Core Principles and Practical Tips for PCB Routing

1. Prioritize Manual Routing

• After component placement, use auto-routing to check the "completion rate": if it’s below 85%, your component layout needs adjustment;
• Identify routing bottlenecks: use auto-routing to quICkly locate potential obstacles at critical connection points;
• Inspiration reference: when stuck on routing ideas, use auto-routing to generate a preliminary plan as a reference.

2. Clarify Manufacturer’s Process Specifications in Advance

• Minimum line width and spacing requirements;
• Maximum supported PCB layer count;
• Manufacturing tolerances for pads and vias.

3. Match Trace Width to Current Requirements

• Calculate minimum line width: Determine the minimum width based on current (combined with copper thickness and ambient temperature) to avoid overheating from excessive current;
• Widen traces when space allows: If PCB space is sufficient, use a width larger than the minimum to enhance thermal management;
• Advantage of outer-layer traces: Outer-layer traces directly contact air, so they have higher heat exchange efficiency and can be slightly narrowed for the same current.

4. Maintain Safe Spacing Between Traces and Pads

• The gap between adjacent traces/pads should not be smaller than the manufacturer’s minimum line spacing;
• Gaps for sensitive signals (e.g., high-voltage, high-frequency) should be enlarged by 20-30% to prevent creepage or crosstalk.

5. Strategically Plan Component Placement

• Separate heat-sensitive and heat-generating components: Keep heat-sensitive components (e.g., electrolytic capacitors) away from heat sources (e.g., Diodes, inductors);
• Prioritize multi-pin components: Components like BGAs or QFPs occupy large space and require early layout planning;
• Unify component orientation: Align similar components (e.g., resistors, capacitors) in the same direction for easier soldering and maintenance;
• Physical pre-verification: If components are already procured, print a 1:1 layout to check if their physical dimensions fit.

6. Isolate Analog and Digital Traces

• Avoid parallel routing of high-frequency digital traces (e.g., data buses) with analog traces to prevent capacitive coupling;
• If PCB space is limited, separate analog and digital areas with a ground plane to block interference paths.

7. Design the Ground Plane Properly

• A full ground plane provides a unified voltage reference for all signals, avoiding resistance/voltage drop differences from scattered grounding;
• In multi-layer boards, place the ground and power planes in inner layers and keep them symmetric to enhance noise immunity and prevent PCB warping;
• Placing a ground plane under signal traces reduces trace impedance and suppresses crosstalk.

8. Reserve Safe Space Around Mounting Holes

• Reserve at least 1mm of empty space beyond the physical size of the mounting hole;
• Do not rely on solder mask as the only insulator—spatial isolation is necessary to avoid electrical shock risks.

9. Alternate Trace Directions Between Layers

• If one layer uses primarily horizontal traces, the adjacent layer should use vertical traces;
• Short, straight traces are preferred—avoid excessive path lengthening when routing around obstacles.

10. Techniques to Suppress Capacitive Coupling

• Assign dedicated layers to power and analog signal traces to avoid overlapping with ground planes;
• Keep decoupling capacitor traces as short as possible and place them close to component power terminals to compensate for component capacitive loads;
• Shorten long parallel trace segments or insert ground vias between them to block coupling paths.

11. Optimize Thermal Vias and Thermal Pads

• Add thermal pads under through-hole components to simplify soldering and improve heat dissipation;
• Place multiple thermal vias under power components (e.g., ICs) to transfer heat from inner layers to outer layers or heat sinks;
• Thermal vias should serve both "electrical connection" and "heat conduction"—use large diameters (e.g., 0.5mm) and dense arrangements.

12. Widen Power and Ground Traces

• Their width should be significantly larger than signal traces (common rule: power/ground width ≥ 0.040 inches, signal trace width ≥ 0.025 inches);
• Wider power/ground traces reduce overcurrent risks and are easier to identify visually, minimizing wiring errors;
• For high-current power supplies, replace traces with copper pours to further enhance current-carrying capacity.

13. Use the Silkscreen Layer Efficiently

• Avoid excessive text that wastes space—there’s no need to label minor parameters like resistor values;
• Use moderate text size (≥1.27mm recommended) to ensure clarity when printed;
• Do not print text on exposed copper pads, as ink can block solder flow and cause cold solder joints.

14. Avoid 90° Trace Corners

• Impaired high-frequency signal integrity: Right angles create impedance discontinuities, increasing crosstalk, radiation, and signal reflection;
• Manufacturing risks: 90° outer corners are prone to over-etching, leading to narrowed traces or short circuits.