1 / 2
Famous High Frequency PCBs from China Suppliers: Solutions for Signal Loss, Crosstalk, EMI, and Impedance Mismatches Manufacturer, Companies
Product Description
What is High Frequency PCB?
High-frequency PCBs are special printed circuit boards specifically designed to handle high-frequency signals (typically referring to frequencies above 500MHz or digital signal rise times less than 1 nanosecond).
Main Application Fields
- Communication infrastructure: Antennas, power amplifiers, filters, and low-noise amplifiers for 5G/6G base stations.
- Automotive electronics: Millimeter-wave radar, advanced driver assistance systems, in-vehicle satellite communication.
- Aerospace and national defense: Radar systems, electronic warfare equipment, satellite communication terminals, seeker heads.
- High-speed computing and data communication: High-speed server/router backplanes, optical modules, 400G/800G switches.
- Test and measurement instruments: Network analyzers, high-frequency oscilloscopes, signal sources.
Core Material Selection Principles
High-frequency signals are easily affected by the dielectric properties and losses of the substrate. Material selection is the core of high-frequency PCBs.
| Material Type | Key Parameters | Recommended Material / Specification | Applicable Scene |
|---|---|---|---|
| Base material |
Dielectric constant (Dk) Dielectric loss tangent of Angle (Df) Coefficient of thermal expansion (CTE) |
High-frequency dedicated substrate – PTFE (polytetrafluoroethylene, Dk=2.1–2.6, Df≤0.0009) – Rogers series (e.g. RO4350B, Dk=3.48, Df=0.0037) – Modified epoxy resin (FR-4 high-frequency version, Dk=3.8–4.2, Df≤0.01) |
PTFE/Rogers: Millimeter wave, radar, 5G base station High-frequency FR-4: Consumer electronics (mobile phones, routers) |
| Copper foil | Surface roughness | Low profile copper foil (LP) / very low profile copper foil (VLP), roughness ≤1.0μm | Reduce the transmission loss of signals on the surface of copper foil (skin effect) |
| Solder mask layer | Dielectric loss | High-frequency special solder mask oil (Df≤0.01) | Avoid increasing signal attenuation by the solder mask layer |
Key Design Points
Precise Impedance Control
- The core of high-frequency PCBs needs to control the characteristic impedance (e.g. 50Ω single-ended, 100Ω differential), with deviation ≤±5% (±10% for ordinary PCBs).
- Impedance calculation: Combine base material Dk, plate thickness, line width/spacing, and copper foil thickness. Simulate using professional software (e.g. Polar SI9000).
- Example: RO4350B substrate (thickness 0.254mm), single-ended impedance of 50Ω corresponds to a line width of approximately 0.8mm.
- Impedance compensation: Considering etching side-etching and solder mask coverage, reserve a compensation amount of ±0.02mm for the line width.
Routing Optimization
- Traces should be as short and straight as possible, avoiding right angles or acute angles (prone to reflection at high frequencies); fillet radius should be no less than 0.5mm.
- Differential traces should be of equal length and spacing (length difference ≤5mil), with ground wrapping treatment (distance between ground wire and differential wire ≤2× line width) to reduce EMI interference.
- Skin effect response: High-frequency current is concentrated on the surface of the copper foil. Silver-plated copper foil can be used (to reduce surface resistance), or traces can be widened (to reduce current density).
Grounding and Shielding Design
- Complete ground layer: High-frequency PCBs need a complete GND Plane — avoid ground layer segmentation and reduce the signal return path length. Distance between ground layer and signal layer should be no more than 0.2mm.
- Shielding measures: For sensitive high-frequency areas (e.g. RF chips), metal shielding covers can be designed. Grounding must be reliable (multiple grounding points, spacing ≤λ/20).
- High-frequency devices (e.g. power amplifiers) generate significant heat — design heat dissipation pads and metallized via arrays (via diameter ≥0.3mm, spacing ≤1mm).
- Device packaging: Prioritize miniaturized, low-parasitic parameter packaging (e.g. QFN, LGA) to reduce signal reflection introduced by packaging.
Manufacturing Process Control
Precision Control
• Line width/line spacing tolerance: ≤±0.01mm (±0.02mm for ordinary PCBs), using high-precision laser direct imaging (LDI) technology to replace traditional film exposure.
• Lamination accuracy: Interlayer alignment deviation ≤0.02mm, avoiding impedance offset. Bonding temperature and pressure must match the base material characteristics (e.g. PTFE requires high-temperature and high-pressure bonding).
Loss Control
• Etching process: Micro-etching technology is adopted to reduce the surface roughness of the copper foil and avoid increasing transmission loss. Lateral erosion is ≤0.01mm.
• Surface treatment: Electroless nickel gold plating (ENIG) or silver plating is preferred to avoid OSP (organic film increases contact resistance). Gold layer thickness should be ≤0.1μm — too thick will easily increase loss.
Core Summary
The core of high-frequency PCBs lies in "reducing signal loss, ensuring precise impedance, and minimizing electromagnetic interference". It requires full-process control from low-loss substrate selection → precise impedance design → high-precision manufacturing. For different high-frequency scenarios (e.g. 1GHz vs 60GHz), the substrate and process parameters need to be adjusted specifically.
Send Inquiry
Frequently Asked Questions (FAQ)
Q
What frequency range qualifies a PCB as a "high-frequency PCB"?
A PCB is generally classified as a high-frequency PCB when it operates at frequencies above 500MHz, or when the digital signal rise time is less than 1 nanosecond. Applications such as 5G base stations, millimeter-wave radar, and satellite communications all fall within this category.
Q
What makes Rogers materials better than standard FR-4 for high-frequency applications?
Rogers materials (e.g. RO4350B) offer a significantly lower dielectric loss tangent (Df=0.0037) and a more stable dielectric constant (Dk=3.48) compared to standard FR-4 (Df up to 0.02). This results in lower signal attenuation, more consistent impedance, and better performance at microwave and millimeter-wave frequencies.
Q
Why is impedance control so critical in high-frequency PCB design?
At high frequencies, any impedance mismatch along signal traces causes reflections that degrade signal integrity and increase losses. High-frequency PCBs require characteristic impedance control within ±5% tolerance (e.g. 50Ω single-ended, 100Ω differential) to ensure reliable signal transmission and minimize return loss.
Q
What surface finish is recommended for high-frequency PCBs and why?
Electroless Nickel Immersion Gold (ENIG) or silver plating is recommended. OSP (Organic Solderability Preservative) is generally avoided because it can increase contact resistance. The gold layer thickness should be kept at ≤0.1μm — excessive thickness can increase signal loss at high frequencies due to the skin effect.
Q
How does the skin effect impact high-frequency PCB trace design?
At high frequencies, electrical current concentrates on the outer surface of the copper conductor rather than flowing through the entire cross-section. This increases effective resistance and signal loss. To mitigate this, designers use low-profile copper foil (surface roughness ≤1.0μm), silver-plated traces, or wider trace widths to reduce current density.
Q
Can standard PCB manufacturers produce high-frequency PCBs?
Not all standard PCB manufacturers are equipped for high-frequency production. High-frequency PCBs require specialized capabilities including laser direct imaging (LDI) for tight line width tolerances (≤±0.01mm), high-temperature/high-pressure lamination for PTFE substrates, micro-etching processes, and strict impedance testing. It is essential to work with a manufacturer experienced in high-frequency and RF/microwave board fabrication.
