DIP, SMD, and COB LED displays: The ultimate guide

With the continuous development of the LBD display industry, LED displays have developed from DIP LED displays to SMD LED displays, and then from SMD LED displays to COB LED displays and IMD LED displays.

DIP, SMD, COB, IMD. What are the differences between them, and what are their advantages and disadvantages?

Today, LEGIDATECH engineers will introduce their stories respectively.

1. DIP LED display

Since LED was invented in the 1970s, until about 2010, it was mainly in-line packaging.

A plug-in LED is a piece of electroluminescent semiconductor material.

In-line packaging places the electroluminescent semiconductor material on a leaded shelf and seals it with epoxy resin glue. This can protect the internal core wires.

The actual picture of the direct plug-in LED

Direct plug-in LED module physical picture

In the plug-in package, the light emitted from the PN junction area is non-directional, that is, the light is emitted in all directions at the same time.

Due to factors such as the light transmittance and structural structure of the in-line LED material, not all the light emitted by the PN junction can be released.

This mainly depends on the quality of the semiconductor material, the PN junction structure, the internal structure of the package and the packaging material.

In the direct plug-in package, the commonly used epoxy resin shell for the top package is generally made into a circle to improve the light emission efficiency of the PN junction and increase the viewing angle.

According to the diameter of the circular shell, plug-in LEDs can be divided into ¢2mm, ¢3mm, ¢5mm, ¢7mm and other types.

In addition, the PN junction luminescence wavelength changes with temperature (0.2~0.3) nm/°C. 90% of the heat of a direct plug-in LED is dissipated into the PCB through the negative metal pin, and 10% of the heat is dissipated into the air.

These technical features of DIP LED displays make the direct plug-in LBD simple in structure, low in manufacturing cost, high in brightness and high in product reliability, which promoted the early commercial application of LED displays.

Currently, in-line LEDs are still widely used in outdoor LED displays above P10mm.

However, shortcomings such as large size, low contrast, small lighting angle, and inconvenient assembly of in-line LEDs have always restricted their development in the LED display industry.

2. SMD LED display

Surface mount packaging is also called SMD (Surface Mounted Devices) packaging.

Surface mount packaging uses automatic patch equipment to directly weld chip-like and miniaturized LEDs to specific locations on the surface of wiring substrates such as PCBs.

Surface-mounted LEDs are made by filling a light-emitting power chip into a metal bracket, then filling it with glue and drying it. Its shape is mainly cubic. The actual picture of surface-mounted LED is shown in Figure 1-3.

SMD LED module physical picture:

Actual production case of SMD LED display: SMD LED. The display can produce LED displays of different shapes.

SMD display advantages

1. The light-emitting surface of surface-mounted LEDs is a single front. Its manufacturing process determines that the surface of surface-mounted LEDs is flatter and smoother than the surface of direct-plug LEDs, so its lighting screen display effect will be better.

2. Surface-mounted LEDs use lighter packaging circuit boards and reflective layer materials, reducing size and weight, and are suitable for indoor and some outdoor LED displays.

3. For surface-mounted LEDs, the solder pad is an important way to dissipate heat. Manufacturers can design the size of the reflow soldering pad according to the size of the LED pins.

4. Surface-mounted LBD developed rapidly around 2012 due to its own advantages. Surface mount packaging is mainly used in P1.0mm~P10mm LED display products.

Compared with plug-in LEDs, surface-mounted LEDs perform better in terms of volume, quality, reliability, consistency, viewing angle, appearance, etc.

At present, surface-mounted LEDs are widely used in the LED display industry.

However, surface-mounted LEDs have evolved from small-pitch 1010 products to 0404 products, and their area has been reduced by 16% of the original.

Regardless of packaging difficulty, device reliability, or terminal placement accuracy, surface-mount packaging is no longer suitable for p1.0 mm products.

3. COB LED display

Integrated packaging includes two types: COB (Chip On Board, chip on board) packaging and IMD (Integrated Matrix Devices, integrated matrix devices) packaging.

COB packaging is a structure that directly connects multiple LED chips to the PCB to achieve heat conduction.

It eliminates the need for a single LBD package and then the patching process, and solves some of the problems faced by surface-mounted LEDs.

The schematic diagram of COB packaging is shown in Figure 1-4.

COB LED module physical picture:

COB LED display screens have the advantages of high resolution and high contrast.

The following are actual COB LED display production cases:

COB LED display VS SMD LED display

At present, the four-in-one-IMD package used more frequently in the industry is as shown in the figure:

1. COB packaging is the integration of upstream chip technology, midstream packaging technology and downstream display technology.

It can not only reduce bracket costs and simplify the manufacturing process, but also reduce chip thermal resistance and achieve high-precision packaging.

2. Compared with SMD packaging, COB packaging eliminates the need to mix lights, so the consistency seems to be particularly poor.

This is why each LED display using COB packaging needs to be calibrated before leaving the factory.

3. Although COB packaging has great advantages in terms of dot pitch, picture display quality, anti-collision ability, and overall reliability.

4. COB LED DISPLAY still has technical difficulties in terms of production efficiency, yield, and product uniformity. These factors also restrict the promotion and application of current COB packaging technology.

IMD packaging adopts multi-pixel integrated packaging, which combines the advantages of SMD packaging and COB packaging.

It is superior to SMD packaging in terms of dimensional accuracy, and superior to COB packaging in terms of ink color consistency and yield.

In addition, the IMD packaging industry chain is mature and can achieve rapid industrialization.

COB LED display actual project case: high refresh rate and high contrast.


We fully understand the shortcomings and advantages of various LED displays such as DIP, SMD, COB, which points out the direction for the production of LED display factories, and also enables engineers to better select appropriate models of LED displays. .Thanks

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