Flexible Printed Circuit (FPC) is an indispensable part of modern electronic devices, widely used in products such as smartphones, tablets, and wearable devices. In the manufacturing process of FPC, release film plays a crucial role.

Manufacturing process of FPC

Flexible circuit boards have the advantages of lightweight and flexible, making electronic devices more compact and lightweight in design. The manufacturing process of FPC includes the following main steps

lSubstrate preparation: Select a suitable substrate, such as polyimide (PI) or polyester (PET), and clean and pre-treat it.

lPattern printing: The circuit pattern is transferred onto the substrate through photolithography technology, which requires photoresist and mask.

lEtching and developing: Using chemical etching methods to remove copper foil parts that are not protected by photosensitive adhesive, forming circuit patterns.

lLaminating and Pressing: Layering and pressing multiple layers of substrates and circuit patterns to form a multi-layer FPC.

lDrilling and Electroplating: Drill holes at designated locations and perform electroplating to form electrical connections.

lSurface treatment and testing: Surface treatment of FPC, such as gold plating or tin spraying, and electrical and physical performance testing.

In these steps, release film is mainly used for lamination and press processes to ensure that the materials of each layer do not stick together during the lamination process and can be easily peeled off in subsequent processing steps.

The key role of release film in the lamination process

Lamination is one of the core steps in the manufacturing of flexible circuit boards. In this process, multi-layer substrates and circuit patterns are laminated and bonded to form a multi-layer structure.

ØPreventing adhesion: The release film is placed between the laminated materials to prevent the layers from sticking together under high temperature and pressure.

ØEnsure flatness: The release film has good flatness, ensuring that the surface of  FPC is smooth and wrinkle free.

ØProtective material: Release film can protect the substrate and circuit pattern, preventing damage or contamination during the lamination process.

For example, in the manufacturing of multi-layer FPC, release films are placed between each substrate layer to ensure smooth separation of materials during the lamination process.

Comparison between PET and PTFE

In FPC manufacturing, polyester (PET) and polytetrafluoroethylene (PTFE) are commonly used material.

PET release film:

1. High temperature resistance: PET release film can withstand high temperatures of 150-200 ℃, suitable for most FPC manufacturing processes.

2. Good mechanical strength: PET release film has high mechanical strength and toughness, and is not easily torn or damaged.

3. Lower cost: Compared to PTFE, PET release film has a lower cost and is suitable for large-scale industrial production.

PTFE release film:

1. Higher temperature resistance: PTFE release film can withstand high temperatures above 260 ℃, suitable for some special high-temperature processes.

2. Excellent chemical resistance: PTFE release film has strong resistance to most chemicals and will not be corroded or dissolved.

3. Good peeling off performance: The surface of PTFE release film is extremely smooth, with a very low friction coefficient and excellent peeling performance.

According to specific process requirements, selecting appropriate release film materials can effectively improve the efficiency and product quality of FPC manufacturing.

With the continuous development of electronic products towards lightweight and flexibility, the demand for FPC is increasing, and the requirements for release films are also becoming higher.

ØHigh performance materials: Develop new release film materials with higher temperature resistance and stronger chemical resistance to meet the higher performance requirements of FPC manufacturing.

ØEnvironmentally friendly materials: With the increasing awareness of environmental protection, biodegradable or recyclable release film materials are being developed to reduce environmental pollution.

ØIntelligent manufacturing: Combining intelligent manufacturing technology to optimize the production and application process of release films, improve production efficiency and product quality.

In summary, the application of release film in flexible circuit board manufacturing is crucial, as its selection and use directly affect the manufacturing efficiency and product quality of FPC. By continuously improving the release film materials and processes, the manufacturing level of FPC can be further enhanced, providing a solid foundation for the development of electronic products.