LED display technology knowledge
In order to produce high-quality LED display screens, technical control needs to be done in the following aspects:
1. The anti-static LED display assembly factory should have good anti-static measures. Dedicated anti-static ground, anti-static floor, anti-static soldering iron, anti-static table mat, anti-static ring, anti-static clothing, humidity control, equipment grounding (especially foot cutting machine), etc. are all basic requirements, and regular testing with an electrostatic meter is required .
2. Design of driving circuit The arrangement of driving circuit board driving IC on LED display module will also affect the brightness of LED. Because the driving IC output current is transmitted too far on the PCB, the voltage drop in the transmission path is too large, which affects the normal working voltage of the LED and reduces its brightness. We often find that the LED brightness around the LED display module is lower than the middle, which is why. Therefore, to ensure the consistency of the brightness of the display screen, it is necessary to design a distribution map of the driving circuit.
3.Design current value The nominal current of the LED is 20mA. It is generally recommended that the maximum current used is not more than 80% of the nominal value, especially for displays with small dot pitch. Due to poor heat dissipation conditions, the current value should also be reduced. . According to experience, due to the inconsistencies in the attenuation speed of the red, green and blue LED, the current values of the blue and green LED are targeted to reduce the consistency of the white balance after the display has been used for a long time.
4. Mixed LED of the same color and different brightness levels need to be mixed, or inserted according to the discrete design of the plug-in diagram, to ensure the consistency of the brightness of each color of the entire screen. If there is a problem in this process, the local brightness of the display will be inconsistent, which directly affects the display effect of the LED display.
5. Control the verticality of the lamp. For in-line LED, there must be sufficient process technology to ensure that the LED are perpendicular to the PCB board when passing through the furnace. Any deviation will affect the brightness consistency of the LED that have been set, and color patches with inconsistent brightness will appear.
6. The temperature and time of wave soldering must be strictly controlled. The temperature and time of wave soldering should be controlled strictly. It is recommended that the preheating temperature be 100 ℃ ± 5 ℃ and the maximum temperature should not exceed 120 ℃. It is 245 ℃ ± 5 ℃, and the soldering time is recommended not to exceed 3 seconds. Do not vibrate or impact the LED after the furnace is heated until it returns to normal temperature. The temperature parameters of the wave soldering machine should be checked regularly. This is determined by the characteristics of the LED. Overheating or fluctuating temperature will directly damage the LED or cause hidden danger to the quality of the LED, especially for small and round LED such as 3mm.
7. Welding control LED display When the LED is not lit, there is often a probability of more than 50% caused by various types of welding, such as LED pin soldering, IC pin soldering, and pin header soldering. Wait. The improvement of these problems requires rigorous process improvement and enhanced quality inspection to solve them. The vibration test before leaving the factory is also a good inspection method.
8. Heat dissipation design LED will generate heat when working. Excessive temperature will affect the attenuation speed and stability of the LED. Therefore, the heat dissipation design of the PCB board and the ventilation and heat dissipation design of the box will affect the performance of the LED.