ACF (Anisotropic Conductive Film), or Anisotropic Conductive Film, is an adhesive film with conductive particles uniformly distributed in a heat-cured resin. It can make electrodes conduct in batches after heating and pressurization, and has the advantages of small encapsulation area and fine pitch connection compared with soldering or connectors.ACF can provide adhesive, conductive and insulating functions in the same material at the same time.
Application Areas
COG (Chip On Glass): Used to connect Driver IC to LCD glass electrodes.
FOG (Film On Glass): Used to connect Flexible Printed Circuit Boards (FPC) to LCD glass electrodes.
| Product name | Model | Model | |
|---|---|---|---|
| Type | COG | COG/COP | |
| Connection material | IC | IC | |
| LCD Glass substrate | OLED Glass substrate/Flexible substrate | ||
| Minimum space [µm] *1 | 5 | 8 | |
| Minimum connection area[µm2] *2 | 400 | 720 | |
| Thickness [µm] | 16 | 10 | |
| Conductive particles | Type | Ni plating on a polymer particle | Ni plating on a polymer particle |
| Particle diameter [µmФ] | 3.2 | 3.0 | |
| Insulation coated particle | Yes | Yes | |
| Main bonding conditions | Temperature [℃] | 130 to 160 | 190 to 230 |
| Time [sec] | 5 | 5 | |
| Pressure[MPa] *3 | 40 to 80 | 60 to 90 *4 | |
Main Functions
1. Conductive connection: Through the hot pressing process, under pressure and heat, the conductive particles in ACF are arranged to form a conductive path, ensuring a reliable connection between the Driver IC, FPC and the glass substrate.
2. Insulation Function: In addition to the direction perpendicular to the contact surface, ACF provides excellent insulation properties to prevent short-circuit phenomena between lines.
Key Parameters and Their Impact
The performance of ACF is affected by its constituent materials, structural design and process conditions. The following are a few key parameters:
1. Conductive particles
Particle size: typically 3μm to 10μm, depending on the electrode spacing. Too small may result in high contact resistance, while too large may cause short circuits.
Number of particles: typically kept between 5000-25000/mm² to ensure stability and avoid short circuits.
2. Hot pressing time and pressure
Temperature: Usually in the range of 180°C to 230°C to ensure that the adhesive fully cures and activates the conductive particles.
Time: Common range is 3 seconds to 10 seconds, depending on specific application requirements.
Pressure: Typically between 2 MPa and 4 MPa to ensure a reliable connection without damaging the conductive particles.
Summarizing
The key parameters of ACF are a complex multivariate system that requires optimization and matching of particles, adhesive layers and process conditions. In order to meet the high quality and reliability requirements of TFT-LCD, The choice of ACF products from Hitach and Sony for the TFT lcd display produced by Hongcai reflects the recognition of the technology and quality of these brands.
