DiClad 880 PCB | Dk 2.17 PTFE Microwave Boards

What Is Rogers DiClad 880?

Rogers DiClad 880 is a PTFE-based microwave laminate reinforced with non-woven fiberglass, offering a dielectric constant (Dk) of 2.17 ± 0.02 at 10 GHz and a dissipation factor (Df) of 0.0009 at the same frequency. Its low Dk makes it one of the lightest-electrically laminates in the Rogers portfolio, ideal for applications where a low effective permittivity is needed—GPS patch antennas, microstrip feed networks, radomes, and airborne phased-array antenna elements. DiClad 880 is often discussed alongside its sibling, DiClad 870 (Dk 2.33), because the two share the same PTFE matrix but use different glass loading to hit different Dk targets.

DiClad 870 vs DiClad 880: Key Differences

Both laminates belong to the Rogers DiClad family and are manufactured with PTFE resin and non-woven fiberglass. The critical distinction is the glass-to-PTFE ratio, which shifts the dielectric constant and slightly alters mechanical behavior.

Choose DiClad 870 when your design needs Dk 2.33—a value shared with many other PTFE grades such as Rogers IsoClad 933—and you want easy cross-referencing with legacy designs. Choose DiClad 880 when you need the lowest possible Dk in a mechanically reinforced PTFE sheet, for example to widen microstrip lines on a GPS antenna or to reduce surface-wave excitation at higher frequencies.

Electrical Properties in Detail

Dielectric Constant and Loss

At 2.17, DiClad 880 sits between unreinforced PTFE (Dk ≈ 2.1) and woven-glass PTFE laminates like RT/duroid 5880 (Dk 2.20). The non-woven reinforcement eliminates the periodic Dk variation caused by glass-weave crossover points, which matters in phased arrays where element-to-element Dk uniformity directly affects beam squint. The Df of 0.0009 at 10 GHz is among the lowest for any reinforced laminate, translating to roughly 0.5–0.8 dB/100 mm of insertion loss for a 50 Ω microstrip at 10 GHz on a 20 mil (0.508 mm) substrate.

Dk Variation with Temperature

DiClad 880’s thermal coefficient of Dk is around −200 ppm/°C, meaning the Dk drops as temperature rises. Over a −40 °C to +85 °C operating swing (125 °C span), the Dk shifts by approximately −0.054 units—from about 2.20 at −40 °C to roughly 2.14 at +85 °C. For a narrowband filter or a resonant patch antenna, that shift can detune the center frequency by roughly 1.2 %. Use the estimator below to check how much Dk drift your specific temperature range introduces.

For example, entering a nominal Dk of 2.17, a thermal coefficient of −200 ppm/°C, and a temperature excursion of 60 °C (say, 25 °C to 85 °C) returns a shifted Dk of approximately 2.144. That 1.2 % Dk change translates to about 0.6 % frequency shift in a resonant microstrip patch—potentially enough to move a GPS L1 patch antenna off its 1575.42 MHz target by around 9 MHz. If your application cannot tolerate that, consider DiClad 870 with its tighter −115 ppm/°C coefficient, or add a tuning element in your matching network.

Dk Isotropy

Because the fiberglass mat is non-woven, DiClad 880 exhibits relatively isotropic in-plane Dk. The x–y Dk anisotropy is typically less than 0.02 units, compared with 0.05–0.10 for woven-glass laminates. This property is valuable for circular or dual-polarized patch antennas where the two orthogonal feed axes must see the same effective Dk.

Mechanical and Thermal Properties

• CTE (z-axis): approximately 250 ppm/°C below Tg. PTFE has no sharp glass transition, so the CTE remains relatively stable across the operating range, but plated through-holes (PTHs) in thick boards should be designed with adequate annular ring to absorb z-expansion.
• Flexural strength: lower than woven-glass PTFE or FR-4. Panels thinner than 20 mil (0.508 mm) may require carrier frames during assembly.
• Moisture absorption: < 0.02 %, which is excellent. DiClad 880 boards can be stored without baking before reflow, unlike many hydrocarbon laminates.
• Flammability: V-0 per UL 94.
• Maximum operating temperature: continuous use to 260 °C (limited by copper adhesion degradation, not the PTFE matrix).

Typical Applications

GPS and GNSS Patch Antennas

A low Dk widens the patch element for a given frequency, which increases bandwidth and eases fabrication tolerances. DiClad 880 at Dk 2.17 on a 60 mil (1.52 mm) substrate gives a half-wave patch width of roughly 62 mm at 1575 MHz—about 3 mm wider than the same antenna on a Dk 2.33 substrate. The wider patch also improves radiation efficiency because conductor loss is spread over a larger area.

Microstrip Feed Networks

Low-loss PTFE feed lines on DiClad 880 minimize power dissipation between the transceiver and the radiating elements. A 50 Ω microstrip on 20 mil DiClad 880 is approximately 1.55 mm wide (60.9 mil), comfortable for standard etching. Compare this with Taconic TLY-5 at Dk 2.20, which produces a nearly identical trace width and can serve as a second-source option.

Radomes and Antenna Covers

Radome panels need a Dk as close to air (1.0) as practical to minimize insertion loss and beam deflection. DiClad 880’s Dk of 2.17 is among the lowest available in a structurally self-supporting laminate. A quarter-wave radome wall at 10 GHz is about 5.1 mm thick in DiClad 880—thin enough for lightweight airborne installations.

Phased-Array Elements

The Dk uniformity of the non-woven reinforcement keeps element-to-element phase error below ±2° across a panel, supporting arrays up to Ku-band without individual element trimming.

Fabrication Guidelines for DiClad 880 PCBs

Drilling

PTFE laminates are soft and can smear during drilling. Use diamond-coated or carbide drills at spindle speeds of 60 000–80 000 RPM with controlled chip loads of 0.05–0.08 mm/rev. Entry and backer boards should be aluminum rather than phenolic to reduce burring. Hole quality is critical because the soft matrix can leave PTFE fibrils inside the barrel, degrading plating adhesion.

Copper Surface Preparation

PTFE is chemically inert, so the exposed substrate in plated through-holes must be activated before electroless copper deposition. Sodium-naphthalene or plasma etch treatments are standard. The IPC-6012 rigid board specification does not prescribe a specific desmear chemistry for PTFE, but most fabricators follow the process notes in Rogers’ DiClad fabrication guidelines to ensure reliable plating.

Etching

Standard alkaline or cupric-chloride etch processes work well. The non-woven glass mat does not cause differential etch undercutting the way woven glass can, so trace-width tolerance is typically ±0.5 mil (±12.7 µm) for 1 oz copper—comparable to FR-4.

Lamination and Hybrid Stackups

DiClad 880 is often used as the antenna or feed layer in a hybrid multilayer stackup with FR-4 or polyimide cores for the digital and power sections. Rogers CuClad or standard PTFE prepreg bonds the layers. If your design calls for higher-temperature resilience in the digital section, consider a polyimide core like Ventec VT-870. Bonding temperature for PTFE-to-PTFE lamination is typically 370 °C (700 °F) at 200–400 psi for 15–30 minutes.

Assembly and Soldering

DiClad 880 withstands standard lead-free reflow profiles (peak 260 °C for 10 s). Because PTFE has very low surface energy, solder mask adhesion can be weak; many designs leave the PTFE surface bare and use copper-defined pads instead of solder-mask-defined pads. Component placement accuracy is important because the soft substrate can shift slightly under reflow if not adequately supported.

Comparing DiClad 880 with Other Low-Dk Laminates

DiClad 880’s advantage over RT/duroid 5880 is mainly cost and availability: the non-woven mat process is simpler than glass-microfiber reinforcement, so lead times are often shorter. Against pure unreinforced PTFE, DiClad 880 trades a small Dk and loss penalty for dramatically better dimensional stability—unreinforced PTFE can cold-flow under clamping pressure, making multilayer registration difficult.

Design Tips and Common Pitfalls

• Do not assume Dk = 2.17 at all frequencies. Rogers specifies Dk at 10 GHz using the clamped-stripline method per IPC-TM-650 2.5.5.5. At 1 GHz the measured Dk may read 0.02–0.03 higher due to relaxation effects. Always use the frequency-specific value from the datasheet.
• Account for copper roughness. ED copper on PTFE laminates typically has an Rz of 5–8 µm. At frequencies above 20 GHz, this roughness can add 0.3–0.5 dB/inch of extra conductor loss beyond what a smooth-conductor model predicts. Use Huray or Hammerstad-Jensen roughness correction in your EM simulator.
• Avoid tight via-to-trace spacing. PTFE’s softness can cause drill wander, so keep annular rings at least 8 mil (0.2 mm) and via-to-trace clearance at 10 mil (0.25 mm) minimum.
• Specify rolled-annealed (RA) copper for flex-prone areas. RA copper has better fatigue life than electrodeposited (ED) copper, useful if the board will be bent during installation.
• Store panels flat. PTFE laminates can take a permanent set if stored on edge or stacked unevenly. Keep them horizontal in a climate-controlled area.

When to Choose DiClad 880 and When Not To

Choose DiClad 880 when your design needs a Dk near 2.2 with very low loss, good in-plane Dk isotropy, and non-woven reinforcement for uniform etching. It excels in single- and double-sided antenna boards, feed networks up to Ku-band, and radome panels.

Avoid DiClad 880 when you need multilayer PTH-heavy digital-RF boards with more than four layers—the PTFE processing cost and z-axis CTE make FR-4 or low-loss hydrocarbon laminates more practical for the digital portion. Also avoid it for cost-sensitive commercial products below 3 GHz where lower-cost PTFE alternatives like Wangling F4BM can meet the electrical requirements at a fraction of the material price.

Frequently Asked Questions

Is DiClad 880 the same as RT/duroid 5880?

No. Both are PTFE-based and have similar Dk values (2.17 vs 2.20), but they use different reinforcement architectures. DiClad 880 uses a non-woven fiberglass mat; RT/duroid 5880 uses random glass microfibers. The electrical performance is nearly interchangeable for many designs, but mechanical properties and pricing differ.

Can DiClad 880 be used above 40 GHz?

Yes, the material itself supports frequencies well into the millimeter-wave range. However, above 40 GHz, copper roughness and via transition losses become dominant, so the board design and copper foil selection matter more than the laminate grade. For 77 GHz automotive radar, most designers prefer thinner laminates with smoother copper profiles such as RT/duroid 5880LZ or RO3003.

What is the standard panel size for DiClad 880?

Rogers typically supplies DiClad 880 in 12 × 18 in (305 × 457 mm) and 18 × 24 in (457 × 610 mm) panels. Larger panels up to 24 × 36 in may be available on special order with longer lead times.

Does DiClad 880 need baking before soldering?

Generally no. Its moisture absorption is below 0.02 %, so delamination from trapped moisture during reflow is extremely unlikely. Baking is only recommended if panels have been stored unsealed in a humid environment for more than six months.

How does DiClad 880 pricing compare to FR-4?

PTFE laminates cost significantly more than FR-4—typically several times the raw material price per panel. The exact multiplier depends on thickness, copper weight, and order volume. For budget-sensitive projects, evaluate whether a lower-cost PTFE or ceramic-filled hydrocarbon laminate can meet your loss budget before committing to DiClad 880.