Rogers RO4835 PCB: Properties, Stackup & Design

What Is Rogers RO4835 and Why Choose It for Your PCB?

Rogers RO4835 is a glass-reinforced, hydrocarbon-ceramic thermoset laminate with a dielectric constant (Dk) of 3.48 ± 0.05 at 10 GHz and a dissipation factor (Df) of 0.0037. What sets a Rogers RO4835 PCB apart from the closely related RO4350B is an oxidation-resistant resin system that withstands multiple lead-free reflow cycles (peak temperatures of 260 °C and above) without the copper-peel degradation or blister formation that can plague standard thermoset laminates. If your design must survive Pb-free assembly and still hold tight impedance tolerances through Ku-band and beyond, RO4835 belongs on your short list.

The material sits in the Rogers RO4000 family, sharing the same FR-4-compatible processing advantages—standard drill bits, oxide treatments, and multilayer lamination—while delivering high-frequency performance that pure PTFE boards provide at much higher fabrication cost. It is available in thicknesses from 6.6 mil (0.168 mm) to 60 mil (1.524 mm) with ED copper foils of ½ oz to 2 oz.

Key Electrical and Mechanical Properties of Rogers RO4835 PCB

The Tg above 280 °C and Td of 390 °C together explain why RO4835 tolerates aggressive Pb-free profiles. By comparison, many mid-range FR-4 laminates have Tg values around 170–180 °C and begin delaminating well before the 260 °C reflow peak that SAC305 solder demands.

RO4835 vs RO4350B vs RO4003C

Engineers often ask whether a Rogers RO4835 PCB is simply an upgraded RO4350B. Electrically, the two are nearly identical—same Dk, same Df at 10 GHz, same CTE profile. The difference is chemical: RO4835’s resin is formulated to resist copper-oxide growth during high-temperature lamination and reflow, reducing the risk of blistering and measling in boards that go through multiple thermal excursions. RO4003C, with its lower Dk of 3.38 and Df of 0.0027, remains the lowest-loss option in the family but does not share the same oxidation-resistant chemistry.

Choose RO4835 when your assembly process involves two or more Pb-free reflow passes (e.g., double-sided SMT plus a rework cycle), or when the board will be laminated as an inner core in a hybrid stackup and must survive bonding temperatures without oxide-related adhesion loss. Choose RO4350B when your thermal profile is less aggressive and you want the widest availability and shortest lead time. Choose RO4003C when loss is the primary concern and you can tolerate the slightly different Dk for impedance matching.

Designing a Rogers RO4835 PCB Layer Stackup

RO4835 cores can be combined with Rogers RO4450B or RO4450F bonding plies to build all-Rogers multilayers, or hybridized with FR-4 cores for cost reduction on non-critical inner layers. A common four-layer arrangement uses RO4835 as the outer signal layers and FR-4 (e.g., Isola 370HR) for the inner ground-power pair, bonded with RO4450F prepreg. This keeps microstrip traces on a controlled, low-loss dielectric while the buried power distribution rides on cheaper material.

Typical 4-Layer Hybrid Stackup

• Layer 1 (Top signal): ½ oz copper on 10 mil RO4835 core
• Layer 2 (Ground): 1 oz copper
• Bonding ply: RO4450F, 4 mil
• Layer 3 (Power): 1 oz copper on 20 mil FR-4 core
• Bonding ply: RO4450F, 4 mil
• Layer 4 (Bottom signal): ½ oz copper on 10 mil RO4835 core

Use the stackup designer below to model your own layer counts, core thicknesses and dielectric assignments. Enter the number of layers, choose RO4835 for your signal cores, and review the resulting total thickness and impedance-critical dimensions.

For the example above, the total board thickness comes out near 62 mil (1.57 mm), which fits standard connector and enclosure dimensions. If your impedance target is 50 Ω microstrip on a 10 mil RO4835 core with ½ oz (0.7 mil) copper, expect a trace width around 22 mil (0.56 mm)—wide enough for comfortable etching tolerances. Increasing the core to 20 mil pushes the trace to roughly 44 mil, which may consume too much routing real estate in dense layouts. Balancing core thickness against trace width is the central trade-off in any Rogers RO4835 PCB stackup.

When building hybrid boards, pay attention to the CTE mismatch between RO4835 (X/Y ≈ 14–16 ppm/°C) and standard FR-4 (X/Y ≈ 14–17 ppm/°C). The in-plane match is close, so warpage risk is low. The Z-axis mismatch is larger, but since the FR-4 core sits between ground and power planes with no through-vias carrying RF signals, barrel fatigue is manageable for most designs. For six-layer or eight-layer builds with multiple RF signal layers, an all-Rogers stack using RO4835 cores and RO4450F bond plies eliminates the mismatch entirely, at higher material cost.

Fabrication and Processing Notes

Drilling

RO4835 drills with standard carbide bits used for FR-4. Recommended entry speed is 150–200 surface feet per minute (SFM) with a chip load of 1.0–2.0 mil per revolution for 12–16 mil diameter holes. Unlike PTFE laminates such as CuClad 233, RO4835 does not smear badly, so a standard desmear cycle (permanganate or plasma) is sufficient.

Copper Plating and Surface Finish

The oxidation-resistant resin means that the copper-dielectric interface stays clean through multiple thermal cycles, preserving peel strength. Standard electroless copper and electrolytic plating processes apply. For surface finish, ENIG (electroless nickel / immersion gold) is the most common choice on RF boards because it maintains a flat pad surface for fine-pitch components and does not degrade solderability over storage. OSP is acceptable for single-reflow designs, but ENIG or ENEPIG is preferred when the board will see rework.

Lamination

Rogers recommends laminating RO4835 with RO4450B or RO4450F prepreg at 375 °F (190 °C), 200–400 psi, for 90 minutes. The bonding ply fills etched-copper relief and maintains a uniform dielectric thickness. If you are hybridizing with FR-4 prepreg instead, verify that the cure temperature of the FR-4 prepreg does not exceed the bond strength of the RO4835 core—most 180 °C Tg FR-4 prepregs cure at 185 °C, which is compatible.

Impedance Control

RO4835’s tight Dk tolerance (± 0.05) supports ± 5 % impedance control on production panels without difficulty. For designs requiring ± 3 %, specify tighter copper-etch tolerances (± 0.5 mil) and confirm the fabricator’s dielectric-thickness tolerance on incoming RO4835 cores. The Rogers RO4835 data sheet lists process-design Dk values for various thicknesses that should be used in your field solver rather than the “typical” 3.48 number alone.

Rogers RO4835 PCB Application Areas

Automotive Radar and ADAS

At 24 GHz and 77 GHz, RO4835 is used for patch-antenna feed networks and power-divider boards in automotive radar modules. The oxidation resistance is critical here: automotive electronics must survive wave soldering, selective soldering and conformal coating cure cycles. For the antenna elements themselves at 77 GHz, many designers move to RO3003G2 with its lower Df, but RO4835 handles the lower-frequency distribution network and digital interface layers cost-effectively.

Base-Station Power Amplifiers

Cellular base-station PAs operate in bands from 700 MHz to 3.5 GHz and dissipate significant heat. RO4835’s thermal conductivity of 0.62 W/m·K is modest compared to thermally enhanced laminates like Rogers TC600, but it is adequate for combiners and matching networks where heat is managed through the chassis. The material’s dimensional stability through reflow means that impedance-critical Wilkinson dividers and Lange couplers hold their designed performance after assembly.

Military and Aerospace

A Rogers RO4835 PCB meets IPC-6012 Class 3/A requirements when fabricated to the appropriate slash sheets. Its UL 94 V-0 rating and low moisture absorption (0.06 %) make it suitable for conformal-coated avionics boards and phased-array antenna sub-assemblies. The material’s ability to survive multiple rework cycles without delamination is particularly valuable in low-volume, high-reliability builds where hand rework of BGA components is common.

Satellite Communication and VSAT

Ku-band (12–18 GHz) and Ka-band (26.5–40 GHz) terminal boards use RO4835 for LNA input matching, filter structures and diplexer networks. At these frequencies, the Df of 0.0037 introduces modest insertion loss—roughly 0.02 dB/cm additional loss compared to RO4003C at 20 GHz on a 10 mil microstrip—so the designer must decide whether the oxidation benefit justifies that loss penalty. For applications where ultra-stable Dk over temperature is the priority, CLTE-MW may be the better fit.

Design Guidelines and Best Practices

• Use process Dk, not design Dk. Rogers publishes two Dk values: a “design” value (3.48) measured in a stripline resonator and a “process” value that varies by thickness and copper roughness. Use the process value in your 2D field solver for accurate impedance predictions on any Rogers RO4835 PCB.
• Account for copper roughness. Standard ED copper on RO4835 has an Rz roughness of roughly 5–7 µm. At frequencies above 10 GHz, this roughness increases conductor loss measurably. Specify rolled or reverse-treated (RT) foil if your loss budget is tight above 20 GHz.
• Via transitions. Back-drill or use blind/buried vias to minimize via stubs in multilayer RO4835 boards operating above 10 GHz. A 40 mil stub can produce a resonant null around 30 GHz that corrupts wideband performance.
• Ground-via fencing. Place ground vias at λ/20 spacing along microstrip-to-stripline transitions and around coupled-line filters to suppress parallel-plate modes. On RO4835 at 24 GHz, λ/20 is about 10 mil (0.25 mm).
• Panel utilization. RO4835 is available in standard panel sizes of 12 × 18 in and 18 × 24 in. Discuss panel utilization with your fabricator early—RF laminates are expensive, and poor panelization wastes material.

Cost Drivers and Procurement Tips

RO4835 carries a moderate premium over RO4350B because of the oxidation-resistant resin chemistry. The premium is small per panel but adds up in volume. Key cost drivers include:

• Core thickness: Thinner cores (6.6 mil, 10 mil) cost more per square foot than 20 mil or 30 mil cores due to lower manufacturing yield at Rogers.
• Copper weight: 2 oz copper on RO4835 is a special order for most distributors; ½ oz and 1 oz are stock items.
• Hybrid vs all-Rogers: An all-Rogers six-layer stack can cost 3–5× more in material alone than a hybrid stack using FR-4 inner cores. Quantify where you actually need low Dk/Df before committing every layer to RO4835.
• Lead time: Stock thicknesses (10 mil and 20 mil, ½ oz copper) typically ship in 1–2 weeks from distribution. Non-standard builds may require 6–8 weeks from Rogers.

When sourcing, request the lot-specific Dk and Df test data from the distributor. Rogers provides this on every shipment, and it lets you feed measured values into your impedance model rather than relying on datasheet typicals.

How Does a Rogers RO4835 PCB Compare to Non-Rogers Alternatives?

Several competitors offer thermoset laminates in the Dk 3.4–3.6 range. Taconic TLF-35 targets similar antenna applications at Dk 3.50 but uses a different resin system without Rogers’ specific oxidation-resistance claim. Isola Astra MT77, with Dk 3.00 and Df 0.0017, offers lower loss but at a higher price point and with different processing requirements. The choice often comes down to supply-chain availability, fabricator experience with the material, and the specific thermal profile your assembly house runs.

Frequently Asked Questions

Is RO4835 a drop-in replacement for RO4350B?

Electrically, yes—Dk, Df, CTE and thickness options are identical. You can swap RO4835 into an existing RO4350B design without re-tuning impedance or changing the stackup. The only change is improved oxidation resistance during Pb-free assembly, which may actually improve your first-pass yield.

What is the maximum operating frequency for RO4835?

Rogers characterizes RO4835 up to 40 GHz in published data. Designers have used it successfully for feed networks at 77 GHz, though conductor loss from copper roughness becomes the dominant loss mechanism above 30 GHz. Specifying low-roughness foil extends the practical ceiling.

Can RO4835 be used with standard FR-4 prepreg in a hybrid stackup?

Yes, provided the FR-4 prepreg cure temperature does not exceed roughly 200 °C and the CTE mismatch is managed. Rogers RO4450F prepreg is the recommended bonding material for best results, but compatible third-party prepregs exist.

Does RO4835 require special desmear or etchback?

No. Standard permanganate or plasma desmear processes used for FR-4 work without modification. This is one of the major processing advantages of the entire RO4000 family over PTFE-based laminates like CuClad 250, which often need sodium-naphthenate surface preparation.

What IPC class can RO4835 boards achieve?

RO4835 boards are routinely fabricated to IPC-6012 Class 3 (high-reliability) and Class 3/A (space and military addendum) when processed by qualified fabricators with appropriate incoming inspection and coupon testing.