Analysis of Micro LED large screen display technology
ABSEN explains about 3 comparisons of the encapsulation forms of Micro LED
Bare LED chip without encapsulation cannot meet the requirements of use and thus reasonable encapsulation should be designed to provide electrical connection, mechanical protection, eﬀective heat dissipation channels and high‐eﬃciency and high‐quality light output.
The reduction of LED chip size and display screen pitch puts forward higher requirements for encapsulation. At present, Chip‐type SMD , N‐in‐one IMD and COB are the commonly used encapsulation forms, as shown in Figure 2.
Chip‐type SMD encapsulation
In Chip‐type SMD encapsulation, a single LED pixel is die bonded on the BT board and then encapsulated using the optical resin to achieve a single Chip‐type encapsulation. The Chip‐type encapsulation is then attached on the PCB using SMD technology to create the LED display module to obtain the LED display module. Chip‐type SMD encapsulation is a single pixel encapsulation with small size, small solder joint area and plenty of solder joints, which will result in the risks of water vapor erosion, poor mechanical protection and short circuit. Based on the above analysis, Chip‐type SMD encapsulation is not suitable for Micro LED displays.
N‐in‐one IMD encapsulation In N‐in‐one IMD encapsulation, N pixel units (mostly 2 or 4) are die bonded on the BT board and then encapsulated as a whole using the optical resin. Compared with Chip‐type SMD encapsulation, IMD encapsulation boasts higher integration, which can eﬀectively relieve risks of water vapor erosion and poor mechanical protection. Meanwhile, IMD encapsulation inherits the advantages of mature process, low technical diﬃculty and cost of the single SMD device. However, the integration of N‐in‐one IMD encapsulation is still low, resulting in issues of process, display eﬀect and reliability for micro pitch displays below 0.6mm.
In COB encapsulatiuon, naked chips of multiple pixel units(mostly hundreds) are die bonded on the PCB and then encapsulated as a whole using the optical resin. Compared with Chip‐type SMD encapsulation and N‐in‐one IMD encapsulation, multiple chips are encapsulated as a whole in the COB encapsulatiuon, which contributes to improved resistance to water vapor nd excellent mechanical protection performance. Moreover, BT board is omitted and the naked LED chips are attached on the PCB directly in COB encapsulatiuon , which provides a shorter heat conduction channel and thus better heat dissipation performance. From the aboveanalysis, it can be demonstrated that COB encapsulatiuon is the optimum form for Micro LED displays with high pixel density.
The characteristics of the abovementioned encapsulation methods are shown in Table 2. COB encapsulation with the highest degree of integration can be used to achieve the smallest pixel pitch, the highest reliability and the longest display life theoretically and is thought to be the best packaging solution for Micro LED.
Conclusion Micro LED is considered to be a nearly perfect display technology and has broad application prospects in the field of large‐screen displays above 85 inches because of its advantages of high brightness, high contrast, wide color gamut, and seamless splicing. Major display manufacturers are actively deploying in the Micro LED display field. The structure and encapsulation of LED chip directly determine the performance of Micro LED display devices.
At present, three kinds of structure, namely the wire‐bonding structure, flip structure and vertical structure, are mainly adopted in the industry. It can be seen from the comparison of those structures that the flip chip with high light emitting eﬃciency, good heat dissipation performance, high reliability and high mass production capacity is more suitable for Micro LED displays.
Typically, Micro LED encapsulation forms include Chip‐type SMD encapsulation, N‐in‐one IMD encapsulation and COB encapsulation.
Among these three kinds of encapsulation, COB encapsulation with the highest integration can be used to achieve the smallest pixel pitch, the highest reliability and the longest display life theoretically and is thought to be the best packaging solution for Micro LED.
The full range of Micro LED products released by Absen are based on Absen proprietary HCCI technology.
· Use the flip chip COB encapsulation technology.
· Integrate Absen’s core algorithm HDR3.0 .
· Integrate the intelligent display technology.
A professional team has been continuously researching on the optical design and image quality processing to improve the display eﬀect. These eﬀorts have contributed to smooth images, high color reproduction, gentle and consistent display. All the results have been applied to products which are widely used in scenarios such as large control centers and conference centers.