CuClad 217 PCB | Dk 2.17 PTFE Woven Glass Laminate

What Is Rogers CuClad 217?

CuClad 217 is a PTFE-based, woven-fiberglass-reinforced laminate manufactured by Rogers Corporation with a dielectric constant (Dk) of 2.17 ± 0.02 at 10 GHz. Its dissipation factor (Df) of 0.0009 at 10 GHz places it among the lowest-loss woven-glass PTFE materials available. The glass reinforcement gives CuClad 217 significantly better dimensional stability than unreinforced PTFE sheets, while the very low Dk keeps signal velocity high and reduces phase delay—critical advantages in microwave feed networks, phased-array antenna boards, and test fixtures operating well into the Ka-band range.

Key Electrical and Mechanical Properties

The table below summarizes the properties most relevant to PCB design and fabrication. Values are drawn from the Rogers CuClad series datasheet conditions (23 °C, 50 % RH unless stated otherwise).

The very low moisture absorption (< 0.05 %) means CuClad 217 exhibits almost no Dk shift in humid environments—an advantage over hydrocarbon ceramic laminates, which can absorb 0.1–0.2 % moisture and experience measurable Dk drift.

Why Dk 2.17 Matters for Microwave Design

A lower Dk translates directly into wider trace widths for a given characteristic impedance, which relaxes fabrication tolerances and lowers resistive loss. For a 50 Ω microstrip on 20 mil (0.508 mm) CuClad 217, the required trace width is roughly 1.52 mm (60 mil)—about 20 % wider than the same impedance on a Dk 2.50 laminate of identical thickness. Wider traces are easier to etch accurately, improving impedance uniformity across a panel.

The low Dk also reduces the effective wavelength compression, keeping guided wavelength closer to the free-space value. In antenna feed networks at 24 GHz, for example, this means quarter-wave matching sections are physically longer and less sensitive to dimensional error—a practical benefit that directly improves first-pass yield.

Where CuClad 217 Excels

• Microstrip and stripline circuits to 40 GHz — Df of 0.0009 keeps insertion loss competitive with unreinforced PTFE.
• Phased-array antenna feed boards — Dk uniformity across a panel (±0.02) supports tight phase matching.
• Test and measurement fixtures — Low loss and stable Dk reduce calibration uncertainty.
• Satellite communication LNBs and BUCs — Operates reliably across the −40 °C to +85 °C service range typical of outdoor electronics.

Where CuClad 217 Is Not the Best Fit

• Multilayer stackups above four layers — PTFE’s high Z-axis CTE (173 ppm/°C) and softness make reliable via metallization more difficult as layer count grows. For complex multilayer microwave boards, thermoset hydrocarbon ceramics like Rogers RO3003G2 offer easier processing.
• High-volume consumer products — Cost per panel is several times that of FR-4. If the design can tolerate Dk ≈ 2.50 and slightly higher loss, CuClad 250 or DiClad 527 may be more economical.
• Boards requiring very fine-pitch SMD assembly — PTFE’s softness under reflow temperatures demands careful fixturing to avoid warpage.

CuClad 217 vs. Similar PTFE Laminates

Several woven-glass PTFE laminates compete in the Dk 2.17–2.55 space. The comparison below helps narrow the selection.

Choose CuClad 217 when you need the absolute lowest Dk with the dimensional stability of woven glass. Choose IsoClad 917 when you need the same Dk 2.17 but prefer isotropic in-plane Dk behavior (important for circular-polarization patch antennas, where Dk anisotropy from woven glass weave can degrade axial ratio). Choose CuClad 233 when a slightly higher Dk is acceptable and you want broader availability and lower cost.

Fabrication Guidelines for CuClad 217 PCBs

Drilling

PTFE woven-glass laminates drill cleanly with carbide bits, but the soft PTFE matrix can smear inside the hole barrel. Use entry and backup boards, and keep spindle speeds in the 40 000–60 000 rpm range with controlled chip loads (typically 0.05 mm/rev for 0.3 mm drill bits). Deburring is essential—PTFE burrs are flexible and hard to detect visually.

Hole Preparation and Plating

PTFE is inherently non-wettable. A sodium-naphthalene or plasma etch treatment is mandatory before electroless copper deposition to achieve adequate adhesion inside plated through-holes. Skipping this step leads to barrel cracking or copper pull-away during thermal cycling. Most fabricators use a plasma desmear cycle followed by the sodium etch for best results. The IPC-6012 rigid board performance specification Class 3 requirements for minimum copper thickness and ductility should be the baseline target for any reliability-critical microwave board.

Etching and Impedance Control

Because CuClad 217’s low Dk produces wider traces for a given impedance, etch factor is somewhat less critical than on higher-Dk materials. Still, alkaline etching is preferred over cupric chloride for fine-line work, and in-process impedance coupons should be included on every panel. A tolerance of ±5 Ω on 50 Ω lines is achievable with proper process control.

Multilayer Bonding

When CuClad 217 is used in a multilayer stackup, a PTFE-compatible bonding film is required. Rogers CuClad 6250 bonding film (Dk 2.32, Df 0.0013 at 10 GHz) is the natural companion—its PTFE base ensures CTE compatibility and maintains low loss through the bond interface. Lamination pressures of 100–200 psi at 370 °C are typical; the cycle must be profiled carefully to avoid delamination pockets.

Laminate Cost Considerations

CuClad 217 sits at the premium end of PTFE woven-glass laminates. Its low Dk requires a higher PTFE-to-glass ratio in the composite, which increases raw material cost relative to CuClad 233 or CuClad 250. Lead times for non-standard thicknesses can reach 8–12 weeks. Use the cost index tool below to compare the relative cost positioning of CuClad 217 against other RF laminate families.

If the tool indicates a cost index noticeably higher than your budget target, evaluate whether CuClad 233 (Dk 2.33) can meet your electrical requirements. The 7 % Dk increase narrows trace widths only slightly and may save 15–25 % on laminate cost depending on thickness and panel size.

Design Tips and Common Pitfalls

Account for Dk Anisotropy

Woven-glass PTFE laminates exhibit some in-plane Dk anisotropy aligned with the warp and fill directions of the glass cloth—typically ±0.02 from the nominal. For most microstrip designs this is negligible, but in tightly phase-matched antenna arrays it can introduce measurable beam squint. Rotating critical feed lines 45° relative to the glass weave, or specifying a finer glass style (e.g., 1080 instead of 7628), can reduce this effect. Rogers provides CuClad laminate technical data including weave-direction Dk measurements on request.

Manage the Soft Substrate During Assembly

PTFE softens noticeably above 200 °C, well within lead-free reflow profiles (peak 245–260 °C). Support thin CuClad 217 boards on a vacuum carrier or palletized fixture during reflow to prevent warpage. For double-sided reflow, complete the heavier-component side first and fixture it during the second pass.

Ground-Plane Via Fencing

CuClad 217’s low Dk means fields extend further from the trace edge compared to higher-Dk materials. In glass-reinforced PTFE PCBs generally, via fences along microstrip edges should be spaced at ≤ λ/20 at the highest operating frequency to suppress parallel-plate modes. At 24 GHz on CuClad 217, that spacing is about 0.6 mm—tight but achievable with 0.2 mm finished-hole vias.

Thermal Management

PTFE has a thermal conductivity of roughly 0.20–0.25 W/m·K, much lower than alumina (25 W/m·K) or even FR-4 (0.3 W/m·K through-plane). For power amplifier boards on CuClad 217, thermal vias beneath active devices are essential. A 5 × 5 array of 0.3 mm vias on 0.6 mm pitch under a GaN MMIC can reduce junction-to-board thermal resistance by 40–50 % compared to an unvented copper plane. Coin insertion or embedded copper slugs are alternatives for higher-power applications, though they add fabrication complexity.

Standards and Qualification

CuClad 217 is qualified to IPC-4103, the specification for base materials used in high-frequency applications. When specifying CuClad 217 on a drawing, reference the IPC-4103 slash sheet number and call out the specific Dk, thickness, and copper weight to avoid substitution ambiguity. Many military and aerospace programs also require qualification to MIL-PRF-55110 for the finished board; ensure your fabricator’s PTFE process line is certified accordingly.

Frequently Asked Questions

What frequency range is CuClad 217 suitable for?

CuClad 217 performs well from DC through at least 40 GHz. Its Df of 0.0009 at 10 GHz keeps insertion loss low even at Ka-band frequencies (26.5–40 GHz). Beyond 40 GHz, unreinforced PTFE or fused-silica substrates are typically preferred to avoid glass-weave scattering effects.

Can CuClad 217 be used in lead-free assembly?

Yes, but with precautions. The laminate withstands solder-float temperatures of 288 °C for 10 seconds per the Rogers datasheet. Lead-free reflow peaks of 245–260 °C are within this window. Mechanical fixturing during reflow is strongly recommended to prevent warpage of thin panels.

Is CuClad 217 the same as IsoClad 917?

No. Both share a Dk of 2.17, but CuClad 217 uses woven fiberglass reinforcement while IsoClad 917 uses randomly oriented (non-woven) microfibers. IsoClad 917 offers more isotropic in-plane Dk at the expense of slightly lower dimensional stability and higher Df (0.0012 vs. 0.0009).

What bonding material should I use for a CuClad 217 multilayer?

Rogers CuClad 6250 bonding film is the recommended prepreg. Its PTFE composition ensures CTE matching and maintains low loss. FEP-based bonding films are an alternative but have a higher Dk (≈ 2.1) and require a different lamination profile.

How does CuClad 217 compare to Rogers RT/duroid 5880?

RT/duroid 5880 has the same Dk (2.20 ± 0.02) and similar Df (0.0009) but is reinforced with randomly oriented glass microfibers rather than woven glass. CuClad 217 offers better dimensional stability and easier handling during fabrication, while RT/duroid 5880 provides more isotropic Dk behavior—a trade-off similar to the CuClad 217 vs. IsoClad 917 comparison.