Heat dissipation is a major factor affecting the lighting intensity of LED lamps. Heat sinks can solve the problem of heat dissipation of low illumination LED lamps. A heatsink is not able to solve the thermal problem of 75W or 100W LED lamps.
In order to achieve the desired lighting intensity, the active cooling technology must be used to solve the heat released by the LED lamp assembly. Some active cooling solutions such as fan life are not high for 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 and lanterns, whose life is similar to or above the lamp source.
Generally speaking, the radiator can be divided into active heat dissipation and passive heat dissipation according to the way to remove heat from the radiator. The so-called passive cooling, refers to the heat source through the heat of the LED light source heat naturally emitted into the air, its heat dissipation effect and the size of the heat sink, but because it is the natural distribution of heat, the effect of course greatly reduced, often used in those who do not require the space equipment, or for the heat dissipation of small parts, such as part of the popular motherboard in the North Bridge also take passive heat, most of the active type of heat dissipation, Active cooling is through the fan, such as heat dissipation equipment forced to remove the heat from the heat, which is characterized by high thermal efficiency, and small equipment.
Active cooling, from the cooling method subdivision, can be divided into air-cooled cooling, liquid cooling, heat pipe cooling, semiconductor refrigeration, chemical refrigeration and so on.
Cold air cooling is the most common way of cooling, compared to the cheaper way. Wind cooling is essentially the use of the fan to take away the heat absorbed by the radiator. With relatively low price, easy installation and other advantages. However, the environmental dependence is high, such as temperature rise and overclocking when its thermal performance will be greatly affected.
Liquid cooling is through the liquid in the pump driven by forced circulation to take away the heat of the radiator, compared with the wind cooling, with quiet, cool stability, small dependence on the environment and so on. The price of liquid cold is relatively high, and the installation is relatively troublesome. Install at the same time as far as possible in accordance with the instructions to guide the method to achieve the best cooling effect. For the sake of cost and ease of use, liquid cooling is usually used as a heat conduction liquid, so the liquid cooled radiator is also often referred to as water cooler.
The heat pipe belongs to a heat transfer element, which makes full use of the heat conduction principle and the fast heat transfer property of the refrigerant medium, and transmits heat through evaporation and condensation of the liquid in the hermetic vacuum tube. With very high thermal conductivity, good isothermal, hot and cold heat transfer area can be arbitrarily changed, long-distance heat transfer, controllable temperature and a series of advantages, and the heat exchanger composed of heat pipe with high heat transfer efficiency, compact structure, small fluid resistance and so on. Its thermal conductivity has far exceeded the thermal conductivity of any known metal.
Semiconductor refrigeration is the use of a special kind of semiconductor refrigeration chip in the power when the temperature difference to refrigeration, as long as the heat at the high temperature can be effectively distributed out, then the low-temperature end is constantly cooled. A temperature difference is generated on each semiconductor particle, and a refrigeration piece is formed in series by dozens of of such particles, forming a temperature difference on the two surfaces of the cooler. Using this temperature difference phenomenon, combined with air cooling/water-cooling to cool the high-temperature end, can get excellent heat dissipation effect. Semiconductor refrigeration with low refrigeration temperature, high reliability, cold temperatures can reach 零下10℃ below, but the cost is too high, and may be due to low temperature caused by short circuit, and now the semiconductor refrigeration chip technology is not mature, not practical.
Chemical refrigeration is the use of cryogenic chemicals that use them to absorb a lot of heat to reduce the temperature during melting. This is more common in the use of dry ice and liquid nitrogen. For example, the use of dry ice can reduce the temperature below the 零下20℃, there are some more ' perverted ' players using liquid nitrogen to lower the CPU temperature to 零下100℃ (theoretically), of course, because of the expensive and the duration is too short, this method more in the laboratory or extreme overclocking enthusiasts.
Heat conduction coefficient (unit:/)
1070 Aluminum Alloy 226
1050 Aluminum Alloy 209
6063 Aluminum Alloy 201
6061 Aluminum Alloy 155
Generally speaking, the common air-cooled radiator naturally chooses metal as the heat sink material. For the selected materials, it is hoped that the high heat conduction coefficient at the same time, silver and copper are the best thermal conductivity materials, followed by gold and aluminum. However, gold and silver are too expensive, so the current heat sink is mainly made of aluminum and copper. In comparison, both copper and aluminum alloys have their advantages and disadvantages: Copper heat conductivity is good, but the price is more expensive, processing difficult, heavy weight, and copper radiator heat capacity is small, and easy to oxidize. On the other hand, pure aluminum is too soft, can not be used directly, is the use of aluminum alloy to provide sufficient hardness, the advantages of aluminum alloy is low price, light weight, but the thermal conductivity than copper is much worse. Therefore, in the development of the radiator has also emerged in the following several materials:
Pure Aluminum Radiator
Pure aluminum Radiator is the most common early radiator, its manufacturing process simple, low-cost, so far, pure aluminum radiator still occupies a considerable part of the market. In order to increase the heat dissipation area of fins, the most commonly used processing method of pure aluminum radiator is aluminum extrusion technology, and the main index of evaluating a pure aluminum radiator is the thickness and pin-fin ratio of radiator base. The pin is the height of the fins of the heatsink, and the fin is the distance between the two adjacent fins. Pin-fin ratio is with the height of the pin (without the base thickness) divided by fin, the larger the pin-fin means the more effective the radiator area, representing the more advanced aluminum extrusion technology.
LED cooling Technology (1) LED
Pure Copper Radiator
Copper heat conduction coefficient is 1.69 times times of aluminum, so in other conditions the same premise, pure copper radiator can be faster to remove heat from the heat. However, the quality of copper is a problem, many of the "pure copper radiator" is not actually 100% of copper. In the list of copper, the copper content of more than 99% is called acid-free copper, the next grade of copper is copper content of 85% under the Dan Copper. The copper content of most pure copper radiators in the market is in between. And some poor pure copper radiator copper content even less than 85%, although the cost is very low, but its thermal conductivity greatly reduced, affecting the heat dissipation. In addition, copper has obvious shortcomings, high cost, processing difficult, radiator quality is too large to hinder the application of the whole copper heat sink. Copper is not as hard as aluminum alloy AL6063, some mechanical processing (such as cleavage, etc.) performance is not as good as aluminum, the melting point is much higher than aluminum, not conducive to extrusion (extrusion) and so on.
Copper and aluminum bonding technology
After considering the shortcomings of both the copper and aluminum materials, at present, some high-end radiator in the market often uses copper and aluminum combined manufacturing technology, these fins are usually used copper metal base, and the fins are aluminum alloy, of course, in addition to the copper bottom, there are also heat sinks using copper pillars and other methods, is the same principle. With a higher thermal conductivity, the copper substrate can quickly absorb the heat released by the CPU; aluminum fins can be made by means of complex technology to form the most conducive to heat dissipation, and provide a large storage space and rapid release, which has been found in all aspects of a balanced point.
To enhance the LED luminous efficiency and service life, to solve the problem of LED product cooling is one of the most important issues at this stage, led industry on the thermal substrate itself of the line of precision requirements are extremely stringent, and need to have high heat dissipation, small size, metal line adhesion good characteristics, therefore, the use of yellow light micro-shadow film ceramic thermal substrate, will be to promote the LED continuously to high power promotion of one of the important catalyst.