Technologies for the production of LED screens: Micro-LED vs. Mini-LED

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Initially, the task was to figure out what Micro LED is, as well as Mini LED in the field of LED screens for indoor use. Because there is confusion in this market due to the use of the words “micro, mini, Nano” for screens created using different technologies. Customers, in turn, thoughtlessly repeat these notorious “micro”, “mini” and “Nano” in the race for the “coolest” screen, not realizing that these set-top boxes are nothing more than a marketing ploy.

Progress on that and progress to go by leaps and bounds. The screen should be brighter, colors richer, consume less, heat less and so on – scientists and engineers are working to improve strong technical features – in every technical detail.

And where there is progress, there is marketing, which uses all kinds of marketing tools to advertise what marketers do not understand. Recognition in the market, sales are important, and technology is a secondary matter.

LED screens

They are divided into internal and external screens. For fixed installation and rental. All new technologies make it possible to improve the technical features of LED screens in terms of power supply, mounts, new boards, as well as the pitch and size of the LED itself or, in other words, a pixel.

Pixel pitch or pitch is the distance in millimeters between two adjacent LED centers. Every year there is a kind of technological mini-breakthrough, when one or another company introduces a record-breaking smaller pixel pitch. By reducing the distance, the size of the LED itself is also reduced.

LED Manufacturing Technologies

DIP – The Direct Inline Package. This technology is used for external screens, where a separate LED is used for each color. The pixel pitch is greater than or equal to 6 mm.

SMD – Surface Mounted Device. This type of “3 in 1” technology is conditionally a technology for the production of LED screens. It is used for internal screens and for external ones – an LED, in the case of which three RGB LEDs with a certain pitch are already installed.

DIP color separation technology into three different packages allows for high color saturation and ease of installation. On the other hand, in SMD 3 in 1, overall colors are more uniform due to the use of RGB in one package. This is the standard technology used in high quality LED screens. Surface mount technology is also used for outdoor screens.

COB – Chip-On-Board. This technology is used for indoor screens, by growing an LED, also consisting of LEDs of three colors, located directly on the board.

SMD 3 in 1

Almost all indoor screens use surface mount technology. To create LED screens, it is required that each LED, also known as a pixel, can emit red, blue, green colors – therefore, each small LED contains 3xLED, respectively, and the technology is called SMD 3in1.

Simple and mature technology. First, crystals are grown on sapphire substrates, then LEDs are created. After that, LED wall manufacturers purchase LEDs and, using SMD technology, create LED modules from which video walls are assembled.

The process is well-established, simple both in installation and maintenance – that is, a non-working LED is removed and a new one is soldered. There are nuances that not all LEDs shine the same way, so when buying a screen, LEDs of the same batch are purchased. There are also differences in the metal used in the conductors – if gold, then the quality is higher, in fact, as is the cost of the LEDs themselves and the finished screen. During commissioning, there is no difference, only after a period of time you can see the differences.

Since the LEDs are soldered to the board, when cleaning the premises efficiently, when wiping the screen with a rag, small LEDs come off their seats. And after a while – the picture becomes not so pleasing to the eye. However, these are already operational problems – after all, you can limit the circle of people who have access to the screen.

The problems began after companies crossed the border of distances between LEDs less than 1mm. Since, in addition to the distance, the LED also decreases, then, firstly, the complexity of soldering has increased, and secondly, the LEDs themselves have become poorly kept in their seats.

Therefore, they came up with the idea of ​​​​assembling each SMD 3in1 LED in a group of 4 LEDs and then soldering them in groups.

IMD 4 in 1

IMD – Integrated Mounted Device. The IMD 4in1 surface mount technology is not just one SMD 3in1 LED, but 4 such LEDs in one group. After, due to the enlarged area, the groups are soldered to the main seat. Right now, the market is dominated by 4in1 bands, but 9in1 and 16in1 bands are expected to appear soon.

At the same time, the pixel pitches have become smaller, the LEDs themselves have also become smaller, and the ease of installation has remained. To date, there are prototypes of screens with a pitch of 0.5mm and 0.6mm, made using this technology. They were presented at ISE2020.

Also, to protect the 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 a LED screen using COB technology, where each pixel has no housing, on the right – using IMD4in1 technology.

An alternative technology for creating crystals and LEDs is to grow them directly on the board itself.

The chip also consists of three RGB LEDs. According to technology, the die can be flipped, soldering is not required, as the die is grown on the board. Accordingly, in the future, manufacturers plan to completely abandon soldering for a small pixel pitch, removing the existing shortcomings of SMD technology.

After growing the LEDs, the 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. From the immediately following pluses – there is protection of the LED canvas from mechanical damage, for example, during cleaning.

Compared with conventional SMD surface mount technology, COB allows for higher LED density in the same area. As a result, even greater uniformity of pixilation for the user is achieved.