Elite EM-891 PCB: Properties, Design & Cost

What Is the Elite EM-891 PCB Laminate?

Elite EM-891 is a glass-reinforced PTFE laminate manufactured by Elite Material Technology (EMC, Taiwan) targeting very low loss RF and millimeter-wave circuits. Engineers choosing an Elite EM-891 PCB gain a dielectric constant (Dk) of approximately 2.20 and a dissipation factor (Df) of roughly 0.0015, both measured at 10 GHz. Those numbers place it squarely in the premium PTFE tier alongside Rogers RT/duroid 5880 and Taconic TLY-5, making it a strong candidate for radar front-ends, satellite communication feeds, and 5G mmWave antenna modules where every tenth of a dB of insertion loss matters.

EMC positions the EM-891 within its broader RF laminate family—which also includes the EM-890 (Dk ≈ 2.20, slightly higher loss) and EM-888 grades—giving designers a cost-performance ladder within a single vendor ecosystem. For a broader look at Elite’s RF product line, see the Elite Material RF laminate overview.

Key Electrical and Mechanical Properties of Elite EM-891 PCB

The table below collects the headline parameters an RF engineer needs when evaluating an Elite EM-891 PCB against a bill-of-materials requirement. Values are typical datasheet figures; always confirm with the latest EMC release for your specific thickness and copper weight.

The Dk of 2.20 is nearly identical to unreinforced PTFE, yet the glass reinforcement gives the Elite EM-891 PCB far better dimensional stability during drilling and routing—a practical advantage over pure PTFE substrates that tend to cold-flow under mechanical stress. For engineers cross-referencing thicknesses across vendors, the RF laminate thickness chart is a useful companion reference.

Where EM-891 Fits: Frequency and Application Map

Target frequency range

With Df at 0.0015 (10 GHz), EM-891 remains practical well into Ka-band (27–40 GHz) and even W-band prototyping. Loss per unit length on a 50 Ω microstrip at 28 GHz on 10 mil EM-891 with 1 oz rolled copper is typically in the 0.20–0.25 dB/cm range (conductor loss dominates at these frequencies). For dedicated Ka-band design considerations, see the Ka-band PCB fabrication guide.

Typical applications

• Automotive radar (77 GHz): An Elite EM-891 PCB can serve as a lower-cost alternative to Rogers RO3003 in patch antenna substrates, though its slightly higher Dk tolerance (±0.02 vs ±0.01 for some Rogers grades) must be budgeted in the impedance margin.
• SATCOM feed networks: Low moisture absorption (≤ 0.03 %) keeps Dk stable outdoors.
• 5G mmWave AiP (Antenna-in-Package) substrates: Thin cores (5–10 mil) enable compact multilayer antenna stackups.
• Test and measurement fixtures: Low loss and repeatable Dk support precision calibration boards.
• Military and avionics radar: V-0 flammability and good peel strength meet baseline qualification requirements.

Elite EM-891 PCB vs Competing Very Low Loss Laminates

Choosing a PTFE laminate is never just about Dk and Df. Lead time, regional availability, hybrid bonding compatibility, and cost per panel all matter. The comparison below benchmarks the Elite EM-891 PCB against the materials RF engineers most often evaluate alongside it.

Choose EM-891 when you need Dk ≈ 2.20 PTFE performance at a more competitive price point than RT/duroid 5880, especially for volume production where EMC’s Asian supply chain delivers shorter lead times. Choose RT/duroid 5880 when absolute lowest Df is the priority and your design can absorb the higher panel cost. Choose RO3003G2 when you need a higher Dk (3.00) for compact antenna patches or when z-axis CTE must match copper plated vias for multilayer reliability.

Fabrication Considerations for Elite EM-891 PCB Designs

Drilling and via formation

Glass-reinforced PTFE drills more cleanly than unreinforced grades, but it still requires carbide tooling with a fresh edge. Recommended drill-to-pad annular ring is ≥ 5 mil (0.127 mm) to absorb the slight positional wander that PTFE’s low modulus can introduce. Entry and backer boards should be aluminum-clad to prevent burring. For plated through-holes, plasma de-smear or sodium-etch surface preparation is essential—standard permanganate chemistry used on FR-4 will not adequately wet PTFE resin.

Via current capacity

Because EM-891’s thermal conductivity (~0.25 W/m·K) is lower than ceramic-filled laminates, heat generated in via barrels dissipates more slowly. Use the calculator below to check whether your via geometry and copper plating thickness can handle the required DC or pulsed current without exceeding the safe temperature rise.

For example, a 0.3 mm (12 mil) finished-hole via with 25 µm (1 mil) copper plating in a 1.0 mm thick EM-891 board can typically carry around 1.5 A continuous with a 10 °C rise. If your design routes power through the RF substrate—common in integrated radar modules—verify that each via stays within budget. Paralleling vias or increasing plating thickness to 30 µm are straightforward mitigations.

Copper foil selection

At frequencies above 10 GHz, conductor loss overtakes dielectric loss as the dominant contributor to total insertion loss. Pairing EM-891 with HVLP (Hyper Very Low Profile) or RTF (Reverse Treated Foil) copper—surface roughness Rz ≤ 2 µm—can recover 0.03–0.05 dB/cm at 28 GHz compared to standard ED foil. EMC offers EM-891 with several foil options; specify the foil grade explicitly at quoting stage. For a deeper discussion of roughness effects, see the guide on HVLP copper foil and RF loss.

Hybrid stackups

EM-891 is often combined with lower-cost prepreg (e.g., EMC’s EM-370 or Megtron 6-class materials) in hybrid multilayer stackups. The PTFE layers carry the RF transmission lines and antenna elements, while the FR-4-class or mid-loss layers handle digital control and power distribution. Bonding PTFE to non-PTFE layers requires a thermoplastic bonding film (such as Rogers CuClad 6700 bondply or EMC’s own bonding sheet) cured at around 220–250 °C. Verify z-axis CTE compatibility across the stackup to avoid barrel cracking after thermal cycling per IPC-6012 Class 3 requirements.

Cost Drivers and Budgeting for EM-891 Boards

An Elite EM-891 PCB sits in the medium-high cost bracket for PTFE laminates. Its pricing is generally 15–25 % below Rogers RT/duroid 5880 for equivalent thickness and copper weight, largely because EMC’s manufacturing base in Taiwan benefits from shorter logistics chains within Asia. However, several factors swing the final panel cost significantly:

• Thickness and copper weight: Thin cores (≤ 10 mil) command a premium due to handling yield loss.
• Foil type: HVLP or rolled copper adds 10–20 % over standard ED foil.
• Panel utilization: Standard EMC panel sizes are 12 × 18 in (305 × 457 mm) and 24 × 18 in. Poor array nesting wastes material on a per-unit basis.
• Volume: PTFE laminates have longer production campaigns than FR-4; ordering full-panel lots (typically ≥ 50 panels) unlocks better pricing.
• Hybrid vs all-PTFE: Confining EM-891 to only the RF layers in a hybrid stackup can cut laminate cost by 40–60 % compared to an all-PTFE build.

Use the laminate cost index tool below to get a relative sense of where EM-891 falls against other substrates in your target thickness and volume range.

If the tool shows EM-891 at a cost index of, say, 3.5× FR-4 for a 10 mil core with 1 oz HVLP copper, that is typical for glass-reinforced PTFE. Switching to standard ED foil or moving to a 20 mil core often drops the index below 3×. For projects where even that is too high, consider hydrocarbon ceramic laminates (Dk ≈ 3.0–3.6, Df ≈ 0.003–0.005) as a mid-tier alternative—though the loss penalty is real and must be modeled.

Design Tips for Elite EM-891 PCB Layouts

Impedance control

With Dk = 2.20, a 50 Ω microstrip on 10 mil (0.254 mm) EM-891 requires a trace width of approximately 27 mil (0.69 mm)—wider than on a Dk 3.5 substrate. This means RF traces consume more board real estate, which can be a constraint on dense antenna feed networks. Consider stripline or grounded coplanar waveguide (GCPW) topologies to narrow the trace while maintaining 50 Ω.

Moisture and storage

Although PTFE itself is hydrophobic, the glass reinforcement can wick moisture along fiber bundles at cut edges. Store EM-891 panels in sealed moisture-barrier bags with desiccant and bake at 105 °C for 2–4 hours before lamination if the bag seal has been broken for more than 72 hours. Post-bake Dk shift due to residual moisture is typically < 0.005—small, but enough to move a narrowband filter off frequency at Ka-band.

Surface finish

Immersion silver and ENIG are the most common finishes for EM-891 RF boards. ENIG’s nickel layer can add measurable loss at frequencies above 20 GHz due to nickel’s ferromagnetic permeability (µr > 1). For wire-bondable pads or the lowest possible surface-finish loss, ENEPIG with a thin palladium barrier is increasingly specified because the gold layer can be kept thin (≤ 0.05 µm), minimizing the nickel contribution while preserving solderability.

Qualification and Standards Compliance

EM-891 carries UL 94 V-0 flammability rating and is listed under UL’s product certification database (UL Product iQ). For aerospace and defense programs, qualification typically follows IPC-6012 Class 3 or Class 3/A with additional requirements from the end customer’s material specification. Key tests to plan for include:

• Thermal shock cycling (–55 °C to +125 °C, 100–500 cycles) per IPC-TM-650 2.6.7.
• Interconnect stress test (IST) for via reliability.
• Dk and Df verification at the operating frequency using split-post dielectric resonator or stripline resonator methods.
• Peel strength after thermal stress and solder float.

If your program requires full traceability, request lot-specific Dk/Df test coupons from EMC at the time of laminate purchase. This adds modest cost but eliminates ambiguity during first-article inspection.

Frequently Asked Questions

Is an Elite EM-891 PCB a drop-in replacement for Rogers RT/duroid 5880?

Electrically, yes—both share Dk ≈ 2.20 and similar thickness options. However, Df differs (0.0015 vs 0.0009), so insertion loss will be measurably higher on EM-891 at the same frequency. Mechanically, the glass weave styles may differ, affecting drill registration. Always re-simulate and run a first-article before switching.

Can EM-891 be used in lead-free assembly?

Yes. PTFE’s decomposition temperature (~400 °C) is well above lead-free reflow peak temperatures (typically 245–260 °C). Ensure the copper peel strength specification is met after three reflow cycles, per IPC-6012 requirements.

What is the maximum operating frequency for EM-891?

There is no hard cutoff. Designers have used glass-reinforced PTFE laminates with similar Dk/Df at 77 GHz (automotive radar) and beyond. The practical limit is set by the Dk tolerance’s impact on impedance accuracy and by conductor loss, not by the dielectric itself.

Does EM-891 support laser via drilling?

CO₂ laser drilling works on PTFE laminates but requires higher energy density than for standard epoxy-glass. UV laser drilling (355 nm) produces cleaner via walls on thin EM-891 cores (≤ 5 mil). Confirm capability with your fabricator before finalizing the design.

How does EM-891 compare to LCP substrates for mmWave?

LCP (liquid crystal polymer) offers comparable Df and superior z-axis CTE, but it is available only in very thin films and is harder to process in standard PCB fabrication lines. EM-891 is more accessible for conventional multilayer builds. For more on LCP, see the LCP PCB fabrication guide.