COF bonding, also known as Chip-on-Film bonding, is a process used in LCD screen repair to connect the COF (Chip-on-Film) component to the ITO (Indium Tin Oxide) glass and PCB (Printed Circuit Board). This bonding process ensures proper electrical connection and functionality of the LCD screen.
The COF bonding process involves several steps, which are outlined below:
1.LCD Fault Mark: Make a mark on the screen where the fault appears before bonding. This helps to identify if the fault disappears after bonding.
2.Glass and Side PCB Fixation: Fixate the glass and side PCB to prevent damage to other COFs during the bonding process .
3.Polarizer Protection: Apply a film, like a preservative film, on the polarizer to prevent scratches during bonding. Ensure the film is smooth and flat .
4.Wind Station Parameter Setting: Set the parameters of the wind station to ensure the COF remains flat, non-deformed, and unshrinking during removal. The temperature range is typically set between 300-330°C, and the wind power is set at 3-4 degrees .
5.COF Disassembly: Remove the sealing glue and disassemble the COF, starting with the PCB side and then the glass side .
6.ACF (Anisotropic Conductive Film) Removing Liquid: Apply the right amount of ACF removing liquid on the ITO glass and COF. Avoid applying the liquid on other parts, as it can damage the polarizer film or protection film. Take precautions to avoid contact with the liquid .
7.ACF Removing Liquid Chemical Reaction: Allow the ACF removing liquid to react for a specific time period (1-5 minutes for G-450) to make the ACF soft, loose, and easy to clean. After the reaction, clean the ACF with alcohol or acetone .
8.ITO and PCB Cleaning: Clean the ITO using cotton swabs with alcohol and electrostatic cloth with acetone until it is clear .
9.Old COF Cleaning: Clean the old COF on a clean glass table using a clean cotton swab with alcohol. Clean the ACF in one direction, following the direction of the pins from the inside to the outside of the COF .
10.ITO Checking: Check the ITO under magnification to ensure there are no residual ACF, dirt, scratches, or corrosion before bonding.
11.Clean ITO Under Microscope: For small residual ACF and dirt, clean the ITO under a microscope using a proper direction and force. Use cotton swabs and alcohol for cleaning.
12.COF Checking: Check the COF under a microscope for residual ACF or dirt on the pins. Scrape them carefully with a toothpick. If the pins are curved or broken, discard the COF. For new COF reels, cut them separately before bonding .
13.ACF Model: Choose the correct ACF for bonding. The ACF for the ITO side and PCB side may differ. Store the ACF in low temperature, and check the expiration date before use .
14.ACF Attaching: Cut the ACF from the reel slightly longer than the COF. Attach the ACF to the COF pins using tweezers and pre-heat it with a T-type iron for a good connection .
15.ITO Moving and Placing: Move the ITO to the bonding machine platform, ensuring it is smooth and steady. Take care not to strike other parts of the machine .
16.Bonding Machine Operation: Set the parameters and align the head, camera, COF fixture, and COF-ITO pins .
17.Teflon Tape and Bonding Pressure: Place a Teflon tape on top of the COF for protection and set the bonding pressure between 2.0Mpa to 4.0Mpa .
18.Alignment Image: Ensure proper alignment between the COF and ITO before starting the bonding process .
19.Double Start: Start the automatic bonding process, ensuring the alignment, parameters, and pressure are set correctly. The head will heat up, apply pressure, cool down, and then retract automatically .
20.Automatic Bonding: After bonding, check the quality of the connection between the COF and ITO. If necessary, disassemble and re-bond carefully. If the bonding is successful, proceed to PCB side bonding .
21.PCB Side Alignment: Align the PCB and COF pins, similar to the ITO side alignment
Please note that this is a general overview of the COF bonding process, and specific procedures may vary depending on the equipment and materials used.
