The basic design process of PCB is as follows:
Preliminary preparation - PCB structural design - PCB layout - wiring - wiring optimization and screen printing - network and DRC inspection and structural inspection - platemaking.
The preliminary preparation includes preparing the component library and schematic diagram
If you want to do well in your work, you must make good use of your tools.Before PCB design, prepare the component library of schematic diagram SCH and PCB.The component library can use peotel's own library, but in general it is difficult to find the appropriate one. It is better to make the component library by yourself according to the standard size data of the selected device.In principle, first make the PCB component library, then make the SCH component library.
2. PCB structure design.In this step, according to the determined circuit board size and various mechanical positioning, the PCB board surface is drawn under the PCB design environment, and the required connectors, buttons/switches, screw holes, assembly holes and so on are placed according to the positioning requirements.And fully consider and determine the wiring area and the non-wiring area (such as the area around the screw hole belongs to the non-wiring area).
3. PCB layout
The layout is essentially putting devices on the board.At this point, if all the preparatory work mentioned above is done, you can generate the network table (design-> Create Netlist) on the schematic diagram and then import the network table (design-> Load Nets) on the PCB diagram.You can see that all the devices are going up, and there are flying wire between the pins.Then you can layout the device.The general layout is based on the following principles:
1 according to reasonable electrical performance, it is generally divided into: digital circuit area (i.e. fear of interference and interference), analog circuit area (fear of interference), power drive area (interference source);
2. The circuit with the same function should be placed as close as possible, and the components should be adjusted to make the connection as simple as possible.At the same time, adjust the relative position between the functional blocks so that the connection between the functional blocks is the most concise;
The installation position and installation strength should be considered for high quality components.The heating element should be placed separately from the temperature sensitive element.
4 I/O drive devices as close as possible to the edge of the printing plate, close to the lead connector;
5 clock generator (such as crystal oscillator or clock vibration) should be as close as possible to the device using the clock;
6. A decoupling capacitance shall be added between the power input pin and the ground of each integrated circuit (generally using a sololite capacitor with high frequency performance);When the circuit board space is relatively dense, a tantalum capacitor can be added around several integrated circuits.
7 discharge diode should be added at relay coil (1N4148 is enough);
8 to have a balanced layout requirements, density and orderly, not top-heavy or YiTouChen - need to pay special attention to, when placed components, components should be considered when the actual size (in the area and height) and the relative position between the components, to ensure the feasibility of the electrical properties and production of circuit boards installed and convenience at the same time, should be on the premise of guarantee the above principle to reflect, appropriate change device, make it tidy and beautiful, such as the same devices to be neat, in the same direction, can't put strewn at random have send.
Wiring is the most important process in PCB design.This will directly affect the performance of the PCB board.In the design process of PCB, the wiring is generally divided into three levels: first, the layout, then the most basic requirements of PCB design.If all the lines are not connected, you will find a flight line everywhere, which will be a disqualified board, so to speak, not yet.Next is the satisfaction of electrical performance.