PCB News - Talking about the structure level of FPC

The development of circuit boards has derived many types, but most of them can be divided into two types: rigid and flexible circuit boards, and today we will talk about the structure of flexible circuit boards.

Generally, circuit boards are divided into layers according to the number and thickness of conductive copper foil. They can be divided into single-layer boards, double-layer boards, multi-layer boards and double-sided boards, and their structures are also different, which will be introduced below. What is their different nature.

Single-layer board structure: This is the simplest flexible board. It is usually a set of base material + transparent glue + copper foil. The protective film + transparent glue is another purchased raw material; first of all, copper The foil needs to be processed by etching and other processes to obtain the required circuit. The protective film needs to be drilled to expose the corresponding pads. After cleaning, use the rolling method to combine the two, and then electroplating gold or plating on the exposed pads. Tin, etc. are used for protection, so that the large board is ready, and then it needs to be stamped into a small circuit board of the corresponding shape.

Double-layer board structure: When the circuit is too complicated, single-layer board cannot be wired, or copper foil is needed for grounding shielding, double-layer board or multilayer board is required.

The structure of the multilayer board: The most typical difference between the multilayer board and the single-layer board is the addition of a via structure to connect each layer of copper foil. Generally, the first processing technology of substrate + transparent glue + copper foil is to make vias; First, drill holes on the substrate and copper foil, and then plate a certain thickness of copper after cleaning, so that the vias are completed, and the subsequent manufacturing process is almost the same as that of the single-layer board.

Double-sided board structure: There are pads on both sides of the double-sided board, which are mainly used for connection with other circuit boards. Although it is similar to the single-layer board structure, the manufacturing process is very different. Its raw materials are copper foil, protective film + transparent glue. First, drill holes on the protective film according to the requirements of the pad position, and then paste the copper foil. Then the pads and leads are etched out, and then another protective film with drilled holes can be attached.

Although these types of structures of flexible circuit boards are different, many manufacturing processes have similarities, but different processes are added in some basic places to correspond to different fields.