refrigeration

　　 The so-called chemical refrigeration is to use some ultra-low temperature chemical substances, and use them to absorb a lot of heat when they melt to reduce the temperature. In this regard, the use of dry ice and liquid nitrogen is more common. For example, the use of dry ice can reduce the temperature to below minus 20°C, and some more "abnormal" players use liquid nitrogen to lower the CPU temperature below minus 100°C (in theory). Of course, due to the high price and the short duration, this The method is more common in the laboratory or extreme overclocking enthusiasts.

　　 Material selection

　　 Thermal conductivity (unit: W/mK)

　　 Silver 429

　　 Copper 401

　　 Gold 317

　　 Aluminum 237

　　 Iron 80

　　 Lead 34.8

　　 1070 aluminum alloy 226

　　 1050 aluminum alloy 209

　 　6063 aluminum alloy 201

　 　6061 aluminum alloy 155

　　 Generally speaking, ordinary air-cooled radiators naturally choose metal as the material of the radiator. For the selected material, it is hoped that it has both high specific heat and high thermal conductivity. It can be seen from the above that silver and copper are the best thermal conductive materials, followed by gold and aluminum. But gold and silver are too expensive, so the current heat sink is mainly made of aluminum and copper. In comparison, both copper and aluminum alloy have their own advantages and disadvantages: copper has good thermal conductivity, but it is more expensive, difficult to process, heavy, and copper radiators have small heat capacity and are easy to oxidize . On the other hand, pure aluminum is too soft to be used directly. The aluminum alloy used can provide sufficient hardness. The advantages of aluminum alloy are low price and light weight, but the thermal conductivity is much worse than copper. Therefore, in the history of the development of radiators, products with the following materials have also appeared:

　　Pure aluminum radiator

　　Pure aluminum radiator is the most common radiator in the early stage. Its manufacturing process is simple and the cost is low. So far, pure aluminum radiator still occupies a considerable part of the market. In order to increase the heat dissipation area of its fins, the most commonly used processing method for pure aluminum radiators is aluminum extrusion technology. The main indicators for evaluating a pure aluminum radiator are the thickness of the radiator base and the Pin-Fin ratio. Pin refers to the height of the fin of the heat sink, and Fin refers to the distance between two adjacent fins. The Pin-Fin ratio is the height of the Pin (excluding the thickness of the base) divided by the Fin. The larger the Pin-Fin ratio means the larger the effective heat dissipation area of the radiator and the more advanced the aluminum extrusion technology.