With the development of science and technology, LED technology is also constantly developing, bringing various conveniences to our lives, providing us with various life information, and benefiting us human beings. With the demand of the economic market and the rapid progress and maturity of micro-pitch LED Display technology, the dot pitch of the micro-pitch LED display is getting smaller and smaller, and now the market has launched P1.4, P1.2, P0.9 and other micro-pitch LEDs It is widely used in video conference, command and control, monitoring center, radio and television media and other fields. In the past few years, the characteristics of high-definition display, high refresh rate, seamless splicing, good heat dissipation system, convenient and flexible disassembly and assembly, energy saving and environmental protection of micro-pitch LED display screens have been well known by the majority of industry users. As for the specific process technology of micro-pitch LED screens, the general public is seldom aware of it, “only one knows one and the other does not know the other”, and the lack of professional knowledge directly leads to the emergence of blind spots in purchasing.
From a technical point of view, the smaller the pixel pitch of the micro-pitch display screen, the higher the requirements for the LED mounting, assembly, splicing process and structure. This article will analyze the various process technologies of the micro-pitch LED display, so that users can understand the micro-pitch LED products more thoroughly.
1. Packaging technology:
Displays with a density above P2 generally use 1515, 2020, and 3528 lamps, and the LED pin shapes use J or L packages. If the pins are welded sideways, there will be reflections in the welding area, and the ink color effect will be poor. It is necessary to add a mask to improve the contrast. If the density is further increased, the L or J package cannot meet the application requirements, and the QFN package must be used. The characteristic of this process is that there are no laterally welded pins, and the welding area is non-reflective, which makes the color rendering effect very good. In addition, the all-black integrated design is molded by molding, and the contrast of the screen is increased by 50%, and the image quality of the display application is better than that of the previous display.
2. Printed circuit board process:
With the development trend of micro-pitch display screens, 4-layer and 6-layer boards are used, and the printed circuit board will be designed with fine vias and buried holes. The mechanical drilling technology can no longer meet the requirements, and the rapidly developed laser drilling technology will meet the micro hole processing.
3. Printing technology:
Too much or too little solder paste and printing offset directly affect the welding quality of the micro-pitch display lamp. The correct PCB pad design needs to be communicated with the manufacturer and then implemented into the design. Whether 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, and 1.0-0.8 thickness stencils are recommended for devices below 1010RGB. 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 functional printers with thickness detection and SPC analysis will play an important role in reliability.
4. Mounting technology:
The slight offset of the position of each RGB device in the micro-pitch display will cause uneven display on the screen, which will inevitably require higher precision of the placement equipment.
5. Welding process:
Excessive temperature rise of reflow soldering will lead to unbalanced wetting, which will inevitably lead to offset of the device during the process of unbalanced wetting. Excessive wind cycles can also cause device displacement. Try to choose a reflow soldering machine with more than 12 temperature zones, chain speed, temperature rise, circulating wind, etc. as strict control items, that is, to meet the requirements of welding reliability, but also to reduce or avoid the displacement of components, and try to control it within the scope of demand. Generally, 2% of the pixel pitch is used as the control value.
6. Box assembly:
The box body is made of different modules spliced together. 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 box and cast aluminum box are the most widely used box types at present, and the flatness can reach within 10 wires. The splicing gap between modules is evaluated by the distance between the nearest pixels of the two modules. lines, two pixels too far will result in dark lines. Before assembling, it is necessary to measure and calculate the joint of the module, and then select a metal sheet of relative thickness as a fixture to be inserted in advance for assembly.
7. Screen assembly:
The assembled box 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 the assembly cannot be ignored for the assembly effect of the micro-pitch display. If the pixel pitch of the nearest device between the cabinet and the cabinet is too large or too small, dark lines and bright lines will be displayed. The problem of dark lines and bright lines is a problem that cannot be ignored and needs to be solved urgently for micro-pitch display screens. Some companies make adjustments by sticking 3m tape and finely adjusting the nut of the box to achieve the best effect.
8. System card selection:
The light and dark lines, uniformity and chromatic aberration of the micro-pitch display screen are accumulative criticisms 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 differences through software correction. all. The 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 achieve a better display effect.
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