1. Introduction

RT/duroid 5870 and 5880 are high-frequency circuit materials manufactured by Rogers Corporation. These materials are widely used in the aerospace and defense industries, as well as in commercial high-frequency circuit applications. Their unique properties make them ideal for microwave and RF applications, but they also require specific fabrication guidelines to ensure optimal performance.

2. Material Properties

Before diving into the fabrication guidelines, it’s essential to understand the properties of RT/duroid 5870 and 5880:

• Composition: PTFE (Polytetrafluoroethylene) composite reinforced with glass microfibers
• Dielectric Constant (εr): 2.33 ±0.02 (5870) and 2.20 ±0.02 (5880)
• Dissipation Factor: 0.0005 to 0.0012 (10 GHz)
• Temperature Range: -55°C to +150°C
• Copper Cladding: Available in various weights (1/4 oz to 2 oz)
• Thickness: Available in various thicknesses (0.005″ to 0.125″)

These properties contribute to the materials’ excellent electrical and mechanical stability across a wide range of frequencies and environmental conditions.

3. Handling and Storage

3.1. Cleanliness

• Keep the material clean and free from contamination.
• Handle with lint-free gloves to prevent oil and dirt transfer.
• Store in a clean, dry environment.

3.2. Temperature and Humidity

• Store at room temperature (20-25°C) and moderate humidity (30-60% RH).
• Avoid extreme temperature fluctuations to prevent warping.

3.3. Packaging

• Keep materials in their original packaging until ready for use.
• Use interleaving materials between stacked sheets to prevent scratching.

4. Cutting and Machining

4.1. Cutting Methods

• Shearing: Use sharp, clean blades and support the material to prevent delamination.
• Sawing: Use a sharp, fine-toothed saw (carbide-tipped blades recommended).
• Routing: Use carbide-tipped router bits with high spindle speeds and slow feed rates.

4.2. Drilling

• Use sharp, clean drill bits (preferably carbide-tipped).
• Recommended drill speeds: 200-500 rpm for small holes, 50-100 rpm for larger holes.
• Use a backing material to prevent exit burrs.
• Clean holes thoroughly after drilling to remove debris.

4.3. Milling

• Use end mills with 30-45° helix angles.
• Recommended spindle speeds: 200-300 sfm (surface feet per minute).
• Slow feed rates to prevent delamination and ensure clean edges.

5. Copper Etching

5.1. Etching Methods

• Chemical etching is the preferred method for RT/duroid materials.
• Common etchants: Ferric Chloride, Ammonium Persulfate, Cupric Chloride.

5.2. Etching Considerations

• Use fresh etchant solutions for consistent results.
• Maintain proper temperature and agitation during etching.
• Rinse thoroughly with deionized water after etching.

5.3. Etch Factor

• Account for the etch factor when designing circuit features.
• Typical etch factors: 1.5-2.0 for 1 oz copper, 2.0-2.5 for 2 oz copper.

6. Plating

6.1. Surface Preparation

• Thoroughly clean and desmear the surface before plating.
• Use chemical or plasma etching to improve adhesion.

6.2. Plating Methods

• Electroless copper plating followed by electrolytic copper plating is common.
• Other finishes (e.g., ENIG, immersion tin) can be applied as needed.

6.3. Plating Considerations

• Monitor plating bath chemistry and temperature for consistent results.
• Ensure proper adhesion between the plating and the substrate.

Read more about:

• Rogers 5870
• Rogers RO3003
• Rogers 4350B
• Rogers 4003C

7. Multilayer Fabrication

7.1. Layer Registration

• Use tooling holes or fiducial marks for accurate layer alignment.
• Consider using a pinning system for improved registration.

7.2. Bonding

• Use appropriate bonding films compatible with RT/duroid materials.
• Follow recommended lamination cycles for temperature, pressure, and time.

7.3. Z-axis Expansion

• Account for the material’s low Z-axis expansion when designing plated through-holes.
• Use appropriate via design and plating techniques to ensure reliability.

8. Circuit Patterning

8.1. Photoresist Application

• Use either dry film or liquid photoresist.
• Ensure proper adhesion and uniform thickness of the photoresist layer.

8.2. Exposure and Development

• Use collimated UV light for exposure to achieve sharp feature definition.
• Develop using recommended chemistry and parameters.

8.3. Fine Line Resolution

• RT/duroid materials can achieve fine line resolution (down to 2-3 mil lines/spaces).
• Use appropriate imaging and etching techniques for best results.

9. Surface Finishing

9.1. Solder Mask

• Use solder masks compatible with high-frequency applications.
• Apply and cure according to the manufacturer’s recommendations.

9.2. Surface Finishes

• Common finishes include HASL, ENIG, Immersion Tin, and OSP.
• Choose a finish compatible with the intended application and assembly process.

10. Assembly Considerations

10.1. Component Attachment

• Use appropriate soldering techniques (e.g., reflow, wave soldering).
• Follow recommended temperature profiles to avoid damaging the substrate.

10.2. Thermal Management

• Consider the low thermal conductivity of RT/duroid materials in designs.
• Use thermal vias or metal-backed variants for improved heat dissipation if needed.

11. Testing and Quality Control

11.1. Electrical Testing

• Perform impedance testing to ensure proper transmission line characteristics.
• Use time-domain reflectometry (TDR) for high-frequency circuit verification.

11.2. Mechanical Testing

• Check for proper layer adhesion in multilayer constructions.
• Perform peel strength tests on copper foil as needed.

11.3. Environmental Testing

• Conduct thermal cycling tests to verify thermal stability.
• Perform humidity and salt spray tests for applications requiring environmental resistance.

12. Safety Considerations

12.1. Material Handling

• Use appropriate personal protective equipment (PPE) when handling and fabricating RT/duroid materials.
• Follow proper ventilation guidelines, especially during machining or high-temperature processes.

12.2. Chemical Safety

• Handle etchants, plating solutions, and other chemicals according to safety data sheets (SDS).
• Dispose of chemicals and waste materials in accordance with local regulations.

13. Conclusion

Fabricating high-frequency circuits using RT/duroid 5870 and 5880 materials requires attention to detail and adherence to specific guidelines. By following these fabrication best practices, manufacturers can ensure optimal performance and reliability of their high-frequency circuits. Always consult the latest technical data sheets and processing guides provided by Rogers Corporation for the most up-to-date information and recommendations.