I. Component Layout Rules

1. Module-Based Layout:
   Group related components that serve the same function into a module. Separate digital and analog circuits to minimize interference.
2. Clearance Around Holes:
   • Non-mounting holes (e.g., positioning holes): Keep a 1.27mm clearance around them.
   • Mounting holes (e.g., screw holes): Maintain 3.5mm clearance for M2.5 screws and 4mm for M3 screws.
3. Avoid Vias Under Components:
   Do not place vias under horizontal resistors, inductors (plug-ins), or electrolytic capacitors to prevent short circuits caused by wave soldering.
4. Edge Clearance:
   Ensure components are at least 5mm away from the PCB edge.
5. Pad-to-Pad Spacing:
   Maintain a spacing of at least 2mm between the outer edges of mounted component pads and adjacent plug-in components.
6. Metal Components:
   • Keep metal-shell components (e.g., shielding boxes) isolated from other components, printed lines, and pads by at least 2mm.
   • Position holes (e.g., fastener or elliptical holes) should be at least 3mm from the board edge.
7. Thermal Considerations:
   • Avoid placing heat-sensitive components near heating elements.
   • Distribute high-heat devices evenly.

1. Power Socket Placement:
   • Position power sockets near the PCB edge for easy access.
   • Arrange busbar terminals on the same side for streamlined cable routing and soldering.
   • Ensure sufficient spacing for easy plugging/unplugging.
2. Other Component Arrangements:
   • Align all IC components on one side.
   • Standardize the polarity marking of polar components; limit markings to two perpendicular directions.
3. Copper Filling:
   For areas with low routing density, fill with mesh copper foil; ensure a mesh size of 8mil (0.2mm) or larger.
4. Avoid Through-Holes on Pads:
   Prevent solder paste leakage and cold soldering by avoiding through-holes on patch pads. Do not route critical signal lines through socket pins.
5. Alignment and Polarity:

• Ensure patches are aligned and character directions are consistent.
• Maintain uniform polarity marking directions for polarized devices across the PCB.

II. Wiring Rules

1. Edge and Hole Clearance:
   • Do not route within 1mm of the PCB edge or around mounting holes.
2. Minimum Trace Width and Spacing:
   • Power lines: ≥18mil.
   • Signal lines: ≥12mil.
   • CPU I/O lines: ≥10mil (or 8mil).
   • Trace spacing: ≥10mil.
3. Vias:
   • Standard vias: Diameter ≥30mil.
4. Component Pads and Apertures:
   • DIP components: 60mil pad, 40mil aperture.
   • 1/4W resistor:
     • Surface mount: 51x55mil (0805).
     • Through-hole: 62mil pad, 42mil aperture.
   • Multilayer capacitor:
     • Surface mount: 51x55mil (0805).
     • Through-hole: 50mil pad, 28mil aperture.
5. Routing Best Practices:
   • Use radial patterns for power and ground lines.
   • Avoid signal loops to maintain signal integrity.

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