RT5880 vs RT5870: Dk, Loss and Design Guide

RT5880 vs RT5870: The Short Answer

RT/duroid 5880 has a design Dk of 2.20 ± 0.02 and a dissipation factor (Df) of 0.0009 at 10 GHz. RT/duroid 5870 has a design Dk of 2.33 ± 0.02 and a Df of 0.0012 at 10 GHz. When engineers compare RT5880 vs RT5870, the core question is whether the lower Dk and loss of 5880 outweigh the routing and dimensional-stability advantages of 5870 for a given frequency and topology. Both are glass-microfiber-reinforced PTFE composites from Rogers Corporation’s RT/duroid family, but the difference in Dk shifts trace widths, antenna patch dimensions and phase velocity enough to matter in any design above a few GHz. Choose 5880 when you need the lowest possible Dk and loss; choose 5870 when a slightly higher Dk gives you more convenient line widths or better dimensional control on thin substrates.

RT5880 vs RT5870: Key Properties Compared

Both laminates share the same PTFE matrix, the same glass-microfiber reinforcement style and the same copper-foil options. The only intentional difference is the filler loading, which raises 5870’s Dk from 2.20 to 2.33 and marginally increases its loss.

How the Dk Difference Affects Your Design

A Dk change from 2.20 to 2.33 is only about 6 %, but the engineering consequences in the RT5880 vs RT5870 decision are not trivial:

• Microstrip width. For a 50 Ω microstrip on 10 mil (0.254 mm) substrate, the trace width drops from roughly 30.5 mil on Dk 2.20 to about 28.5 mil on Dk 2.33. That 2 mil difference can ease or complicate etching tolerances depending on your fabricator’s capability.
• Patch antenna dimensions. A half-wave patch at 10 GHz is approximately 10.1 mm long on 5880 and 9.8 mm on 5870. In large phased arrays the cumulative space saving with 5870 can reduce aperture size.
• Phase velocity. Guided wavelength scales as 1/√Dk. A 6 % Dk increase shortens guided wavelength by about 3 %, which shifts every quarter-wave stub, coupler arm and filter resonator. Swapping grades mid-design requires a full re-simulation.
• Insertion loss. At 10 GHz over a 100 mm microstrip, the conductor loss dominates, but the dielectric loss difference (Df 0.0009 vs 0.0012) adds roughly 0.01–0.02 dB. At 77 GHz the gap widens to around 0.1 dB per 10 mm—significant in automotive radar front-ends.

If your link budget is tight at millimeter-wave frequencies, 5880’s lower Df is worth the wider traces. If your layout is already cramped and you need narrower lines for routing density, 5870’s higher Dk helps. For a broader look at how PTFE stacks up against other substrate technologies, see the PTFE vs ceramic PCB trade-off analysis.

Dk Drift with Temperature and Frequency

Both 5880 and 5870 have negative thermal coefficients of Dk, meaning the dielectric constant decreases as temperature rises. Over a −55 °C to +125 °C operating range the Dk of 5880 can shift by roughly −0.05 (from ~2.23 to ~2.18), enough to detune a narrowband filter by several megahertz at X-band. RT/duroid 5870 behaves similarly but starts from a higher baseline, so the absolute shift is slightly larger. Understanding this thermal behavior is essential when evaluating RT5880 vs RT5870 for temperature-sensitive circuits.

Use the estimator below to see how much Dk drift to expect for your operating temperature range. Enter the nominal Dk, the thermal coefficient of Dk (TCDk) in ppm/°C, and the temperature excursion.

For example, entering Dk = 2.20, TCDk = −125 ppm/°C and a temperature swing of 100 °C returns a Dk shift of roughly −0.028. That moves a 10 GHz bandpass filter center frequency by about 60 MHz—acceptable for most radar receivers but potentially out-of-spec for a tight channelized diplexer. If the drift is too large, consider hybrid stackups with a thermally stable ceramic-filled laminate for the filter layer. Comparing materials like RT/duroid 6002 vs 6010 can reveal lower-TCDk alternatives within the Rogers family.

Fabrication and Processing Differences

Drilling and Plating

PTFE is notoriously difficult to plate because the surface is non-wetting. Both 5880 and 5870 require sodium-naphthalene or plasma etch surface preparation before electroless copper deposition. There is no processing difference between the two grades here; the same etchant chemistry, dwell times and rinse cycles apply. The high z-axis CTE (237 ppm/°C for both) makes plated through-holes vulnerable to barrel cracking during thermal cycling, so IPC-6012 Class 3 designs often limit aspect ratios to 6:1 or less on these substrates.

Bonding in Multilayer Stackups

Rogers offers RT/duroid 5880 and 5870 with optional pre-treatment for bonding with their 3001 bonding film (Dk 2.28, Df 0.003 at 10 GHz) or Taconic FastRise 27 prepreg. The bonding film’s Dk sits between the two laminate grades, which simplifies impedance modeling in hybrid stackups. When building multilayers that combine PTFE cores with thermoset cores, the RF laminate comparison hub is a useful starting point for matching Dk and CTE across layers.

Dimensional Stability

RT/duroid 5870 has lower in-plane CTE (22/28 ppm/°C vs 31/48 ppm/°C for 5880). For large-format panels—think 18 × 24 inch phased-array tiles—this translates to tighter registration between layers after lamination and less copper-to-pad misalignment. If your design is a single-layer microstrip antenna, the difference is negligible, but in a six-layer beamforming network it can save a registration tolerance class.

RT5880 vs RT5870: Frequency Range and Application Guidance

Both laminates are used from UHF through W-band (77 GHz and above). The RT5880 vs RT5870 choice rarely comes down to frequency ceiling; it comes down to which Dk gives the best combination of line width, patch size and loss for a specific topology.

For designs where neither 5880 nor 5870 offers the right Dk, Rogers’ broader portfolio includes RT/duroid 6002 (Dk 2.94) and 6010 (Dk 10.2), plus ceramic-filled thermoset options like RO4350B (Dk 3.48). If you are evaluating whether a lower-cost non-PTFE material could work, the Rogers vs FR4 real loss data comparison quantifies the penalty at various frequencies.

Cost, Lead Time and Availability

RT/duroid 5880 is the more widely stocked of the two. Most RF laminate distributors carry 5880 in 10, 20, 31 and 62 mil thicknesses with ½ oz and 1 oz ED copper. RT/duroid 5870 is typically available in the same thicknesses but may require a minimum order quantity or longer lead time depending on the distributor. Panel pricing is nearly identical; the material cost difference is under 5 % and often zero at volume.

The real cost driver is fabrication. PTFE processing adds 20–40 % to the bare-board price compared to a thermoset laminate of the same layer count, regardless of whether you use 5880 or 5870. If your design can tolerate Dk 3.48 and Df 0.0037, switching to RO4350B eliminates sodium-etch preparation entirely and drops fabrication cost significantly—see the I-Tera MT40 vs RO4350B comparison for a detailed look at thermoset alternatives.

Design Checklist: Choosing Between RT5880 and RT5870

1. Determine your Dk requirement. Run an impedance and guided-wavelength calculation for your target topology. If 50 Ω trace width on 5880 is too wide for your pitch, try 5870.
2. Check loss budget. Calculate total dielectric loss over your longest RF path at the operating frequency. If the Df difference (0.0003) costs you more than 0.1 dB of margin, stay with 5880.
3. Evaluate thermal drift. Use the Dk drift estimator above with your worst-case temperature range. If the predicted shift exceeds your filter or phase-shifter tolerance, add margin or choose a lower-TCDk laminate.
4. Assess dimensional stability needs. For multilayer stackups over 12 × 12 inches, 5870’s lower in-plane CTE may improve registration yield.
5. Confirm availability. Check distributor stock for your chosen thickness and copper weight before committing. Swapping between RT5880 and RT5870 after layout is a full re-spin.

Frequently Asked Questions

Can I substitute RT5870 for RT5880 without re-simulating?

No. A Dk change from 2.20 to 2.33 shifts impedance, guided wavelength and resonant frequencies. Every transmission line, stub and resonator must be re-simulated and the layout adjusted. The RT5880 vs RT5870 swap is never drop-in.

Which grade is better for millimeter-wave frequencies above 60 GHz?

RT/duroid 5880 is generally preferred above 60 GHz because its lower Df (0.0009 vs 0.0012) reduces dielectric loss that becomes increasingly significant at millimeter-wave frequencies. The wider 50 Ω trace width on 5880 also eases fabrication tolerances at fine feature sizes.

Are RT5880 and RT5870 RoHS compliant?

Yes. Both laminates are RoHS compliant and do not contain restricted substances per IEC 62321. Rogers publishes material declarations on request.

What bonding materials are compatible with both grades?

Rogers 3001 bonding film, Taconic FastRise 27 prepreg and low-flow thermoset prepregs (e.g., Arlon CLTE-XT) are commonly used. Match the bonding layer’s Dk as closely as possible to the core Dk to minimize impedance discontinuities at layer transitions.

Is there a lead-free soldering concern with these PTFE laminates?

PTFE itself withstands lead-free reflow temperatures (peak 260 °C) without degradation. The concern is z-axis CTE: 237 ppm/°C can stress plated through-holes during the higher thermal excursion of lead-free profiles. Use filled vias or limit aspect ratios for Class 3 reliability.