Circuit Board Composition and Function

The PCB is made of different components and various complicated process technologies. The PCB structure has a single-layer, double-layer and multi-layer structure. Different layer structures have different manufacturing methods.

First, the printed circuit board is mainly composed of pads, vias, mounting holes, wires, components, connectors, filling, electrical boundaries, etc. The main functions of each part are as follows:

Pad: It is used to weld metal holes of component pins.

Via Holes: It is used to connect metal holes of component pins between layers.

Mounting Hole: It is used to fix the printed circuit boards.

Wire: It is used to connect the electrical network copper film of component pins.

Connector: It is used for components connected between circuit boards.

Filling: It is used for copper plating of the ground wire network, which can effectively reduce the impedance.

Electrical boundary: It is used to determine the size of the circuit board, and all components of the circuit board must not exceed this boundary.

Second, the common layer structure of printed circuit boards includes three types of single-layer boards, double-layer boards and multi-layer boards. The brief descriptions of these three layer structures are as follows:

Single layer board: A circuit board with copper on only one side and no copper on the other side. The components are usually placed on the side without copper, and the copper side is mainly used for routing and soldering.

Double layer board: A circuit board with copper on both sides, usually called one side as a top layer and the other side as a bottom layer. Generally, the top layer is used as the component placement surface, and the bottom layer is used as the component welding surface.

Multi-layer board: That is, a circuit board containing multiple working layers, in addition to the top layer and the bottom layer, also contains several intermediate layers. Generally, the intermediate layer can be used as a wire layer, a signal layer, a power layer, and a ground layer. The layers are insulated from each other, and the connection between layers is usually achieved via holes.

Third, the printed circuit board includes many types of working layers, such as signal layer, protective layer, silkscreen layer, internal layer, etc. The functions of various layers are briefly introduced as follows:

Signal Layer: It is mainly used to place components or routing. Protel DXP usually contains 30 middle layers, namely Mid Layer1 ~ Mid Layer30. The middle layer is used to lay out signal lines, and the top and bottom layers are used to place components or copper.

Protective Layer: It is mainly used to ensure that parts of the circuit board that do not require tinned are not tinned.

Silkscreen Layer: It is mainly used to print the serial number, production number, company name, etc. of components on the printed circuit board.

Internal Layer: It is mainly used as a signal routing layer. Protel DXP contains a total of 16 internal layers.

Other layer: It is mainly includes 4 types of layers.

Drill Guide: It is mainly used for the position of drilling holes on the printed circuit board.