The basic general PCB design process is as follows: preparation -> PCB Design -> PCB Layout -> Wiring -> wiring optimization and printing -> Network and the DRC and structural inspection -> plate.
First: preparation. This includes preparing libraries and schematics. "We must first of its profits", to make a good board, in addition to good design principles, should also draw well. Before PCB design, the first to be ready SCH schematic and PCB component library component library. Component library can peotel own libraries, but under normal circumstances it is difficult to find a suitable, preferably standard size based on their own data for the selected device own component libraries. In principle, do first PCB component library, do SCH component library. Higher PCB component library requirements, which directly affects the board installation; SCH component library requires relatively loose, as long as the attention to the definition of a good correspondence between the pins and the PCB attributes and elements on the line. PS: Note that the standard library hidden pins. After that the schematic design, ready to do well after the PCB design.
Second: PCB design. This step has been determined according to the board size and the mechanical positioning, draw PCB board in the PCB design environment, according to the positioning requirements of the connector, button / switch, screw holes, mounting holes placement required and so on. And fully consider and determine the wiring area and the non-wiring area (such as screw holes around what extent are non-wiring area).
Third: PCB layout. Layout it means to put the device on the board. Then if the preparations are mentioned above do, then you can generate a netlist (Design-> Create Netlist) on the schematic, and then import the netlist (Design-> Load Nets) on the PCB Fig. I saw the device crashed whole heap up, as well as the connection between the fly line prompt pins. Then you can layout the device. The general layout of the following principles:
①. Press the electrical performance and reasonable zoning, generally divided into: digital circuit area (ie fear of interference, and interference), analog circuit area (fear of interference), power driver region (interference source);
②. Perform the same function circuit, should be placed as close as possible, and adjust various components to ensure the connection of the most simple; at the same time, adjusting the relative position of each block to make the connection between the function blocks between the most simple;
③. For large mass components should consider the installation location and mounting strength; the heating elements should be placed separately from the temperature-sensitive components, thermal convection should consider measures when necessary;
④. I / O device driver as close to the edge of the printing plate, near the lead connector;
⑤. A clock generator (eg: Crystal or Restructure) of the clock to try to close the device used;
⑥. Between each IC power input pin and ground, you need to add a decoupling capacitor (generally use good high-frequency performance monolithic capacitors); when board space is more dense, but also add a few integrated circuits around tantalum capacitors.
⑦. To increase at the relay coil discharge diode (1N4148 can);
⑧. Layout requirements should be balanced, density and orderly, not a top-heavy or heavy
- Require special attention when placing components, be sure to consider the actual size (occupied area and height) components, the relative position between the components, in order to ensure the feasibility of the electrical performance of the circuit board production and installation and convenience at the same time, it should be under the guarantee to reflect the principles of the above premise, the proper place to modify the device to make it neat appearance, such as the same device to be placed neatly in the same direction, can not put too "patchwork."
This step is related to the degree of difficulty and the overall image of the next board wiring, so they do take great efforts to consider. When the layout of the place can be quite sure that the preliminary wiring, full consideration.