PCB Layout Principles
Generally, basic PCB design process follows seven steps: pre-preparation- structural design- layout- optimization and silkscreen- net check, DRC check, and structural check- board fabrication.
Generally speaking, PCB layout is to put components on the best place. At this time if the preparatory work mentioned in the previous article is done, you can make a network table in the schematic, and then import the network table on the PCB drawing. After all components and pins appear, then you can layout them. The general layout is based on the following principles:
1. A decoupling capacitor is needed between pin and ground of the power input in each integrated circuit, generally the performance of high-frequency monolithic capacitor is better. If the spacing on the PCB board is intensive, you can just put a tantalum capacitor to serve several integrated circuits.
2. According to the electrical performance of reasonable partition, generally divided into: digital circuit area (fear of interference but also generate interference), analog circuit area (fear of interference), power drive area (interference source).
3. Big components should consider the installation location and installation strength; heating elements should be placed separately with the temperature sensitive components, if necessary, thermal convection measures should be considered.
4. Circuits that required to complete the same function should be placed as close as possible, and adjust components to ensure the most concise connection. At the same time, adjust the relative position between the functional blocks to ensure the most concise connection.
5. PCB layout requires balanced, dense but orderly effect.
6. Put the I/O driver as close as possible to the board edge and the lead-out connector.
7. The clock generator (eg, crystal or bell oscillator) should be put as close as possible to the component that uses the clock.
8. The discharge diode should be put beside the relay coil.