The basic process of PCB bord design in SMT chip processing requires special attention. One of the main purposes of the design of the circuit schematic is to provide a netlist for the design of the PCB circuit board, and to prepare the basis for the design of the pcb board. The design process of multi-layer PCB circuit boards is basically the same as that of ordinary PCB boards. The difference is that the routing of the intermediate signal layer and the division of the inner electrical layer need to be carried out. On the whole, the design of the multi-layer PCB circuit board is basically Divided into the following steps:

1. The planning of the circuit board is mainly to plan the physical size of the pcb board, the packaging form of the component, the component mounting method, and the layer structure, that is, single-layer board, double-layer board and multi-layer board.

2. Working parameter setting mainly refers to working environment parameter setting and working layer parameter setting. Setting the pcb environment parameters correctly and reasonably can bring great convenience to the design of the circuit board and improve work efficiency.

3. Component layout and adjustment. After the current period of work is ready, the net list can be imported into the pcb, or the net list can be imported directly in the schematic diagram by updating the pcb. Component layout and adjustment are more important tasks in PCB design, which directly affect operations such as the subsequent wiring and the division of the internal electrical layer.

4. Wiring rules are set, mainly to set various specifications of circuit wiring, wire width, parallel wire spacing, safety distance between wires and pads, and via size, etc., no matter what wiring method is adopted, the wiring rules are indispensable. An indispensable step, good wiring rules can ensure the safety of circuit board routing, and meet the manufacturing process requirements, saving costs.

5. Other auxiliary operations, such as copper depositing and teardrop filling, as well as document processing work such as report output and save printing. These files can be used to check and modify PCB circuit boards, and can also be used as a list of purchased components.

Component wiring rules

1. Draw the wiring area within 1mm from the edge of the PCB board, and within 1mm around the mounting hole, wiring is prohibited;

2. The power cord should be as wide as possible and should not be less than 18mil; the signal line width should not be less than 12mil; the cpu input and output lines should not be less than 10mil (or 8mil); the line spacing should not be less than 10mil;

3. The normal via is not less than 30mil;

4. Dual in-line: pad 60mil, aperture 40mil; 1/4W resistance: 51*55mil (0805 surface mount); when in-line, pad 62mil, aperture 42mil; electrodeless capacitor: 51*55mil (0805 surface mount); When in-line, the pad is 50mil and the aperture is 28mil;

5. Note that the power line and the ground line should be as radial as possible, and the signal line must not be looped.