Hybrid PCB RO4835 and 370HR Multilayer Circuits Immersion Gold

Introducing the RO4835 and 370HR Hybrid PCB.

This 6-layer rigid PCB leverages the unique capabilities of Rogers' RO4835 laminates and Isolar's 370HR laminates to deliver a best-of-both-worlds solution for demanding high-frequency applications.

The RO4835 laminates from Rogers Corporation are part of the company's family of high-frequency circuit materials. Offering enhanced stability at elevated temperatures, RO4835 provides low loss and cost-effective circuit fabrication using standard FR-4 processes. With a dielectric constant (Dk) of 3.48 ± 0.05 and a dissipation factor (Df) of 0.0037 at 10 GHz, RO4835 delivers excellent high-frequency performance.

Complementing the RO4835 layers are Isolar's 370HR laminates, which are engineered for the most demanding multilayer PCB applications. The 370HR material utilizes a patented 180°C Tg FR-4 multifunctional epoxy resin system that provides superior thermal performance, low coefficient of thermal expansion (CTE), and exceptional mechanical, chemical, and moisture resistance properties. With a Dk of 3.92 and a Df of 0.025 at 10 GHz, the 370HR laminates also offer solid high-frequency characteristics.

By combining the strengths of these two advanced laminate technologies, the hybrid PCB delivers an uncompromising solution that exceeds the capabilities of standard FR-4 materials. Let's take a closer look at some of the key features:

Exceptional Thermal and Mechanical Performance
One of the primary advantages of this hybrid approach is the ability to leverage the superior thermal and mechanical properties of the 370HR laminates. The 180°C glass transition temperature (Tg) of the 370HR material provides significantly better resistance to thermal stresses compared to conventional FR-4, which typically has a Tg around 135°C.

This enhanced thermal stability translates to improved reliability, especially in applications that see wide temperature swings or exposure to elevated heat levels. The low CTE of the 370HR laminates - just 13/14 ppm/°C on the X/Y-axis (pre-Tg) - also helps to minimize issues like delamination and board warpage that can plague high-reliability designs.

Additionally, the 370HR material's excellent chemical and moisture resistance properties make it highly suitable for harsh environments. It's no surprise that Isolar's 370HR laminates are a popular choice for mission-critical applications like defense and aerospace.

High-Frequency Performance with Cost-Effective Fabrication
While the 370HR laminates provide the thermal and mechanical backbone, the RO4835 materials contribute exceptional high-frequency capabilities. With a Dk of 3.48 and a Df of just 0.0037 at 10 GHz, the RO4835 layers offer extremely low signal loss - crucial for maximizing efficiency and fidelity in high-speed digital and RF circuits.

Importantly, the RO4835 laminates share similar electrical and mechanical properties with standard FR-4, allowing for cost-effective circuit fabrication using well-established manufacturing processes. This makes the hybrid PCB an attractive option for applications that demand leading-edge RF performance without the premium price tag associated with some specialized high-frequency materials.

The combination of low-loss RO4835 and high-performance 370HR layers also enables precise impedance control, with 50Ω and 100Ω single-ended traces implemented on the top copper layer. This level of design flexibility is critical for optimizing signal integrity in high-speed, high-frequency circuits.

Reliability and Quality Assurance
To ensure the hybrid PCB meets the stringent requirements of target applications, the designers have incorporated a variety of quality assurance measures. The boards are RoHS-compliant and UL 94 V-0 flammability rated, giving designers confidence in their environmental and safety credentials.

100% electrical testing is performed on every board, providing an extra layer of reliability assurance. And the use of Rogers' proprietary LoPro Reverse treated copper foil on the RO4835 layers helps to minimize insertion loss and further enhance signal integrity.

Pushing the Boundaries of High-Frequency PCB Design
By thoughtfully combining the strengths of Rogers' RO4835 and Isolar's 370HR laminate technologies, this hybrid PCB raises the bar for high-frequency, high-reliability circuit design. The superior thermal and mechanical properties, coupled with excellent high-frequency performance and cost-effective fabrication, make it an ideal solution for a wide range of demanding applications.

From automotive radar and sensors to phased-array antennas and power amplifiers, this hybrid PCB demonstrates how innovative material choices can unlock new possibilities in electronic system design. As the relentless march of technology continues, solutions like this will undoubtedly play a crucial role in pushing the boundaries of what's achievable.