Use of LEDs for full color display:
High-quality LEDs also need a good method of use and environment, which comes down to the following eight main points of use:
1. The anti-static display assembly factory should have good anti-static measures. Special anti-static grounding, anti-static floor, anti-static soldering iron, anti-static mat, anti-static ring, anti-static clothing, humidity control, equipment grounding (especially cutting machine) are basic requirements, and should be regularly tested by static electricity meter. .
2, the wave soldering temperature and time must be strictly controlled wave soldering temperature and furnace time, the recommended: preheating temperature 100 ° C ± 5 ° C, the maximum does not exceed 120 ° C, and the preheating temperature rise requires smooth, welding temperature For 245 °C ± 5 °C, the welding time is recommended not to exceed 3 seconds. After the furnace is over, avoid vibrating or impacting the LED 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. The overheated or fluctuating temperature will directly damage the LED or cause LED quality hazard, especially for small and thin LEDs such as 3mm.
3, design current value LED nominal current is 20mA, it is generally recommended that its maximum use current is not more than 80% of the nominal value, especially for display screens with small dot spacing, due to poor heat dissipation conditions, should also reduce the current value . According to experience, due to the inconsistency of the red, green and blue LED attenuation speeds, the current values ​​of the blue and green LEDs are specifically reduced to maintain the consistency of the white balance after the display is used for a long time.
4. The LEDs of the same color and different brightness files need to be mixed with the lights, or the light patterns according to the discrete rule design are inserted to ensure the consistency of the brightness of each color of the whole screen. If there is a problem in this process, the local brightness of the display will be inconsistent, which will directly affect the display effect of the LED display .
5, control the verticality of the lamp For the in-line LED, there must be enough process technology to ensure that the LED is perpendicular to the PCB. Any deviation will affect the brightness consistency of the already set LEDs, and the color blocks with inconsistent brightness will appear.
6. Heat dissipation design LED will generate heat when working. If the temperature is too high, it 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 cabinet will affect the performance of the LED.
7. The virtual welding control LED display often has more than 50% probability of various types of virtual welding when the LED is not bright, such as LED pin soldering, IC pin soldering, pin header soldering Wait. Improvements in these problems require rigorous improvements in the process and enhanced quality inspections. The vibration test before leaving the factory is also a good test method.
8. Drive circuit design The layout of the driver circuit board driver IC on the display module will also affect the brightness of the LED. Since the driving IC output current is too far away on the PCB, the voltage drop of the transmission path is too large, which affects the normal operating voltage of the LED and causes its brightness to decrease. We often find that the brightness of the LEDs around the display module is lower than the middle, which is why. Therefore, to ensure the consistency of the display brightness, it is necessary to design the drive circuit distribution map.
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