Process technology analysis of small pitch LED display screen

With the demand of the economic market and the rapid progress and maturity of small pitch LED display screen technology, the dot pitch of small-pitch LED display screens is getting smaller and smaller. Now the market has launched P1.4, P1.2, P0.9 and other small-pitch LEDs. Display screens are widely used in video conferencing, command and control, monitoring centers, radio and television media and other fields.
In the past few years, the characteristics of small-pitch LED display such as high-definition display, high refresh rate, seamless splicing, good heat dissipation system, convenient and flexible disassembly and assembly, energy saving and environmental protection have been well-known by the majority of industry users. However, go further and say As for the specific process technology of small-pitch LED screens, the general public seldom knows, “only know one but not the other”, the lack of professional knowledge directly leads to the emergence of blind spots in the purchase.

From a technical perspective, the smaller the pixel pitch of the small-pitch display screen, the higher the requirements for the mounting, assembly, and splicing process and structure of the LED. This article will analyze the various process technologies of the small-pitch LED display, allowing users to have a more thorough understanding of the products of the small-pitch LED display.

1. Packaging technology:

Displays with density above P2 generally use lights of 1515, 2020, 3528, and the shape of LED pins uses J or L packaging. When the pins are welded from the side, there will be reflections in the welding area, and the ink color effect is poor. It is bound to increase the mask to improve the contrast. With further increase in density, L or J packaging cannot meet application requirements, and QFN packaging must be used.
The characteristic of this process is that there is no lateral welding of the pins, and the welding area is non-reflective, which makes the color rendering effect very good. In addition, it adopts all-black integrated design and compression molding, the contrast of the picture is increased by 50%, and the picture quality of the display application is better than that of the previous display.

2. Printed circuit board technology:

With the development trend of micro-pitch display screens, 4-layer and 6-layer boards are adopted. Printed circuit boards will adopt micro-via and buried-hole designs. Mechanical drilling technology can no longer meet the requirements, and the rapidly developing laser drilling technology will meet the requirements of micro-hole processing.

3. Printing technology:

Too much or too little solder paste amount and printing offset directly affect the welding quality of the micro-pitch display tube. The correct PCB pad design needs to be communicated with the manufacturer and implemented into the design. The opening size of the stencil and the correct printing parameters are directly related to the amount of solder paste printed.
Generally, 2020RGB devices use electro-polished laser stencils with a thickness of 0.1-0.12mm. 

For devices below 1010RGB, it is recommended to use stencils with a thickness of 1.0-0.8. The thickness and opening size increase in proportion to the amount of tin. The quality of micro-pitch LED soldering is closely related to solder paste printing. The use of printing machines with functions such as thickness detection and SPC analysis will play an important role in reliability.

4. Mounting technology:

The slight deviation of the position of each RGB device of the fine-pitch display screen will cause the display of the screen body to be uneven, which will inevitably require the placement equipment to have higher precision.

5. Welding process:

Excessive temperature rise in reflow soldering will result in unbalanced wetting, which will inevitably cause the device to shift during the process of unbalanced wetting. Excessive wind circulation will also cause displacement of the device. Try to choose a reflow soldering machine above 12 temperature zones, chain speed, temperature rise, circulating wind power, etc. as strict control items, that is, to meet the requirements of soldering reliability, and to reduce or avoid component displacement, and try to control it within the required range. Generally, the range of 2% of the pixel pitch is used as the control value.

6. Cabinet assembly:

The box body is spliced by different modules, and the flatness of the box body and the gap between the modules are directly related to the overall effect of the box body after assembly. Aluminum plate processing boxes and cast aluminum boxes are currently widely used box types. The flatness can reach within 10 wires. The splicing gap between the modules is evaluated by the distance between the nearest pixels of the two modules. 

When the two pixels are too close, they will be bright. Line, two pixels too far will cause dark lines. Before assembling, it is necessary to measure and calculate the seam of the module, and then select the metal sheet of relative thickness as the jig to be inserted in advance for assembling.

7. Screen body assembly:

The assembled cabinet needs to be assembled into a screen before it can display refined pictures and videos. However, the dimensional tolerance of the box itself and the cumulative tolerance of assembly cannot be ignored for the assembly effect of the fine pitch display. If the pixel pitch of the nearest device between the cabinet and the cabinet is too large or too small, it will cause dark and bright lines to be displayed. 

The problem of dark and bright lines is a difficult problem that cannot be ignored in fine-pitch displays and needs to be solved urgently. Some companies make adjustments by sticking 3m tape and fine-tuning nuts on the box body to achieve the best results.

8. System card selection:

The light and dark lines and uniformity and color difference of the micro-pitch display are the accumulated criticism of LED device differences, IC current differences, circuit design layout differences, assembly differences, etc. Some system card companies can reduce light and dark lines, brightness, and chromaticity through software correction. 

Both. A high-performance system card is selected to correct the brightness and chromaticity of the micro-pitch LED display, so that the display can achieve better brightness and chromaticity uniformity, and a better display effect has been achieved.

Through the above content, we have a detailed understanding of the process technology of small pitch LED display screen. If you want to view more LED display content, you can click: LED display factory, if you want to know more detailed information about the product, please feel free to contact us via email sale20@sz-ledscreen.com.https://hola-led.com/

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