Views: 86 Author: Site Editor Publish Time: 2020-03-03 Origin: Site
Nowadays, many people are using LED lights, and those who have carefully observed LED lights will find that they have a feature: there always is a heatsink at the rear of the lamp.
Regarding the importance of heat dissipation, it is almost popular from the beginning of the use of LED lights, because the light source used before is not afraid of heat, such as tungsten lamp, the light is generated by heat, as long as the tungsten lamp is not too hot to burn people, it doesn't matter.
However, LED lights, no matter how many watts of light bulbs, we should pay attention to its heat dissipation.
LED is essentially a semiconductor device (a semiconductor is actually a very fragile device), and higher temperature will reduce the performance and lifetime of LED.
In the LED chip, there are various heat-conducting medias and there is a heatsink in the bottom, so that the heat emitted by the LED can escape from the inside of the lamp in time, thus the temperature of the LED lighting itself has a stable low temperature value.
In physics, there are three basic ways of heat conduction, they are conduction, convection, and radiation.
The first is conduction. Conduction means that heat travels through the heat conductor to the lower temperature part from the part where the object temperature is high.
The factors that affect the heat dissipation are:
① Thermal conductivity of heat dissipation material
② Thermal resistance caused by heat dissipation structure
③ Shape and size of heat conductive materials
The above three factors will affect the speed and efficiency of heat conduction.
Radiation is a phenomenon that a high-temperature object directly dissipates heat outward. Its efficiency depends on the thermal resistance of the surrounding medium and the characteristics of the heat-radiating material itself.
Convection is to use the flow of gas or liquid to carry away the heat generated.
After analyzing the ways that the lamps dissipate heat, when we get a LED light, how do we judge whether its heat dissipation is good or not?
Of course, the easiest and quickest way is to use professional equipment to measure temperature, but in daily life, most people doesn’t have these equipments, so we will recommend a simpler way for everyone, that is, touch the lights with your own hands, feel the temperature to judge whether it is hot.
When a LED light has been working for 15-20 minutes, its surface temperature may reach 80 °C. Since the temperature inside the light is transmitted to the surface, it will suffer some obstacles. If the outside temperature is 80 degrees, the light source may reach 150 degrees.
Therefore, if the light you touch is very hot, the heat dissipation of this light must not be good. However, if the touched light is not hot, it does not necessarily mean that its heat dissipation performance is good.
The LED emits heat, and then the heat is led out through the substrate and the glue layer, and it is quickly released. The heat transfer is good and the temperature is not high.
If the filling material in the middle of the LED chip is not good and the substrate contains some impurities, when the heat is transferred to the part of the thermal interface filler material, the heat will accumulate inside the chip, and the temperature inside may reach 200 degrees, but the outside surface of the light is still not hot when touched.
This situation is very troublesome, the two lights are both not hot when touched, it is impossible to judge whose heat dissipation performance is better.
But don't worry, there is another way, which is called the half-hour illumination method. In general, the junction temperature of the LED (which refers to the temperature generated by the PN junction inside the LED chip) increases, and the luminous flux decreases. Then, we only need to measure the illuminance change of the lights in the same position indirectly, and we can reverse the change of the junction temperature (only the illuminometer is needed).
