The full name of COF is chip on film, which is different from the traditional COG technology (chip on glass). The main difference between the two is the position of the chip (ie driver ic). COF technology can bring larger display area and narrower frame.
COF is the abbreviation of Chip on Film, which is the technology of chip on film assembly in Chinese. COF is a flexible film with the ability to carry ICs and passive components by using the characteristics of the COG technology process, and in terms of flexibility, COF not only helps to enhance the functionality of products, high density of the assembly, thin and light, but also increases the added value of products.
Different types of COF
Front of COF
Backside of COF
What is COF /TCP and what is the structure of COF?
COF is the abbreviation of chip on film. This technology is mainly used in mobile phone products. Similar to COF, there is TCP technology. TCP is the abbreviation of tape carrier package, which is mainly used for medium and large-sized displays. Due to the high resolution and smaller size of mobile phone products, COF products are more precise.
Substrate of COF
The structure of COF is similar to that of single-layer display fpc, which is a layer of Base film PI plus a layer of Copper, the difference between the two is the adhesive material at the joints, plus both have to put on another layer of insulating Coverley, so the structure of the two is at least two layers of adhesive, and the Copper used in COF is about 1/3oz, so the thickness and flexibility of COF is much better than that of FPC.
The structure of COF
COG structure and driver IC used in COG technology
In the COG structure, the driver IC and display FPC are respectively bonded on the lcd panel. Since the lcd panel uses glass as the substrate, the glass has good stability and supporting force, so this technology has low requirements for equipment and personnel. The most widely used technology now.
COF structure and driver IC used in COF technology
COF and TCP technologies are for narrower borders. Only bonding COF or TCP is needed on the lcd panel, which saves the space of bonding driver IC, so the goal of narrower borders can be achieved. COF and TCP technologies have certain requirements for equipment and personnel, and the cost is higher.
Comparison of TCP, COG and COF technologies
|TCP (tape carrier package）
|COG (chip on glass)
|COF (chip on film)
|Suitable panel size
|Large size such as laptops, monitors, etc.
|Fits all sizes for a wide range of applications
|Suitable for all sizes, mainly used for mobile phone products
|High yield rate and high production efficiency
|Low cost, mature technology
|High yield rate, high reliability, high production efficiency
|High cost, only suitable for large size products
|The yield rate is poor, and the product has a wider bezel
|High cost and difficult to operate
Advantages of using COF technology
Larger screen to body ratio
Nowadays, COG and COF are the most popular technologies for LCD modules to achieve a smaller and thinner volume. However, due to the limitation of panel line layout, the same size of panel can be achieved in COF type with larger resolution than COG type module.
COF performance is better
COF is far superior to other technologies in terms of flexibility, thickness, and the area where it meets the panel. And the main Driver IC and peripheral components can be directly bonding on the film, which can save the space and thickness of PCB or FPC, and also can save the cost of this material.
Products using COF technology are easier to rework because only one bonding is performed, resulting in a higher yield.
COF is known by the public to start from mobile phones. Apple began to use COF technology on the iPhone X to obtain a very narrow border. COF technology is widely used in the field of OLED, not only on AMOLED, but also on PMOLED. A major problem with tft screen is the relatively large width of the frame. When COF technology is used, the mobile phone of tft screen will also be very amazing.
COF technology also has its own shortcomings:
1. COF is to attach the driver IC to the FPC. This process has very strict requirements on precision. Only a few factories in the world can produce it, and the price is relatively high.
2. The combination of COF and LCD panel requires high precision and poor yield.
3. Tft display has also developed a new technology. The frame width is only about 1.5mm wider than that of OCF products, and the yield rate is very high, but there is a big difference in price.