FPC flexible circuit board is a printed circuit board with high wiring density, light weight and thin thickness, which is made of polyimide or polyester film. It is mainly used in mobile phones, tablet computers, medical devices, LED, automotive electronics, smart wear and other products. FPC types can be divided into single-sided FPC, double-sided FPC, multi-layer FPC and soft-hard FPC.

The single-sided FPC has a layer of chemically etched conductive graphics, and the conductive graphics layer is calendered copper foil. Insulation substrates may be polyimide, polyethylene terephthalate, aromatic amide fiber ester, and polyvinyl chloride. Single-sided FPC can be divided into the following four categories:

No covering single surface connection wire graphics on the insulation substrate, the surface of the wire without covering layer, its interconnection is achieved by tin welding, fusion welding or pressure welding.
2. Compared with the single side connection without covering layer, there is only one more covering layer on the wire surface. Cover with the solder pad exposed, simple can be in the end area is not covered.

3. Non-covering double-sided connection the connection disc interface can be connected on the front and back of the wire. A passage hole can be made on the insulation substrate at the welding pad.

4. Double-sided connection with covering layer and non-covering layer are in different places. There is a layer of covering layer on the surface.

The two-sided FPC has a layer of conductive pattern etched on both sides of the insulating substrate film, which increases the wiring density per unit area. The metallized hole connects the two sides of the insulating material to form a conductive path to meet the design and use function of flexural property. The covering film can protect the single and double sides of the wire and indicate the placement of the element.

Multilayer FPC laminates 3 or more layers of single-sided or double-sided flexible circuits together and forms metallized holes through drilling and electroplating to form conductive paths between different layers. In this way, no complicated welding process is needed. Its advantage is that the substrate film weight is light and has excellent electrical characteristics. Multi-layer FPC can be further divided into the following types:

Flexible insulation substrate finished products
If made on a flexible insulating substrate, the finished product shall be defined as flexible. This structure usually bonds the two ends of a flexible FPC with many single-sided or double-sided microstrips, but the central part is not bonded together, resulting in a high degree of flexibility.

2. Finished products of soft insulation substrates

If made on a soft insulating substrate, the end of the finished product shall be subject to deflection.

The combination of hard and soft FPC is the flexible circuit board and hard circuit board, after pressing and other processes, according to the relevant process requirements combined together, the formation of FPC characteristics and PCB characteristics of the circuit board. The combination of hard and soft board has the characteristics of FPC and PCB at the same time. It can be used in some products with special requirements. It has a certain flexible area and a certain rigid area.