The reliability of LED lighting fixtures depends largely on the level of heat dissipation, so improving the cooling rate is one of the key technologies. The main solution is to solve the problem that the chips generate excess heat through heat sink and heat dissipation. This is a very complicated technical problem.

Here we go:

The power of LED lamps, which leds need to consider heat dissipation, power leds need to heat up. A power LED is a light-emitting diode with a working current of 100mA or more. Line is our country the ASSIST union, defined by reference to the United States, according to the existing two LED the forward voltage of typical value of 2.1 V and 3.3 V, the input power of over 210 mw and 330 mw leds are power LED, all need to consider the device heat dispersion problem, some people may have different views, but practice has proved, to improve the reliability of power LED (life), consider the power LED heat dissipation problem.

The main parameters related to heat dissipation are thermal resistance and mild temperature rise.

Thermal resistance is the difference between the effective temperature of the device and the external reference point temperature divided by the steady-state power dissipation of the device. It is the most important parameter for the heat dissipation of the device. The heat dissipation good power LED thermal resistance of 10 ℃ / W or less, domestic reports the best thermal resistance of 5 ℃ / W or less, foreign can reach thermal resistance 3 ℃ / W or less, if do this level can ensure the service life of power LED.

The junction temperature is the temperature of the semiconductor junction in the main heating part of the LED device. It is an indication of the temperature of the LED device under working conditions. To this end, the U.S. SSL program sets up a goal to raise heat resistance. Chip and heat resistance of phosphor is very high, the current has reached chip junction temperature under 150 ℃, the phosphor powder under 130 ℃, the basic life won't have any influence on the device. Note that the higher heat resistance of chip fluorescent powder, the lower the requirement for heat dissipation.

There are several different kinds of temperature rise, and what we are talking about here is the case of shell - environment temperature rise. It refers to the temperature difference between the temperature and the environment (in the luminescent plane of the lamp, 0.5 meters from the lamp). It is a temperature can be measured directly, and can directly reflect the LED device peripheral cooling degree, practice has proved that in the ambient temperature of 30 ℃, if measured LED tube shell for 60 ℃, the temperature rise shall be the 30 ℃, this basically ensures the service life of LED device value, such as temperature rise too high, LED light source, maintain rate will decrease greatly.

New radiation problems of LED lamps:

With the development of LED lighting products, there are two new techniques: first, in order to increase the flux of the single pipe, into the larger current density, such as mentioned below, so that the chip produce more heat, need to heat dissipation. Secondly, encapsulate the new structure, with the increase of the LED light source power, need more power LED chip set packaging together, such as lamps and lanterns of COB structure, modular, will produce more heat, the need for more effective heat dissipation structure and measures, which in turn to put forward new task heat dissipation, otherwise it will greatly affect the performance and life of LED lamps and lanterns.

Currently, the total efficiency of LED lamps is only 50%, and there is still a lot of power to become hot. Second, LED large current density and modularized lamps and lanterns will produce more concentrated residual heat, which requires good heat dissipation.

To improve the cooling rate, we offer the following Suggestions:

1) in the case of LED chips, it is necessary to adopt new structure and new technology to improve heat resistance of LED chip and heat resistance of other materials, so as to reduce heat dissipation requirements.

2), and reduce the thermal resistance of LED device, adopts the new encapsulation structure, new technology, selection of thermal conductivity, good heat resistance, new materials, include metal adhesive materials, fluorescent powder mixed glue, etc., between the thermal resistance of 10 or less ℃ / W or lower.

3), reduce the heating up, as far as possible USES the heat dissipation material with good thermal conductivity, good vent way on the design requirements, make the heat spread out as soon as possible, for temperature should be less than 30 ℃. In addition, the heat dissipation of modularized lamps should be mentioned on the agenda.

4) there are many ways to heat the heat, such as the use of thermal catheters, which is good, but the cost factor should be taken into consideration and cost performance should be considered in the design.

In addition, the design of LED lamps and lanterns in addition to improving the efficiency of lamps and lanterns and light distribution requirements, good appearance, to improve the level of heat dissipation, USES the material with good thermal conductivity, it is reported that the cooling body coated with some nano materials, the thermal conductivity increases by 30%. In addition, want to have good mechanical properties and sealing, heat dissipation and dustproof, the rise of temperature of the requirements of LED lamps and lanterns should be 30 ℃.