🙄 🐝 🃏 Types of protective technology LEDs LED screens 👷🏼 🤰🏻 🥄

The higher the resolution of the LED screen with a small physical screen size - the smaller the LEDs themselves and the distance between them become. This implies the technical difficulties of placing LEDs, the method of their fastening, and protection during transportation and operation. The article is devoted to the analysis of existing technologies for protecting LED LED screens for internal use from external influences.

SMD3in1 surface mount technology is used to create small pixel pitch LED displays for indoor applications. Recently, we are talking about the application of COB technology for growing LEDs directly on the board. SMD3in1 SMD3in1 surface mount technology has been widely used due to its balanced technical characteristics - color uniformity, saturation, viewing angle, power consumption, convenient maintenance method and others. COB, with all the pros, has a sufficient number of minuses, which makes mass production difficult, so the era of large LED screens using crystal growing technology directly on the board has not yet arrived.

Due to the fact that manufacturers reduce the pixel pitch every year, achieving greater resolution with a smaller physical screen size, there are many problems associated with overheating of the screen, which means that LEDs burn out, tearing LEDs due to the small solder area during transportation and installation , problems with oxidation of contacts, moisture, dust and so on.

Accordingly, some screen protection is required to extend the life of both the LEDs themselves and the components during transportation and operation, especially with a small pixel pitch. On the other hand, there are areas in which the use of a protective coating is necessary to provide a small, but anti-vandal protection.

In total - there are several areas for protection from physical external influences. This article will discuss the main technological methods associated with changing technical specifications by applying special protective layers or changing the production technology and fixing LEDs to a printed circuit board.

SMD - Surface Mounted Device

Proven technology, on the basis of which 95% of LED screens are produced.

The structure of the SMD LED, placed in a plastic or ceramic case in white / black, in the context is as follows.

Considering the fact that almost all screens were produced and are still manufactured using this technology until recently, it has both its advantages and some disadvantages.

pros	Minuses
color uniformity; : 0,6-0,9; : 140°-160°; .	( <1) «» ; .

But since SMD technology allows you to create screens with uniform color uniformity, balanced characteristics of consumption, brightness, color saturation and the ability to create screens in steps of less than one millimeter: 0.6-0.9 mm - manufacturers are developing various ways to protect these screens from external influences and extending the “life” of LEDs.

As a result, today, there are two main technologies for the production of LEDs (LED screens) for indoor: SMD3in1 and, gaining momentum, COB. SMD3in1 has IMD4in1 options, and in addition, coating with special compounds - AOB and GOB technology. Additionally, LED display modules in production can be coated with nanocoating - “vacuum coating”.

IMD 4 in 1

This technology, also often called mini-LED, was also described in detail in a previous article . It allows you to protect the LED screen by using a group of 4 SMD3in1 LEDs, while having an increased “cushion” of solder, thereby improving the “grip” properties of the LEDs on the circuit board, as well as simplifying the maintenance of LED modules.

One area is four pixels, and the step is determined by the average value. Since the distance between the LEDs on the same site and on adjacent sites is different. The difference is microscopic, but it is.

The standard "soldering intensity" SMD is about 1-1.5 kg per separation, and IMD 4in1 increases this figure to about 4.5 kg.

An important point is that the surface of the LEDs is “rough, matte”, and it is not “mirror” that this was done specifically to protect the screen from the reflection of rays and to achieve high contrast.

AOB and GOB technology

These technologies are based on the addition of special adhesives to protect the LED strip.

AOB - Adhesive on Board

The technology is based on pouring only “legs” of LEDs, that is, conclusions, with a special adhesive composition. Thus, the pouring technology allows to increase the degree of protection against contact oxidation, and also increases the coefficient of “adhesion” of the diodes to the board. And after it is covered with a protective transparent layer. The protective layer is a polymer material applied by nano-technology (similar to vacuum coating).

The screen, assembled using SMD technology, additionally acquires protection against moisture, as well as from slight damage and scratches that the screen may receive during transportation and installation.

This technology has the following structure.

The result is a fairly strong structure with the following features.

pros	Minuses
. , , . « » 1 , AOB 6 ; ; ( , 170° 140°-160°).	«», , ( , .) – , . (, / ); .

GOB – Glue on Board

This technology is reminiscent of COB, only SMD is used for creating LEDs, and SMD is used after placing the LEDs on the boards - the modules themselves are coated with a special adhesive composition followed by a transparent protective layer.
The coating technology is similar to AOB, but in this case, the entire surface is covered with a protective layer, as in the figure below.

P.S. Glue-on-Board , . , GOB AOB, , , AOB «». , , GOB ( AOB), ( ), -.

Modules coated in this way - with adhesive and protective transparent layers, using AOB and GOB technology, increase the protection of the screen from mechanical damage, moisture and dust. This protection does not mean that the screens can be used outdoors, they are intended only for indoor use.

Summing up the GOB technology, we get the following features.

pros	Minuses
provides protection of separation of LEDs; protection against mechanical damage, moisture, dust; with the correct selection of compositions - do not greatly reduce the brightness of the LEDs; with the correct selection of compositions - contribute to heat dissipation; due to the "tight" layout - extend the life of LEDs.	maintainability worse. On the one hand, LED burnout appears less frequently, but when replacing it will be necessary to change the entire module (replacing the LEDs is only possible at the factory so far); lack of filling between the modules leads to visible joints; glare from a bright light source appears.

In comparison, the two technologies are as follows:

Nano-coating or special mask

A technology called “vacuum coating” is a process that uses vacuum technology to create a medium with a certain pressure (below atmospheric) for applying thin films and coatings by depositing an atomic or molecular source of condensed vapor (gas).

This technology can be used in conjunction with any technology LED screens, providing protection not only diodes, but also electronic components.

The sources of coatings used can be made of many different materials: from metals to oxides and compounds, each of which has different properties. For example, the deposited film may have chemical resistance to corrosion, scratches, high heat conductivity and electrical resistivity, which together saves and extends the "life" of both the LEDs themselves and microelectronics. This coating is not visible to the human eye, but at the same time protects the elements of the chip.

COB

About COB technology to a large extent was written in a previous article . In short, this technology should replace the widely used SMD3in1 and IMD4in1 surface mount technologies in the future. It has several options for creating LEDs - but they all come down to growing diodes directly on the board. Scientists suggest that this technology will completely abandon contacts made of gold (currently alloys of gold or other metals are used, gold increases the cost of LEDs and the screen as a whole by several times, compared with the use of alloys of other metals). Visually - when the screen is working, the difference is not noticeable, only after several years of operation, this difference will become noticeable.

Using COB, you can get the following features.

pros	Minuses
, ( GOB); (, ).	, ; ;

At the moment (the first half of 2020), a small number of manufacturing companies are beginning to use this technology for the production of LED screens. In the meantime, technology will not gain mass, the price will not fall, and technological difficulties will not be fixed. But when the difficulties are overcome - perhaps the COB technology will become one of the best in the class of LED screens with a very small pixel pitch. But it is still unknown when this future will come.

While COB technology is at an early stage of development, manufacturers continue to improve the surface mounting technology of SMD3in1 and IMD4in1 LEDs, using various methods to protect the LEDs themselves directly by completely or partially filling them with a special compound - compound.

Types of protective technology LEDs LED screens