How to solve the problem of out of control pixels of full-color LED display?

　　The pixel of LED display screen is out of control, which means that the smallest imaging unit (pixel) of the display screen is not working properly. The ratio of out of control pixels to the total number of full screen pixels is called "out of control rate of full screen pixels". There are two modes of pixel runaway: one is blind spot, that is, blind spot. When it needs to be lit, it is not lit, which is called blind spot; Second, the constant bright spot, which is always on when it is not needed, is called the constant bright spot.

　　Generally, common LED display screen pixels consist of 2R1G1B (2 red lights, 1 green light and 1 blue light, the same below) and 1R1G1B. The runaway generally does not mean that all the red, green and blue lights in the same pixel are out of control at the same time, but as long as one of the lights is out of control, we think that the pixel is out of control. Therefore, it can be concluded that the main reason for the out of control pixel of full-color LED display screen is the out of control LED lamp. The main causes of LED lamp failure can be divided into two aspects: first, LED's own quality is poor; Second, improper use methods.

　　The LED lamp out of control cannot be found in the routine inspection and test of LED. Under harsh conditions such as high temperature, low temperature and rapid temperature change, due to the difference of thermal expansion coefficient of LED chips, epoxy resins, brackets, inner leads, solid crystal adhesives, PPA cups and other materials, the internal stress is different. The mechanism of LED runaway caused by electrostatic discharge is very complex. Equipment, tools, utensils and human body may have static electricity and discharge it. This static electricity can range from hundreds of volts to tens of thousands of volts, and the discharge time is at the nanosecond level. If the blue-green tube is out of control, the LED-PN junction is often broken down by electrostatic discharge. Due to the complicated production process of LED display screen, electrostatic discharge cannot be prevented. Therefore, electrostatic protection must run through the whole production process.

　　In different situations, the actual requirements of pixel out of control rate are different, and the indicators of full-color LED display screen are required to be controlled within 1%; The indicators of monochrome LED display shall be controlled within one tenth. At present, there is no good solution for the pixels of full-color LED display screen. It is recommended to contact the service manufacturer to return to the factory for repair. If the repair cost is too high, you can consider replacing the defective module unit board.

　　At present, LED displays in China are subject to aging test before leaving the factory, and LED lights of out of control pixels are repaired and replaced. It is no problem to control the "out of control rate of whole screen pixels" within 1/104 and the "out of control rate of regional pixels" within 3/104. Even some manufacturers' enterprise standards require that out of control pixels are not allowed before leaving the factory, but this will inevitably increase the manufacturing and maintenance costs of manufacturers and extend the shipping time.

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