Heat dissipation is a major factor affecting the intensity of LED lighting. Heat sink can solve the problem of heat dissipation of low illumination LED lamps. A heat sink can not solve the 75W or 100W LED lamp cooling problem.

In order to achieve the desired illumination intensity, 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; its life is similar to or higher than the light source.

Cooling method

Generally speaking, in accordance with the way from the radiator to take away the heat, the radiator can be divided into active cooling and passive cooling. The so-called passive heat, is through the heat sink heat source LED light source naturally distributed to the air, the cooling effect is proportional to the size of the heat sink, but because it is naturally distributed heat, the effect of course greatly reduced, often used in those space No demand for the equipment, or for the heat of the parts of the heat dissipation, such as some popular motherboard in the North Bridge also take a passive cooling, the vast majority of take the initiative to heat, active cooling is through the fan and other cooling equipment forced The heat will be sent out of the heat sink, which is characterized by high thermal efficiency, and equipment, small size.

Active cooling, subdivided from the way heat can be divided into air-cooled heat, cooling heat, heat pipe cooling, semiconductor refrigeration, chemical refrigeration and so on.

Air-cooled air cooling is the most common way of cooling, in comparison, is also cheaper way. Air cooling is essentially a fan that takes away the heat absorbed by the radiator. With the price is relatively low, easy installation and so on. But the environmental dependence is relatively high, such as the temperature rise and overclocking its thermal performance will be greatly affected.

Liquid cool

Liquid cooling heat is driven by the liquid in the pump driven by the heat to take away the radiator, compared with the air-cooled, with a quiet, cooling stability, the advantages of small dependence on the environment and so on. The price of liquid cooling is relatively high, and the installation is also relatively cumbersome. At the same time as installed in accordance with the instructions to install the instructions in order to get the best cooling effect. For cost and ease of use considerations, liquid cooling heat is usually used as a 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 which makes full use of the heat conduction principle and the rapid heat transfer property of the refrigerant. It conveys heat by evaporation and condensation of the liquid in the fully enclosed vacuum tube, has extremely high thermal conductivity, good isothermal The heat transfer area on both sides of the hot and cold can be arbitrarily changed, can be a long distance heat transfer, can control the temperature and a series of advantages, and heat pipe composed of heat exchanger with high heat transfer efficiency, compact structure, advantage. Its thermal conductivity has far exceeded the thermal conductivity of any known metal.

Semiconductor refrigeration

Semiconductor refrigeration is the use of a special semiconductor cooling film in the electricity generated when the temperature difference to cool, as long as the high temperature side of the heat can be effectively distributed, the low temperature side is constantly cooling. A temperature difference is generated on each of the semiconductor particles, and a cooling sheet is formed by concatenating dozens of such particles so as to form a temperature difference on both surfaces of the cooling sheet. The use of this temperature phenomenon, with the air-cooled / water-cooled high-temperature side of the cooling, can get excellent cooling effect. Semiconductor cooling has the advantages of low cooling temperature and high reliability. The cold surface temperature can reach below 10 ℃, but the cost is too high, and it may cause short circuit due to the low temperature, and the process of semiconductor refrigeration is not mature enough practical.

Chemical refrigeration

The so-called chemical refrigeration, is the use of some ultra-low temperature chemical substances, the use of them in the melting time to absorb a lot of heat to reduce the temperature. It is more common to use dry ice and liquid nitrogen. Such as the use of dry ice can be reduced to below 20 ℃ temperature, there are some more 'abnormal' players use liquid nitrogen to CPU temperature down to minus 100 ℃ below (theoretically), of course, because the price is too expensive and the duration is too short, this Methods 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 type Aluminum Alloy 226

1050 type Aluminum Alloy 209

6063 type aluminum alloy 201

6061 type aluminum alloy 155

In general, the ordinary air-cooled radiator naturally choose metal as a radiator material. For the selected material, it is expected that it has a high specific heat and high thermal conductivity, and it can be seen that silver and copper are the best thermal materials, followed by gold and aluminum. But gold, silver too expensive, so the current heat sink is mainly made of aluminum and copper. In contrast, both copper and aluminum alloys have their advantages and disadvantages: copper thermal conductivity is good, but the price is more expensive, the processing is more difficult, the weight is too large, and the copper radiator heat capacity is small, and easy to oxidize The On the other hand, pure aluminum is too soft, can not be used directly, are used in the aluminum alloy to provide sufficient hardness, the advantages of aluminum alloy is cheap, light weight, but the thermal conductivity is much worse than copper. So the history of the development of the radiator also appeared in the following materials:

Pure aluminum radiator

Pure aluminum radiator is the most common early radiator, the manufacturing process is simple, low cost, so far, pure aluminum radiator still occupy a considerable part of the market. To increase the cooling area of ​​its fins, pure aluminum radiator is the most commonly used processing means aluminum extrusion technology, and evaluation of a pure aluminum radiator is the main indicator of the thickness of the radiator base and Pin-Fin ratio. Pin refers to the height of the fins of the fins, Fin refers to the distance between two adjacent fins. Pin-Fin ratio is the height of Pin (excluding base thickness) divided by Fin, Pin-Fin ratio means that the greater the effective heat dissipation area of ​​the radiator, the more advanced the aluminum extrusion technology.

LED cooling technology (1) LED

Pure copper radiator

Copper heat transfer coefficient is 1.69 times the aluminum, so the same conditions in the same premise, pure copper radiator can be faster to heat away from the heat. But the texture of copper is a problem, many advertised 'pure copper radiator' is actually not really 100% copper. In the list of copper, copper content of more than 99% is called acid- free copper, the next grade of copper for the copper content of 85% or less of the Dan copper. Currently on the market most of the copper radiator copper content is between the two. And some poor quality copper cooler copper content even 85% are less than, although the cost is very low, but its thermal conductivity greatly reduced, affecting the heat dissipation. In addition, copper has obvious shortcomings, high cost, difficult processing, radiator quality is too large to hinder the application of copper heat sink. Bronze hardness is not as good as aluminum alloy AL6063, some mechanical processing (such as groove, etc.) performance as aluminum; copper melting point much higher than aluminum, is not conducive to extrusion (Extrusion) and so on.

Copper and aluminum bonding technology

After taking into account the shortcomings of copper and aluminum, the current market part of the high-end heat sink is often used copper and aluminum manufacturing process, these heat sinks are usually used copper metal base, and cooling fins are used aluminum, of course, In addition to copper bottom, there are heat sinks using copper pillars and other methods, is the same principle. With a high thermal conductivity, copper bottom can quickly absorb the heat released by the CPU; aluminum fins can be made with the help of complex means of the most conducive to the shape of heat, and provide a large storage space and rapid release, which In all respects to find a balance 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 cooling substrate itself, the accuracy of line alignment is extremely demanding, and need to have high heat dissipation, small Size, good adhesion of metal lines and other characteristics, therefore, the use of yellow light film production of thin film ceramic heat dissipation substrate, LED will continue to promote high power to enhance one of the important catalyst.