原创 basic printed circuit board design guidelines

1. High frequency pcb design requires careful  grounding. Use ground plane for control circuit. Try to make most of  signal ground connections through vias to this ground plane rather then    through PC traces.

2. For each power supply stage, keep power  ground and control ground separately. Tight them together [If they are  electrically connected] in one point near DC output return of the given       stage.

3. Minimize areas and lengths of loops which contain high  frequency switching currents.

4. Place capacitors that bypass supply voltage and reference pins of all ICs close to these      pins

5. Place filter capacitors so that their terminals physically go right into the printed circuit board  traces that carry mainstream of the current to be filtered.

6. When doing PCB layout try to use symmetrical routing for paralleled power devices.

7. Choose the width of circuit board traces based on the rated current and acceptable       temperature rise. Make sure however that the PC trace will not fuse at any  abnormal current (such as short circuit current) that could develop in the  circuit.

8. PWB creepage and clearance between primary circuits,  secondary circuits and safety ground should be determined according to the  requirements of applicable standards. For example, in a typical commercial application with 120-230 VAC input, creepage between primary and secondary circuitry per UL 60950 or IEC 60950 should be 6.4 mm min.

The main generic standard for PCB design is currently IPC-2221A (the old standard was IPC D-275). Quality and inspection issues for Rigid Printed Boards are covered by Qualification and Performance Specification IPC-6012B.