ACF (Anisotropic Conductive Film) is an important connecting material in TFT LCD, ACF is a kind of adhesive film with conductive particles uniformly distributed in heat-curing resin, and after heating and pressurization, it can make the electrode conductive in batches. Compared with welding or connectors, ACF also has a small package area, and can realize the advantages of Fine Pitch connection. It can simultaneously combine the functions of bonding, conduction and insulation.
ACF is mainly used in COG and FOG in displays, where ACF for COG is used to connect Driver IC to LCD glass electrode and ACF for FOG is used to connect FPC to LCD glass electrode.
1. Conductive connection:
Used for soldering Driver IC and Flexible Printed Circuit (FPC) to glass substrate.ACF can realize reliable connection between multiple electrodes. Through the hot pressing process, the conductive particles distributed in the ACF are arranged under pressure and heat to form a conductive path that connects the circuit board (PCB) to the ITO electrodes on the LCD glass.
2. Insulation function:
Except for the conductive direction (perpendicular to the contact surface), ACF has excellent insulating properties to prevent short circuits between lines.
3. Main production countries:
1. Japanese brands: Hitachi Chemical and Sony account for about 60-70% of the global market share.
2. Korean brands: 20-30%, mainly in the OLED and small equipment applications, strong competitiveness. 3.
3. Chinese brands: Ningbo Liansen, Dechuang High-tech Although less than 10%, but the growth rate is faster, mainly concentrated in the low-end market. 4.
4. Competition characteristics:
1. Japanese brands are suitable for high-end market due to leading technology and high quality. 2.
2. Korean brands focus more on cost performance and application in emerging fields. 3.
3. Chinese brands are on the rise, thanks to the domestic TFT-LCD/OLED production capacity enhancement, and gradually improve market recognition.
5. The importance of ACF in TFT:
Specific parameters affecting the performance of ACF (anisotropic conductive film) are mainly related to its constituent materials, structural design and process conditions. These parameters directly affect the conductivity, insulation, adhesion and long-term reliability of ACF. The following are the main key parameters and their effects:
5.1. Parameters of conductive particles
Conductive particles are the most important component of ACF, which determines the stability and effectiveness of the conductive properties.
5.1.1 Particle Size:
5.1.2 Particle too small: may not be able to contact effectively, resulting in high contact resistance.
5.1.3 Particles too large: may lead to short circuits, especially in micro-pitch (fine-pitch) applications.
5.1.4 Common range: 3μm-10μm, depending on electrode pitch.
5.1.5 Particle Density:
5.1.6 Low Density: Insufficient conductive paths, reducing the stability of the connection.
5.1.7 High Density: Easy to generate short circuits, increasing the difficulty of manufacturing.
5.1.8 Typical densities are designed to be between 5000-25000 particles/mm². 5.1.9 Conductive particles are designed to have a high density.
5.1.2. Hot pressing time and pressure parameters for conductive particles
5.2.1 Typically in the range of 180°C-230°C to ensure that the adhesive cures and activates the conductive particles to form the connection.
5.2.2 Too low a temperature: insufficient curing and unstable connection.
5.2.3 Excessive temperatures: may damage the electrodes or FPC material, or even lead to destruction of the particle coating.
5.2.4 common range: 3 seconds -10 seconds, depending on the type of adhesive and hot pressing equipment.
5.2.5 too short a time: can not be fully compacted and cured.
5.2.6 The CTE of the adhesive layer needs to be matched with the substrate (e.g. ITO glass or FPC) in order to avoid delamination or open-circuit phenomenon caused by thermal expansion and contraction.
5.2.7 Too long: may lead to material aging or electrode damage.
5.2.8 Usually between 2 MPa-4 MPa. Pressure is too low to form a reliable connection, too high will easily destroy the conductive particles or lead to short circuit.
Summary:
The key parameters of ACF is a complex multivariate system involving the optimization and matching of particles, adhesive layer and process conditions. For different application scenarios, all TFT lcd display produced by Hongcai tft lcd display screen use the brands Hitachi and SONY to meet the high quality and reliability requirements of TFT-LCD.
