In the manufacturing process of printed circuit boards (PCBs), release films play an inconspicuous but crucial role. As a type of functional release film, it is widely used in various processes such as multi-layer board lamination,  flexible circuit die-cutting due to its excellent "controllable peeling" characteristics. Its surface is treated with special treatments such as silicone oil or fluorine, allowing it to "easily detach" within the required time after bonding with the adhesive material, without leaving residue or damaging the functional layer.

Especially in the current market context of continuous growth of HDI boards, high multi-layer boards, and flexible circuit boards (FPC), the requirements for cleanliness, accuracy, and material compatibility in manufacturing processes are becoming increasingly stringent. The selection and performance control of release films have become one of the important factors affecting PCB yield.

Isolation and protection during the lamination process of multi-layer boards

With the popularization of multi-layer PCB board design, lamination process has become a key process in circuit board manufacturing. During the lamination process, various interlayer materials such as prepreg, copper foil, and core board need to undergo high temperature and high pressure treatment simultaneously. At this point, the role of the release film is mainly reflected in the following aspects

1. Isolation function: used to prevent adhesive materials (such as resins, semi cured sheets) from adhering to the surface of the hot pressing plate or mold during the hot pressing process;

2. Reduce stress transmission: buffer layer pressure, improve the uniformity of interlayer adhesion;

3. Prevent pollution: Protect the copper surface or outer graphic from resin contamination or oxidation during the lamination process.

4. Some high-end PET release films also have high temperature resistance (>200 ℃) performance, which can maintain surface stability during long-term hot pressing process without foaming, curling, or shrinkage, thereby improving the qualification rate and consistency of laminated products.

High precision carrier support in flexible circuit die cutting

Flexible Circuit Boards (FPCs) are widely used in fields such as mobile phones, wearable devices, and camera modules due to their lightweight and bendable characteristics. But its softness also poses challenges to the die-cutting process, requiring the use of high flatness and high strength release films as die-cutting carriers. In this type of application, the main functions of the release film include:

1. Supporting functional layer: Enhance the rigidity of FPC or cover film during die-cutting, ensuring that the cutting pattern does not shift;

2. Provide peeling function: After die-cutting is completed, the release film can be easily peeled off without tearing or residue;

3. Improve die-cutting accuracy: Control the heat shrinkage rate to ensure stable graphic size and meet the precision requirements of automatic die-cutting equipment within ± 0.1mm.

4. Some high-end FPC application scenarios also require release films to have multiple properties such as anti-static, scratch resistant, and dust-proof to ensure the cleanliness and assembly of the final die cut components. Especially in industries such as camera modules and display panels that require extremely high cleanliness levels, the quality of release film almost determines the yield of die cut products.

Although release film is only an "auxiliary material" in PCB manufacturing, its functions of isolation, protection, and auxiliary processing in multiple key links are indispensable. A small film layer often determines the success or failure of a process and the yield of a component.

For the PCB industry that is developing in terms of high-level, flexible, and fine graphic design, selecting high-performance and stable release films will be a key step in improving process yield, optimizing manufacturing efficiency, and ensuring product reliability.