COG(Chip on Glass)は、異方性導電接着剤(ACF)を介して液晶画面上にICを封入し、ICの電極とガラス上の電極の相互接続と封止を実現するもので、キャラクターLCDやセグメントLCD、およびほとんどのTFT液晶ディスプレイがこの方式を採用している。また、COG技術に似たCOF(Chip On Film)方式もある。FPC上にICチップを直接パッケージングするため、小型化でき、自由に曲げることができる。
FOGとはどういう意味ですか?
FOGモジュールとは、液晶ディスプレイの製造工程における重要なプロセスの一つを指す。FOGの正式名称はfilm on glassで、液晶パネルにFPCを固定するためにACFを使用する。この工程もCOG工程と同様、精度と安定性を確保するために温度と圧力のコントロールが必要です
Key material of COG and FOG process
driver IC
The driver IC is the key component of the LCD display. Usually, each resolution corresponds to a driver IC. The driver IC is a very precise semiconductor device that can analyze the signals transmitted by the MIPI interface, RGB interface, and SPI interface into the control signals of the LCD panel.
ACF
ACF is the abbreviation of Anisotropic Conductive Adhesive, which is mainly used in the lcd display industry to connect the driver IC, display FPC and the lcd panel, which can not only play the role of bonding, but also conduct the circuit. ACF needs to be stored at low temperature and heated and pressurized when used. Once cured, it cannot be reversed.
ACF bonding process
First attach the ACF to the lcd panel, and then fix the driver IC or display FPC on the lcd panel under pressure and heat. During this process, the ACF will solidify, and the driver IC and lcd panel will create a circuit higher than other areas at the position that needs to be turned on, which is called bump. These bumps will crush the conductive particles, thus conducting up and down.
After bonding, it can be seen that the metal lines on the LCD panel will have traces, which indicates that the conduction is good, and the conductive particles corresponding to each clear indentation are called effective conductive particles. Different ACF manufacturers have different requirements for the number of effective conductive particles on each bump: SONY’s ACF requires more than 5 effective conductive particles; HITACHI’s ACF requires more than 3 effective conductive particles.
COG and FOG process
Process of COG and FOG
Attach ACF (Anisotropic Conductive Adhesive) to the LCD panel
Attach the driver IC to the lcd panel through a certain temperature and pressure
Use ACF to bond the display FPC to the lcd panel
Use special glue to fix the driver IC and FPC after bonding to prevent the entry of moisture and impurities and ensure stability