PCB Component Layout Best Practices

1. Basic Rules of PCB board Component Layout

• Consider circuit modules with components of the same function densely concentrated.
• Separate digital and analog circuits.
• Avoid mounting components near non-mounting holes and mounting holes.
• Avoid vias below horizontally mounted components.
• Maintain a 5mm distance between outer components and the board edge.
• Keep a 2mm distance between the outer pad of a mounted component and adjacent components.
• Avoid contact between metal shell components and other parts.
• Distribute heating elements evenly and keep them away from wires.
• Arrange power sockets around the printed board.
• Align IC components on one side with clear polarity markings.
• Ensure proper wiring density on the board.
• Avoid through-holes on patch pads.
• Ensure consistency in patch alignment and polarity marking.

2. Component Wiring Guidelines

• Avoid wiring within 1mm of the PCB edge and around mounting holes.
• Maintain specific widths for power and signal lines.
• Ensure proper dimensions for via holes and component pads.
• Radial arrangement for power and ground wires.
• Avoid looping signal wires.

3. Enhancing Anti-Interference and EMC

Strategies to improve anti-interference and electromagnetic compatibility in electronic product development:

• Pay attention to systems with high clock frequencies and fast bus cycles.
• Address systems with high-power drive circuits.
• Focus on systems with weak analog signal circuits.

Tips for reducing noise and interference:

• Opt for low-speed chips when possible.
• Use resistors in series to reduce edge transition rates.
• Provide damping for components like relays.
• Utilize clock generators meeting system requirements.
• Keep clock wires short and ground clock areas.

The Best Practices for PCB Layout

• Place the I/O drive circuit close to the edge of the printed board to minimize signal travel time.
• Filter incoming signals and those from high-noise areas to improve signal quality.
• Utilize serial terminal resistance to reduce signal reflection.
• Connect unused ends of MCD to high, ground, or define as output.
• Ensure integrated circuit ends meant for power supply ground are connected.
• Avoid leaving input terminals of unused gate circuits floating.
• Ground the positive input terminal of unused operational amplifiers and connect the negative input terminal to the output terminal.
• Prefer 45-fold lines over 90-fold lines on printed boards to reduce external emission and signal coupling.
• Divide the printed board based on frequency and current switching characteristics.
• Use single-point power supply and grounding for boards, ensuring thick power and ground lines.
• Keep clock, bus, and chip select signals away from I/O lines and connectors.
• Separate analog voltage input and reference voltage terminals from digital circuit signal lines.
• Unify digital and analog parts for A/D devices rather than crossing them.
• Ensure clock lines are perpendicular to I/O lines to minimize interference.
• Keep component pins and decoupling capacitor pins as short as possible.
• Use thick lines for key signals and add protective ground on both sides.
• Avoid routing wires under quartz crystals and noise-sensitive devices.
• Avoid forming current loops around low-frequency circuits in weak signal circuits.
• Minimize loop areas for any signal routing.
• Include one decoupling capacitor per IC and add high-frequency bypass capacitors near electrolytic capacitors.
• Opt for tantalum or polycooled capacitors over electrolytic ones for circuit charge and discharge energy storage.
• Ground the case of tubular capacitors on the PCB board.