LED display quality eight factors
Like other items, the LED display screen will inevitably encounter problems and precautions of one kind or another in use. When using a full-color LED large screen, there may be eight problems that may cause difficulties or affect the use of the large screen and prolong its service life.
1. Heat dissipation design
The LED will generate heat when it is working. If the temperature is too high, the decay speed and stability of the LED will be affected. 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
The LEDs of the same color with different brightness levels need to be mixed, or inserted according to the lamp insertion diagram designed by the discrete law 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 large LED screen.
3. Design current value
The nominal current of the LED is 20mA. It is generally recommended that the maximum use 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 of the attenuation speed of red, green and blue LEDs, the current value of blue and green LEDs is reduced in a targeted manner to maintain the consistency of 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. Since the transmission distance of the output current of the driver IC is too long on the PCB board, the voltage drop in the transmission path will be too large, which will affect the normal operating voltage of the LED and reduce its brightness. We often find that the brightness of the LEDs around the large screen module is lower than that in the middle, which is the reason. Therefore, in order to ensure the consistency of the brightness of the large screen, it is necessary to design the distribution diagram of the driving circuit.
5. Control the verticality of the light
For in-line LEDs, there must be enough process technology to ensure that the LEDs are perpendicular to the PCB board when passing through the furnace. Any deviation will affect the brightness consistency of the LEDs that have been set, and color blocks with inconsistent brightness will appear.
6. virtual welding control
When the LED does not light up on the large LED screen, there is often more than a 50% probability that it is caused by various types of soldering, such as soldering of LED pins, soldering of IC pins, soldering of pin headers and mothers, etc. The improvement of these problems needs to strictly improve the process and strengthen the quality inspection to solve. The vibration test before leaving the factory is also a good inspection method.
7. Over wave soldering temperature and time
It is necessary to strictly control the temperature and passing time of wave front soldering. It is recommended that the preheating temperature be 100℃±5℃, the maximum should not exceed 120℃, and the preheating temperature should 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 the oven until it returns to normal temperature. The temperature parameters of the wave soldering machine should be checked regularly, which is determined by the characteristics of the LED. Overheating or fluctuating temperature will directly damage the LED or cause hidden dangers to the quality of the LED, especially for small-sized round and oval LEDs such as 3mm.
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 should be checked regularly with an electrostatic meter .