Flexible PCB

 

What is FPC?

FPC, or Flexible Printed Circuit, originated in the 1970s in the United States as a technology developed for aerospace rocket technology. It is a printed circuit made from polyester film (PET) or polyimide (PI) as the substrate, characterized by high reliability and excellent flexibility. FPC can be freely bent and folded in three-dimensional space. The structure of flexible circuits includes insulating films, conductors, and adhesives, acting like a universal glue in the electronic world, bonding various components together to enable communication and collaboration.

Advantages of FPC

• High-Density Wiring Capability: The ability to bend and connect circuits to necessary positions allows soft boards (flexible PCB) to be used in small-sized, high-density applications.
• High Reliability: R-FPC utilizes advanced manufacturing processes and materials to ensure circuit stability while enhancing the reliability of the flexible circuit board.
• Good Mechanical Performance: The combination of hard boards (PCB) and soft boards (flex rigid PCB) provides the circuit board with excellent rigidity and elasticity, offering better vibration and distortion resistance than conventional circuit boards.
• Longer Lifespan: Compared to standard circuit boards, R-FPC has a longer lifespan and better performance stability, maintaining excellent performance in various harsh climates and environments.
• Space-Saving:R-FPC combines hard boards (PCB) with soft boards (flexible PCB board), enabling more compact designs than traditional circuit boards and offering greater flexibility and design freedom.

Differences Between FPC and PCB

FPC, or flexible circuit board, is indeed a type of printed circuit board but differs significantly from traditional printed circuit boards, which is why it is referred to as FPC or Flexible Printed Circuit Board.

FPC typically uses PI as the substrate, which is a flexible material that can be bent and flexed freely. Flexible PCB soft boards are commonly used in applications requiring repeated flexing and connections of small components, but their use has expanded to include technologies in modern smartphones, which require flexibility to prevent damage.

PCB, or printed circuit board, is usually referred to as a PCB circuit board and serves as a support structure for electronic components. Flexible circuit boards are typically made from FR4 material, which is rigid and cannot be bent or flexed. PCBs are commonly used in applications that do not require bending and have higher rigidity, such as computer motherboards and smartphone motherboards.

FPC soft boards are not only flexible printed circuit boards; they are also an important design approach for creating three-dimensional circuit structures. When paired with other electronic product designs, they can enable a wide variety of applications, highlighting the significant differences between FPC and PCB.

FPC soft boards can certainly use terminal connections for circuit connectivity, but they can also avoid these connections by utilizing flex rigid PCB. A single FPC can configure many rigid boards and connect them through layout designs. This approach minimizes connector and terminal interference, enhancing signal quality and product reliability.

FPC soft boards are not only flexible circuit boards; they are also an important design approach for creating three-dimensional circuit structures. When paired with other electronic product designs, they can enable a wide variety of applications, highlighting the significant differences between FPC and PCB.

FPC soft boards can certainly use terminal connections for circuit connectivity, but they can also avoid these connections by utilizing rigid-flex boards. A single FPC can configure many rigid boards and connect them through layout designs. This approach minimizes connector and terminal interference, enhancing signal quality and product reliability.

For PCBs, unless the circuit is molded into a three-dimensional form using potting compounds, circuit boards are generally flat. To make full use of three-dimensional space, FPC presents a viable solution. For hard boards, a common spatial extension approach involves using slots and interface cards. However, with FPC, similar structures can be created using adapter designs, allowing for greater design flexibility in orientation. A single connecting FPC can connect two rigid boards into a parallel circuit system and can be angled to accommodate different product shapes.

Differences in Material, Cover Film, and PI Reinforcement for FPC

FPC flexible circuit boards are made from PI polyimide or polyester film, known for their high reliability and excellent flexibility, featuring high wiring density, light weight, thin thickness, and good flexibility.

• PI Substrate: FPC flexible circuit board substrates are divided into adhesive and non-adhesive types. Regardless of whether the substrate has adhesive, PI polyimide is essential.
• PI Cover Film: Its main function is to provide circuit insulation.
• PI Reinforcement: Commonly applied to the areas behind the FPC’s gold fingers. PI reinforcement is used to increase the thickness and hardness of the fingers for easy plugging and unplugging.

Thickness Differences in FPC Substrate, Cover Film, and PI Reinforcement

• PI Substrate: Common thicknesses include 1/2 mil and 1 mil, with thicknesses reaching up to 4 mil and 5 mil (DuPont non-adhesive PI material).
• PI Cover Film: There are two thickness options for the cover film: 1/2 mil or 1 mil.
• PI Reinforcement: Various thicknesses are available based on customer needs, including 0.075mm, 0.1mm, 0.125mm, 0.15mm, 0.175mm, 0.2mm, 0.225mm, and 0.25mm.

Color Selection Differences in FPC Substrate, Cover Film, and PI Reinforcement

• PI Substrate: No color options available.
• PI Cover Film: Available in three colors: yellow, white, and black.
• PI Reinforcement: Color changes with thickness; thicker materials tend to be darker. For example, a 0.075mm PI reinforcement appears brown, while a 0.25mm PI reinforcement is closer to black.