How to solve the problem of pixel loss of full-color LED display?

The loss of control of the pixel of the full-color LED display is a relatively common problem. What is the cause of this phenomenon? How to solve it?

The pixel point of the LED display is out of control, meaning that the smallest imaging unit (pixel) of the display is not working properly. The ratio of the number of uncontrolled pixels to the total number of pixels in the full screen is called the “full screen pixel runaway rate”. There are two kinds of pixel out-of-control modes. One is a blind spot, and it is a blind spot. When it needs to be bright, it does not light up, which is called a defect. The second is a constant bright spot. When it needs to be off, it is always lit. It is called the constant bright spot.

Generally, common indoor LED display pixels are composed of 2R1G1B (2 red lights, 1 green light and 1 blue light, the same reason below) and 1R1G1B, and the runaway is generally not red or green in the same pixel. The blue light is out of control at the same time, but as long as one of the lights is out of control, we think that this pixel is out of control. Therefore, it can be concluded that the main cause of the loss of control of the full-color LED display pixel is that the LED light is out of control. The main cause of LED lamp failure can be divided into two aspects: one is the poor quality of the LED itself; the other is the improper use of the method.

The loss of control of the LED light is undetectable in the routine inspection test of the LED. Under the harsh conditions of high temperature, low temperature and rapid temperature change, due to the difference in thermal expansion coefficient between LED chip, epoxy resin, bracket, inner lead, solid crystal adhesive, PPA cup and other materials, the internal stress is different. Electrostatic discharge causes the mechanism of LED runaway to be very complicated. Equipment, tools, utensils and human body may have static electricity and discharge it. This static electricity is as low as several hundred volts, high is tens of thousands of volts, and discharge time is in the nanosecond level. . If the blue-green tube is out of control, it is often the LED-PN junction that is broken down by electrostatic discharge. Due to the complicated production process of the full-color LED display , the electrostatic discharge is insurmountable. Therefore, the electrostatic protection must pass through the whole process of production.

In different occasions, the practice requirements of pixel runaway rate are different. The full-color LED display index is required to be controlled within one percent; the monochrome LED display index is required to be controlled within one tenth. At present, there is no good solution for full-color LED display pixels. It is recommended to return to the factory for repair. If the repair cost is too high, consider replacing the defective module unit board.

At present, the domestic LED display will undergo aging test before leaving the factory. The LED lights of the out-of-control pixel will be repaired and replaced. The "full-screen pixel runaway rate" is controlled within 1/104, and the "region pixel out of control rate" is controlled at 3/. There is no problem within 104. Even some enterprise manufacturers' standards require that out-of-control pixels are not allowed before leaving the factory, but this will inevitably increase the manufacturer's manufacturing repair cost and extend the shipping time.

In different use cases, the practice requirements of the pixel out of control rate can be quite different. Generally speaking, the LED display screen is used for video playback, and the index requirement control is acceptable within 1/104, and can also be achieved; If used for simple character information distribution, it is reasonable for the indicator to require control within 12/104.

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