Choose RO4003C when your priority is lower dielectric loss and cost-efficient RF performance, provided the finished board does not require a UL 94 V-0 laminate. Choose RO4350B when flame resistance, lower Z-axis thermal expansion and plated-through-hole reliability are more important.
RO4003C offers the lower dissipation factor, while RO4350B offers UL 94 V-0 performance and a lower Z-axis coefficient of thermal expansion.
Both materials belong to the same RO4000 family of glass-reinforced hydrocarbon ceramic laminates. They can be processed using methods similar to standard epoxy-glass boards and do not require the special through-hole preparation normally associated with PTFE-based microwave materials.
That shared processing platform can make the two materials appear nearly interchangeable. Electrically and mechanically, however, they solve different design priorities.
The correct choice is not determined by which material has the more familiar name. It is determined by which failure your product cannot tolerate:
- excessive insertion loss;
- inability to meet a flame-retardant requirement;
- plated-through-hole fatigue;
- impedance deviation;
- unnecessary material cost;
- an unstable transition from prototype to volume production.
The 30-Second Comparison
| Property | RO4003C | RO4350B | Why It Matters |
| Process dielectric constant | 3.38 ± 0.05 | 3.48 ± 0.05 | Affects impedance and trace dimensions |
| Design dielectric constant | 3.55 | 3.66 | Commonly used for circuit modelling |
| Dissipation factor at 10 GHz | 0.0027 | 0.0037 | RO4003C has lower dielectric loss |
| Z-axis CTE | 46 ppm/°C | 32 ppm/°C | Lower expansion can improve PTH reliability |
| Thermal conductivity | 0.71 W/m·K | 0.69 W/m·K | Similar bulk heat-spreading capability |
| Water absorption | 0.04% | 0.05% | Both are relatively low |
| Peel strength with 1 oz ED copper | 6.0 lb/in | 5.0 lb/in | Relevant to copper adhesion and processing |
| Density | 1.8 g/cm³ | 1.9 g/cm³ | RO4350B is slightly denser |
| UL 94 flammability | Non-FR | V-0 | Often the decisive compliance difference |
| Lead-free process compatible | Yes | Yes | Both support modern assembly processes |
The values above are published typical or specification values and must be interpreted with the relevant test methods, copper construction and finished stackup. (罗杰斯公司)
Decision Gate 1: Does the Finished Product Require UL 94 V-0?
This is the fastest way to separate the two materials.
RO4350B is UL 94 V-0 rated. RO4003C is non-brominated but is not rated UL 94 V-0. The material manufacturer specifically points designers requiring a V-0 flame rating toward RO4350B or another rated material. (罗杰斯公司)
When UL 94 V-0 is a mandatory product, customer or certification requirement, standard RO4003C may be eliminated before RF performance is compared.
This distinction can matter in:
- active RF devices;
- base-station electronics;
- power-amplifier assemblies;
- industrial equipment;
- telecommunications infrastructure;
- products installed in enclosed systems;
- assemblies evaluated under customer flammability standards.
Do not assume that the finished PCB automatically inherits a particular material rating. The board construction, laminate thickness, copper configuration and fabrication facility may all affect the applicable recognition.
The procurement team should confirm:
- the exact laminate designation;
- required UL rating;
- recognized construction;
- finished board thickness;
- copper weight;
- whether a hybrid stackup changes the compliance route;
- whether the selected fabricator can supply the required certification documentation.
Practical conclusion
If V-0 is mandatory, RO4350B is usually the more direct choice.
If V-0 is not required, continue to the electrical-loss decision before selecting the material.
Decision Gate 2: Is Every Fraction of a Decibel Important?
RO4003C has a published dissipation factor of 0.0027 at 10 GHz, compared with 0.0037 for RO4350B. Within the standard RO4000 product family, RO4003C is positioned as the lower-dielectric-loss option and is commonly considered for performance-sensitive, cost-conscious microwave circuits. (罗杰斯公司)
This gives RO4003C an advantage when dielectric attenuation is a critical part of the link budget.
Examples include:
- long RF feed networks;
- low-noise receiver paths;
- microwave filters;
- phased-array distribution networks;
- antenna feed boards;
- couplers and power dividers;
- test and measurement circuits;
- low-power signals with limited gain margin.
For the same frequency, geometry and copper system, RO4003C generally provides lower dielectric loss than standard RO4350B.
However, the difference between their published Df values does not directly equal the difference in finished-board insertion loss.
Total insertion loss can also include:
- copper skin-effect loss;
- copper-foil roughness;
- conductor width and thickness;
- surface finish;
- solder-mask effects;
- connector launches;
- via transitions;
- radiation;
- impedance mismatch.
If rough copper or ENIG covers the RF path, conductor-related losses may reduce the practical advantage expected from the lower laminate Df.
Do not compare Df without checking the test method
The values in a material table are useful for initial selection, but the final channel model should reflect:
- operating frequency;
- transmission-line structure;
- material thickness;
- copper profile;
- resin and glass construction;
- process or design Dk;
- fabricated trace geometry.
A designer should not conclude that RO4003C will reduce total loss by a fixed percentage simply because its Df number is lower.
Consider LoPro copper when conductor loss dominates
Both material systems are available in lower-profile copper constructions within the wider RO4000 platform. Reverse-treated, low-profile copper can reduce conductor loss and improve insertion loss, particularly as frequency rises. (罗杰斯公司)
For a loss-critical project, the real comparison may therefore be:
- standard RO4003C;
- RO4003C with low-profile copper;
- standard RO4350B;
- RO4350B with low-profile copper.
The foil construction can be almost as important as the resin system once surface-current effects become significant.
Decision Gate 3: How Severe Is the Thermal and PTH Reliability Environment?
RO4350B has a lower published Z-axis coefficient of thermal expansion: 32 ppm/°C compared with 46 ppm/°C for RO4003C. (罗杰斯公司)
Z-axis expansion matters because the laminate expands through its thickness during:
- lead-free reflow;
- thermal cycling;
- environmental testing;
- high-power operation;
- field temperature changes.
The copper plating inside a through-hole does not expand at exactly the same rate as the surrounding laminate. Repeated mismatch can place mechanical strain on the plated barrel, especially in thick multilayer boards or high-aspect-ratio holes.
RO4350B’s lower Z-axis CTE can provide a stronger starting point for multilayer boards exposed to demanding thermal cycles or PTH reliability requirements.
This does not mean an RO4003C board automatically has poor via reliability. The result also depends on:
- total board thickness;
- finished hole diameter;
- plating thickness;
- aspect ratio;
- number of reflow cycles;
- peak assembly temperature;
- via structure;
- copper quality;
- drilling and desmear process.
Both materials have a resin-system glass-transition temperature above 280°C and are compatible with lead-free assembly. Their processing guidance also notes that desmear is often unnecessary for simple double-sided boards because the high-Tg resin minimizes smear, although multilayer constructions may still require treatment depending on the bonding system. (罗杰斯公司)
RO4350B deserves priority when:
- the PCB is thick;
- through-holes have a high aspect ratio;
- several lead-free reflow cycles are expected;
- field temperature cycling is severe;
- the design contains active or high-power devices;
- via reliability is more critical than the difference in dielectric loss.
RO4003C remains attractive when:
- the construction is relatively simple;
- RF loss dominates the decision;
- via geometry is conservative;
- the assembly profile is well controlled;
- flammability certification is not required.
Decision Gate 4: Will the Board Be Multilayer, Hybrid or Double-Sided?
Both laminates can be used in double-sided and multilayer RF PCBs. They can also be incorporated into hybrid stackups that place the RF material only on electrically critical layers while using another compatible material elsewhere.
The RO4000 family is designed to use processing methods similar to conventional epoxy-glass fabrication. Standard imaging, copper etching, drilling, plating and common final finishes can be used when the process is properly controlled. (罗杰斯公司)
That compatibility is one reason both materials are used as alternatives to more fabrication-sensitive PTFE laminates.
Double-sided microwave boards
For a straightforward double-sided RF board, the material decision may focus primarily on:
- dielectric loss;
- Dk;
- thickness availability;
- copper type;
- flame rating;
- cost.
RO4003C may be attractive when loss and budget dominate. RO4350B may be preferred when V-0 certification or high-power operation is involved.
Multilayer RF boards
A multilayer board introduces additional concerns:
- bonding-layer selection;
- registration;
- resin flow;
- buried RF layers;
- plated-through-hole reliability;
- sequential lamination;
- mixed dielectric systems.
RO4400-series bondply materials are designed for use with both RO4003C and RO4350B multilayer constructions and support lead-free processing and sequential lamination. (罗杰斯公司)
The Rogers PCB manufacturing discussion should therefore include the complete stackup rather than only the core material name.
Hybrid Rogers and FR-4 constructions
A hybrid board may use an RF laminate for:
- antennas;
- filters;
- low-noise signal layers;
- high-frequency transmission lines;
while conventional epoxy-glass layers support:
- power distribution;
- control circuits;
- digital logic;
- mechanical thickness;
- cost reduction.
Hybrid construction can reduce material cost, but it adds engineering variables:
- different X-, Y- and Z-axis expansion;
- different Dk and Df;
- press-cycle compatibility;
- layer registration;
- bonding-layer selection;
- drill behavior;
- stackup symmetry;
- warpage.
The choice between RO4003C and RO4350B should therefore consider how the selected core interacts with the rest of the board.
Decision Gate 5: What Will Procurement Actually Buy and the Factory Reproduce?
Material selection is not complete until the proposed construction can be sourced and repeated.
RO4003C is positioned for cost-sensitive microwave and RF designs, while RO4350B is commonly selected where its flame-retardant and thermal-mechanical advantages justify the material choice. (罗杰斯公司)
The actual quotation can still be affected by:
- laminate thickness;
- panel size;
- copper weight;
- low-profile foil requirement;
- regional stock;
- minimum purchase quantity;
- bonding material;
- hybrid stackup complexity;
- UL documentation;
- prototype volume.
Do not assume that the laminate with the lower nominal material cost will always create the lower finished-board price. A less common thickness, special foil or complex hybrid build may have a greater effect than the base material family.
Ask the fabricator to confirm
- Exact laminate designation;
- Core thickness and tolerance;
- Copper foil type;
- Copper weight;
- Glass style where relevant;
- Bondply or prepreg;
- UL requirement;
- Material lead time;
- Approved substitutions;
- Prototype-to-production availability.
A controlled Rogers PCB fabrication process should prevent unapproved substitution between RO4003C and RO4350B. They are not drop-in replacements from an impedance or compliance perspective.
The Dk Difference Changes the PCB Geometry
RO4003C has a process Dk of 3.38 and a published design Dk of 3.55. RO4350B has a process Dk of 3.48 and a design Dk of 3.66. (罗杰斯公司)
The process and design values serve different engineering purposes.
Process Dk
Process Dk is associated with the laminate’s controlled material specification and a particular test method.
Design Dk
Design Dk is intended to provide a more representative starting value for practical circuit modelling. It reflects how the material behaves in a microstrip-based evaluation rather than only a clamped raw-material test.
The field solver should use the value appropriate to:
- transmission-line type;
- frequency;
- copper roughness;
- laminate thickness;
- supplier stackup;
- modelling method.
Changing from RO4003C to RO4350B without recalculating trace geometry can shift impedance, electrical length, resonant frequency and phase response.
This matters in:
- 50-ohm transmission lines;
- impedance transformers;
- filters;
- matching networks;
- branch-line couplers;
- phased-array feeds;
- resonators;
- delay-sensitive circuits.
Even when both materials can physically fit into the same nominal stackup, they should not be swapped by procurement without engineering review.
Which Material Fits Which Application?
| Application | More Likely Starting Point | Reason |
| Cost-sensitive antenna board | RO4003C | Lower Df and strong RF performance when V-0 is unnecessary |
| Base-station power amplifier | RO4350B | V-0 rating and lower Z-axis CTE |
| Low-loss microwave filter | RO4003C | Lower published dielectric loss |
| Thick multilayer RF board | RO4350B | Lower Z-axis expansion supports PTH reliability |
| Laboratory RF prototype | Either | Depends on whether the prototype must represent final compliance and stackup |
| High-power active RF circuit | RO4350B | Flame rating and thermal-mechanical priorities |
| Passive antenna feed network | RO4003C | Lower loss may be more valuable than V-0 |
| Hybrid RF and digital board | Either | Selection depends on loss, compliance and full stackup interaction |
| Automotive or industrial product | Project-specific | Customer standards and system certification may control the decision |
| Phase-sensitive antenna array | Often RO4003C | Lower dielectric loss, but Dk consistency and fabricated geometry remain critical |
These are starting points, not automatic material assignments.
For example, an antenna board installed inside a regulated powered assembly may still require RO4350B. A power-amplifier evaluation board used only in a laboratory may be able to use RO4003C.
A Better Selection Method Than “Which One Is Better?”
Use the following order.
1. Check mandatory compliance
Does the product or customer require UL 94 V-0?
- Yes: prioritize RO4350B.
- No: continue.
2. Calculate the loss budget
Does the RO4003C Df advantage create meaningful system margin?
- Yes: keep RO4003C as the electrical baseline.
- No: compare thermal and production requirements.
3. Review thermal and via stress
Is the board thick, high-power or exposed to repeated thermal cycles?
- Yes: evaluate RO4350B’s lower Z-axis CTE.
- No: either material may remain viable.
4. Build the actual stackup
Include:
- copper profile;
- material thickness;
- bondply;
- transmission-line geometry;
- surface finish;
- solder mask;
- fabrication tolerance.
5. Compare finished-board quotations
Compare the same controlled construction rather than asking for generic prices for “Rogers 4003” and “Rogers 4350.”
Common Selection Mistakes
Choosing RO4003C Only Because Its Df Is Lower
Lower Df does not resolve flame-rating, via-reliability or product-certification requirements.
Choosing RO4350B Because It Is Assumed to Be “Higher Grade”
RO4350B is not universally superior. RO4003C has the lower published dielectric loss and may be the more appropriate material for a passive low-loss RF network.
Treating Process Dk as the Only Simulation Value
The field solver should use a Dk appropriate to the circuit structure and modelling method.
Allowing Material Substitution Without Recalculating Impedance
The two materials have different Dk values. The same trace geometry will not produce exactly the same electrical result.
Ignoring Copper Profile
Standard and low-profile copper versions can produce different conductor losses even when the dielectric material name is unchanged.
Comparing Core Price Instead of Finished PCB Cost
Material utilization, panel size, bonding layers, hybrid processing and availability can change the final quotation.
Assuming “Processes Like FR-4” Means No Special Control Is Needed
The materials use familiar fabrication methods, but ceramic filler can accelerate drill wear, and stackup, registration, drilling and oxide processes still require appropriate controls. Rogers’ processing guidance recommends standard carbide tools and defines drilling ranges specific to these materials. (罗杰斯公司)
What to Include in a Rogers PCB RFQ
Provide the PCB manufacturer with:
- selected material or approved alternatives;
- required UL rating;
- core thickness;
- copper weight and foil profile;
- controlled impedance;
- operating frequency;
- maximum insertion loss where applicable;
- finished board thickness;
- layer count;
- bondply or prepreg requirements;
- surface finish;
- via structure;
- thermal and assembly requirements;
- prototype and production quantities.
Ask the manufacturer to return:
- proposed production stackup;
- actual core and bonding-layer designations;
- modelled trace dimensions;
- material availability;
- impedance tolerance;
- copper-profile confirmation;
- compliance documentation;
- any proposed substitutions.
Mars-PCB can review these requirements through its Rogers PCB manufacturing service before the fabrication data is finalized.
FAQ
Is RO4350B better than RO4003C?
Neither material is universally better. RO4003C has lower dielectric loss, while RO4350B provides UL 94 V-0 performance and lower Z-axis thermal expansion. The correct choice depends on RF loss, compliance and reliability requirements.
What is the main difference between RO4350B and RO4003C?
The main differences are dielectric constant, dissipation factor, Z-axis CTE and flame rating. RO4003C has a Df of 0.0027 at 10 GHz and is non-FR; RO4350B has a Df of 0.0037 and is UL 94 V-0 rated.
Is RO4003C UL 94 V-0 rated?
No. Standard RO4003C is not UL 94 V-0 rated. When a V-0 laminate is required, RO4350B is one of the RO4000 materials intended to meet that requirement.
Which material has lower insertion loss, RO4003C or RO4350B?
RO4003C has the lower published dielectric loss. Actual insertion loss also depends on copper roughness, trace geometry, surface finish, frequency and circuit length.
Can RO4003C and RO4350B use the same trace dimensions?
The same geometry can be physically fabricated, but it will not produce exactly the same impedance because the materials have different Dk values. The transmission line should be recalculated before substitution.
Can RO4350B and RO4003C be processed like FR-4?
Both use fabrication methods similar to standard epoxy-glass boards and do not require PTFE-specific through-hole treatment. The fabricator must still use suitable drilling, bonding and registration controls.
Which laminate is better for an RF power amplifier?
RO4350B is commonly a strong starting point for active and high-power RF designs because it is UL 94 V-0 rated and has lower Z-axis CTE. The final choice should still account for insertion loss and stackup requirements.
Which material is better for an antenna PCB?
RO4003C can be attractive for passive antenna and feed-network designs because of its lower Df. RO4350B may be required when the finished product needs V-0 compliance or stronger thermal-mechanical margins.
Is RO4003C cheaper than RO4350B?
RO4003C is positioned for cost-sensitive RF applications, but actual PCB price depends on material thickness, copper foil, stock availability, layer count and fabrication complexity. Compare finished-stackup quotations rather than generic laminate prices.
Can RO4003C and RO4350B be used in hybrid PCBs?
Yes. Both can be used in multilayer or hybrid constructions with suitable bonding materials. The manufacturer must account for CTE, registration, resin flow and press-cycle compatibility across the complete stackup.
Conclusion
The RO4350B vs RO4003C decision is not a simple comparison between a premium laminate and a lower-grade alternative.
RO4003C provides lower dielectric loss and is well suited to cost-sensitive microwave circuits where flame-retardant certification is not required. RO4350B provides UL 94 V-0 performance, lower Z-axis expansion and a stronger starting point for active, high-power or thermally demanding multilayer assemblies.
Use RO4003C when loss dominates the design; use RO4350B when compliance and thermal-mechanical reliability dominate it.
Before releasing the design, confirm the actual material designation, Dk model, copper profile, bonding system, UL requirement and production stackup.
For project evaluation, submit the RF specifications and preliminary construction through the Mars-PCB website so that material availability, impedance geometry and fabrication requirements can be reviewed together.
