Overview of Duroid PCB Materials

Duroid PCB materials are engineered laminates and prepregs designed for use in high frequency and high speed digital applications. Some key properties of Duroid materials include:

• Low dielectric loss for optimal high frequency performance
• Controlled dielectric constant for impedance matching
• Low thermal coefficient of dielectric constant for stable electrical performance
• Good thermal conductivity to dissipate heat
• Low Z-axis CTE for reliability

Some commonly used Duroid materials include:

Rogers RT/duroid 5870 PTFE Glass Microfiber

The 5870 laminate is made of glass microfiber reinforced PTFE composites. It has a low dielectric constant of 2.33 and low loss tangent of 0.0012. 5870 is suitable for microwave circuits up to mm-wave frequencies.

Rogers RT/duroid 6002 PTFE Ceramic Filled

6002 is filled PTFE composite reinforced with a ceramic. It has a dielectric constant of 2.94 and loss tangent of 0.0012. 6002 provides excellent thermal conductivity of 1.44 W/m/K.

Rogers RT/duroid 6006/6010 PTFE Ceramic Filled

The 6000 series materials have slightly higher dielectric constants of 6.15 and 10.2 respectively. They provide tighter impedance control for striplines and microstrips.

Selecting the Right Duroid Material

The key factors to consider when selecting a Duroid material include:

• Operating frequency – Materials with lower dielectric constants are preferred for higher mm-wave frequencies
• Impedance control requirements – Materials with higher dielectric constants allow better control of stripline impedances
• Thermal management – Materials with higher thermal conductivity like 6002 dissipate heat better
• CTE requirements – Materials with low Z-axis CTE provide reliability during thermal cycling
• Loss requirements – 5870 and 6002 provide the lowest loss tangents for optimal HF/microwave performance

The intended application will determine which Duroid material provides the right electrical, thermal, and mechanical properties.

Fabricating Duroid PCBs

Fabricating PCBs using Duroid materials requires following their specialized processing requirements:

• Lamination – Stack-up design must account for glass transition temps of Duroid prepregs during lamination
• Drilling – Carbide drills and diamond-coated drills are recommended
• Plating – Electroless copper is preferred for plating holes and vias
• Etching – Ammonium persulfate or nitric acid etchants can be used
• Solder mask – Liquid photoimageable solder mask with high Tg is recommended
• Gold plating – Hard gold plating yields best results for connector contacts

Careful process control is needed to fabricate high quality Duroid PCBs suitable for microwave and mm-wave circuits.

Comparison of Duroid PCB Materials

Material	Dielectric Constant	Loss Tangent	Thermal Conductivity
RT/duroid 5870	2.33	0.0012	0.69 W/m/K
RT/duroid 6002	2.94	0.0012	1.44 W/m/K
RT/duroid 6006	6.15	0.0027	1.1 W/m/K
RT/duroid 6010	10.2	0.0023	1.44 W/m/K

Applications of Duroid PCBs

Some examples of high frequency applications using Duroid PCB materials include:

• Microwave radios – 5870 used in microwave link PCBs for wireless backhaul
• Satcom antennas – 6010 used in printed antennas for satellite communication
• 5G equipment – 6002 used in phased array antennas for 5G base stations
• Aerospace/defense – 6002 used in radar and electronic warfare PCBs
• Automotive radar – 5870 used in 77 GHz and 24 GHz radar PCBs

Duroid materials enable optimal performance in these cutting-edge microwave and mm-wave applications.

Frequently Asked Questions

Q: What is the difference between RT/duroid 5870 and Rogers RO4350B laminates?

A: RT/duroid 5870 is PTFE glass microfiber composite while RO4350B is a ceramic-filled PTFE composite. 5870 has lower Dk, DF and Z-axis CTE than RO4350B but also lower thermal conductivity. 5870 is more suitable for mm-wave frequencies.

Q: Can Duroid materials be used for multilayer PCB designs?

A: Yes, Duroid prepregs like 5870 prepreg can be used to bond multiple laminate layers into a multilayer board. Careful lamination process control is needed to achieve quality multilayer boards.

Q: Is Rogers RO4000 series a type of Duroid material?

A: No, the RO4000 series are different PTFE-ceramic composites compared to Duroid. RO4350B is most similar to Duroid 6002 in properties. The RO4000 series offer a wider range of Dk values.

Q: How are Duroid materials different from FR-4 PCB materials?

A: FR-4 is a glass-reinforced epoxy laminate while Duroid uses PTFE composites. Duroid has much lower loss, stable electrical properties, and can perform well at microwave frequencies compared to FR-4.

Q: Can Duroid materials be used for multilayer designs?

A: Yes, Duroid prepreg bonding sheets are available that allow multiple Duroid laminate layers to be bonded into a multilayer board construction. Careful lamination process control is needed to achieve flat, void-free multilayer boards.