Basic knowledge of soft PCB board

With the continuous increase of the production ratio of soft PCB and the application and promotion of rigid flexible PCB, it is more common to add soft, rigid or rigid flexible PCB when saying PCB, and say how many layers it is. Usually, PCB made of soft insulating material is called soft PCB or flexible PCB, rigid flexible PCB. It ADAPTS to the current electronic products to high-density and high reliability, miniaturization, lightweight direction development needs, but also meets the strict economic requirements and market and technical competition needs.

Abroad, soft PCB has been widely used in the early 1960s. In our country, production and application began in the 1960s. In recent years, with the global economic integration and open city, and the introduction of technology to promote its use is constantly growing, some small and medium-sized rigid PCB factory aimed at soft hard do technology on this opportunity, tooling and process to make use of existing equipment improvement, transformation and adaptive soft soft PCB PCB production consumption growing needs. In order to further understand PCB, soft PCB process is introduced here.

I. Classification of soft PCB and its advantages and disadvantages

1. Soft PCB classification

Soft PCBS are usually classified according to the layer and structure of the conductor as follows:

1.1 Single-sided soft PCB

Single-sided soft PCBS, with only one layer of conductor, may have or may not have a coating on the surface. The insulation base material used varies with the application of the product. Commonly used insulating materials have polyester, polyimide, polytetrafluoroethylene, soft epoxy-glass cloth.

Single-sided soft PCB can be further divided into the following four categories:

1) Single-side connection without covering layer

The wire pattern of this type of soft PCB is on an insulating substrate, and the surface of the wire is not covered. Like a normal single-sided rigid PCB. These products are the cheapest and are usually used in non-critical, environmentally friendly applications. The interconnection is realized by tin welding, fusion welding or pressure welding. It was often used in early telephones.

2) single-sided connection with covering layer

Compared with the previous class, this kind of conductor only has one more coating layer on the surface according to the customer’s requirements. When covering, the pad should be exposed, simply not covered in the end area. Requirements of precision can be used in the form of clearance holes. It is one of the most widely used single-sided soft PCB, which is widely used in automobile instrument and electronic instrument.

3) There is no double-sided connection of covering layer

This type of connection plate interface can be connected on both the front and back of the wire. To do this, a path hole is made in the insulating substrate at the pad. This path hole may be made by punching, etching or other mechanical means at the desired position of the insulating substrate. It is used for both sides mounting elements, devices and applications requiring tin welding. The access pad area has no insulating substrate and such pad area is usually chemically removed.

4) Double-sided connections with covering layers

The difference between this class and the previous class is that there is a covering layer on the surface. But the cladding has access holes that also allow it to be terminated on both sides while still maintaining the cladding. These soft PCBS are made of two layers of insulating material and a metal conductor. It is used where the covering layer is required to be insulated from the surrounding device, and to be insulated from each other, with both the front and back ends connected.

1.2 Double-sided soft PCB

Double-sided flexible PCB with two layers of conductors. The applications and advantages of this type of double-sided flexible PCB are the same as those of single-sided flexible PCB, with the main advantage being increased wiring density per unit area. It can be divided into: a without metallized hole and without covering layer according to the presence and absence of metallized hole; B without metallized holes and covered; C having metallized holes and no covering layer; D having metallized holes and covering layers. Double-sided soft PCBS without overlays are rarely used.