Rogers RO4835 is a ceramic-filled hydrocarbon thermoset laminate in the RO4000 series. It targets RF and microwave circuits that need low loss, controlled dielectric properties, standard epoxy/glass-compatible fabrication, and better resistance to long-term thermal oxidation than conventional thermoset microwave laminates.
The material is often considered for automotive radar and sensors, point-to-point microwave radios, power amplifiers, phased-array radar, and other RF components. Selecting it by application name alone is risky. Process Dk, design Dk, laminate thickness, copper foil, temperature exposure, bondply, hybrid stackup, and finished geometry all influence the electrical result.
This guide uses the Rogers official RO4835 Laminate Data Sheet, revision 1686 092425, publication 92-160. Its values are typical material data, not automatic finished-PCB guarantees. QFPCB confirms the exact construction, material availability, impedance model inputs, drilling plan, inspection, and test requirements for each project.
What Is Rogers RO4835?
RO4835 is a rigid, thermoset high-frequency laminate designed to combine RO4000-series electrical performance with improved stability during elevated-temperature exposure. Rogers states that thermoset laminates can oxidize over time and temperature, slightly changing Dk and Df. RO4835 was developed to reduce that oxidation-driven change compared with typical hydrocarbon thermoset microwave materials.
The laminate can be processed with standard epoxy/glass methods and does not require the specialized via preparation associated with PTFE. That does not make it ordinary FR-4. Material-specific thickness control, copper treatment, dimensional compensation, bondply selection, press behavior, and RF inspection remain important.
RO4835 and RO4835T are not interchangeable names. RO4835T is a spread-glass, 3.3-Dk thin-core family intended to complement RO4835 in multilayer designs. This article covers RO4835 only.
Rogers RO4835 Datasheet Properties
The table keeps the official frequencies, methods, conditions, and footnotes visible. Process Dk and design Dk answer different engineering questions and should not be merged into a single unlabeled number.
| Property | Typical value | Unit | Test condition / method |
|---|---|---|---|
| Process Dk | 3.48 ± 0.05 | – | 23°C, 10 GHz; IPC-TM-650 2.5.5.5 |
| Design Dk | 3.66 | – | 8-40 GHz; differential phase length method |
| Dissipation factor | 0.0037 | – | 23°C, 10 GHz; IPC-TM-650 2.5.5.5 |
| TCDk | +50 | ppm/°C | -50°C to 150°C; IPC-TM-650 2.5.5.5 |
| Tg / Td | >280 / 390 | °C | TMA condition A / TGA; IPC-TM-650 2.4.24.3 / ASTM D3850 |
| CTE X / Y / Z | 10 / 12 / 31 | ppm/°C | -55°C to 288°C; IPC-TM-650 2.4.41 |
| Thermal conductivity | 0.66 | W/(m·K) | 80°C; ASTM C518 |
| Dimensional stability X/Y | <0.5 | mm/m | After etch, +E2/150°C; IPC-TM-650 2.4.39a |
| Copper peel strength | 0.88 (5.0) | N/mm (pli) | After solder float, 35 µm ED foil; IPC-TM-650 2.4.8 |
| Moisture absorption | 0.05 | % | 50°C, 48 h; ASTM D570 |
| Density / flammability | 1.92 / V-0 | g/cm³ / class | 23°C ASTM D792 / UL 94 |
Process Dk Versus Design Dk
The 3.48 ± 0.05 process Dk is measured at 10 GHz using the IPC clamped stripline method. Rogers notes that this method can artificially lower the measured Dk because air gaps may exist between the laminate and resonator card. The value is useful for material specification and incoming control under the stated method.
The 3.66 design Dk is an average derived from tested production lots and common thicknesses using differential phase length measurements from 8 to 40 GHz. It is usually the better starting point for transmission-line modeling, but the final model still needs the actual laminate thickness, copper thickness and profile, solder mask, trace geometry, and frequency band.
One more exception matters: the official footnote gives 4 mil RO4835 a process Dk of 3.35 ± 0.05 and IPC-4103A/240 conformance. Do not apply the general 3.48 value to that thickness without checking the released material callout.
Standard Thicknesses, Panels and Copper
Rogers lists standard dielectric thicknesses of 0.004, 0.0066, 0.010, 0.020, 0.030, and 0.060 inch, corresponding approximately to 0.10, 0.17, 0.25, 0.51, 0.76, and 1.52 mm. Each thickness has its own published tolerance, from ±0.0007 inch on the thinnest offerings to ±0.0040 inch on 0.060 inch material.
Standard panel sizes include 12 × 18, 24 × 18, 24 × 36, and 48 × 36 inches. Standard cladding is 0.5 oz or 1 oz electrodeposited copper. Other configurations require confirmation; a catalog panel size is not the same as an unrestricted finished-board size.
QFPCB’s general RO4000 review window includes single-, double-sided, multilayer, and hybrid constructions. Final usable panel, registration allowance, edge clearance, copper profile, and material yield depend on the selected thickness and stackup.
Why Oxidation Resistance Matters
Temperature and time can oxidize hydrocarbon thermoset systems and gradually change dielectric behavior. In an RF channel, even a small shift can affect phase, impedance, insertion loss, filter response, or antenna matching. RO4835 is designed to improve oxidation resistance for performance-sensitive and higher-volume applications.
That benefit is not a lifetime guarantee. Operating temperature, oxygen exposure, copper interfaces, enclosure conditions, board design, and duty cycle still matter. If stability after aging is a contractual requirement, define the conditioning profile, measurement method, sample count, acceptance limit, and frequency rather than relying on the phrase “oxidation resistant.”
RO4835 Versus RO4350B and RO4835T
Rogers states that RO4835 has electrical and mechanical properties similar to RO4350B while offering enhanced high-temperature oxidation resistance. That makes it a candidate when the design already fits the general RO4000 process approach but long thermal exposure or automotive conditions increase concern about property drift.
RO4835T is not simply a thinner RO4835 sheet. It is a spread-glass, 3.3-Dk thin-core product family designed for multilayer inner layers and compatible material sets. Its Dk, thickness options, glass construction, and slash-sheet details are different. Procurement drawings should state the exact laminate family, thickness, copper type, and acceptable alternatives.
For a broader material decision, compare the Rogers RO4003C and RO4350B guide using the same frequency, method, copper, and construction assumptions.
RO4835 Hybrid Stackups and Bonding Materials
RO4835 can be used in multilayer and mixed-dielectric constructions, including RO4835 with compatible RO4000 bonding materials or an engineered FR-4 hybrid. A hybrid stackup can limit the higher-frequency laminate to the RF layers while using another material for power, control, or mechanical thickness.
The tradeoff is that different materials introduce different Dk, Df, CTE, moisture, cure, flow, and thickness behavior. The design must define RF layer placement, reference planes, copper balance, bondply, finished dielectric thickness, via spans, and thermal history. QFPCB supports high-frequency PCB manufacturing and reviews compatibility before confirming the press structure.
Because RO4835 is a high-frequency material, QFPCB does not describe it as an HDI or Any-Layer HDI stackup. We can provide impedance simulation, stackup design, and technical support for a high-frequency hybrid stackup or a mechanically drilled blind-via stackup, subject to material, blind-via span, copper, press-cycle, and manufacturability review.
Impedance Modeling and Copper Roughness
Controlled impedance depends on more than a datasheet Dk. Trace width, etched trapezoid, copper thickness, dielectric thickness, reference-plane geometry, solder mask, copper roughness, glass-resin distribution, and frequency all contribute. LoPro reverse-treated copper may reduce conductor loss in suitable configurations, but the exact copper offering must be confirmed.
QFPCB can review the PCB layer stackup and support impedance-controlled PCB manufacturing for RO4835 projects. PCB engineer Alan has more than 10 years of PCB CAM engineering experience. Technical email: [email protected]. Send the impedance table, layer assignment, differential spacing, copper callout, finished dielectric targets, and coupon requirements with the RFQ.
Do not use one generic Dk for both material purchasing and field-solver input without documenting why. We identify the source and method of the selected model value so later revisions can be compared consistently.
Drilling, Plating and Mechanical Blind Vias
RO4835 uses standard epoxy/glass-compatible fabrication techniques and does not require PTFE-specific hole treatment. Even so, drill diameter, material thickness, aspect ratio, copper thickness, smear removal, hole-wall preparation, plating, and thermal stress must be reviewed together.
For a mechanically drilled blind-via construction, provide the blind layer pair, drill and finished-hole sizes, capture pads, dielectric thickness, press sequence, and required reliability evidence. A competitor’s published blind-via example does not establish QFPCB capability for every combination. Final approval is project-specific.
Low Z-axis expansion and a copper-like in-plane CTE support plated-through-hole reliability, but they do not replace microsection, electrical test, thermal conditioning, or customer acceptance requirements. Specify the required inspection and coupon plan in the fabrication drawing.
Applications and Qualification Boundaries
The official typical applications are automotive radar and sensors, point-to-point microwave, power amplifiers, phased-array radar, and RF components. These examples establish intended use, not automatic automotive, aerospace, defense, or radar certification of a finished board.
For automotive radar, define frequency band, RF loss budget, thermal environment, material revision, lot traceability, copper profile, surface finish, dimensional tolerances, cleanliness, and qualification documents. For power amplifiers, include the heat path, copper weight, via plan, attachment method, and maximum local temperature.
RO4835 is RoHS compliant and suitable for applications requiring UL 94 V-0, according to Rogers. The purchase package should still identify the applicable certification, IPC-4103 slash sheet, customer specification, and evidence required for the finished PCB.
RFQ Checklist for an RO4835 PCB
- Gerber, ODB++, or IPC-2581 data and a controlled fabrication drawing.
- Exact RO4835 thickness, copper type and weight, acceptable alternates, and slash-sheet requirement.
- Layer stack, bondply or prepreg, finished thickness, copper by layer, and material placement.
- Frequency range, impedance targets and tolerances, loss budget, and coupon/test requirements.
- Finished holes, drill spans, mechanical blind vias, backdrill, aspect ratio, and plating requirements.
- Board outline, array or delivery format, quantity, revision, and target schedule.
- Surface finish, solder mask, edge plating, cavity, controlled depth, and mechanical tolerances.
- Operating temperature, aging or qualification profile, traceability, reports, and acceptance criteria.
QFPCB uses these inputs to review material availability, stackup, impedance, copper compensation, lamination, drilling, inspection, and quotation assumptions before production.
Rogers RO4835 FAQs
What is the dielectric constant of RO4835?
The official datasheet reports a process Dk of 3.48 ± 0.05 at 10 GHz by IPC-TM-650 2.5.5.5 and a design Dk of 3.66 from 8 to 40 GHz by differential phase length. The 4 mil laminate is an exception with a process Dk of 3.35 ± 0.05.
What is the dissipation factor of RO4835?
Rogers reports a typical Df of 0.0037 at 10 GHz and 23°C using IPC-TM-650 2.5.5.5. Treat this as method- and condition-specific material data. Finished channel loss also depends on copper roughness, trace geometry, dielectric thickness, connectors, launches, frequency, and board fabrication.
Is RO4835 the same as RO4835T?
No. RO4835T is a spread-glass, 3.3-Dk thin-core family intended to complement RO4835 in multilayer designs. The materials have different constructions, electrical values, thickness offerings, and specification details. Use the exact Rogers product name and thickness in the drawing and purchase order.
How does RO4835 compare with RO4350B?
Rogers describes their electrical and mechanical properties as similar, while RO4835 provides enhanced resistance to high-temperature oxidation. The better choice depends on frequency, thermal aging, approved material list, thickness, copper option, availability, qualification, and cost. Compare values under matching test methods before substituting.
Can RO4835 be processed like FR-4?
Rogers states that RO4000 laminates can use standard epoxy/glass fabrication techniques without specialized via preparation. However, RO4835 still requires material-specific stackup, dimensional compensation, copper, lamination, drilling, and RF verification. “FR-4 process compatible” does not mean the material can be substituted or fabricated without engineering controls.
Can RO4835 be used for an HDI stackup?
QFPCB does not market high-frequency RO4835 projects as HDI or Any-Layer HDI stackups. We can review RO4835 hybrid constructions or mechanically drilled blind-via structures and provide impedance and stackup support. Feasibility depends on the exact material combination, blind-via layers, drill geometry, dielectric thickness, copper, and press sequence.
Is RO4835 suitable for automotive radar?
Automotive radar and sensors are official typical applications, but the material name alone does not qualify a finished board. The project must define frequency, temperature, aging, RF loss, traceability, dimensional control, copper profile, surface finish, test coupons, and the relevant customer or automotive qualification requirements.
What should I send for an RO4835 PCB quote?
Send fabrication data, drawing, material and copper callouts, stackup, bondply, impedance table, frequency and loss requirements, drill and blind-via plan, finish, quantity, thermal profile, inspection criteria, and required reports. These inputs allow QFPCB to review the complete RF construction rather than quote from the laminate name alone.
Request an RO4835 Engineering Review
RO4835 is most useful when low RF loss, controlled dielectric behavior, oxidation resistance, and standard-process compatibility must work together. The correct design still depends on choosing the right Dk input, thickness, copper, bondply, layer placement, via structure, and verification plan.
Send QFPCB your stackup, fabrication files, impedance table, frequency band, thermal environment, copper callout, quantity, and acceptance requirements. We will review the high-frequency hybrid or mechanically drilled blind-via construction and confirm the manufacturable approach before production.
