What is Rogers 4350b?

Key Features of Rogers 4350b

Rogers 4350b offers several key features that make it an ideal choice for High-frequency PCB designs:

1. Low dielectric loss tangent (tan δ)
2. High thermal conductivity
3. Excellent dimensional stability
4. Tight thickness tolerance
5. Low moisture absorption
6. Flame retardant properties (UL 94 V-0 rated)

These attributes contribute to the material’s superior performance in RF and microwave applications, enabling the design of compact, high-reliability circuits.

Composition and Structure

Rogers 4350b is a ceramic-filled PTFE (polytetrafluoroethylene) composite laminate. The material consists of a PTFE matrix reinforced with a ceramic filler, typically silica or titanium dioxide. This combination provides a balance of electrical and mechanical properties.

The laminate is available in various thicknesses and copper cladding options to suit different design requirements. Standard copper foil thicknesses include 0.5 oz/ft² (18 μm), 1 oz/ft² (35 μm), and 2 oz/ft² (70 μm). The copper cladding can be electrodeposited (ED) or rolled annealed (RA) depending on the application needs.

Electrical Properties

One of the key advantages of Rogers 4350b is its excellent electrical performance at high frequencies. The material has a low Dielectric Constant (Dk) and a low loss tangent (tan δ), which minimize signal loss and distortion in RF and microwave circuits.

The typical electrical properties of Rogers 4350b at 10 GHz are:

• Dielectric Constant (Dk): 3.48 ± 0.05
• Dissipation Factor (tan δ): 0.0037

These values remain stable over a wide frequency range, making Rogers 4350b suitable for applications from 1 GHz to over 77 GHz.

Thermal Properties

Rogers 4350b exhibits excellent thermal stability and conductivity, which help to dissipate heat generated by high-power components and maintain consistent performance over a wide temperature range.

The key thermal properties of Rogers 4350b are:

• Thermal Conductivity: 0.62 W/m·K
• Coefficient of Thermal Expansion (CTE):
• X-Y plane: 24 ppm/°C
• Z-axis: 46 ppm/°C
• Glass Transition Temperature (Tg): >280°C
• Decomposition Temperature (Td): >500°C

These properties enable Rogers 4350b to withstand the thermal stresses encountered in demanding applications, such as high-power amplifiers, radar systems, and satellite communications.

Mechanical Properties

Rogers 4350b provides a robust mechanical structure that can withstand the rigors of manufacturing processes and operational environments. The material has high flexural strength and modulus, low water absorption, and excellent dimensional stability.

The key mechanical properties of Rogers 4350b are:

• Density: 2.1 g/cm³
• Water Absorption: 0.02%
• Flexural Strength:
• Machine Direction (MD): 16.7 MPa
• Cross Direction (CD): 14.2 MPa
• Flexural Modulus:
• Machine Direction (MD): 5.23 GPa
• Cross Direction (CD): 4.09 GPa
• Dimensional Stability (after thermal stress):
• X-Y plane: -0.05%
• Z-axis: -0.9%

These properties contribute to the material’s durability and reliability, ensuring consistent performance over the lifetime of the PCB.

Applications

Rogers 4350b is widely used in various RF and microwave applications that require high performance, reliability, and compact designs. Some common applications include:

1. Wireless communication systems (5G, LTE, Wi-Fi, Bluetooth)
2. Radar systems (automotive, aerospace, defense)
3. Satellite communications
4. GPS/GNSS receivers
5. High-speed digital circuits
6. Aerospace and defense electronics
7. Medical imaging and diagnostic equipment
8. Test and measurement equipment

The material’s low loss, high thermal stability, and excellent mechanical properties make it an ideal choice for these demanding applications.

PCB Fabrication and Assembly Considerations

When fabricating and assembling PCBs using Rogers 4350b, there are a few key considerations to ensure optimal performance and reliability:

1. Controlled impedance design: Rogers 4350b’s stable dielectric constant enables precise control of impedance in transmission lines and interconnects.

2. Hole wall preparation: Proper hole wall preparation, such as desmear and metallization, is crucial for reliable plated through-hole (PTH) connections.

3. Soldermask selection: Choose a soldermask with good adhesion and compatibility with the laminate to protect the circuit and prevent solder bridging.

4. Soldering profile: Use a suitable soldering profile that balances the need for proper reflow while minimizing thermal stress on the material.

5. Handling and storage: Store the laminate in a cool, dry place and handle it with care to prevent damage or contamination.

By following these guidelines and working closely with experienced PCB fabricators and assemblers, designers can leverage the full potential of Rogers 4350b in their high-frequency applications.

Comparison with Other High-Frequency Laminates

Rogers 4350b is one of several high-performance laminates available for RF and microwave applications. Some other popular materials include:

1. Rogers RO4000 series (RO4003C, RO4835)
2. Isola I-Tera MT40
3. Taconic RF-35
4. Arlon AD250

The table below compares some key properties of these materials:

While each material has its strengths, Rogers 4350b offers a balanced combination of low loss, high thermal conductivity, and mechanical stability, making it a versatile choice for many high-frequency applications.

Frequently Asked Questions (FAQ)

1. Q: What is the main difference between Rogers 4350b and FR-4?
   A: Rogers 4350b is a high-performance laminate designed for RF and microwave applications, offering lower dielectric loss, higher thermal conductivity, and better dimensional stability compared to standard FR-4 laminates.

2. Q: Can Rogers 4350b be used for multilayer PCBs?
   A: Yes, Rogers 4350b can be used in multilayer PCB constructions. However, special care must be taken during the fabrication process to ensure proper layer alignment, bonding, and drilling.

3. Q: Is Rogers 4350b suitable for high-power applications?
   A: Yes, Rogers 4350b’s high thermal conductivity and stability make it well-suited for high-power applications, such as power amplifiers and radar systems.

4. Q: What is the maximum operating frequency for Rogers 4350b?
   A: Rogers 4350b can be used for applications up to and beyond 77 GHz, making it suitable for a wide range of high-frequency designs.

5. Q: How does the cost of Rogers 4350b compare to other high-frequency laminates?
   A: Rogers 4350b is generally more expensive than standard FR-4 laminates due to its high-performance properties and specialized manufacturing process. However, its cost is competitive with other high-frequency laminates in its class.

Conclusion

Rogers 4350b is a high-performance laminate material that offers excellent electrical, thermal, and mechanical properties for demanding RF and microwave applications. Its low dielectric loss, high thermal conductivity, and dimensional stability make it an ideal choice for designs requiring superior signal integrity, power handling, and reliability.

By understanding the key features and properties of Rogers 4350b, designers can leverage its capabilities to create compact, high-performance PCBs for a wide range of applications, from wireless communications and radar systems to aerospace and defense electronics.

When working with Rogers 4350b, it is essential to partner with experienced PCB fabricators and assemblers who can provide the necessary expertise and capabilities to ensure optimal results. By following best practices in design, fabrication, and assembly, designers can unlock the full potential of this advanced material and achieve superior performance in their high-frequency applications.