Once Rogers is chosen, many designs put a single part number in the stackup, such as RO4350B or RO3003, and send it out. Those two parts belong to different material families, and they take different routes through the fab. Change the family and the hole wall treatment, the multilayer bonding material and the routing approach all change with it. Without knowing where the routes split, it is hard to judge whether the stackup and drawing notes say enough.
Material selection itself (FR-4 or Rogers) is covered in FR-4 vs Rogers substrate selection. This post covers only how the two Rogers families differ in fabrication.
How the two families are built
- RO4000 series (e.g. RO4003C, RO4350B, RO4835): glass-reinforced, ceramic-filled hydrocarbon resin system. Structurally close to a conventional thermoset laminate and fairly rigid.
- RO3000 series (e.g. RO3003, RO3006, RO3010): ceramic-filled PTFE composites. The matrix is PTFE, so the material is softer and its surface is chemically inert.
Almost every process difference traces back to this: one is a thermoset resin system, the other is PTFE.
Divergence 1: drilling
Both contain ceramic filler and wear drill bits faster than standard FR-4, so the fab adjusts tool life and drilling parameters for either one.
The difference is hole wall quality. RO4000 is harder; the main concerns are tool wear and wall roughness. RO3000 is soft, so drilling is more prone to PTFE smear, burrs and deformed hole entries, which calls for sharp tools and suitable entry and backup material. Smaller holes and thicker boards make the gap wider.
Divergence 2: hole wall prep before plating
This is where the families differ most.
RO4000 hole walls can go through a conventional FR-4 metallization line. Rogers' fabrication guidance does not call for the dedicated activation that PTFE needs.
RO3000 PTFE hole walls are chemically inert, and electroless copper does not bond to them directly. The walls must be activated before metallization, typically with sodium naphthalene etch or plasma treatment. Skip it and copper adhesion is weak, and the walls are prone to separation under thermal stress.
Plasma desmear and activation details are in high-frequency PCB drilling and plasma desmear.
Divergence 3: multilayer bonding material
RO4000 cores can be laminated with Rogers' RO4400 series prepreg, or combined with FR-4 prepreg into hybrid boards with RF layers plus FR-4 layers. The press cycle stays close to a standard multilayer.
RO3000 is PTFE, and standard FR-4 prepreg bonds poorly to it. Multilayer builds need a PTFE-compatible bonding material (for example Rogers 2929 bondply; follow the Rogers multilayer guidance for the specific choice), and press parameters change with it. The bonding layer has its own dielectric constant and loss, which enter the impedance calculation.
Bond strength on PTFE is covered in high-frequency PCB lamination and PTFE bonding; hybrid stackup constraints are in hybrid PCB stackup.
Divergence 4: copper surface prep before soldermask and finish
RO4000 copper prep usually follows standard mechanical brushing or chemical microetch.
RO3000 is soft. Aggressive brushing can stretch or distort the panel, hurting dimensional stability and registration, so prep leans toward chemical methods or reduced brush pressure. Where soldermask covers exposed PTFE, mask adhesion needs its own review.
Divergence 5: routing and profiling
RO4000 can be routed or punched much like FR-4, with similar edge quality.
RO3000 tends to leave burrs and stringers when routed, which calls for sharp cutters and controlled feed. Sharp corners, narrow slots and long thin tabs deform more easily, so outline tolerances and slot widths should account for that.
Summary of divergence points
| Step | RO4000 (ceramic-filled hydrocarbon) | RO3000 (ceramic-filled PTFE) |
|---|---|---|
| Drilling | Filler wears tools; set tool life by material | Same tool wear, plus smear and burr risk |
| Hole wall prep | Conventional metallization line | Sodium naphthalene or plasma activation required |
| Multilayer bonding | RO4400 prepreg or FR-4 prepreg | PTFE-compatible bonding material |
| Copper prep | Standard brushing or microetch | Chemical prep preferred to avoid stretch |
| Routing | Close to FR-4 | Burr-prone; allow margin at corners and slots |
Design inputs to adjust accordingly
- List the full part number and thickness in the stackup, not just "Rogers". The family sets the process route; the part number sets the dielectric properties.
- State the bonding material on multilayers. If a specific bondply or prepreg is required, list it in the stackup. If the fab may choose, note that impedance is to be calculated and confirmed by the fab using the actual bonding material.
- State each layer's material on hybrid builds. List which layers are Rogers and which are FR-4, in layer order.
- Say whether substitution is allowed. Substituting within a family and across families have very different process impact; see high-frequency laminate substitution approval.
- Flag small holes, thick boards and narrow outline features on RO3000 for early review. These are most affected by the drilling and routing differences.
- Put surface finish and soldermask coverage on the drawing. Whether exposed PTFE areas get soldermask should be agreed with the fab.
Overall process control for RF boards is in high-frequency PCB fabrication process control; see also high-frequency PCB and materials.
Summary
RO4000 and RO3000 are both Rogers, but one is a thermoset hydrocarbon system and the other is PTFE. The routes split at hole wall activation, multilayer bonding, copper prep and routing, with hole wall prep the largest difference. A drawing that lists the full part number, bonding material, hybrid layer order and substitution rule lets the fab pick the process route at quotation. To have a specific stackup reviewed, request a quote.
FAQ
Q: RO4350B and RO3003 are both Rogers. Is the fabrication process the same?
A: No. RO4350B is in the RO4000 hydrocarbon family and can use a conventional metallization line; RO3003 is RO3000 PTFE and needs hole wall activation first.
Q: Why do PTFE hole walls need separate activation?
A: PTFE is chemically inert and electroless copper does not bond to it directly. Sodium naphthalene or plasma treatment changes the wall surface so the plating bonds reliably.
Q: Can RO3000 multilayers be laminated with standard FR-4 prepreg?
A: Standard FR-4 prepreg bonds poorly to PTFE. A PTFE-compatible bonding material is normally used, and its dielectric properties go into the impedance model.
Q: Can RO4000 be combined with FR-4?
A: Yes. RO4000 is a thermoset system and is commonly built into hybrid boards with FR-4; list layer order and materials explicitly in the stackup.
Q: Is writing just "Rogers" on the drawing enough?
A: No. The family sets the process route, and the part number and thickness set the dielectric properties. Give part number, thickness, copper foil and the substitution rule.
Q: What should I watch for when routing RO3000?
A: The material is soft and burrs easily. Sharp corners, narrow slots and long thin tabs deform more readily, so review outline tolerances with the fab early.