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

In the past, when the LED was blackened (vulcanized), our company and the lamp beads factory could not determine who was responsible, nor could we find an influential third party that was recognized by both parties. In the end, nothing could be left to replace the lamp beads solve. -Fang Mou

There are many reasons for the blackening of the lamp beads, and the judgment of responsibility is really not conclusive. Find out for yourself whether any raw materials will blacken the lamp beads. There can be a small experiment: put the glue, auxiliary materials, devices and lamp beads used together in a closed container for baking.

2. How to control the LED junction temperature?

At present, everyone says that the luminous flux maintenance rate of LED products can be above 70% for 50000 hours, so to ensure this indicator, how much is the junction temperature of the LED? What is the appropriate temperature of the corresponding lamp surface temperature? ——Chengdu Dongxu Energy Saving River R

The life of the device is 50,000 hours at the specified pin temperature, and then the junction temperature is calculated, which is calculated based on TM-21. If the whole lamp is assembled, the case temperature and the temperature difference between the device pins should be fully calculated.

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

The experimental conditions of the high temperature working life test in the evaluation method mentioned in your lecture are the ambient temperature and the solder pin temperature does not exceed a certain value. I think we should judge the junction temperature in the chip. Is anyone using the method of judging the junction temperature? ——Fate is you

Control the TS temperature to calculate the junction temperature. In fact, when we test the reliability of the LED, we are controlling the temperature of the TS point and delaying the junction temperature of the LED. It mainly means what the life of the LED is under different junction temperature conditions.

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

4. Comparison of three methods of direct coating, spraying and filming

What do you think of the direct coating, spray coating, and filming methods in high-power packaging, which will have higher light output efficiency, light color consistency, and reliability? ——Wang Leiming-Jingrui

I think this question you asked is very good, I haven't done any experiments one by one.

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

5. Penetrability of LED street lights and traditional sodium lamps in foggy days

Do you have research on the penetration of LED street lights and traditional sodium lamps in foggy weather? Now, some experts have prevented the promotion of LED street lights on the ground that traditional sodium lamps have good permeability in foggy days. I wonder if you could explain it to us? ——Nengbao Optoelectronics Steven

In fact, I have actually seen this problem myself. Under the same environment, the contrast of LED street lights and high-pressure sodium lamps in foggy weather may not be as good as that of high-pressure sodium lamps.

I suggest you find a way, you can go and see for yourself in the misty day and you will know. In the foggy day, the transmittance of LED and its illuminance on the ground are indeed worse than that of traditional sodium lamps.

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

Pin or solder joint temperature, substrate or heat sink temperature are the common thermal conditions of LEDs in work, but the temperature values that can usually be measured have only an indirect relationship with the junction temperature inside the light emitting device. The structure is very different. ——Leets

You are particularly right, that is, the temperature of the lead or the solder joint includes the temperature of the substrate. It is just a thermal condition for LEDs, it really just has an indirect relationship.

Different packages contain different chips, and due to the differences in their internal thermal resistance, there are indeed large differences. We can only say that estimating my device through our pin and solder joint temperature is not a direct proportional relationship.

7, the method of accelerated aging lamp beads

Teacher, claiming a life of 25000H, find a way to accelerate the aging of the lamp beads, and find that many companies' calculation methods are inconsistent, which is more convincing? ——Roy Chao

Accelerated aging, I personally don't think there is a particularly authoritative method. I just suggest that there is really a company to do this test for such a long time, and then do a so-called destructive test. Comparing this test may be more persuasive.

At present, many people are saying to find its attenuation rate, which is to evaluate the semiconductor evaluation method. Of course I don't know if that method is really effective, but no one has tested it for so long.

8.Filament junction temperature, filament fog and oil cause

What is the normal temperature of the filament junction temperature? What are the main causes of filament fog and oil? How to control similar problems? ——Ai Yidi ~ Xiao Mengmeng

The junction temperature of the filament should be tested by different methods, because if it is sealed and then tested, it is difficult to seal the test probes. May use some infrared test methods will be better. As for the fogging of the glue, I think it may be related to the playability of the material of your glue.