Since the LED’s are soldered to the board, during high-quality cleaning of the premises, when wiping the screen with a rag, the small LED come off their seats. And after a while, the picture becomes not so pleasing to the eye. However, these are operational problems – after all, you can limit the circle of people who have access to the screen.
The problems began after companies crossed the line of distances between LEDs of less than 1mm. Since, in addition to the distance, the LED also decreases, firstly, the complexity of soldering has increased, and secondly, the LEDs themselves began to poorly stay in their seats.
Therefore, we came up with the idea of assembling each SMD screen 3in1 LED into a group of 4 LEDs and then soldering them in groups.
IMD – Integrated Mounted Device. IMD 4in1 surface mount technology represents not one SMD 3in1 LED, but 4 such LEDs in one group. Afterward, due to the enlarged platform, the groups are soldered onto the main seat. Currently, the market mainly features 4in1 groups, but 9in1 and 16in1 are expected to appear soon.
At the same time, the pixel pitches have become smaller, and the LEDs themselves have also become smaller, but the ease of installation remains. Today there are prototypes of screens with pitches of 0.5mm and 0.6mm made using this technology. They were presented at ISE2020.
Also, to protect LEDs at such pixel pitches, GOB and AOB technologies are used to fill both the LEDs completely and only the “legs”.
COB – Chip-on-board
The picture on the left shows an example: on the left is an LED screen using COB technology, where each pixel does not have housing, on the right is using IMD4in1 technology.
An alternative technology for creating crystals and LEDs is to grow them directly on the board itself. The technology has been known for a long time but has recently become widespread – for mounting LEDs on a board with very small pixel pitches.
The chip also consists of three RGB LEDs. According to the technology, the crystal can be turned upside down; no soldering is required since the crystal is grown on the board. Accordingly, in the future, manufacturers plan to completely abandon soldering for small pixel pitches, eliminating the existing shortcomings of SMD Screen technology.
After growing the LEDs, manufacturers of LED screens using this technology fill the modules or cabinets with LEDs with a special optically transparent compound or gel to protect the LEDs.
The screen becomes smooth, similar to the screen of LCD panels. One of the immediate advantages is that the LED strip is protected from mechanical damage, for example, during cleaning. The compound does not protect against mechanical stress.
Compared with conventional surface mount SMD technology, COB allows for higher LED density in the same area. As a result, even greater uniformity of pixelation for the user is achieved.
Compared with DIP and SMD technology, COB LED screens have significant advantages.
Less depth. By allowing the use of thinner boards, manufacturers can reduce the thickness of the overall structure. Accordingly, the overall weight of the screen will decrease. Gain in the thickness of the structure, the ability not to reinforce some types of walls, as well as the final cost.
Increased viewing angle. A screen based on Outdoor SMD Screen technology is created by installing three LEDs inside the housing, thus placing the RGB LEDs in a small recess. Plus, difficulties are added when replacing LEDs, when installing them again, as well as unevenness of the mask and other factors. while when using SMD technology and bending the PCB there are significant restrictions on the bending angle.
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