The difference between single-layer, double-sided and multi-layer FPC
Electronic products all use PCB, and the market trend of PCB is almost the vane of the electronics industry. With the development of high-end and miniaturized electronic products such as mobile phones, notebook computers and PDAs, the demand for flexible PCBs (FPCs) is increasing, and PCB manufacturers are accelerating the development of thinner, lighter and denser FPCs. Guangzhou The editor of Mankun Electronics pcb circuit board manufacturer will introduce the types of FPC to you.
Multilayer flexible and rigid board
1. Single-layer FPC
It has a layer of chemically etched conductive pattern, 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. Single-layer FPC can be divided into the following four subcategories:
1. Single-sided connection without covering layer
The wire pattern is on the insulating base material, and the surface of the wire has no covering layer. The interconnection is realized by soldering, fusion welding or pressure welding, which is commonly used in early telephones.
2. One-sided connection with covering layer
Compared with the former class, only a layer of covering layer is added on the surface of the wire. When covering, the pads need to be exposed, and the end area can be simply not covered. It is one of the most widely used single-sided flexible PCBs and is used in automotive instruments and electronic instruments.
3. Double-sided connection without covering layer
The connection pad interface can be connected on the front and back of the wire, and a via hole is opened on the insulating substrate at the pad. This via hole can be punched, etched or fabricated by other mechanical methods at the desired position of the insulating substrate. to make.
4. Double-sided connection with covering layer
Unlike the previous class, the surface has a cover layer with via holes, allowing it to be terminated on both sides while still maintaining the cover layer, made of two layers of insulating material and one layer of metal conductor.
2. Double-sided FPC
Double-sided FPC has a conductive pattern etched on both sides of the insulating base film, which increases the wiring density per unit area. 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. According to the needs, metallized holes and cover layers are optional, and this type of FPC is less used.
3. Multilayer FPC
Multilayer FPC is to laminate 3 or more layers of single-sided or double-sided flexible circuits 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.
The advantage is that the substrate film is light in weight and has excellent electrical properties, such as low dielectric constant. The multi-layer flexible PCB board made of polyimide film is about 1/3 lighter than the rigid epoxy glass cloth multi-layer PCB board, but it loses the advantages of single-sided and double-sided flexible PCB. flexibility, most of these products do not require flexibility. Multilayer FPC can be further divided into the following types:
1. Finished flexible insulating substrate
This category is manufactured on a flexible insulating substrate, and the finished product is specified to be flexible. This kind of structure usually bonds the two sides of many single-sided or double-sided microstrip flexible PCBs together, but the central part is not bonded together, so it has a high degree of flexibility. For a high degree of flexibility, a thin, suitable coating, such as polyimide, can be used on the conductor layer instead of a thicker laminated cover.
2. Finished product of soft insulating substrate
This type is manufactured on a soft insulating substrate, and its finished product is not required to be flexed. This type of multilayer FPC is made of a flexible insulating material, such as a polyimide film, laminated into a multi-layer board, which loses its inherent flexibility after lamination.