RO4350B and High Tg FR-4 4-Layer Hybrid PCB with Immersion Gold (ENIG) in Microstrip and Stripline Circuits

4-Layer Hybrid PCB with RO4350B and High Tg FR-4

The 4-Layer Hybrid PCB combining Rogers RO4350B and High Tg170°C FR-4 materials is a high-performance circuit board designed for applications requiring excellent high-frequency performance, thermal stability, and durability. With a 10mil dielectric thickness of RO4350B and 1.55mm finished board thickness, this PCB is optimized for RF and microwave circuits, offering precise impedance control and superior mechanical stability.

1. PCB Specifications

2. PCB Stackup

The 4-layer stackup combines Rogers RO4350B and High Tg FR-4, leveraging the strengths of both materials for high-frequency performance and mechanical stability.

3. Material Overview: RO4350B

Rogers RO4350B is a hydrocarbon/ceramic laminate reinforced with woven glass, offering the high-frequency performance of PTFE but with the manufacturability of traditional FR-4 materials.

Key Features of RO4350B:

• Dielectric Constant (Dk): 3.48 ± 0.05 at 10GHz
• Dissipation Factor (Df): 0.0037 at 10GHz
• Thermal Conductivity: 0.69 W/m/°K
• Tg: >280°C (high thermal stability)
• CTE (Coefficient of Thermal Expansion): Low Z-axis CTE of 32ppm/°C ensures reliable plated through-hole quality.
• Moisture Absorption: Just 0.06%, ideal for humid environments.
• RO4350B offers consistent electrical performance, excellent dimensional stability, and is UL 94 V-0 rated for flame retardancy. It is easy to process using standard PCB manufacturing techniques, reducing production costs compared to PTFE materials.

4. Benefits of the Hybrid Design

The combination of RO4350B and High Tg FR-4 materials provides a versatile and high-performance PCB solution:

• Precise Impedance Control: The RO4350B dielectric ensures consistent impedance at high frequencies, essential for RF and microwave circuits.
• Thermal Stability: With a Tg of over 280°C, RO4350B maintains stability during high-temperature operations, while High Tg FR-4 provides additional mechanical support.
• Low Signal Loss: The low dissipation factor (0.0037) minimizes signal degradation, ensuring superior performance for high-frequency applications.
• Cost Efficiency: The hybrid design leverages the affordability of FR-4 while utilizing RO4350B only where needed for high-frequency performance.
• Reliability: Low Z-axis expansion ensures plated-through holes remain robust even in severe thermal shock conditions.

5. Applications

This hybrid PCB is ideal for a wide range of high-frequency and RF applications, including:

Telecommunications: Millimeter-wave circuits, antennas, and RF modules.

Aerospace and Defense: Radar systems, guidance systems, and satellite communications.

Networking: Point-to-point digital radio antennas and broadband equipment.

Test Equipment: Microstrip and stripline circuits for RF and microwave testing.

Commercial Electronics: Wireless communication devices and airline broadband antennas.

6. Why Use a Hybrid PCB?

A hybrid PCB combines materials like RO4350B and FR-4 to achieve high performance at a fraction of the cost of pure high-frequency laminates. While RO4350B ensures electrical stability and signal integrity, FR-4 enhances mechanical durability and reduces overall costs. Additionally, the ability to process both materials with standard PCB manufacturing techniques makes hybrid designs highly practical for mass production.

Conclusion

The 4-layer hybrid PCB with RO4350B and High Tg FR-4 materials is a robust, high-performance solution for RF and microwave applications. Its precise impedance control, low signal loss, and excellent thermal stability make it ideal for industries like telecommunications, aerospace, and networking. By combining the best properties of RO4350B and FR-4, this hybrid PCB delivers unparalleled performance at a competitive cost, ensuring reliability in even the most demanding environments.