Specialized solutions for signals from 500 MHz to 100 GHz. Engineered for minimal loss, precise impedance, and peak RF performance.
In the era of 5G, IoT, and advanced radar systems, standard FR4 materials often fail to meet the rigorous demands of high-frequency signal transmission. High-Frequency PCBs are specifically designed to manage electromagnetic challenges, ensuring signal integrity where every decibel of loss counts.
To achieve reliable transmission in the GHz range, materials must exhibit stability across thermal and environmental changes:
Stable Dk (εr)
Low and stable Dielectric Constant ensures consistent signal velocity and minimizes phase distortion.
Ultra-Low Df (Tan δ)
Dissipation factor below 0.003 is essential to prevent signal energy from converting into heat.
Matched CTE
Coefficient of Thermal Expansion matched to copper to ensure reliability during thermal cycling.
Moisture Resistance
Water absorption <0.02% to prevent Dk shifts in humid environments like outdoor 5G stations.
1. Precision Routing Guidelines
- Avoid Sharp Corners: Use smooth curves or 45° miters. 90° corners create parasitic capacitance, causing impedance discontinuities.
- Trace Geometry: Maintain consistent width. For HF, Microstrip (outer layer) or Stripline (inner layer) configurations must be calculated with precision.
- Via Minimization: Every via is a capacitive load (~0.5pF). Use back-drilling to remove "via stubs" which act as resonant antennas at high frequencies.
2. EMI & Crosstalk Suppression
- 3W Rule: Keep spacing between traces at least 3x the trace width to reduce mutual inductance.
- Ground Stitching: Use via stitching around RF traces to create a Faraday cage effect, isolating sensitive signals.
- 20H Rule: Ensure the power plane is smaller than the ground plane by 20x the dielectric thickness to suppress edge radiation.
Rogers Corporation laminates are the industry benchmark for microwave and mmWave designs. They provide significantly lower insertion loss compared to standard FR4.
| Material Series | Dk (@10 GHz) | Df (@10 GHz) | Ideal Application |
|---|---|---|---|
| Rogers RO4003C | 3.38 | 0.0027 | RF Identification (RFID), LNBs, Small Cells |
| Rogers RO4350B | 3.48 | 0.0037 | Cellular Base Station Antennas, Power Amplifiers |
| Rogers RO3003 | 3.00 | 0.0010 | 77 GHz Automotive Radar, ADAS Systems |
| RT/duroid 5880 | 2.20 | 0.0009 | Aerospace, Military Radar, Point-to-Point Digital Antennas |
Focuses on Analog/RF signals. Priority is Insertion Loss and Frequency-Domain stability. Common in Antennas and SATCOM.
Focuses on Digital signals with fast rise/fall times. Priority is Timing, Jitter, and Time-Domain integrity. Common in CPU/Memory boards.
What should you include in your PCB stack-up?
PCB Stack-Up: Plan, Design, and Manufacture | Sierra Circuits
At PCBPath, we integrate advanced LDI imaging and precise etching controls to ensure your HF designs perform as simulated.
| Feature | Technical Capability |
|---|---|
| Supported Materials | Rogers (Full Range), Arlon, Taconic, Isola (High-speed/Low-loss) |
| Precision Impedance | Controlled to ±5% (Standard is ±10%) |
| Hybrid Stackup | FR4 + Rogers Hybrid (Cost-effective solution for RF designs) |
| Min. Track/Spacing | Up to 2 mil (0.05 mm) for high-density RF layouts |
| Finished Copper | 0.5 oz to 13 oz (Heavy copper for power RF) |
| Surface Finishing | ENEPIG / Immersion Silver (Best for skin effect in HF) |
| Via Processing | Back-drilling, Blind/Buried Vias, Resin Filled & Capped |
| Quality Control | TDR Testing (Impedance), 100% AOI, Flying Probe |
