LED Heat Dissipation Technology And Heat Dissipation Materials.
- Apr 14, 2018 -

LED cooling technology (1)LED.

    Heat dissipation is one of the main factors that influence the illumination intensity of LED lamps.Heat sink can solve the heat dissipation problem of low illumination LED lamps.A heatsink is unable to solve the heat dissipation problem of 75W or 100W LED lamps.

    In order to achieve the ideal lighting intensity, the active cooling technology must be used to solve the heat released by the LED lamp components.Some active cooling solutions such as fan life without LED lamps.In order to provide a practical active cooling solution for high luminance LED lamps, the heat dissipation technology must be low energy consumption;And can be applied to small lamps and lanterns;Its life should be similar to or higher than the lamp source.

    The cooling way

    Generally speaking, according to the way of taking heat from the radiator, the radiator can be divided into active heat dissipation and passive heat dissipation.So-called passive cooling, it is to point to through the radiator to heat source, the LED light source as natural heat into the air, the heat dissipation effect is proportional to the size of heat sink, but because it is a natural send out quantity of heat, the effect of course, is often used in those without the requirements of the equipment to the space, or used to heat cooling small parts, such as part of the affordable motherboard also take passive cooling on north bridge, the vast majority of taking active cooling type, active cooling is through the fan cooling device, such as compulsive to heat away from the heat sink, its characteristic is high cooling efficiency, small volume and equipment.

    Active heat dissipation can be divided into air cooling, liquid cooling, heat pipe cooling, semiconductor refrigeration, chemical refrigeration and so on.

Cold air cooling is the most common heat dissipation method, compared to the cheaper way.Air cooling is essentially the use of a fan to take away heat from the radiator.It has the advantages of relatively low price and convenient installation.But high environmental dependence, such as rising temperatures and overfrequency, will have a big impact on their heat dissipation performance.

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    Liquid cooled heat dissipates the heat of the radiator through the forced circulation of the liquid through the pump. Compared with the air cooling, it has the advantages of silence, cooling and stability, and little dependence on the environment.The price of liquid cooling is relatively high, and the installation is relatively troublesome.At the same time the installation can be installed according to the instruction manual method to obtain the best heat dissipation effect.Because of the cost and ease of use, liquid cooled heat is usually used as a heat conducting liquid, so the liquid cooling radiators are often referred to as water-cooled radiators.

    Heat pipe

    Heat pipe belongs to a kind of heat transfer element, it makes full use of the heat transfer principle and rapid heat transfer properties of cooling medium, through the liquid evaporation and condensation in the vacuum tube to transmit heat, high thermal conductivity, excellent isothermal property, heat transfer area on either side of the hot and cold can be arbitrary change, which can be heat transfer and temperature can be controlled at and a series of advantages, and composed of a heat pipe heat exchanger has high heat transfer efficiency, compact structure, small fluid resistance loss, etc.Its thermal conductivity is far greater than that of any known metal.

    Semiconductor refrigeration

    Semiconductor refrigeration is the use of a special kind of semiconductor refrigeration to produce temperature difference when the power is energized, so long as the heat of the high temperature can effectively dissipate, the cold end is continuously cooled.The temperature difference is produced on each of the semiconductor particles, and a refrigerated sheet is made of dozens of such particles, forming a temperature difference between the two surfaces of the cooling sheet.This kind of temperature difference can be used to cool the high temperature with air cooling/water cooling, and it can get excellent heat dissipation effect.Semiconductor refrigeration refrigeration temperature low, high reliability, etc. The temperature can reach below 10 ℃ below zero is grim, but the cost is too high, and may cause short circuit caused by low temperature, and a process of semiconductor refrigeration is not mature now, not practical enough.

    Chemical refrigeration

    Chemical refrigeration is the use of some ultra-low temperature chemicals that absorb a large amount of heat to reduce the temperature when they melt.This is more common with dry ice and liquid nitrogen.Such as the use of dry ice temperature can be reduced to below 20 ℃ below zero, there are some of the more 'abnormal' players using liquid nitrogen to CPU temperature has dropped below 100 ℃ below zero (in theory), and, of course, due to the expensive and duration is too short, this method in laboratory or more extreme overclocking enthusiasts.

    Material selection

    Thermal conductivity (unit: W/mK)

    Silver 429

    Copper 401

    Gold 317

    Aluminum 237

    Iron 80

    Lead is 34.8

    1070 aluminium alloy 226.

    Type 1050 aluminum alloy 209.

    Type 6063 aluminum alloy 201.

    Type 6061 aluminum alloy 155.

    Generally speaking, ordinary air - cooled radiator naturally choose metal as the radiator material.For the selected materials, it is hoped that it has the high ratio heat and high heat conduction coefficient. As can be seen from the above, silver and copper are the best thermal conductive materials, followed by gold and aluminum.However, gold and silver are too expensive, so the current heat sinks are mainly made of aluminum and copper.Comparison, copper and aluminum alloy both have their advantages and disadvantages: the thermal conductivity of copper is good, but the price is more expensive, the processing difficulty is higher, the weight is too big, and copper radiator heat capacity is small, and easy to oxidation.Pure aluminium too soft on the other hand, cannot be used directly, all is the use of aluminum alloy can provide sufficient hardness, aluminum alloy has the advantage of low cost, light weight, but the thermal conductivity will be far worse than copper.Therefore, in the development history of radiators, there are several kinds of products:

    Pure aluminium 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 fins, the most commonly used processing method of pure aluminum radiator is aluminum extrusion technology, and the main index of a pure aluminum radiator is the thickness of the radiator base and the pin-fin ratio.The Pin refers to the Fin height of the Fin, which refers to the distance between two adjacent fins.The pin-fin ratio is the height of the Pin (excluding the base thickness) divided by Fin, and the larger the pin-fin ratio means the greater the effective heat dissipation area of the radiator, the more advanced the aluminum extrusion technology is.

    LED cooling technology (1)LED.

    Pure copper radiator

    Copper's thermal conductivity is 1.69 times that of aluminum, so the pure copper radiator is able to take heat away from the heat source faster than other conditions.But the quality of copper is a problem, and a lot of 'pure copper radiator' is not really 100% copper.In the copper list, copper containing more than 99 percent of the copper is called acid-free copper, and the next level of copper is copper, which contains less than 85 percent copper.Most of the pure copper radiators on the market are in between.However, some of the low-quality pure copper radiators are not even 85% copper, although the cost is very low, but their thermal conductivity is greatly reduced, which affects the heat dissipation.In addition, copper also has obvious shortcomings, high cost, difficult to process, the heat sink quality is too much to block the application of the whole copper radiator.The hardness of red copper is not as good as AL6063, and some mechanical processes (such as cutting and cutting) are not as good as aluminum.The melting point of copper is much higher than aluminium, which is unfavorable for Extrusion forming (Extrusion), and so on.

    Copper and aluminium technology.

    Considering both copper and aluminum material after their respective shortcomings, high-end radiator is often part of the market at present is based on copper and aluminum manufacturing process, these usually have the heat sink copper metal base, while aluminum alloy heat dissipation fins, of course, in addition to the copper base, also have a heat sink using methods of copper column, the principle is the same.With the higher thermal conductivity, the copper base can absorb the heat released by the CPU quickly.Aluminum fins can be used to make the shape that is most favorable to heat dissipation by means of complex technological means, and provide large storage space for heat storage and release quickly, which has found a balance point in all aspects.

    To promote LED luminous efficiency and service life, solve the problem of LED products is one of the most important subject at this stage, the LED industry line registration accuracy requirements for heat dissipation substrate itself is extremely harsh, and high heat dissipation, small size, good metal line adhesion characteristic, therefore, radiating ceramic substrate Huang Guangwei shadow system is used as the film, will be to promote LED to high power continuously improve one of the most important catalyst.