The introduction

Liquid Display Module (LCM) is a component that combines Liquid crystal Display devices, connectors, integrated circuits, control components, drive circuits, printed circuit boards, backlight, and other structural components. Generally speaking, Interface technology of LCD panel and driving IC system can be roughly divided into the following three kinds: Tape Automated bond-ing; TAB), grain - Glass bonding technology (Chip on Glass; COG), grain-soft plate bonding technology (Chip on :COF). Liquid crystal glass, naked IC and Flexible Printing CIR-CUIT; The mechanical connection and electrical conduction of FPC are one of the core parts of LCM production, and their corresponding production processes are COG and FOG (FPC on Glass) binding process.

ACF materials

Anisotropic Conductive Film (Anisotropic Conductive Film; ACF is characterized by obvious difference between the electrical conduction direction of Z axis and the resistance characteristics of XY insulation plane. When the difference between the z-axis conductance resistance and the XY plane insulation resistance exceeds a certain ratio, it is called good conductance heterotropy. It is the use of conductive particles to connect the IC chip and the substrate between the electrodes to make it a conduction, at the same time can avoid the conduction between the two adjacent electrodes short circuit, and only in the Z axis direction of the purpose of conduction.

FOG binding process

FOG binding process is a process of mechanical connection and electrical conduction between liquid crystal glass and flexible circuit board by ACF bonding and hot pressing at certain temperature, pressure and time. There are four steps:

1, ACF pre-paste: in a certain temperature and pressure, in the LCD glass terminal part and flexible circuit board (FPC) to bind the pin paste specified length of ACF. The process requires that the length and position of ACF pre-pasted are accurate, and the surface is smooth without bubbles.

2. Pre-binding: In this step, the alignment is the key factor. Because the lead pitch is getting smaller and smaller, the most section distance has reached 0.05mm, the alignment accuracy should be within ±0.005mm. Therefore, hd cameras are required (GZC-MY200 four HD cameras)

3. Main binding: Under high temperature and pressure, pulse hot press GZC-MY200 is used to carry out the main binding of pre-bound LCM products. In this process, the electrical connection between FPC and LCD glass is realized through the elastic deformation of conductive particles of ACF and the rupture of insulating layer. Meanwhile, the glue in ACF is polymerized and hardened at high temperature. Form a strong physical connection between two different materials.

4. Detection: THE HD camera carries out visual detection on the products after the main pressure, and confirms the technological conditions and materials in the binding process mainly through the deformation of conductive particles in each part.

Key technology of FOG binding process

1, pressure control, because the binding pressure size directly determines the degree of breakage of ACF particles, thus determining the qualified rate of the product, so the binding process of the binding pressure precision control is very important, GZC-MY200 pulse hot press is used to control the binding pressure is precision pressure regulating valve. As shown in the picture? When the binding pressure is too small, ACF conductive particles cannot be reasonably broken, which leads to the failure of longitudinal electrical conduction. When the binding pressure is too large, ACF particles will be crushed too much, and longitudinal electrical conduction cannot be achieved, and the insulation effect of transverse electrical is also poor. . ?

2. Temperature control. There are two main factors affecting the curing of ACF: first, the initial heating rate; The second is the peak temperature, heating rate determines the surface quality after curing, and the peak temperature determines the bonding strength after curing. Gzc-my200 adopts PID self-diagnosis temperature control module + titanium alloy cutter head, the initial temperature is fast, the peak temperature is accurate and stable.

3, the head flatness is high, the head is not parallel to the guide column ACF particles are not evenly broken, because the ACF particles are very small, generally about 4um in diameter, ACF is very sensitive to pressure. When the head working surface is not smooth, part of ACF particles will be completely broken, while the other part can not be reasonably broken, resulting in poor electrical conduction between ITO glass and FPC. Pulse hot press GZC-MY200 has carried out a strict test on the flatness of the head before leaving the factory.