About LED light source device 15 questions and brilliant solutions

The day before yesterday, we pushed how to evaluate and use LED light source devices? Today, continue to deliver the wonderful interactive part of the second part!

1. Who is responsible for the blackening of the lamp bead?

Before encountering LED blackening (vulcanization), our company and the lamp factory can not judge who is responsible, and can not find the third party to identify the influential third party to judge, and finally can only be replaced, to reissue the lamp beads solve. - Fang Mou

There are many reasons for the blackening of the lamp bead, and the judgment of responsibility is really not good. Find the reason from yourself, whether there are raw materials that will blacken the lamp beads. There can be a small experiment: the glue, accessories, devices and lamp beads used are placed in a closed container for baking.

2. How to control the LED junction temperature?

At present, everyone says that the lumen maintenance rate of LED products can be more than 70% in 50,000 hours. Then, to ensure this indicator, how many degrees of LED junction temperature control? What is the appropriate temperature for the corresponding luminaire surface temperature? ——Chengdu Dongxu Energy Saving River R

The device's lifetime of 50,000 hours is at the specified pin temperature, and then the junction temperature is calculated, based on the TM-21. If assembled into a full lamp, the temperature difference between the case temperature and the device pins should be fully calculated.

3. Does anyone use the method of junction temperature judgment?

The experimental conditions for the high-temperature working life test in the evaluation method mentioned in your lecture are the ambient temperature, and the soldering iron temperature does not exceed a certain value. I think it should be judged the junction temperature inside the chip. Does anyone use the junction temperature judgment method? - The reason is you

Control the TS temperature to calculate the junction temperature. In fact, when testing the reliability of the LED, we are controlling the temperature of the TS point and delaying the junction temperature of the LED. The main thing is that the life of the LED is different under different junction temperature conditions.

In the test report of the LM-80, it also delays the life curve of the LED according to different ambient temperatures.

4, direct coating, spraying, filming three ways to compare

Do you think that there are several ways of direct coating, spraying and filming in high-power packaging, which will have higher light extraction efficiency, light color consistency, and reliability? ——Wang Leiming-Jingrui

I think the question you asked is very good. I have not tried it one by one.

But I think that when spraying and potting, you mainly want to see if the LED phosphor particle size distribution is uniform. If the particle size distribution is uniform, it may have certain benefits for the improvement of light efficiency.

5, the penetration of LED street lights and traditional sodium lamps in foggy days

Do you have research on the penetration of LED street lamps and traditional sodium lamps in foggy days? Some experts now block the promotion of LED street lights on the grounds that traditional sodium lamps are worn in foggy weather. I don't know if you can explain it to us? ——Nengbao Optoelectronics Steven

In fact, I have actually seen this problem. In the same environment, the contrast between the street lights of the foggy weather and the high-pressure sodium lamp, the color temperature penetration of the LED may not be as good as the high-pressure sodium lamp.

I suggest that you can find a way, you can go and see if you can see it in the foggy day. The penetration of LEDs in foggy days and its illumination on the ground are indeed worse than traditional sodium lamps.

6. The structure of different light source devices is very different.

The pin or solder joint temperature, substrate or heat sink temperature is the thermal condition of the commonly used LED in operation, but the temperature value that can usually be measured, and the junction temperature inside the light emitting device, are only indirectly related to different light source devices. Structure, there is a big difference. ——Leets

You are particularly right, that is, the temperature of the pin or solder joint contains the temperature of the substrate. It's just a hot condition for LEDs, it really only has an indirect relationship.

Different packages contain different chips, and because of the difference in their internal thermal resistance, there is a big difference. We can only say that our device is estimated by our pin and solder joint temperature, not a direct proportional relationship.

7. Method of accelerating aging lamp beads

The teacher, claiming 25000H life, seeking a method to accelerate the aging of the lamp beads, found that many companies inconsistent calculation methods, more convincing? ——Roy Chao

Accelerated aging, I personally feel that there is not a particularly authoritative way out, I just suggest that there really be a company to do, such a long test, and then do a destructive test, compare this test may compare persuasive.

At present, many people are asking for the attenuation rate, which is the evaluation method of semiconductors. Of course, I don't know if that method is really effective, but no one has tested it for so long.

8, the temperature of the filament junction, the reason for the filament fogging oil

What is the normal temperature of the filament junction temperature? What are the main factors of the filament fogging hair oil? How to control similar problems? ——Love Yidi~ Xiaomeng

The junction temperature of the filament should be tested in different ways, because if it is tested after sealing, it is difficult to seal the test probe into the test. It may be better to use some infrared test methods. As for the fogging of the glue, I think it may be related to the materiality of your glue itself.