RO4003C vs RO4835 | Oxidation Resistance Compared

RO4003C vs RO4835: The Short Answer

RO4003C and RO4835 are both thermoset hydrocarbon ceramic laminates from Rogers Corporation with a design Dk of 3.48 ± 0.05 at 10 GHz. The critical difference is resin chemistry: RO4835 uses a proprietary oxidation-resistant resin system developed specifically to withstand the thermal stress of multiple lead-free solder reflow cycles (peak temperatures of 260 °C and above). RO4003C, while an excellent RF laminate, can exhibit surface oxidation—visible as brown discoloration on exposed copper-free areas—and a measurable rise in dissipation factor after repeated high-temperature excursions. If your board will see lead-free assembly with multiple reflow passes, RO4835 is the safer choice. If you solder with tin-lead profiles or have a single reflow pass, RO4003C delivers the same RF performance at a lower cost.

Why Oxidation Resistance Matters in RF PCBs

Lead-free soldering pushed peak reflow temperatures from roughly 215 °C (SnPb) to 245–260 °C (SAC305 and similar alloys). At those temperatures, thermoset resin systems can undergo thermo-oxidative degradation: oxygen diffuses into the resin matrix, breaks polymer chains, and creates polar by-products that raise the dissipation factor (Df). On a PTFE vs hydrocarbon laminate level, hydrocarbon ceramics are more susceptible to this than fluoropolymers because their C–H bonds are more reactive with oxygen at elevated temperatures.

For a single-sided SMT board with one reflow pass, the effect is usually negligible. But in complex RF assemblies—think a multilayer stackup with top-side and bottom-side components requiring two or three reflow cycles plus selective soldering—cumulative thermal exposure can push Df high enough to affect insertion loss budgets, especially above 5 GHz where loss per unit length is already significant.

Head-to-Head Specification Comparison

Data above is drawn from the Rogers RO4003C product page and the corresponding RO4835 datasheet. Always confirm against the latest revision for your design.

Electrical Performance: How Close Are They Really?

At room temperature, fresh out of the box, the two laminates are close but not identical. RO4003C’s Df of 0.0027 at 10 GHz is genuinely lower than RO4835’s 0.0037—a difference of roughly 0.001. In a 50 Ω microstrip at 10 GHz on 0.020 in (0.508 mm) substrate, that translates to approximately 0.15–0.2 dB/in of extra dielectric loss for RO4835 under ideal conditions. For many designs operating below 6 GHz, this gap is swallowed by conductor loss and is not the dominant contributor.

The picture flips after thermal stress. Rogers’ own application notes show that RO4003C’s Df can rise by 10–20% after multiple lead-free reflow cycles, while RO4835’s Df remains essentially flat. At that point the two materials converge, and the RO4835 board in the field may actually have lower loss than the RO4003C board that went through the same assembly process.

If you are comparing RO4003C against other members of the RO4000 family, our RO4350B vs RO4003C comparison covers the Dk 3.66 variant in detail.

Resistance, Geometry and Trace Dimensions

Both RO4003C and RO4835 are processed with standard FR-4 fabrication equipment—no special PTFE handling like plasma or sodium etching is required. Because the Dk values are nearly identical, a microstrip trace designed for 50 Ω on one material will be within a few percent on the other. The slight Dk difference (3.38 process vs 3.48 process) does shift the required trace width by roughly 1–2 mil (0.025–0.05 mm), so re-run your impedance model when switching.

When laying out traces, you also need to account for the DC and low-frequency resistance of the copper itself—particularly for bias-tee networks, DC feeds, and thin traces in dense layouts. Use the calculator below to check resistance for a given trace geometry and copper weight.

For example, a 10 mil (0.254 mm) wide trace in 1 oz copper (1.4 mil / 35 µm thick) over a 2-inch run gives roughly 0.18 Ω at DC—negligible for most RF signal paths, but worth checking for long bias lines that carry tens of milliamps to active devices, where voltage drop can shift the operating point.

Z-Axis CTE and Via Reliability

One often-overlooked advantage of RO4835 is its lower Z-axis CTE: 31 ppm/°C below Tg compared with 46 ppm/°C for RO4003C. During each reflow cycle, the board heats from room temperature to 260 °C, and the Z-axis expansion stresses plated through-hole barrels. A lower CTE means less strain per cycle, which directly improves via fatigue life—important for boards that will see multiple assembly passes or field-level rework.

For high-layer-count hybrid stackups where Rogers laminates are bonded with FR-4 or other prepregs, the CTE mismatch between layers drives delamination risk. RO4835’s 31 ppm/°C is closer to typical FR-4 Z-CTE values (about 40–70 ppm/°C depending on glass content), which can reduce interlayer stress in mixed-material builds.

Processability and Fabrication

Drilling and Plating

Both materials drill cleanly with standard carbide bits and produce good smear-free hole walls without plasma desmear—a significant cost advantage over PTFE-based laminates. Electroless copper plating adhesion is comparable, and both support the full range of surface finishes (ENIG, ENEPIG, immersion silver, OSP, HASL).

Lamination

Rogers specifies similar lamination profiles for both: 350–400 °F (177–204 °C) at 200–400 psi for 60–120 minutes, depending on panel size and stackup. They can be bonded with RO4450F or RO4450T prepregs, or with standard FR-4 prepregs in hybrid constructions. No special atmosphere (nitrogen blanket) is needed.

Solder Mask Adhesion

Surface oxidation on RO4003C after reflow can occasionally affect solder mask adhesion on reworked areas. RO4835’s oxidation-resistant surface stays cleaner, giving more consistent mask adhesion even after thermal cycling—a practical benefit that does not show up on any datasheet but matters on the production floor.

When to Choose RO4003C

• Tin-lead assembly: peak reflow at ~215 °C causes minimal oxidation on either material, so the lower Df and lower cost of RO4003C win.
• Single reflow pass: even with SAC305, one pass at 260 °C does not degrade RO4003C enough to matter in most designs below 10 GHz.
• Loss-critical designs at 10 GHz+: the 0.001 Df advantage of RO4003C is meaningful when every tenth of a dB counts—provided the assembly process is gentle.
• Cost-sensitive high-volume products: the 10–20% price premium of RO4835 adds up at scale.

When to Choose RO4835

• Lead-free assembly with multiple reflow passes: this is the primary use case Rogers designed RO4835 for.
• Mixed-technology boards (SMT + through-hole + selective solder): the cumulative thermal budget can be three or more high-temperature excursions.
• Automotive and aerospace applications: where reliability standards (e.g., IPC-6012 Class 3) demand proven thermal cycling endurance and the lower Z-CTE matters.
• Designs that may require field rework: the board must survive an additional reflow or hot-air rework without performance drift.
• Hybrid multilayer stackups: the lower Z-CTE reduces stress at bonded interfaces.

Comparing Within the Broader Laminate Landscape

RO4003C and RO4835 sit in the mid-range of RF laminates: better loss than FR-4, easier to fabricate than PTFE, and more affordable than ultra-low-loss options like Megtron 7 or Tachyon 100G. If you need even lower loss and are willing to handle PTFE processing, materials like RT/duroid 5880 (Dk 2.20, Df 0.0009) are available—our RT/duroid 5880 vs Taconic TLY-5 comparison covers that tier. For a broader survey across manufacturers, the RF laminate comparison hub organizes all the head-to-head matchups.

If your decision is between Rogers and another vendor entirely, Rogers vs Isola may also be relevant, especially if Isola’s I-Tera MT40 is on your shortlist as a lower-cost alternative.

Practical Decision Checklist

1. Define your assembly profile: How many reflow passes? What peak temperature? SnPb or SAC?
2. Set your loss budget: Calculate the maximum acceptable insertion loss per unit length at your operating frequency. If RO4835’s Df of 0.0037 still meets it, oxidation resistance comes free of electrical penalty.
3. Check via reliability requirements: For Class 3 or automotive-grade boards, RO4835’s lower Z-CTE is a tangible advantage.
4. Confirm thickness and copper foil availability: Both materials share most standard constructions, but check Rogers’ current availability matrix for your specific thickness and foil combination.
5. Price the delta: Get quotes for both materials at your required panel size and volume. The 10–20% premium may shrink at higher volumes or when ordered alongside other RO4000 laminates.
6. Prototype on one, qualify on the other if needed: Because the Dk values are so close, a design proven on RO4003C can usually migrate to RO4835 with only minor trace-width adjustments and a re-run of the impedance simulation.

FAQ

Can I drop RO4835 into an existing RO4003C design without changes?

Nearly. The process Dk differs slightly (3.38 vs 3.48), so controlled-impedance traces will shift by about 1–2 mil in width. Re-simulate your stackup and adjust trace geometry before committing to fabrication.

Does RO4835 have any disadvantage besides cost?

Its Df at 10 GHz is 0.0037 versus 0.0027 for RO4003C—about 37% higher in relative terms. For loss-critical front-end filters or long feed networks above 10 GHz on a gently assembled board, RO4003C may still be the better pick.

Is RO4835 necessary for single-sided lead-free reflow?

Usually not. A single SAC305 reflow cycle at 260 °C peak with a well-controlled thermal profile causes minimal oxidation on RO4003C. RO4835 earns its premium when the board faces two or more high-temperature passes.

Are RO4003C and RO4835 both compatible with standard FR-4 prepregs in hybrid stackups?

Yes. Both can be laminated with FR-4 prepregs (e.g., Isola 370HR, Panasonic Megtron) using conventional press cycles. RO4835’s lower Z-CTE provides a better CTE match to FR-4 cores, reducing interlayer stress.

What other RO4000-series materials offer oxidation resistance?

RO4835T (a spread-glass version) and RO4360G2 also incorporate oxidation-resistant resin systems. RO4350B does not; it shares RO4003C’s standard resin chemistry with a higher Dk of 3.48/3.66.