1. Soft PCB classification
Soft PCBs are usually classified as follows according to the number of layers and structure of the conductor:
1.1 single-sided flexible PCB
A single-sided flexible PCB with only one layer of conductor and a surface with or without a cover. 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-sided flexible PCBs can be further divided into the following four categories:
1) No cover layer single-sided connection
The wire pattern of such a flexible PCB is on an insulating substrate, and the surface of the wire has no cover layer. Like a normal single-sided rigid PCB. These products are the cheapest and are often used in applications where environmental protection is not critical. The interconnection is achieved by soldering, welding or pressure welding. It is commonly used in early telephones.
2) Covered single-sided 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-sided flexible PCB, and is widely used in automotive instruments and electronic instruments.
3) Uncovered double-sided 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, and such pad areas are typically removed chemically.
4) Covered with double-sided connection
This type differs from the former class in that it has a layer of cover on the surface. However, the cover layer has via holes, which also allows both sides to be terminated and still maintain 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.