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

　　① Single sided flexible board is the lowest cost printed board when it does not require high electrical performance. When wiring on one side, a single-sided flexible board should be selected. It has a layer of chemically etched conductive patterns, and the conductive pattern layer on the flexible insulation substrate surface is rolled copper foil. The insulation substrate can be polyimide, polyethylene terephthalate, aramid fiber ester, and polyvinyl chloride.

　　② Double sided flexible board is a conductive pattern made by etching one layer on each side of the insulating substrate film. Metallized holes connect the patterns on both sides of the insulating material to form a conductive path, in order 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 components.

　　③ Multi layer flexible board is a process of laminating three or more layers of single-sided or double-sided flexible circuits together, forming metalized holes through drilling and electroplating, and forming conductive paths between different layers. In 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. When designing the layout, the mutual influence of assembly size, number of layers, and flexibility should be considered.