1. Heat dissipation design
LEDs 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.
2. Mixed lights
LEDs of the same color but with different brightness levels need to be mixed or inserted according to a lighting diagram designed with discrete rules to ensure the consistency of the brightness of each color on the entire screen. If there is a problem in this process, the local brightness of the large screen will be inconsistent, which will directly affect the display effect of the LED large screen.
3. The current value is too high
The nominal current of LED is 20mA. It is generally recommended that the maximum current should not exceed 80% of the nominal value. Especially for large screens with small dot spacing, the current value should be reduced due to poor heat dissipation conditions. According to experience, due to the inconsistency in the attenuation speed of red, green, and blue LEDs, the current values of blue and green LEDs should be reduced in a targeted manner to maintain the consistency of the white balance after long-term use of the large screen.
4. Drive circuit design
The arrangement of the driver IC on the driver circuit board on the large screen module will also affect the brightness of the LED. Because the output current of the driver IC is transmitted too far on the PCB board, the voltage drop in the transmission path will be too large, affecting the normal operating voltage of the LED and causing its brightness to decrease. We often find that the brightness of the LEDs around the large screen module is lower than in the middle. This is the reason. Therefore, in order to ensure the consistency of the brightness of the large screen, it is necessary to design the drive circuit distribution diagram.
5. Control the verticality of the light
For direct plug-in LEDs, sufficient process technology is required to ensure that the LEDs are perpendicular to the PCB board when passing through the furnace. Any deviation will affect the consistency of the LED brightness that has been set, resulting in color blocks with inconsistent brightness.
6. Welding control
When the LED does not light up on a large LED screen, there is often more than a 50% chance that it is caused by various types of soldering, such as soldering of LED pins, IC pins, pin headers, etc. The improvement of these problems requires strict improvement of processes and strengthening of quality inspection. Vibration testing before leaving the factory is also a good inspection method.
7. Exceeding wave soldering temperature and time
The temperature and furnace passing time of wave front welding must be strictly controlled. It is recommended that the preheating temperature is 100℃±5℃, and the maximum does not exceed 120℃. The preheating temperature must rise steadily. The welding temperature should be 245℃±5℃. It is recommended that the time should not exceed 3 seconds. Do not vibrate or impact the LED after passing through the furnace until it returns to normal temperature. The temperature parameters of the wave soldering machine must be tested regularly. This is determined by the characteristics of the LED. Overheating or fluctuating temperatures will directly damage the LED or cause LED quality hazards, especially for small-sized round and oval LEDs such as 3mm.
8. Anti-static
LED large screen assembly factories should have good anti-static measures. Special 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 they must be tested regularly with an electrostatic meter.