1. Single-layer FPC
A single layer PCB has only one layer of conductor and the surface may or may not have a cover layer. The insulating substrate material used will vary with the application of the product. Commonly used insulating materials are polyester, polyimide, polytetrafluoroethylene, soft epoxy-glass cloth, and the like.
Single-layer Flex Board (FPCs) are divided into the following four categories:
Firstly, No cover layer single-sided connection
The wiring pattern of such a flex board FPC is on an insulating substrate with no coating on the surface of the wire. Usually used in non-critical and environmentally friendly applications. The interconnection is achieved by soldering, welding or pressure welding. It is commonly used in early telephones.
Secondly, Covered single layer connection
Compared with the previous class, this type only has a layer of cover on the surface of the wire according to customer requirements. The pad needs to be exposed when covering, and it can be easily covered in the end area. If precision is required, it can be in the form of a clearance hole. It is the most widely used and widely used single-layer flex board PCB and is widely used in automotive instruments and electronic instruments.
Thirdly, Uncovered double-layer connection
This type of land interface can be connected to both the front and the back of the wire. In order to do this, a via hole is formed in the insulating substrate at the pad, which can be formed by etching, etching or other mechanical means at a desired position of the insulating substrate. It is used for two-sided mounting elements, devices, and where soldering is required. There is no insulating substrate in the pad area of the via, thereby chemically removing the pad area.
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Fourthly, Covered with double layer connection
This type differs from the former class in that it has a layer of cover on the surface. However, the cover layer has through holes, and both sides can terminate and retain the cover layer. This type of flexible PCB is made of two layers of insulating material and a layer of metal conductor. It is used when the cover layer and the surrounding devices are required to be insulated from each other, and they are insulated from each other, and the ends need to be connected to both the front and the back.
2. Double layer FPC
The double-layer FPC has two layers of conductors. The application and advantages of this type of double-layer flexible PCB are the same as those of a single-sided flexible PCB. The main advantage is the increased wiring density per unit area.
3. Multi-layer FPC
Flexible multilayer PCBs, such as rigid multilayer PCBs, can be fabricated into multilayer flexible PCBs using multilayer lamination technology. The advantage of a multilayer FPC is that the substrate film is lightweight and has excellent electrical properties. The multilayer flexible PCB board made of the polyimide film is about 1/3 lighter than the rigid epoxy glass cloth multilayer PCB board.