FPC Factory’s Flexible Circuit Board

The double-sided FPC has a layer of etched conductive pattern on both sides of the insulation base film, which increases the wiring density per unit area. Metallized holes connect the patterns on both sides of the insulation material to form conductive pathways to meet the design and functional requirements of flexibility. And the covering film can protect single and double sided wires and indicate the position of the component placement. According to demand, metallized holes and covering layers are optional, and this type of FPC is rarely used. 3、 Multilayer FPC Multilayer FPC is the process of laminating three or more layers of single-sided or double-sided flexible circuits together, forming metallized holes through drilling and electroplating, and forming conductive paths between different layers. This way, there is no need to use complex welding processes. Multilayer circuits have significant functional differences in terms of higher reliability, better thermal conductivity, and more convenient assembly performance.



Its advantage is that the substrate film is lightweight and has excellent electrical properties, such as low dielectric constant. The multilayer flexible PCB board made of polyimide film as the substrate weighs about 1/3 less than the rigid epoxy glass cloth multilayer PCB board, but it loses the excellent flexibility of single-sided and double-sided flexible PCBs. Most of these products do not require flexibility. Multilayer FPCs can be further divided into the following types:



1. Flexible insulation substrate finished products are made on flexible insulation substrate, and their finished products are specified as flexible. This structure usually bonds the two ends of many single or double-sided microstrip flexible PCBs together, but the central part is not bonded together, resulting in high flexibility. In order to be highly flexible, a thin and suitable coating, such as polyimide, can be used on the conductor layer to replace a thicker laminated coating.



2. Soft insulation substrate finished products



This type is made on soft insulation substrates, and the finished product is not specified to be flexible. This kind of multilayer FPC is made of flexible insulating materials, such as polyimide film, laminated into multilayer boards, which lose their inherent flexibility after lamination.