In other countries, has been widely used soft PCB in the early sixties . Country , then in the sixties began production applications. In recent years , as the global economic integration and open the city to try to introduce technology to promote their usage constantly growing, some small and medium -rigid PCB Factory targeting this opportunity to make use of soft hardware technology, the use of existing tools and tooling equipment technology for improvement, restructuring production of soft PCB and flexible PCB dosage adaptation growing needs . To further understanding of PCB, PCB here on soft classification are introduced.
Flexible PCB usually classified according to the following conductor layers and structures :
1 soft -sided PCB
Soft -sided PCB, only the conductor layer , the surface layer or covering can not cover. The insulating base material used , different applications with different products . Commonly used insulating materials are polyester , polyimide, polytetrafluoroethylene, soft epoxy - glass cloth.
2 soft -sided PCB
Soft -sided PCB, there are two conductors. Such soft -sided PCB applications and soft -sided PCB with the same advantages , its main advantage is increased wiring density per unit area. It may be there , and there are no metal holes without covering layer is divided into :
. a non- metallized holes, no cover layer ;
. b non- metallized holes covering layer ;
. c metallized holes, no cover layer ;
d. metallized holes with a covering layer.
Soft -sided PCB without overlay rarely used.
3 multilayer flexible PCB
Multilayer PCB as soft as rigid multilayer PCB , multilayer lamination technology , can be made flexible multilayer PCB. The simplest multilayer soft -sided PCB on both sides of the PCB is covered with two layers of copper shield and the formation of three soft PCB. This three-layer flexible PCB or equivalent coaxial conductor shielded wire on the electrical characteristics. The most common structure is a four-layer PCB multilayer flexible structure, with inter- layer metal interconnection holes to achieve the intermediate floor is generally the power source layer and the ground layer .
Advantages of the multi-layer flexible PCB substrate film is lightweight, and has excellent electrical characteristics , such as low dielectric constant. Multilayer flexible PCB board as a base film made of polyimide , the weight ratio of the rigid multi-layer epoxy glass board PCB light about 1/ 3, but it lost sided, double-sided flexible PCB excellent the flexible , most of these products are not required can be flexible.
