Rigid printed circuit boards (PCBs) in complex electronic systems are susceptible to electromagnetic interference (EMI) and radio frequency interference (RFI), which can degrade signal integrity and cause system malfunctions. Effective anti-interference wiring techniques are critical to minimize noise coupling and ensure reliable operation, especially in high-speed or high-power applications.

Trace routing strategies are foundational for reducing interference. Separating analog and digital traces prevents cross-talk, as digital signals (with fast switching edges) generate EMI that can disrupt sensitive analog circuits. Designers use physical separation (≥5 mm gap) or ground planes as barriers between these trace types. For high-speed signals (≥100 MHz), controlled-impedance routing is essential: traces are designed with specific widths (e.g., 0.2-0.3 mm for 50Ω impedance on FR-4) and spacing from ground planes to maintain signal integrity and reduce radiation. Additionally, keeping high-speed traces short and straight minimizes their length as antennas, while avoiding sharp corners (using 45° angles or curves) reduces signal reflection and EMI emission.

Ground plane design is another key technique. A solid ground plane (covering most of the PCB’s area) provides a low-impedance return path for signals, reducing loop area and EMI. In multi-layer PCBs, placing ground planes adjacent to signal layers creates a  effect, shielding signals from external interference. For mixed-signal boards, split ground planes (analog and digital) connected at a single point (star grounding) prevent ground loops—circulating currents that induce noise. However, split planes must be used cautiously to avoid creating isolated "islands" that trap noise.

Power distribution optimization reduces noise in power lines. Using wide, short power traces (or power planes in multi-layer boards) minimizes resistance and inductance, preventing voltage drops and noise propagation. Decoupling capacitors (0.1 μF ceramic capacitors placed near IC power pins) filter high-frequency noise, providing a local energy reservoir for fast-switching components. For high-power circuits, adding ferrite beads in power lines attenuates high-frequency noise without affecting DC current flow.

Shielding and component placement further enhance anti-interference performance. Sensitive components (e.g., sensors, oscillators) are placed away from noise sources (e.g., motors, transformers) to minimize coupling. Metal shields (connected to ground) around noisy components or sensitive circuits block EMI radiation. Additionally, orienting components to align with trace directions reduces cross-talk—for example, placing ICs so that their I/O pins align with signal traces to avoid perpendicular crossings, which increase capacitance between traces.

anti-interference wiring in rigid PCBs requires a holistic approach combining trace routing, ground/power plane design, component placement, and shielding. These techniques ensure that electronic systems operate reliably in noisy environments, making them essential for applications like industrial controls, medical devices, and communication equipment.