An RF PCB (Radio Frequency Printed Circuit Board) is a specialized circuit board designed to handle high-frequency signals (typically above 300 MHz) in wireless communication systems, including smartphones, radar systems, satellite transceivers, and IoT devices. Unlike standard PCBs, RF PCBs require precise design and material selection to minimize signal loss, maintain impedance matching, and reduce electromagnetic interference (EMI), ensuring reliable transmission and reception of RF signals.

Material selection is critical for RF PCBs. Substrates with low dielectric constant (Dk) and low dissipation factor (Df) are preferred to minimize signal attenuation. Common materials include PTFE (Teflon)-based substrates (e.g., Rogers 4350) with Dk values around 3.48, which offer excellent high-frequency performance but are costly. For lower-frequency applications (300 MHz–2 GHz), FR-4 with modified epoxy resins (Dk 4.2–4.7) is used as a cost-effective alternative, though it has higher loss at frequencies above 10 GHz. The substrate thickness (typically 0.2–1.6 mm) and copper weight (1–2 oz/ft²) are chosen to control characteristic impedance, often 50 Ω for RF systems, matching the impedance of antennas and connectors.

Layout design for RF PCBs focuses on signal integrity. RF traces are routed as microstrip or stripline structures to maintain controlled impedance, with width and spacing calculated based on substrate thickness and Dk. Sharp corners in traces are avoided to prevent signal reflection; instead, rounded bends (with radius ≥3x trace width) are used. Ground planes are essential, covering unused areas to provide a low-impedance return path and shield RF signals from noise. Separate ground planes for analog and digital components reduce crosstalk, a critical issue in mixed-signal RF systems.

EMI mitigation is another key consideration. Components like RF filters (SAW or BAW filters), inductors, and capacitors are placed close to RF ICs to minimize parasitic effects. Shielding cans (metal enclosures) are often used to isolate sensitive RF circuits from other components, preventing interference. Vias are strategically placed to connect ground planes, with sufficient density to reduce ground bounce and improve shielding effectiveness.

Manufacturing tolerances for RF PCBs are tight, with trace width and spacing variations controlled to ±0.025 mm to maintain impedance accuracy. Plating uniformity (especially for via walls) ensures consistent conductivity, while surface finishes like immersion silver or electroless nickel immersion gold (ENIG) provide excellent solderability and RF performance.

 RF PCBs require careful material selection, precise layout, and strict manufacturing controls to handle high-frequency signals efficiently, making them essential for reliable wireless communication in modern electronic systems.