Rogers RO4350B is a popular high frequency circuit board laminate designed for performance-demanding wireless and radar applications from 500 MHz to 77 GHz. This guide provides a detailed overview of RO4350B material properties, key datasheet parameters, design considerations, and dielectric constant specifications that engineers need to know when designing with this high speed PCB substrate.
Rogers RO4350B Overview
RO4350B is a ceramic-filled PTFE composite laminate reinforced with woven glass fabric. It was engineered by Rogers Corporation specifically to meet the needs of high frequency and high data rate PCB applications.
Some key attributes that make RO4350B suitable for RF and microwave boards include:
- Stable dielectric constant of 3.48
- Low loss tangent of 0.0037
- Tight εr and Dk tolerances
- Low Z-axis CTE for reliability
- High thermal conductivity
- Lead-free compatible processing
- Excellent mechanical strength
- Good chemical resistance
- UL 94 V-0 flame rating
RO4350B achieves an optimal balance of electrical, thermal, and mechanical properties for precision RF circuit fabrication. Let’s look closer at the RO4350B datasheet specs.
RO4350B Datasheet Parameters
Here are some of the most important characteristics and parameters from the Rogers RO4350B datasheet for PCB design and fabrication:
| Parameter | Value |
|---|---|
| Dielectric Constant (εr) | 3.48 |
| Loss Tangent | 0.0037 |
| Dielectric Tolerance | ±0.05 |
| Dk Tolerance | ±0.002 (up to 10 GHz) |
| Z-Axis CTE | 41 ppm/°C |
| XY CTE | 17 ppm/°C |
| Tg | 280°C |
| Td | 340°C |
| Dissipation Factor | 0.0019 (10 GHz) |
| Breakdown Voltage | 1.5 kV/mil |
| Thermal Conductivity | 0.69 W/m/K |
| Moisture Absorption | <0.2% |
| Copper Peel Strength | 1.3 lb/in |
| Surface Resistivity | 1.5 x 10^13 ohm |
| Volume Resistivity | 1 x 10^15 ohm-cm |
| Lead-Free Process | 260°C Max |
These parameters highlight why RO4350B is advantageous for controlled impedance RF boards. Let’s look deeper at some key material properties.
Dielectric Constant and Loss Tangent
The dielectric constant (Dk) indicates how much capacitance a material generates relative to air. Loss tangent quantifies signal loss.
RO4350B provides a stable Dk of 3.48 from 500MHz to over 40GHz with minimal variation versus frequency. This allows engineers to design controlled impedance transmission lines and matching networks that work consistently across the entire frequency range with excellent loss characteristics.
The low loss tangent of 0.0037 ensures minimal signal attenuation as RF energy propagates through the board. It remains under 0.004 up to 77GHz.
Tight Dielectric Tolerances
In addition to stable Dk over frequency, RO4350B also provides tight lot-to-lot dielectric constant tolerances of ±0.05. The variance in Dk from panel to panel is very consistent.
This makes it easier for designers to account for material variations during layout and ensures stable performance across fabricated boards. Tighter εr tolerance provides more margin for meeting impedance targets.
Low Z-Axis CTE
RO4350B has a low coefficient of thermal expansion (CTE) along the z-axis of 41 ppm/°C. This provides reliability by minimizing dimensional changes and movement of dielectric layers during thermal cycling.
High z-axis CTE can lead to copper cracking on inner signal layers which limits board lifetimes. RO4350B resists plating separations and electrical opens caused by excessive z-axis expansion and contraction.
High Thermal Conductivity
With a thermal conductivity of 0.69 W/m/K, RO4350B provides good heat spreading in the dielectric layers to prevent component hot spots. This helps maintain signal fidelity and component lifetime at high RF power levels.
Lead-Free Compatibility
RO4350B is compatible with lead-free soldering processes up to 260°C, meeting the processing needs for modern electronics assembly and manufacturing.
The stable dielectric and low expansion minimizes electrical and physical changes even through multiple reflow cycles at high temperatures.
Excellent Mechanical Strength
The woven glass fabric reinforcement in RO4350B gives the laminate excellent dimensional stability and flexural strength while maintaining low CTE and loss. It also resists microcracking or fracturing during fabrication and assembly handling.
RO4350B Material Grades
Rogers offers several grades of RO4350B for applications ranging from low cost commercial usage to high reliability aerospace and defense:
- RO4350B High Reliability (HR) – For mission-critical aerospace apps
- RO4350B High Frequency (VF) – For 77GHz mmWave designs
- RO4350B Low Dk – Minimizes loss tangent
- RO4350B Bondply – Adhesiveless multilayers
- RT/duroid 5870 – Low cost version
Consult Rogers to determine the optimal RO4350B variant for your specific RF performance, cost and reliability requirements.
RO4350B Design Considerations
Here are some key design practices engineers should follow when working with RO4350B material:
- Use impedance calculators like Saturn PCB Toolkit to determine stripline dimensions
- Account for frequency-dependent Dk in models
- Include pad and anti-pad shapes in impedance calculations
- Model discontinuities like stubs, vias, and bends
- Use teardrop pads on vias for reliability
- Minimize dielectrically exposed copper for lowest loss
- Watch for resin starvation, voids and thickness variations
- Limit glass weave skew to under 5 degrees
- Allow for Dk and etch tolerances in impedance budgets
Paying attention to these factors when designing on RO4350B ensures stable electrical performance that matches simulations and measurements.
Typical RO4350B PCB Applications
Some common applications leveraging Rogers RO4350B laminate include:
- 5G NR base stations and user equipment
- Radio transceivers and receivers
- Satellite communication systems
- Wireless infrastructure
- Radar and automotive sensors
- Test and measurement equipment
- Aerospace and defense electronics
- High speed data links and backplanes
- Medical diagnostic devices
Its stable dielectric properties and low loss make RO4350B a top choice for reliable wireless and high frequency boards.
Comparing RO4350B to Other Popular RF Laminates
| Parameter | RO4350B | RO4835 | RO4003C | Arlon 85N |
|---|---|---|---|---|
| Dielectric Constant | 3.48 | 3.38 | 3.55 | 3.5 |
| Loss Tangent | 0.0037 | 0.0031 | 0.0027 | 0.0025 |
| Dk Tolerance | ±0.05 | ±0.05 | ±0.079 | ±0.05 |
| Z-Axis CTE | 41 ppm/°C | 52 ppm/°C | 60 ppm/°C | 20 ppm/°C |
| Lead-Free Process | 260°C | 288°C | 260°C | 280°C |
| Cost | Medium | Low | Medium | High |
RO4350B provides the best overall balance at moderate cost. But alternative laminates may be optimal for specific applications.
Availability of RO4350B Material
Rogers Corporation partners with authorized laminators worldwide to stock various thicknesses of RO4350B cores and prepregs. Common offerings include:
- 0.005′′ – 0.062′′ dielectric thicknesses
- Prepregs with 106-211 glass styles
- Copper foil bonds from 0.5 to 3 oz.
- Isola 370HR resin system
- Panels and cut sheets
- Quick-turn lead times
Work with your PCB manufacturer to ensure availability and consistent supply of RO4350B material tailored to your board thickness and copper weight needs.
FQA about Rogers RO4350B Laminates
What is the z-axis CTE of RO4350B?
RO4350B has a low z-axis CTE of 41 ppm/°C which minimizes dimensional changes through temperature excursions to avoid reliability risks.
Can Rogers RO4350B be used at frequencies above 10 GHz?
Yes, RO4350B provides stable dielectric performance up to at least 40 GHz. The VF version extends the upper frequency range to 77GHz and beyond.
Does Rogers RO4350B meet UL flammability ratings?
RO4350B achieves a UL 94 V-0 rating for flame resistance meeting safety requirements for consumer and industrial electronics.
What is the breakdown voltage of Rogers RO4350B?
RO4350B has a high breakdown voltage of 15 kV/mil minimizing risk of electrical punch-through in thin dielectric layers.
Can Rogers RO4350B laminates withstand lead-free soldering?
Yes, RO4350B remains stable through lead-free reflow profiles up to 260°C and multiple soldering cycles.
Conclusion
Rogers RO4350B circuit board laminate provides an ideal microwave substrate solution for precision RF circuits up to 77GHz needing stable dielectric properties and low loss. Its tight tolerances, high thermal conductivity, lead-free process capability, and strong mechanical properties make RO4350B a versatile high frequency PCB material. Careful modeling of impedances and discontinuities when designing on RO4350B results in repeatable RF performance across fabricated boards. For wireless systems requiring precision electrical properties at microwave frequencies, RO4350B delivers.
