LED display production workshop process production process

From a technical point of view, the smaller the pixel pitch of the micro-pitch display, the higher the requirements for the placement, assembly, splicing process and structure of the LED. This article will analyze the various process technologies of micro-pitch LED displays, so that users can have a more thorough understanding of micro-pitch LED products.

 

 

 

 

1. Encapsulation technology:

The display screen with a density above P2 generally uses 1515, 2020, and 3528 lights, and the LED pin shape adopts J or L packaging. Lateral welding pins, the welding area will be reflective, the ink effect is poor, and 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. This process is characterized by the absence of lateral welding pins and the absence of reflection in the welding area, resulting in very good color rendering. In addition, the all-black integrated design is molded and molded, and the screen contrast is increased by 50%, and the image quality of the display application is better than that of the previous display screen.

 

2. Welding process:

Rapid temperature rise in reflow soldering will lead to uneven wetting, which will inevitably cause the device to drift during the wetting imbalance process. Excessive wind circulation can also cause displacement of the device. Try to choose a reflow soldering machine with more than 12 temperature zones, chain speed, temperature rise, circulating wind force, etc. as strict control items, that is, to meet the needs of welding reliability, but also to reduce or avoid the displacement of the device, and try to control it within the range of demand. Generally, the range of 2% of the pixel pitch is used as the control value.

 

3. Box assembly:

The cabinet is spliced by different modules, and the flatness of the cabinet and the gap between the modules are directly related to the overall effect of the box after assembly. Aluminum plate processing box and cast aluminum box are widely used box types at present, and the flatness can reach within 10 wires. The splicing gap between the modules is evaluated by the distance between the two modules with the closest pixels, and if the two pixels are too close to each other, they will be a bright line, and if the two pixels are too far away, they will cause a dark line. Before assembling, it is necessary to measure and calculate the module joint, and then select the metal sheet of relative thickness as a fixture to insert it in advance for assembly.

 

4. 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 assembly cannot be ignored on the assembly effect of micro-pitch display. If the pixel spacing of the nearest device between the cabinet is too large or too small, it will cause dark and bright lines to be displayed. The problem of dark line and bright line is a problem that cannot be ignored and needs to be overcome urgently. Some companies adjust by sticking 3M tape and box fine-tuning nuts to achieve the best results.

 

5. Printed circuit board process:

With the development trend of micro-pitch display screen, 4-layer and 6-layer boards are adopted, and the printed circuit board will adopt micro-via and buried hole design, and the printed circuit graphic wire is fine, micro-porous and narrow-spacing, and the mechanical drilling technology used in the processing can no longer meet the requirements, and the rapidly developing laser drilling technology will meet the micro-hole processing.

 

6. Printing technology:

Too much or too little solder paste and the offset of printing directly affect the soldering quality of the micro-pitch display tube. The correct PCB pad design needs to be implemented in the design after communicating with the manufacturer, and the correct opening size and printing parameters of the stencil are directly related to the amount of printed solder paste. Generally, 2020RGB devices use electropolished laser stencil with a thickness of 0.1-0.12mm, and devices below 1010RGB are recommended to use a stencil 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, and the use of functional printing machines with thickness detection and SPC analysis will play an important role in reliability.

 

7. Placement technology:

The slight shift in the position of each RGB device in the micro-pitch display will lead to uneven display of the screen, which will inevitably require higher precision of the placement equipment.

 

8. System card selection:

Micro-pitch display light and dark lines and uniformity, chromatic aberration is the accumulation of LED device differences, IC current differences, circuit design layout differences, assembly differences, etc., some system card companies can reduce light and dark lines and brightness, chromaticity unevenness through software correction. 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.