What are the common types of FPC flexible circuit boards?

Common types of FPC flexible circuit boards

At present, there are four types of FPC flexible circuit boards: single-sided, double-sided, multi-layer flexible circuit boards and rigid-flex circuit boards.

1. Single-sided flexible circuit boards are the lowest cost printed boards that do not require high electrical performance. When single-sided wiring, a single-sided flexible circuit board should be used. It has a layer of chemically etched conductive patterns, and the conductive pattern layer on the surface of the flexible insulating substrate is rolled copper foil. The insulating substrate can be polyimide, polyethylene terephthalate, aramid and polyvinyl chloride.

2. Double-sided flexible circuit board is a conductive pattern etched on both sides of the insulating base film. The metallized hole connects the patterns on both sides of the insulating material to form a conductive path to meet the flexible design and use function. The cover film protects single and double-sided conductors and indicates where the components are placed.

3. Multi-layer flexible circuit board is to laminate 3 or more layers of single-sided or double-sided FPC flexible circuit board together, form metallized holes by drilling and electroplating, and form conductive paths between different layers. In this way, no complicated welding process is required. Multilayer circuits have huge functional differences in higher reliability, better thermal conductivity, and easier assembly performance. When designing the layout, the interaction of assembly size, number of layers and flexibility should be considered.

4. Traditional rigid-flex circuit boards are composed of rigid and flexible substrates selectively laminated together. The structure is compact, and the conductive connection is formed by metallization. If a printed board has components on the front and back, a rigid-flex circuit board is a good choice. But if all the components are on one side, it is more economical to use a double-sided flexible circuit board with a layer of FR4 reinforcement laminated on the back.

5. The hybrid structure FPC flexible circuit board is a multi-layer board,and the conductive layer is composed of different metals. An 8-layer board uses FR-4 as the inner dielectric and polyimide as the outer dielectric, with leads extending fr om the motherboard in three different directions, each made of a different metal. Constantan alloy, copper and gold are used as independent leads. This kind of hybrid structure is mostly used in low temperature situations where the relationship between electrical signal conversion and heat conversion and electrical performance is relatively harsh, and it is the only feasible solution. The convenience and total cost of the interconnect design can be evaluated to achieve the best price-performance ratio.