With the rapid development of the economy, high-power LED lamps are used almost everywhere. It has many advantages such as environmental protection and energy saving, but the fly in the ointment is that its heat dissipation performance is very poor. When the internal temperature of the lamp is too high, the luminous power of the lamp will be greatly reduced and the lifespan will be shortened. Therefore, in order to further develop LED lamps, it is necessary to solve the problem of heat dissipation. This article aims at the problem of heat dissipation of high-power LED lamps and puts forward some specific and feasible solutions in combination with some advanced heat dissipation technologies at present. By improving the heat dissipation structure of LED lamps, the heat dissipation effect is greatly improved.
Light Emitting Diode (Light Emitting Diode) LED is a new type of cold light source that currently exists. Because it has the advantages of high efficiency, energy saving, and long life, and it will not affect the environment during use, it has been widely used in various fields. , becoming a light source with the broadest development prospects in the 21st century. The reason why LEDs can emit light is that there are a large number of active electrons in the PN junction, and the movement of electrons generates a large amount of light energy. The so-called high-power LED lighting is to assemble many LEDs to form a large module. However, not all the light energy generated is used for LED to emit light, and part of the heat energy will cause the internal temperature of the LED lamp to rise. As the internal temperature rises, the luminous efficiency and service life of the IED will be reduced. In the worst case, the LED chip will be burned out. Therefore, the problem of heat dissipation is the biggest obstacle to the development of high-power LEDs. How to dissipate the heat energy as quickly as possible is one of the issues that people are more concerned about.
There are many heat dissipation technologies for high-power LED lamps, the most important ones are heat sinks, heat pipes, vapor chambers, fans, and thermal paste. The heat dissipation principle of the heat sink is to dissipate the heat convection to the environment by enlarging the surface area. The heat dissipation performance of the heat sink is affected by many aspects. In order to have a better heat dissipation effect, there are also strict requirements on the material selection and installation process of the heat sink. The working principle of the heat pipe is to export the high heat generated by the LED and dissipate it to the outside through the constantly changing condensed liquid phase. Usually, we use the two in combination, so that the heat dissipation effect will be better. The vapor chamber is used to make the heat sink, so that the heat can be evenly distributed on the heat sink, and the heat can be dissipated faster. The role of thermal paste is to fill the gap, increase the contact area between the heat sink and the LED lamp, and reduce the thermal resistance.
heat sinks
thermal paste
heat pipes
vapor chambers
The heat dissipation defects of LED lamps mainly include the following four points:
(1) The selection and installation of heat sinks for LED lamps are unreasonable. In the selection of heat sinks, various factors were not fully considered, and the integrity and mechanical strength of the lamps were not considered during installation, so the best heat dissipation effect was not achieved from the surface.
(2) The design of LED lamps focuses on heat conduction but does not fully consider the convection heat dissipation link, so the effect is not obvious. Usually, the thermal resistance is reduced through the heat conduction of heat pipes and thermal grease, etc., but in the end, the heat is still dissipated on the outer surface of the lamp, so a better way is to coat a layer of radiation coating on the outer surface to improve the heat resistance effect, to avoid the excessive temperature of the lamp.
(3) LED lamps do not fully consider the balance of heat transfer. If the temperature distribution on the fins is not balanced, then some of the fins will play little or no role. We can consider using a uniform temperature plate to balance the temperature.
(4) The key to the heat dissipation of lamps is to release more heat into the atmosphere at the fastest speed, but the interface thermal resistance is the biggest obstacle, so it should be improved on the interface thermal conductivity material, and the thermal conductivity should be better. s material.
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There are two types of cooling technologies: active cooling and passive cooling. Passive heat dissipation is mainly realized through heat sinks, and the working principle is to dissipate heat through the natural convection of air. There are many technologies for active cooling, including heat pipes, thermoelectric cooling technology, micro-spray cooling technology, micro-channel cooling technology, fan installation, vapor chamber, cold plate, etc. To improve the heat dissipation structure of high-power lamps to achieve better heat dissipation, we first consider optimizing the selection of heat sinks and installing them scientifically and rationally, then study the influence of the selection of interface materials on the heat dissipation process, and design two other schemes. Adding a heat pipe on the chip and changing the heat sink to the material of the vapor chamber, through the above improvements, the lamp has achieved the expected heat dissipation goal.
The part where the heat sink is in contact with the heating object is the heat-absorbing bottom and the heat sink. Their design directly determines the cooling effect of a heat sink. A good radiator has the following three aspects of performance: fast heat absorption, small thermal resistance, and fast heat removal.
(1) Small thermal resistance. The overall thermal resistance of the heat sink is obtained by adding layer by layer from the contact surface of the LED module, and the heat conduction resistance inside the heat-absorbing bottom accounts for the largest proportion in the whole. To transfer most of the absorbed heat to the fins, one should
Ensure that the heat-absorbing bottom has a good enough lateral heat conduction capacity. Therefore, when designing lamps, the heat-absorbing bottom should have sufficient thickness. At the same time, when installing the LED module, in order to make the lamp have better integrity and stronger mechanical strength, the holes should be reinforced
(2) Fast heat absorption. In order to make the heat absorption capacity better, the contact area between the heat sink and the LED module should be increased, as far as possible to achieve complete direct contact. In addition, in order to fundamentally improve the heat absorption capacity of the heat absorption bottom of the heat sink, the bottom surface should be increased. flatness. The flatter the heat-absorbing bottom of the heat sink, the smaller the thermal resistance, which is more conducive to heat absorption. However, since the process cannot be completed perfectly, this design uses thermal paste, which has a lower thermal resistance and better adaptability, so as to achieve a better heat absorption effect.
(3) Go to heat quickly. In this design, the heat-absorbing bottom of the LED module is welded on the cooling fins to make them a whole, so that the heat absorbed from the LED can be transferred to the fins at the fastest speed because the lamp body and the cooling fins are completely exposed In the air, so the heat can be dissipated quickly. During the welding process, the direction in which the fins dissipate heat should be consistent with the direction of the airflow, so that the heat can be smoothly taken away by the flowing airflow and the heat can be dissipated at the fastest speed.
The heat pipe has excellent thermal conductivity, and its working principle is to export the heat emitted by the LED and dissipate it through the cyclical change of the liquid-gas two-phase. In LED, the heat pipe has many uses. It can directly install the LED chip on the top of the heat-absorbing end of the heat pipe, or process it into various styles before installing it. Generally, it is processed into a flat type or a loop type. The heat pipe is very convenient in practical application, and its biggest feature is that it can transmit heat to a place far away and easy to dissipate heat.
The working principle of the vapor chamber is almost the same as that of the heat pipe. The only difference is that their heat transfer methods are different. The heat pipe conducts heat in one direction, while the vapor chamber is a two-dimensional surface heat transfer method. This heat transfer method can disperse the heat and reduce the thermal resistance of diffusion from the surface.
In the manufacturing process of lamps, interface materials such as heat-conducting silica gel or silver glue are generally used to reduce contact thermal resistance. But their own thermal conductivity is not high, which seriously hinders the heat dissipation effect.
When the thermal conductivity of the interface material changes slightly, the cooling effect will change greatly. Therefore, in order to improve the heat dissipation capacity of the LED, the selection of the interface material is a very critical step. Only when designing lamps and lanterns, we first choose interface materials with relatively high thermal conductivity, so that it is easier to achieve better heat dissipation. When selecting materials, we should not only consider whether the thermal conductivity of the interface material is high but also consider the following aspects: the mechanical properties, price, ductility, and availability of the material, etc. At present, the best choice of heat dissipation material is aluminum alloy, which is made by adding various formula materials to pure aluminum. This material not only has the excellent performance of aluminum but also has a low price and is lightweight. In different applications, aluminum alloy materials can obtain various characteristics by adjusting the composition and proportion of formula materials, so that they can be used in different fields.
