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Eight parameters that should be paid attention to in the application of LED lamp beads in the display field
time：
2021-09-15
As the component with the highest cost and consumption of LED display screen, LED lamp bead plays a leading role in the quality of LED display screen. Today, let's introduce why led beads are the most key components of LED display screen and how to identify the advantages and disadvantages of LED beads?
As the component with the highest cost and consumption of LED display screen, LED lamp bead plays a leading role in the quality of LED display screen. Today, let's introduce why led beads are the most key components of LED display screen and how to identify the advantages and disadvantages of LED beads?
The key component of full-color LED display screen is led bulb. There are three reasons:
First, LED is the most used key device in the full-color screen machine, and thousands to tens of thousands of LEDs will be used per square meter;
Second, LED is the main body that determines the performance of the whole screen optical display, which directly affects the audience's evaluation of the display screen;
Third, LEDs account for the largest proportion of the overall cost of the display screen, ranging from 30% to 70%.
How to identify the advantages and disadvantages of LED display beads?
1、 Look at the solder joint. The LED lamp belt produced by regular LED lamp belt manufacturers is produced by SMT patch process, solder paste and reflow soldering process
2、 Look at FPC quality. FPC is divided into copper clad and calendered copper. The copper foil of copper clad plate is convex. If you look closely, you can see from the connection between pad and FPC
3、 Look at the cleanliness of the surface of the LED light strip. If the LED light belt produced by SMT process is adopted, the surface cleanliness is very good, and there are no impurities and stains
4、 Looking at the chip and production process of LED lamp, you can't see the difference with your eyes. You should use aging equipment and testing equipment. If you put the LEDs of several manufacturers on the aging instrument and age them with high current for 24 hours or more, you can measure the LED brightness of several manufacturers to see that the LED with the least attenuation of luminous intensity and the best quality.
What are the effects of LED light beads on LED display
1. Perspective
The viewing angle of LED display screen depends on the viewing angle of LED lamp beads. At present, most outdoor display screens use horizontal viewing angle of 100 ° Vertical viewing angle 50 °; Oval LED, indoor display screen is 120 ° horizontally and vertically; Patch LED. Because of its particularity, the display screen on expressway is generally 30 °; The circular LED of the viewing angle is enough. The display screens on some high-rise buildings have high requirements for vertical viewing angle. The angle of view and brightness contradict each other, and a large angle of view will inevitably reduce the brightness. The choice of perspective needs to be determined according to the specific purpose.
2. Brightness
LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the greater the margin of the current used, which is good for saving power consumption and maintaining the stability of the LED. LEDs have different angle values. When the brightness of the chip is fixed, the smaller the angle, the brighter the LED, but the smaller the viewing angle of the display screen. Generally, 100 degree led shall be selected to ensure sufficient viewing angle of the display screen. For displays with different point spacing and different viewing distance, a balance should be found in brightness, angle and price.
3. Inefficiency
Because the full-color display screen is composed of tens of thousands or even hundreds of thousands of pixels composed of red, green and blue LEDs, the failure of any color LED will affect the overall visual effect of the display screen. Generally speaking, according to industry experience, the failure rate of LED display screen 72 hours before shipment shall not be higher than 3 / 10000 (referring to the failure caused by the LED bulb itself).
4. Antistatic ability
LED is a semiconductor device, which is sensitive to static electricity and is easy to cause static failure. Therefore, the anti-static ability is very important to the service life of the display screen. Generally speaking, the failure voltage of LED human body electrostatic mode test shall not be lower than 2000V.
5. Life span
The theoretical life of LED devices is 100000 hours, which is much longer than the working life of other components of LED display screen. Therefore, as long as the quality of LED devices is guaranteed, the working current is appropriate, the heat dissipation design of PCB is reasonable and the production process of display screen is rigorous, LED devices will be one of the most durable components in the whole display screen.
LED devices account for 70% of the price of LED display screen, so LED devices can determine the quality of LED display screen. China is not only a large producer of LED devices, but also a gathering place for the manufacture of LED display screens. The high-tech requirements of LED display screen are the development trend in the future. The high-quality requirements of LED display screen are not only about the trend of LED display screen manufacturers, but also related to the development of LED display device manufacturers. From the control of LED devices, promote the transformation of China from a large LED display manufacturing country to a powerful LED display manufacturing country.
6. Attenuation characteristics
The brightness of LED display screen will decrease and the color of display screen will be inconsistent after working for a long time, which is mainly caused by the brightness attenuation of LED devices. The attenuation of LED brightness will reduce the brightness of the whole display screen. The inconsistent brightness attenuation amplitude of red, green and blue LED will cause the inconsistent color of LED display screen, which is the phenomenon that we often say the display screen is spent. High quality LED devices can well control the brightness attenuation. According to the standard of 20mA lighting at room temperature for 1000 hours, the attenuation of red should be less than 2%, and the attenuation of blue and green should be less than 10%. Therefore, 20mA current should not be used for blue and green LEDs in the design of display screen, and it is best to use only 70% to 80% of rated current.
In addition to the characteristics of red, green and blue LEDs, the attenuation characteristics are affected by the use current, PCB heat dissipation design and the ambient temperature of the display screen.
7. Dimensions
The size of LED devices affects the pixel distance of LED display screen, that is, the resolution. 5mm oval lamp is mainly used for outdoor display above p16, and 3mm oval lamp is mainly used for p12 5. P12 and P10 outdoor displays, 3528 patch LED is mainly used for P6 and P8 indoor displays, and 2020 patch LED is mainly used for P2, P3 and other indoor displays. On the premise of constant point spacing, the size of LED device increases, which can increase the display area and reduce the sense of particles. However, due to the reduction of black area, the contrast will be reduced; On the contrary, the LED size is reduced, the display area is reduced, the particle sense is increased, the black area is increased, and the contrast is increased.
8. Consistency
The full-color display screen is composed of countless pixels composed of red, green and blue LEDs. The brightness consistency and wavelength consistency of each color LED determine the brightness consistency and white balance consistency of the whole display screen.
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