Full screen processes: Differences between COF, COG and COP

At present, there are three kinds of packaging processes in the industry, which are COG packaging process, COF packaging process and COP packaging process.

COG: Traditional package

Before entering the 18:9 "full screen" era, the screen of smart phones generally adopts a packaging technology of "COG" (Chip On Glass), that is, the IC chip is directly bound to the glass surface of the LCD LCD screen, and this packaging technology can greatly reduce the volume of the entire LCD module. High yield, low cost and easy mass production. The problem is that the glass can't be folded or curled, and with the lines connected to it, it is destined to need a wider "jaw" to match it.

The traditional COG technology generally integrates the chip into the glass backplane, due to the large size of the chip, the frame is still relatively wide, mainly reflected in the end of the line. Xiaomi's MIX is the COG packaging process used, so the chin will be so wide, because many lines are concentrated at the bottom of the 4mm. In addition to the Mi MIX, LG's G6 and V30 also use COG packaging technology.

COF: The best partner for full screen

"COF" (Chip On Flex or Chip On Film), also known as coated crystal film, and COG after the biggest improvement is the touch IC chip fixed on the flexible circuit board of the grain soft film assembly, and the use of soft additional circuit board as a package chip carrier chip and soft substrate circuit joint technology. A more intuitive statement is that the IC is embedded on the FPC softboard, that is, attached to the line between the screen and the PCB motherboard.

The COF packaging process is a very important packaging technology in the current popular full-screen era, which is generally used in flagship mobile phones. The so-called COF package means that the driver IC originally packaged on the substrate is placed on the row line, and it can be folded backwards. The COF packaging process can be used for LCD screens and OLED screens.

The reason why Huawei Mate 20 Pro can achieve ultra-narrow bezels and ultra-narrow jaws, and does not have a chin like the Xiaomi MIX series is because it uses Synaptics' cof packaging process, including ClearView driver IC and ClearPad touch IC. There are still many COF packages in the industry, vivo X21, vivo nex, OPPO R17, millet MIX 2S, Apple iPhone XR, Samsung S9, Meizu 16, Meizu X8, etc., all use COF packaging process.

The difference between COG and COF

Samsung S9 packaging mostly uses COF technology, rather than the traditional COG packaging technology, COF technology puts the chip on the glass backplane on the screen line, so that it can be placed directly at the bottom of the screen, so that 1.5mm more screen space than COG.

COP: The perfect solution for flexible OLED exclusives

COF packaging technology can be used for OLED materials (including AMOLED) screens, but it does not 100% play the full potential of OLED variable flexibility. The "COP" (Chip On Pi) package technology can be seen as the perfect package solution customized for flexible OLED screens.

COP packaging technology can also maximize the compression of the screen module, but the higher the compression ratio, the higher the cost and lower the yield. In order to achieve the "chinless" design of the iPhone X, the early yield is said to be less than 10%, and nine of the 10 units produced will be scrapped. As far as the current mobile phone manufacturers are concerned, they have the courage to optimize and improve the COP package regardless of the cost, and it can be said that there is no one except Apple.

Before the Huawei Mate 20 Pro, Apple's iPhone X used the COP packaging process, which is how Apple successfully removed the chin of the iPhone X. But the COP packaging process is extremely expensive, in addition to the iPhone X, the current industry, Find X is the second phone to use this screen packaging technology, there should be more in the future.

COP English full name "Chip On Pi", COP packaging process a new screen packaging process, the use of flexible screen can be bent characteristics, the edge of the screen bent, so as to reduce the border can achieve almost no border effect. Since the LCD screen cannot be bent, only the OLED flexible screen can be bent, so the COP package is basically used with the flexible OLED.

The biggest feature of COP packaging technology is that it can maximize the compression of the screen module, but the higher the compression ratio, the higher the cost, and the lower the yield. So if you want to achieve a "chinless" design, it is technically feasible, but the cost is still very high. According to rumors, in order to achieve the "chinless" design of the iPhone X, the early yield is said to be less than 10%.

The difference between COF and COP

iPhoneX benefits from the use of Samsung flexible OLED unique COP packaging process, because its backplane is not glass, the material used is actually the same as the line, on the basis of COG directly fold the backplane back on the line, the thickness is further reduced, and the screen of the COP packaging process can be truly four sides without borders.

Sum up

In terms of cost, COP is the highest, followed by COF, and COG is the most economical. The most advanced technology is also COP screen packaging. The packaging process is related to the screen proportion, and in fact, which packaging process is used can also reflect the screen proportion to a large extent. In the future, the full screen can be bezel-free on all four sides, and the screen can fully cover the front panel of the mobile phone, rather than the current "front full screen" and "opposite sex screen", from the current packaging technology, there is no problem to achieve, but for various reasons, it can not really achieve mass production.