What substrate is Rogers RT Duroid 5880?

Introduction

Rogers RT/duroid 5880 is a popular microwave laminate material used as a substrate for designing high frequency printed circuit boards (PCBs). It is widely utilized in applications like radars, satellite communication, 5G systems, automotive electronics and more.

This article provides an in-depth understanding of Rogers RT/duroid 5880 substrate in terms of its composition, key properties, available forms, typical applications and comparisons with other substrates. We also look at some guidelines for designing with RT/duroid 5880 material.

Composition of Rogers RT/duroid 5880

Rogers RT/duroid 5880 is a ceramic-filled, PTFE (Polytetrafluoroethylene) composite substrate designed for exacting high-frequency circuit applications.

The composite matrix is formed using PTFE polymer with a proprietary inorganic ceramic filler. PTFE provides excellent electrical and mechanical stability across a wide temperature range. The filler allows modifying dielectric properties like permittivity while retaining electrical and thermal performance characteristics of PTFE.

Some key attributes of the composite matrix are:

• Excellent dielectric constant and loss tangent stability over frequency
• Low thermal coefficient of dielectric constant for consistent electrical performance
• Tight control of material properties for consistent circuit response
• Good flexural strength for thick film metallization and double-sided boards
• Low Z-axis thermal expansion coefficient

Rogers RT/duroid 5880 material leverages this composite matrix formulation to achieve a unique combination of properties required in high frequency microwave/RF designs.

Dielectric Properties

Dielectric properties are critical parameters that determine how signals propagate in high frequency PCB substrate materials. Rogers RT/duroid 5880 stands out with its stable low-loss dielectric constant over wide frequency ranges.

Some key dielectric properties of RT/duroid 5880 material are:

• Dielectric constant (er) of 2.2 +/- 0.02
• Loss tangent (tan δ) of 0.0009 at 10 GHz

This provides consistent performance over microwave and mm-wave frequencies, unlike some materials which demonstrate substantial dielectric variation across frequency bands.

The low dielectric constant facilitates better impedance control compared to traditional microwave substrates. The ultra-low loss tangent enables the design of high Q RF circuits.

These stable dielectric properties make RT/duroid 5880 suitable for broad range of microwave and millimeter wave applications.

Electrical and Mechanical Properties

In addition to the exceptional dielectric performance, RT/Duroid 5880 exhibits several other useful electrical and mechanical characteristics:

Electrical Properties

• Volume resistivity – 1 X 1014 ohm-cm typical
• Surface resistivity – 5 X 1014 ohms typical
• Dielectric strength – 3.0 x 106 V/m typical

Mechanical Properties

• Flexural strength – 20,000 psi (138 MPa) typical
• Tensile strength – 10,000 psi (69 MPa) typical
• Compressive strength – 30,000 psi (207 MPa) typical
• Density – 2.2 g/cm3 nominal
• Maximum continuous use temperature – 170°C
• Decomposition temperature – >280°C
• Thermal conductivity – 0.71 W/m/K
• Coefficient of thermal expansion – 17 ppm/°C
• Young’s modulus – 540 ksi (3716 MPa)
• Poisson’s ratio – 0.17
• Water absorption – <0.02%

This combination of electrical stability, mechanical rigidity, dimensional stability, thermal conductivity and low expansion behavior makes Rogers RT/duroid 5880 a strong candidate for high reliability RF/microwave PCB applications.

Available Forms

Rogers RT/duroid 5880 laminate is commercially available in sheet stock and roll stock forms in a range of thicknesses.

Sheet Stock

Available sheet sizes:

• 12 x 18 inches
• 18 x 24 inches
• 24 x 36 inches

Standard thicknesses:

• 0.005 inches
• 0.010 inches
• 0.015 inches
• 0.020 inches
• 0.025 inches
• 0.030 inches
• 0.060 inches
• 0.125 inches

Other custom thicknesses can also be procured.

Roll Stock

Available roll widths:

• 12 inches
• 24 inches
• 48 inches

Standard roll lengths are 250 feet (76 m)

Thickness range:

• 0.005 inches to 0.062 inches

This wide range of sheet and roll sizes along with various thickness options allows designers to choose the right RT/duroid 5880 laminate form suited for their PCB fabrication process.

Bonding to Other Layers

Rogers RT/duroid 5880 laminate can be bonded using either fusion bonding or adhesive bonding techniques to manufacture multilayer boards.

Fusion Bonding

Multiple layers of RT/duroid 5880 material can be fused together into a monolithic structure without adhesives under heat and pressure. This creates a void-free interface for optimum electrical and mechanical performance.

Fusion bonding allows fabricating multilayer circuits with:

• High bond strengths > 2000 psi
• No delaminations or outgassing issues
• Thinner and lighter assemblies
• Simplified fabrication without adhesive handling

Adhesive Bonding

RT/duroid 5880 layers can also be bonded using Rogers’ own RO4000 or RO3000 series bondply adhesives. Thermoset polyimide or epoxy films like FR-4 can also be used.

Adhesive bonding provides high flexibility for:

• Combining dissimilar dielectrics
• Bonding to metal layers or heat sinks
• Selective bonding in multilayers
• High yield for complex circuit stacks

Rogers offers a wide range of adhesive options for integration with RT/duroid 5880 material.

Typical Applications

Some typical applications leveraging Rogers RT/duroid 5880 material include:

• Radar Systems – Used in radar antennas, phased arrays, T/R modules, filters etc. due to its stable electrical performance and low loss.
• Military & Aerospace Electronics – Utilized in avionics systems, satellite payloads, flight termination systems requiring reliable high frequency boards.
• Wireless Communications – Employed in 5G NR base stations, small cells, test equipment and broadband communication systems.
• Automotive Radar – Used for radars in autonomous vehicles, collision detection and other applications given its thermal and mechanical stability.
• High-Speed Digital Circuits – Leveraged in very high speed digital applications up to 20+ Gbps like SERDES, interfaces and interconnects.
• Medical Electronics – Used in RF ablation, MRI coils, and imaging systems given its durability and biocompatibility.

How does RT/duroid 5880 Compare to Other Substrates?

Rogers RT/duroid 5880 provides a beneficial combination of electrical and mechanical characteristics. Here is how it compares with some other common microwave substrate materials:

Substrate	Dielectric Constant	Loss Tangent	Key Features
RT/duroid 5880	2.20	0.0009	Ultra-low loss, stable dielectric
RT/duroid 6002	2.94	0.0012	Higher permittivity, low loss
Nelco 4000-13SI	3.66	0.0021	Low cost, moderate performance
Rogers RO3003	3.00	0.0013	Solid all-round performance
Rogers RO4003C	3.38	0.0027	High frequency, low loss
Taconic RF-60A	6.15	0.0028	Higher permittivity
Rogers TMM10i	9.80	0.0020	High dielectric constant

RT/duroid 5880 provides the best combination of low dielectric constant and ultra-low loss tangent enabling exceptional performance in high Q, low loss microwave circuits.

Design Guidelines

Here are some key guidelines to follow when designing PCBs using Rogers RT/duroid 5880 material:

• Stackup Design – Use symmetric constructions with balanced lamination ratios to minimize warpage. Follow Rogers’ guidelines for layer counts, grain direction and lamination sequences.
• Trace Width and Spacing – Maintain at least 3x dielectric thickness spacing between conductors for leakage control. Use wider lines on outer layers if higher current capacity is needed.
• Impedance Control – The stable dielectric properties help maintain tight impedance tolerances. But allow for +/- 8% fabrication tolerance.
• Signal and Power Integrity – Leverage Rogers’ material models for simulation. Use sufficient decoupling and maintain isolation from noisy digital circuits.
• Thermal Management – RT/duroid 5880’s thermal conductivity helps heat spreading. Use thermal vias under hot components. Allow sufficient air flow.
• Fabrication Considerations – Specify workmanship, lamination cycles, drill/rout tolerances etc. clearly. Use Rogers certified circuit facilities.

Following Rogers’ guidelines and best practices for the material ensures optimum board performance.

Rogers RT/duroid 5880 – Frequently Asked Questions

Here are some common questions around Rogers RT/duroid 5880 high frequency laminate material:

Q1. Can Rogers RT/duroid 5880 material be used for multilayer PCBs?

Yes, RT/duroid 5880 laminates can be fabricated into multilayer PCBs using fusion bonding as well as adhesive bonding techniques. Fusion bonding using multiple sheets of RT/duroid 5880 provides highest performance while adhesive bonding offers more flexibility. Rogers offers compatible bonding adhesives like RO4000 and RO3000 series for multilayer boards using RT/duroid 5880.

Q2. Is Rogers RT/duroid 5880 an RF material?

Yes, RT/duroid 5880 is specifically designed as an RF/microwave substrate with excellent high frequency characteristics. Its stable low dielectric constant and ultra-low loss tangent make it suitable for a wide array of RF applications like radars, 5G, satellite communication, automotive sensors etc. It maintains consistent performance across microwave and mmWave bands.

Q3. Can Rogers RT/duroid 5880 be used for flex PCB applications?

RT/duroid 5880 material is too rigid for fabricating flex PCBs which require highly flexible substrates. While it provides good flexural strength, it is not suited for continuous flexing applications. Rogers FlexWave series of polyimide substrates would be a much better fit for high frequency flex PCB needs.

Q4. Is RT/duroid 5880 suitable for space and aerospace applications?

Yes, RT/duroid 5880 is an ideal aerospace grade material. Its stable electrical properties under varying temperature/humidity, mechanical rigidity, dimensional stability, low outgassing and high reliability make it suitable for mission-critical space applications like satellites, flight systems, launch vehicles etc. leading companies regularly utilize RT/duroid 5880 for aerospace PCB needs.

Q5. What are the pros and cons compared to FR-4 material?

Pros vs FR-4:

• Far more stable electrical properties under temperature variations
• Extremely low loss for high Q RF circuits
• Better impedance control thanks to consistent dielectric constant
• Withstands higher temperatures than FR-4
• Lower moisture absorption

Cons vs FR-4

• Significantly more expensive
• Special material certification and handling requirements
• Fabrication limited to Rogers approved circuit shops
• Overkill for many commercial grade PCB needs

So RT/duroid 5880 provides major advantages for mission-critical, high-reliability microwave and mm-wave boards but with higher cost. FR-4 may be adequate for many commercial grade digital and analog PCB needs.