Eight LED display board quality assurance technology

- May 15, 2019-

In display technology,LCD is composed of liquid crystal display, and LED is composed of LED display. Each pixel in an LED digital display is a light-emitting diode (LED). Here is a look at eight LED display board quality assurance technology.


Eight LED display board quality assurance technology


In order to produce led displays with good quality, technical control should be made in the following aspects:


1, anti-static LED display electronic display screen assembly factory should have good anti-static measures. Special anti-static ground, anti-static floor, anti-static soldering iron, anti-static radio pad, anti-static ring, anti-static clothes, humidity control, equipment grounding (especially cutting machine) are basic requirements, and to use the electrostatic instrument regularly tested.


2. Driver circuit design the layout of the driver circuit board driving IC on the led display module will also affect the led brightness. Because the drive IC output current travels too far on the PCB board, the voltage drop in the transmission path will be too large, which will affect the normal working voltage of the LED and reduce its brightness. We often find that the led brightness around the led display module is lower than the center, which is the reason. Therefore, to ensure the consistency of the brightness of the display screen, it is necessary to design a driving circuit distribution diagram.


3. The nominal current of the design current value LED is 20mA, and it is generally recommended that its maximum operating current should not exceed 80% of the nominal value. Especially for the display screen with small point spacing, the current value should be reduced due to poor cooling conditions. According to experience, due to the inconsistency of red, green and blue LED attenuation speed, the current value of blue and green LED should be specifically reduced to maintain the consistency of white balance after long use of the display screen.


4. LED lights with different brightness levels of the same color need to be mixed, or the lights can be inserted according to the lamp insertion diagram designed according to the discrete law, so as to ensure the consistency of brightness of each color on the whole screen. If there is any problem in this process, the local brightness of the display screen will be inconsistent, which will directly affect the display effect of the led display screen.


5. Control the verticity of the lamp. For the straight plug LED, there should be enough technology to ensure that the LED is perpendicular to the PCB board when passing through the furnace. Any deviation will affect the already set LED brightness consistency, brightness inconsistent color block.


6, wave soldering temperature and time are required to strictly control the wave crest welding temperature and furnace time, recommended for: preheat temperature 100 ℃ + / - 5 ℃, the highest do not exceed 120 ℃, and the requirement of preheating temperature increasing is smooth, the welding temperature is 245 ℃ + 5 ℃, welding time suggest no more than 3 seconds, after furnace vibration or shock LED of avoid by all means, until the normal temperature state. Wave soldering machine temperature parameters to be regularly tested, which is determined by the characteristics of the LED, too hot or fluctuating temperature will directly damage the LED or cause LED quality problems, especially for small size such as 3mm round and oval LED.


7, virtual welding control led display in the led is not bright, there is often more than 50% of the probability of various types of virtual welding caused by, such as led pin virtual welding, IC pin virtual welding, line pin virtual welding and so on. The improvement of these problems requires strict process improvement and quality inspection. Vibration test before delivery is also a good test method.


8. Heat dissipation design of LED will generate heat when working, and excessively high temperature will affect LED attenuation speed and stability. Therefore, heat dissipation design of PCB board and ventilation and heat dissipation design of box will affect LED performance.