Hybrid PCB RO3003 bonded by FastRise-28 Prepreg

Rogers RO3003 is a high-frequency circuit material designed for commercial microwave and RF applications. It is a ceramic-filled PTFE composite that offers exceptional electrical and mechanical stability at competitive prices. The material exhibits consistent mechanical properties, allowing designers to develop multilayer board designs without encountering warping or reliability issues.

The coefficient of thermal expansion (CTE) of RO3003 in the X and Y axes is 17 ppm/°C, which is matched to that of copper. This provides excellent dimensional stability, with typical etch shrinkage of less than 0.5 mils per inch after etch and bake. The Z-axis CTE is 24 ppm/°C, which ensures exceptional plated through-hole reliability, even in severe environments.

Typical applications for RO3003 include:

1. Automotive radar

2. Cellular telecommunications systems

3. Datalink on cable systems

4. Direct broadcast satellites

5. Global positioning satellite antennas

6. Patch antennas for wireless communications

7. Power amplifiers and antennas

8. Power backplanes

9. Remote meter readers

Taconic's FastRise-28 is a semi-solidified sheet specially designed for high-speed digital signal transmission and millimeter-wave RF multilayer printed board manufacturing. It is matched with other Taconic microwave substrate materials to enable the fabrication of multilayer microwave printed circuit boards.

FastRise-28 can meet the design requirements for stripline structures with low dielectric loss, and its thermosetting properties allow it to meet the design requirements for multiple lamination cycles. The material contains a large number of ceramic powder fillers, which provides excellent dimensional stability.

It is recommended to refrigerate FastRise-28 prior to lamination, as it can be quite tacky, especially for freshly manufactured material. The recommended press temperature for lamination is 215.5°C, which is within the capabilities of most board houses.

An example of an RF PCB built on a Rogers RO3003 core and bonded using FastRise-28 is provided, with a 6-layer stack-up and 1oz copper on each layer, resulting in a 1.2mm thick board with immersion gold plated pads and 2+N+2 steps blind vias from layer 1 to layer 4.

When choosing a hybrid PCB design, there are several key factors to consider:

1. Application requirements:

- Determine the specific requirements of your application, such as operating frequency, power handling, signal integrity, and environmental conditions.

- This will help you select the appropriate materials and layer stack-up for your PCB.

2. Layer count and stack-up:

- Decide on the number of layers needed based on your circuit complexity and routing requirements.

- Ensure the layer stack-up is designed to optimize signal integrity, power distribution, and thermal management.

3. Material selection:

- Choose materials that meet the electrical, mechanical, and thermal requirements of your application.

- Common materials used in hybrid PCBs include PTFE, ceramic-filled PTFE, and high-frequency laminates like Rogers RO3003.

- Consider the dielectric constant, loss tangent, coefficient of thermal expansion, and other relevant properties.

4. Impedance control:

- Maintain consistent and controlled impedance throughout the design, especially for high-speed or high-frequency signals.

- Use appropriate trace widths, layer spacing, and dielectric materials to achieve the desired impedance.

5. Thermal management:

- Ensure effective heat dissipation, especially for high-power components or circuits.

- Consider using thermal vias, copper pours, or other thermal management techniques.

6. Mechanical considerations:

- Evaluate the mechanical properties of the materials, such as flexibility, rigidity, and dimensional stability.

- Ensure the PCB can withstand any physical stresses or environmental conditions it may encounter.

7. Manufacturing feasibility:

- Consult with your PCB fabricator to ensure the design is manufacturable and aligns with their capabilities.

- Consider factors like minimum feature sizes, copper thickness, and via plating requirements.

8. Cost and availability:

- Evaluate the cost-effectiveness of the materials and manufacturing process.

- Ensure the chosen materials and components are readily available and can be delivered within your required timeframe.