With the continuous development of communication science and technology, mobile phone screens are getting larger and the bezels are getting narrower to meet market demands. The pursuit of a nearly 100% screen-to-body ratio has become a global trend for full-screen smartphones. However, achieving a true full-screen display depends on the packaging technology used for smartphone screens, which primarily includes three types: COG, COF, and COP.
COG Chip Packaging Technology
COG is the most traditional and cost-effective screen packaging technology. The chip is directly placed on top of the glass, integrating the IC chip and wiring directly onto the glass substrate. This design results in a larger bottom bezel, limiting the achievable screen-to-body ratio. Currently, the 18:9 aspect ratio display can still use COG technology, but in recent years, as full-screen displays have evolved from 18:9 to 19:9 or even 20:9, COG packaging technology has gradually been abandoned.
COF Chip Packaging Technology
COF, as the best partner for full-screen displays, improves upon COG by fixing chips such as touch ICs onto flexible printed circuit boards (FPCs) using chip-on-film (COF) construction. It also utilizes flexible additional circuit boards as packaging chip carriers to bond the chip with the flexible substrate circuit.
The advantage of COF is its ability to achieve narrow bezels by directly bonding the chip to the FPC, thus reducing the space occupied by the glass substrate. Compared to COG, COF can reduce the bezel size to around 1.5mm, reducing the length of terminal parts. Currently, high-end products mainly use COF technology.
COP Chip Packaging Technology
COP, as the top-level packaging technology, overcomes the limitation of leaving some bezels at the bottom of the screen in both COG and COF packaging. COP refers to directly bending and packaging a part of the screen, integrating screen wiring and IC chips below the screen. Traditional LCD screens cannot be folded due to the physical properties of liquid crystals.
Therefore, COP packaging technology is designed for flexible screens, which currently mainly refers to OLED. COP packaging allows smartphone screens to achieve near-borderless effects, improving the screen-to-body ratio. However, smartphones using this packaging technology are generally expensive.
Achieving the ultimate full-screen display means covering the entire front panel of the phone and eliminating or hiding components such as receivers, sensors, and cameras. The choice of packaging technology is closely related to the screen-to-body ratio and significantly.