We all know that the heat dissipation of LED lamp is very important, but how to evaluate lamp’s heat dissipation? Why does the traditional light source not pay attention to heat dissipation, but pay much attention for LED lamp? Because the traditional light source cannot get damaged by heat. LED, although it does not produce much heat, but the built-in chip is very afraid of heat. The chip can work safely only when the heat is dispersed. Otherwise, the heat will be concentrated in the light source, which will reduce the lamp’s performance and lifetime.
How to Conduct Heat from LED?
Now we should have the same question: How to conduct heat from LED?
The heat produced by the chip is transferred to the heatsink through PCB, and the heatsink releases the heat through its dissipation surface. Therefore, the size and area of heatsink determine its thermal ability.
In order to increase the area, the heatsink is generally made in columns, reticulation or other shapes, which requires complex machining process and high cost. This leads many factories allow for shoddy and inferior to save costs.
So the question is: How we can judge whether the thermal performance is good or not? For sure, the easy way is to test whether the temperature of the LED chip is high or not. In technical terms, this is called “junction temperature”, that is, the temperature of the LED PN junction. As long as the junction temperature is controlled within an acceptable range, the quality will pass. However, it is difficult to measure the junction temperature, as the LED chip is hidden in the lamp. It requires a series of professional equipment, but sometimes even with the best equipment, we can just see the appearance temperature from the outside, and never know the inside junction temperature.
How to judge the heat dissipation?
Now you must ask how to judge the heat dissipation.
When people choose lamps, they can’t measure the junction temperature, what will they do? The most way for them is to touch by hand to see hot or not. Well, some people say, my lamp is very good, as its surface temperature is only 27 ℃. Is it really good? In fact, when the LED lamps work properly, the heatsink temperature should be low but it will not reach a temperature of 27 ℃. In addition, you feel that this temperature is only for the external heatsink.
Even if the surface temperature is low, it is not necessarily good. Why?
There are two possibilities for low temperature of the heatink:
One possibility is that the heat from the LED chip is well emitted, which is certainly a good way for buyers, but a waste of material for manufacturers.
Another possibility is that the heat of the chip did not dissipate at all but still store inside. If there is no good contact between the chip and the heatsink, the heat of the chip does not radiate, only a small part of the heat is transmitted from the surface. So it’s not necessarily good if you touch it outside with a low temperature. It’s possible that it’s too hot inside.
In another case is that, if the light is only turned on for a little while and it feels particularly hot, the heat dissipation must be not good enough to conduct the heat from LED chip to air quickly. The heat gathers on the surface of the heatsink, so feel very hot.
Therefore, we come to conclusion that: it is not scientific to measure the lamp temperature with hand touch.