Rigid PCB Fabrication

High-Precision, Cost-Optimised Rogers PCB Boards for Robust Electronics

What Is a Rigid PCB?

Rigid PCBs employ glass-reinforced (FR-4), composite (CEM-1), or paper-phenolic (FR-1 / FR-2) laminates that lock into shape once etched; they do not bend after fabrication. The result is dimensional stability, tight layer registration, and excellent production economics for high-volume assembly lines.

Glass-transition temperature Tg

Typical Value : FR-4: 135 – 200 °C† CEM-1: ~110 °C Phenolic (FR-1/FR-2): 100 – 130 °C
Relevance : Determines survivability during lead-free reflow or wave solder

Dielectric constant εr @ 1 MHz

Typical Value : FR-4: 4.2 (3.7–4.5 range) CEM-1: 4.5 Phenolic: 5.1
Relevance : Affects impedance in high-speed traces

CTE, Z-axis (below Tg)

Typical Value : FR-4: 50–70 ppm/°C CEM-1: 70–85 ppm/°C Phenolic: 75–95 ppm/°C
Relevance : Lower CTE reduces via barrel cracking

Thermal conductivity

Typical Value : 0.3–0.4 W/m·K (FR-4, CEM-1) ≈0.25 W/m·K (phenolic)
Relevance : Drives heat spreading from power devices

values are typical — always confirm with laminate datasheets.
† High-Tg FR-4 grades (170 – 200 °C) are mandatory for Pb-free reflow.

Advantages of Rigid PCB Fabrication

Mechanical Strength – ideal for heavy connectors, heat-sinks, press-fit pins.
Cost Efficiency – mature panelisation, automated insertion, no stiffeners.
Layer Scalability – 1-layer appliance boards through 14-layer server backplanes.
Material Range – FR-4 mainstream, CEM-1 budget, phenolic ultra-budget.
Thermal Stability – high-Tg FR-4 endures ≥260 °C reflow; CEM-1 survives leaded wave.

Core Markets

Consumer appliances • LED drivers • Automotive ECUs • Industrial I/O & HMIs • Power supplies • Instrumentation backplanes.

Manufacturing Flow (Rigid Boards)

Step	Process	Critical Control
1. CAM & panelisation	Netlist compare, impedance modelling	Min annular ring 0.25 mm; aspect ≤ 6:1
2. Drilling	CNC, entry/exit films	≤120 k rpm; ≤200 hits per bit
3. Cu deposition (PTH)	1 µm electroless + 25 µm electro	Dimple < 20 µm
4. Imaging & etch	LDI ≤ 75 µm lines; cupric chloride	Etch factor 3:1
5. Solder mask / legend	LPI mask, UV cure	Mask clearance ≥ 80 µm
6. Finish	HASL-LF, ENIG, or OSP	Au 0.05 µm ± 0.02
7. Test & AOI	Flying-probe, X-ray (BGA)	Isolation ≥ 10 MΩ @ 250 V

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Material Deep-Dive: Single-Layer Budget Substrates

1 CEM-1 PCB – 1 Layer

Structure: glass-cloth (copper side) + cellulose paper, epoxy bonded.
Electrical: εr ≈ 4.5; suitable to ~100 MHz digital.
Thermal: Tg ≈ 110 °C → wave solder yes; Pb-free reflow marginal.
Processing: punches cleanly; V-cut 30°; use peelable mask for test pads.
Use-cases: coffee-machine controllers, CFL/LED bulb drivers, audio amps ≤50 kHz, remote-control keypads.

2 Phenolic PCB – 1 Layer (FR-1 / FR-2)

Structure: paper core + phenol-formaldehyde resin (SRBP). No glass.
Electrical: εr ≈ 5.1; good to ~30 MHz analog.
Thermal: Tg 100 – 105 °C → wave/hand solder only; reflow not recommended.
Processing: carbide tooling, punch/rout; vias via rivets or jumpers.
Use-cases: toy circuits, analog TV tuner modules, wall-charger primaries, disposable medical testers.

Design Rules (Cost-Optimised 1-Layer Rigid Boards)

Parameter	CEM-1	Phenolic
Min track / gap	0.20 / 0.20 mm	0.25 / 0.25 mm
Min NPTH drill	0.80 mm	0.90 mm
Copper weight	35 µm standard	35 µm (50 µm for >1 A)
Board thickness	1.0 / 1.6 mm	1.2 / 1.6 mm
Max punched panel	450 × 600 mm	350 × 450 mm

Engineering tip: on phenolic boards, keep continuous currents >1 A on ≥2 mm tracks or add external Cu jumpers / Al heat-sinks.

Cost & Performance Snapshot

Property	FR-4	CEM-1	Phenolic
Relative cost	1.0×	0.7×	0.4×
Punchability	Moderate	Excellent	Excellent
Wave-solder survival	Excellent	Good	Fair
Pb-free reflow	✔	Borderline	✖
Mechanical strength	High	Medium	Low
UL-94 rating	V-0	V-0	HB (> some grades V-0)

highpcb is one of the largest PCB assembly factories in China, click here to see more.

Why Choose HighPCB?

Material breadth: 30+ laminate SKUs, including halogen-free CEM-3.
DFM expertise: impedance modelling & stack-up optimisation delivered in 48 h.
Rapid lead time: 3-day quick-turn on single-layer CEM and phenolic.
Integrated assembly: in-house SMT lines, IPC-A-610 Class 2 certified.

Turn your concept into a robust, production-ready rigid PCB—request a fast, no-obligation quote today.

FAQ

What distinguishes rigid PCB fabrication from flexible PCB fabrication?

Rigid laminates (FR-4, CEM-1, phenolic) remain flat; flex PCBs use polyimide films that bend, enabling dynamic motion but at higher cost per area.

Can single-layer CEM-1 PCBs support SMT?

Yes—provided peak solder temperature stays below ~245 °C and component density is moderate.

Are phenolic PCBs RoHS-compliant?

Modern SRBP laminates meet RoHS 2 and REACH; disposal must avoid uncontrolled incineration.

What is HighPCB’s minimum order quantity for rigid PCBs?

Prototype runs start at 5 panels, scaling to high-volume production.

Epoxy-Based Rigid PCBs

From Low-Cost FR-1/FR-2 to High-Tg FR-4 for Pb-Free Reflow

Epoxy PCB Family Overview

Epoxy PCB is an umbrella term for rigid laminates whose binder system is epoxy-based (fully or partially). IPC-4101 groups them as follows:

IPC slash sheet	Trade name	Core reinforcement	Resin system	Typical Tg
/21, /22	FR-1	Paper	Phenolic*	125–135 °C
/10, /11	FR-2	Paper	Phenolic*	100–110 °C
/12	FR-3	Paper	Epoxy	120–135 °C
/126, /130	FR-4 High-Tg	Glass cloth	Epoxy (enhanced)	170–200 °C

* Although FR-1/FR-2 use phenolic resin, they are routinely classified with epoxy boards in low-layer rigid fabrication because the production route is identical.

Why Choose an Epoxy-Class Rigid PCB?

Advantage	FR-1/FR-2	FR-3	High-Tg FR-4
Ultra-low BOM cost	✔✔✔	✔✔	✔
Punch & V-cut friendly	✔✔✔	✔✔	—
Pb-Free Reflow capable	✖	✖/borderline	✔
Mechanical strength	Low	Medium	High
Thermal robustness	Wave only	Wave/selective	Reflow to 260 °C
Layer count	1-layer	1–2 layers	1–16+ layers

Individual Sub-Grades in Detail

3.1 FR-1 PCB — Paper + Phenolic, Tg ≈ 130 °C

Positioning: Cheapest rigid laminate on the market.
Electrical: εr ≈ 5.1 (1 MHz), loss tan ≈ 0.03 → fine for < 30 MHz analog, chargers, toys.
Thermal: Handles Sn-Pb wave solder (< 245 °C, 4–6 s). Pb-free reflow not allowed.
Processing: One-shot steel-rule punching, NPTH Ø ≥ 0.9 mm, trace/space ≥ 0.25 mm.
Typical uses: Battery toys, wall-plug chargers ≤ 15 W, throw-away medical strips.

3.2 FR-2 PCB — Paper + Phenolic, Tg ≈ 105 °C

Difference from FR-1: Slightly lower Tg, lower cost, broader availability in Asia.
Limitations: Even less thermal headroom; avoid heavy through-hole transformers.
Ideal for: AM/FM radios, IR remote controls, very low-cost LED night-lights.

3.3 FR-3 PCB — Paper + Epoxy, Tg 120–135 °C

Upgrade path from FR-2 when you need epoxy bond strength but still want punchability.
Electrical: εr ≈ 4.8, loss tan ≈ 0.025 — good to ~80 MHz digital clocks.
Manufacturing perks: Accepts selective Pb-free solder if peak ≤ 245 °C & dwell < 10 s.
Applications: CFL/LED drivers ≤ 40 W, appliance controllers, budget IoT sensor hubs.

3.4 High-Tg FR-4 PCB — Glass-Epoxy, Tg 170–200 °C

Key feature: Survives lead-free reflow (JEDEC J-STD-020 up to 260 °C) with minimal Z-axis expansion (CTE ≈ 45–55 ppm/°C).
Electrical: εr ≈ 4.2 @ 1 GHz, loss tan ≈ 0.015. Impedance-controlled to multi-Gb/s.
Stack-up versatility: 1- to 16-layer, blind/buried vias, microvia laser drilling.
Target markets: Automotive ADAS, industrial drives, server motherboards, LED Head-lamps.

Manufacturing Flow & Design Tips (Single-Layer Epoxy Boards)

Step	FR-1 / FR-2	FR-3	Note
Panel size (punch)	350 × 450 mm	350 × 450 mm	± 0.15 mm tolerance
Min trace / gap	0.25 / 0.25 mm	0.20 / 0.20 mm	LDI optional on FR-3
Copper weight	35 µm (50 µm if >1 A)	35 µm standard
Surface finish	OSP or Sn ≥ 8 µm	OSP / Sn / ENIG	FR-3 can accept ENIG
Thermal relief	4 spokes, 0.30 mm width	0.25 mm spokes	avoid cold joints
Hole plating	not economical	optional, but cost↑	consider rivets on FR-1/2

Power Hint: Combine 70 µm copper + 2 mm trace width to carry 1 A continuous at 25 °C rise on FR-1/2 boards.

Epoxy PCB Selection Cheat-Sheet

Requirement	Recommended Grade	Rationale
BOM minimisation, throw-away device	FR-1	Lowest raw-laminate cost
Very thin margins but slight thermal margin	FR-2	Even cheaper, Tg still > 100 °C
Punchability and stronger epoxy bond	FR-3	Paper-epoxy hybrid
Lead-free reflow, multi-layer, high reliability	High-Tg FR-4	Glass-epoxy, Tg ≥ 170 °C

Why Source Epoxy-Class PCBs from HighPCB?

Material breadth: FR-1, FR-2, FR-3, CEM-1, standard & high-Tg FR-4 in stock.
Dual tooling lines: steel-rule punch for paper boards, CNC routing for FR-4 multilayers.
Quick-turn: 3-day prototypes (single-layer) to 7-day multilayer FR-4.
Full service: DFM review, impedance modelling, SMT assembly, ICT & functional test.

Need guidance choosing the right epoxy laminate? Chat with our engineers and receive a same-day quotation tailored to your cost, thermal, and reliability targets.