2024-05-10
Suggestions to improve the heat dissipation level of LED lamps
Suggestions to improve the heat dissipation level of LED lamps
The reliability (life) of LED lighting fixtures largely depends on the level of heat dissipation, so improving the level of heat dissipation is one of the key technologies. It is mainly to solve the excess heat generated by the chip through the heat sink and the heat dissipation body, which is a very complex technical problem.
Let's describe them separately:
The power of LED lamps, which LED need to consider heat dissipation, power LED need heat dissipation. Power LED is a light-emitting diode with an operating current of more than 100mA. Is China's line standard with reference to the United States ASSIST alliance definition, according to the existing two kinds of LED forward voltage typical value 2.1V and 3.3V, that is, the input power in 210mw and 330mw above the LED are power LED, need to consider the device heat dispersion problem, some people may have different views, but practice has proved that, To improve the reliability (life) of the power LED, it is necessary to consider the heat dissipation of the power LED.
The main parameters related to LED heat dissipation are thermal resistance, junction temperature and temperature rise.
Thermal resistance is the difference between the effective temperature of the device and the temperature of an external specified reference point divided by the steady-state power dissipation in the device. It is an important parameter indicating the degree of heat dissipation of the device. At present, the thermal resistance of the power LED with better heat dissipation is less than 10 ° C /W, the thermal resistance reported in China is less than 5 ° C /W, and the thermal resistance abroad can reach less than 3 ° C /W, such as doing this level can ensure the life of the power LED.
Junction temperature refers to the temperature of the semiconductor junction in the main heating part of the LED device. It reflects the temperature value that the LED device can withstand under working conditions. To this end, the US SSL program has set a goal of improving heat resistance. The heat resistance of the chip and phosphor is still very high, and the chip junction temperature has been reached at 150 ° C, and the phosphor is at 130 ° C, which will not have any effect on the life of the device. The higher the heat resistance of the chip phosphor, the lower the requirement for heat dissipation.
There are several different temperature rises, and the one we are talking about here is: shell - ambient temperature rise. It refers to the difference between the temperature of the LED device shell (the hot spot that can be measured by the LED lamp) and the temperature of the environment (on the luminaire's luminous plane, 0.5 meters from the lamp). It is a temperature value that can be directly measured, and can directly reflect the degree of heat dissipation of the LED device, practice has proved that when the ambient temperature is 30 ° C, if the LED shell is measured at 60 ° C, the temperature rise should be 30 ° C, at this time basically to ensure the life value of the LED device, such as the temperature rise is too high, the maintenance rate of the LED light source will be greatly reduced.
Junction temperature refers to the temperature of the semiconductor junction in the main heating part of the LED device. It reflects the temperature value that the LED device can withstand under working conditions. To this end, the US SSL program has set a goal of improving heat resistance. The heat resistance of the chip and phosphor is still very high, and the chip junction temperature has been reached at 150 ° C, and the phosphor is at 130 ° C, which will not have any effect on the life of the device. The higher the heat resistance of the chip phosphor, the lower the requirement for heat dissipation.
There are several different temperature rises, and the one we are talking about here is: shell - ambient temperature rise. It refers to the difference between the temperature of the LED device shell (the hot spot that can be measured by the LED lamp) and the temperature of the environment (on the luminaire's luminous plane, 0.5 meters from the lamp). It is a temperature value that can be directly measured, and can directly reflect the degree of heat dissipation of the LED device, practice has proved that when the ambient temperature is 30 ° C, if the LED shell is measured at 60 ° C, the temperature rise should be 30 ° C, at this time basically to ensure the life value of the LED device, such as the temperature rise is too high, the maintenance rate of the LED light source will be greatly reduced.
New heat dissipation problems of LED lamps:
With the development of LED lighting products, there are two new technologies: First, in order to increase the luminous flux of a single tube, a larger current density is injected, as mentioned below, so that the chip generates more heat and needs to dissipate heat. Second, packaging new structure, with the increase of LED light source power, the need for multiple power LED chip collection package together, such as COB structure, modular lamps, etc., will produce more heat, the need for more effective heat dissipation structure and measures, which put forward new topics for heat dissipation, otherwise it will greatly affect the performance and life of LED lamps.
At present, the total heat dissipation efficiency of LED lamps is only 50%, and there is a lot of electricity to become hot. Secondly, LED high current density and modular lamps will produce more concentrated waste heat, which needs good heat dissipation.
At present, the total heat dissipation efficiency of LED lamps is only 50%, and there is a lot of electricity to become hot. Secondly, LED high current density and modular lamps will produce more concentrated waste heat, which needs good heat dissipation.
To improve the level of heat dissipation we provide the following suggestions:
1), from the LED chip, it is necessary to adopt a new structure and new process to improve the heat resistance of the LED chip junction temperature, as well as the heat resistance of other materials, so that the heat dissipation conditions are reduced.
2), reduce the thermal resistance of LED devices, the use of new packaging structure, new process, the selection of new materials with good thermal conductivity and heat resistance, including the bonding material between metals, the mixture of phosphors, etc., so that the thermal resistance is ≤10℃/W or lower.
3), reduce the temperature rise, try to use good thermal conductivity of heat dissipation materials, in the design requires a good ventilation channel, so that the waste heat as soon as possible to disperse, the temperature should be less than 30℃. In addition, improving the heat dissipation level of modular lamps should be mentioned on the agenda.
4), there are many ways to heat dissipation, such as the use of heat conduits, of course, very good, but to consider the cost factor, in the design should consider the cost performance.
In addition, the design of LED lamps in addition to improve the efficiency of lamps, light distribution requirements, beautiful appearance, to improve the level of heat dissipation, the use of good thermal conductivity materials, it is reported that the heat dissipation body coated with some nanomaterials, its thermal conductivity increased by 30%. In addition, to have better mechanical properties and tightness, the heat dissipation body should also be dust-proof, requiring the temperature rise of the LED lamp should be less than 30 ° C.
2), reduce the thermal resistance of LED devices, the use of new packaging structure, new process, the selection of new materials with good thermal conductivity and heat resistance, including the bonding material between metals, the mixture of phosphors, etc., so that the thermal resistance is ≤10℃/W or lower.
3), reduce the temperature rise, try to use good thermal conductivity of heat dissipation materials, in the design requires a good ventilation channel, so that the waste heat as soon as possible to disperse, the temperature should be less than 30℃. In addition, improving the heat dissipation level of modular lamps should be mentioned on the agenda.
4), there are many ways to heat dissipation, such as the use of heat conduits, of course, very good, but to consider the cost factor, in the design should consider the cost performance.
In addition, the design of LED lamps in addition to improve the efficiency of lamps, light distribution requirements, beautiful appearance, to improve the level of heat dissipation, the use of good thermal conductivity materials, it is reported that the heat dissipation body coated with some nanomaterials, its thermal conductivity increased by 30%. In addition, to have better mechanical properties and tightness, the heat dissipation body should also be dust-proof, requiring the temperature rise of the LED lamp should be less than 30 ° C.
