The FOG (Film on Glass) process is a key step in the production of TFT LCD display, which directly affects the quality and performance of the module. This process precisely binds the flexible circuit board (FPC) to the glass substrate to achieve electrical and physical connections. The entire process includes glass cleaning, ACF (anisotropic conductive film) attachment, FPC pre-alignment, hot pressing bonding, testing, reinforcement and other links. The accuracy of each step is crucial to the final bonding effect.
FOG is the abbreviation of Film on Glass, which refers to the manufacturing process of binding the flexible circuit (FPC, Flexible Printed Circuit) to the glass substrate during the production of TFT liquid crystal screens. This is a very important step in the production process of TFT LCD display modules (LCM, Liquid Crystal Module).
The main steps of the FOG production process:
- Glass + POL cleaning
The TFT glass substrate needs to be ultrasonically cleaned before bonding to remove dust, oil and other impurities to ensure a good bonding effect.
- ACF attachment
Attach ACF (Anisotropic Conductive Film) to the welding position of the glass substrate. ACF can provide conductive connection and protect the circuit from the external environment.
- FPC pre-alignment
Pre-align the position of FPC and glass substrate (fully automatic equipment program) to ensure that there is no offset during welding.
- FPC binding
Use high temperature and pressure process to physically and electrically connect FPC and glass substrate through ACF. Usually use FOG bonding machine to complete this step. The temperature is generally controlled between 160~200℃ and the time ranges from a few seconds to tens of seconds.
- Inspection and testing
Use tools such as microscopes to check the effect of bonding ACF particle welding to ensure that there are no foreign matter and bubbles in the ITO binding characters. Then perform electrical performance tests to ensure normal signal transmission.
- Reinforcement and protection
After the binding is completed, UV glue or epoxy resin and other materials can be added to the binding position for reinforcement to improve the connection strength and anti-bending ability, ensuring that the connection is not easy to fall off during the subsequent assembly process.
- Aging test
After a period of electrical aging test, ensure the stability of the connection and the reliability of the product. Then assemble the backlight and other subsequent processes.
The stability of the FOG process has a huge impact on the reliability and display effect of the TFT LCD display screen, so it is also one of the important links for LCD screen manufacturers to optimize and improve. The TFT LCD display produced by Hongcai Technology has a one-time COG/FOG pass rate of 99.3%, ensuring stability and quality. The stability of the FOG process determines the signal transmission quality and long-term reliability of the TFT LCD module. If the binding is cold soldered, short-circuited or falls off, it will affect the display effect and even cause the module to fail. Therefore, by optimizing process parameters such as temperature, pressure, time, etc., ensuring firm welding and stable signal transmission, the overall performance and reliability of the TFT LCD module can be significantly improved.
