What Is FPC? What Types Of FPC Are Divided Into?

Flexible printed circuit boards are based on polyimide or polyester film, with high reliability, and flexible printed circuit boards. Referred to as soft board or FPC. Features: high wiring density, light weight, thin thickness; mainly used in mobile phones, notebook computers, PDAs, digital cameras, LCMs and other products.

FPC

Types of FPC

Single layer FPC

It has a chemically etched conductive pattern, and the conductive pattern layer on the surface of the flexible insulating substrate is a rolled copper foil. The insulating substrate may be polyimide, polyethylene terephthalate, aramid cellulose ester, and polyvinyl chloride. Single-layer FPC can be divided into the following four categories:

Single side connection without covering layer

The wire pattern is on the insulating substrate, and there is no covering layer on the wire surface. The interconnection is realized by welding, welding or pressure welding, which is often used in early telephones.

Single-sided connection cover

Compared with the previous type, there is only one covering layer on the surface of the wire. The pads should be exposed when covering, and the end area can be simply not covered. It is the most widely used and most widely used single-sided flexible PCB for automotive instruments.

Double-sided connection without covering layer

The interface of the connecting pad can be connected on the front and back of the wire, a channel hole is opened on the insulating substrate of the pad, and the required position of the insulating substrate can be washed, etched or other mechanical methods.

Double-sided covering connection

The difference between the former is that there is a covering layer on the surface, and the covering layer has via holes, allowing both sides to be terminated and still maintaining the covering layer. It is made of two layers of insulating materials and a layer of metal conductors.

Double-sided FPC

The double-sided FPC has a layer of etched conductive patterns on both sides of the insulating base film, which increases the wiring density per unit area. The metal hole connects the patterns on both sides of the insulating material to form a conductive path to meet the soft use function. The cover film can protect single-sided and double-sided wires and indicate the location of the components. According to needs, metallized holes and covering layers are optional, and this type of FPC is less used.

Multilayer FPC

Multi-layer FPC laminates 3 or more layers of single-sided or double-sided flexible circuits together, and metal holes are formed by drilling L. electroplating to form conductive paths between different layers. Therefore, no complicated welding process is required. Multilayer circuits have great functional differences in terms of higher reliability, better thermal conductivity, and more convenient assembly performance.

The advantage is that the base film is light in weight and excellent in electrical properties, such as low dielectric constant. The multilayer flexible PCB board made of polyimide film is about 1/3 lighter than the rigid epoxy glass cloth multilayer PCB board, but it loses the excellent flexibility of single-sided and double-sided flexible PCBs. These products Most do not need flexibility. Multi-layer FPC can be further divided into the following types:

Finished flexible insulating substrate

This category is manufactured on a flexible insulating substrate, and its finished product is specified as a flexible insulating substrate. This structure usually bonds the two ends of many single-sided or double-sided microstrip flexible PCBs together, but the central part is not bonded together, so it has high flexibility. In order to have a high degree of flexibility, the wire layer can use a thin coating, such as polyimide, instead of a thick coating.

Finished soft insulating substrate

This type is manufactured on a soft insulating substrate, and the finished product is not flexible. This multi-layer FPC uses soft insulating materials such as polyimide film to be laminated into a multi-layer board, which loses its inherent flexibility after lamination.