Electronic products are to use PCB, PCB market is almost the electronics industry vane. With the development of mobile phones, laptops and PDA high-end, miniaturization of electronic products, the demand for flexible PCB (FPC) is growing, PCB manufacturers are speeding up the development of thinner, lighter and higher density of FPC.
Single layer FPC
The utility model is characterized in that the utility model is provided with a layer of chemically etched conductive patterns. The insulating substrate may be polyimide, poly (ethylene terephthalate), aramid fiber and polyvinyl chloride. Single layer FPC can be divided into the following four categories:
One side connection without covering layer
A conductor pattern on the insulating base, without covering the conductor surface of the interconnect is used in soldering, welding or welding to achieve, commonly used in the early days of the telephone.
2.Covered with one side connection
Compared with the former, there is only one layer of covering layer on the surface of the conductor. Cover the need to expose the pad, simply can not cover the end area. PCB is one of the most widely used, one of the most widely used in automotive instrumentation, electronic equipment.
3. No cover double connection
Connect the disk interface for wire connection in the front and back of the pad can be, the insulation on a via hole, the hole in the insulating substrate access a desired position on the first punch, etching or other mechanical method.
4. Covered double sided connection
The utility model is characterized in that the surface of the utility model is provided with a layer of covering layer, and the cover layer is provided with a through hole, and the two ends of the cover layer can be terminated, and the covering layer is still maintained, and is made of two layers of insulating material and a layer of metal conductor.
Two, double-sided FPC
The two sides of the FPC are respectively provided with a conductive pattern which is etched on the two sides of the insulating base film, and the wiring density of the unit area is increased. The metal holes connect the two sides of the insulating material to form a conductive path to meet the flexibility of the design and use of the function. The covering film can protect the position of single and double wires and indicate the position of the elements. According to the demand, the metallization hole and the cover layer are dispensable, this kind of FPC application is few.
Three, multilayer FPC
FPC is a multi-layer single-sided or double-sided flexible printed circuit laminate 3 or more layers together, through boreholes L, electroplating forming hole metallization, conductive paths formed in different layers. In this way, it is not necessary to adopt complex welding process. Multilayer circuits have great functional differences in higher reliability, better thermal conductivity and more convenient assembly performance.
The advantage is that the substrate film is light weight and has excellent electrical properties, such as low dielectric constant. Multilayer soft PCB board is made of polyimide film substrate, epoxy glass cloth than rigid multilayer PCB light weight is about 1/3, but it lost the single-sided and double-sided soft PCB excellent flexibility, most of these products are not required to be flexible. Multilayer FPC can be further divided into the following types:
flexible insulating substrate products
This class is made on a flexible insulating substrate, and the finished product is specified to be flexible. Such a structure is usually bonded to both ends of a plurality of single-sided or double-sided microstrip flexible PCB, but the central portion is bonded together at the end, thus having a high degree of flexibility. In order to have a high degree of flexibility, a thin layer of suitable coating, such as polyimide, may be used instead of a thick laminated coating.
2. soft insulating substrate products
This class is made of a soft insulating substrate, and the finished product can be bent. This kind of multilayer FPC is made of soft insulating materials, such as polyimide film, laminated multilayer board, after the loss of the inherent flexibility.