I. From the schematic diagram to the PCB design process to establish component parameters - "Input Principle Netlist -" Design Parameter Settings - "Manual Layout -" Manual Wiring - "Verification Design - "Review -" CAM output.
2. Parameter setting The spacing of adjacent conductors must meet the electrical safety requirements, and the spacing should be as wide as possible for ease of operation and production. The minimum spacing should be at least suitable for the voltage to withstand. When the wiring density is low, the spacing of the signal lines can be appropriately increased. The signal lines with high and low levels should be as short as possible and the spacing should be increased. Set the trace spacing to 8 mil.
The distance from the edge of the pad to the edge of the board is greater than 1mm, which avoids pad defects during processing. When the traces connected to the pads are thinner, the connection between the pads and the traces is designed to be a drop-shaped shape. This has the advantage that the pads are not easily peeled off, but the traces are not easily disconnected from the pads.
Third, the component layout practice proves that even if the circuit schematic design is correct, the printed circuit board design is improper, it will have an adverse impact on the reliability of electronic equipment. For example, if the two thin parallel lines of the printed board are close together, a delay of the signal waveform will be formed, and reflection noise will be formed at the end of the transmission line; the interference caused by the inconsistency of the power supply and the ground line will cause the product to be Performance is degraded, so when designing a printed circuit board, care should be taken to use the correct method.
4. The wiring switching power supply contains high frequency signals. Any printed circuit on the PCB can function as an antenna. The length and width of the printed circuit will affect its impedance and inductance, thus affecting the frequency response. Even a printed line that passes a DC signal can couple to an RF signal from an adjacent printed line and cause a circuit problem (even radiating an interference signal again).
5. After checking the wiring design, it is necessary to carefully check whether the wiring design meets the rules set by the designer, and also to confirm whether the established rules meet the requirements of the printed board production process, and generally check the lines and lines, lines and components. Whether the distance between the pad, the line and the through hole, the element pad and the through hole, the through hole and the through hole is reasonable, and whether the production requirement is satisfied. Is the width of the power and ground wires appropriate? Is there a place in the PCB where the ground wire can be widened? Note: Some errors can be ignored. For example, some of the connectors' Outline are placed outside the board frame, and errors are detected when checking the spacing. In addition, each time the traces and vias are modified, the copper is re-copied once.
6. Review according to the “PCB checklist”, including design rules, layer definition, line width, spacing, pad, and via settings, and also focus on reviewing the rationality of device layout, routing of power and ground networks, Wiring and shielding of high-speed clock networks, placement and connection of decoupling capacitors, etc.