FR3 PCB

Paper-Epoxy Boards That Bridge the Gap Between Ultra-Budget Phenolic and Full Glass-Epoxy FR3 PCB

What Is FR-3?

FR-3 is the IPC-4101 /12 laminate that combines a cellulose-paper core with an epoxy resin binder and copper foil on one or both sides.
It delivers better solder-mask adhesion and bond strength than phenolic FR-1/FR-2, yet remains punch-friendly and cost-efficient (≈ 55 % of FR-4).

Property	Typical Value*	Design Significance
Dielectric constant εr (1 MHz)	4.7 – 4.9	Stable up to ≈ 80 MHz clocks
Loss tangent (1 MHz)	≈ 0.025	Lower loss than phenolic, still budget-friendly
Glass-transition Tg	120 – 135 °C	Survives Sn-Pb wave / selective Pb-free ≤ 245 °C
Z-axis CTE (< Tg)	70 – 85 ppm / °C	Punch vias ≤ 6:1 AR to avoid barrel cracks
Thermal conductivity	≈ 0.30 W / m·K	Manage heat with wider traces or jumpers
UL-94 flame class	HB or V-0 (optional)	Specify V-0 for appliance safety

*Always confirm the exact datasheet grade for production.

HIGHPCB is one of the largest Epoxy PCB Board and Rigid PCB manufacturing factories in China, click on the link to see more.

Why Choose FR-3?

Better bond strength vs. FR-1/2

Epoxy resin resists delamination, improves solder-mask adhesion.

Selective Pb-free capable

Low-temp BiSnAg or selective hand-reflow at ≤ 245 °C – useful for mixed-SMT designs.

Punchable & V-scorable

Steel-rule punching up to 350 × 450 mm cuts outline + I/O slots in one hit.

Lower εr than phenolic

Cleaner signal edges; reliable up to ~80 MHz digital or 40 kHz PWM drivers.

Moderate cost

Roughly half the raw-laminate price of standard FR-4.

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

Typical Applications

CFL / LED driver boards up to 40 W
Microwave-oven, dishwasher & washing-machine controllers
Smart plugs, Wi-Fi power meters, low-cost IoT nodes
Low-frequency audio amplifiers (≤ 80 kHz)
Appliance keypads & capacitive touch PCBs

FR-3 Manufacturing Flow

Step	Process Note	Key Control
CAM & panelisation	Punch map, impedance DRC	Min. clearance 0.25 mm
Die-punch / drilling	Steel-rule outline; carbide drill < 1 mm	≤ 200 hits per bit
Cu imaging & etch	Dry-film 50 µm; alkaline etch	Trace / gap ≥ 0.20 mm
Through-hole plating	Optional – cost↑; flush rivets common	Aspect ratio ≤ 6:1
Solder mask	LPI epoxy, UV cure	Opening ≥ 0.10 mm
Surface finish	OSP / Sn-Pb HASL (≥ 8 µm) ENIG (for selective Pb-free)	Wave dwell < 6 s @ 245 °C
Depanelisation	Hydraulic punch	Burr ≤ 0.05 mm
Electrical test	Flying-probe + 250 V HiPot	Isolation ≥ 10 MΩ

5 | Design Guidelines (Engineer’s Cheat-Sheet)

Layers: 1 layer is standard; simple 2-layer possible with plated vias.
Board thickness: 1.0 – 1.6 mm (avoid < 1 mm due to warpage).
Copper weight: 35 µm standard; 70 µm for ≥ 2 A traces (add 2 mm / A width).
Pads & annular rings: ≥ 0.30 mm; square pads reduce peel-off.
Thermal reliefs: 4 spokes, spoke ≥ 0.25 mm.
Creepage / clearance: ≥ 2.5 mm for 250 V basic insulation (IEC 60335-1).
Selective Pb-free: Keep peak ≤ 245 °C, dwell ≤ 10 s; use BiSnAg paste.

Heat-Management Tip: For TO-220 regulators on FR-3, add a thick-copper jumper or external aluminium slug – k ≈ 0.30 W/m·K limits in-plane spreading.

6 | FR-3 vs. FR-1 / FR-2 / High-Tg FR-4 (Single Layer)

Metric	FR-1	FR-2	FR-3	High-Tg FR-4
Relative laminate cost	0.40	0.35	0.55	1.00
Punchability	★★★	★★★	★★☆	☆
Pb-free reflow	✖	✖	♦ (≤ 245 °C selective)	✔
Max frequency	30 MHz	30 MHz	80 MHz	Multi-GHz
Mechanical strength	Low	Low-Medium	Medium	High
Flame rating	HB / V-0	HB / V-0	HB / V-0	V-0

♦ = feasible with low-temp solder & brief dwell

Support All Types of PCB Fabrication

Biggest PCB Manufacturers

Everything About PCB Fabrication in HIGHPCB

Why Order FR-3 PCBs from HighPCB?

Dedicated punch & CNC lines – rapid turn on large appliance panels.
Process-controlled Sn-Pb & low-temp Pb-free profiles – no blistering, no delam.
3-day prototype service (single-layer) & 7-day two-layer production.
Add-on services: stencil, selective-solder jig, conformal coating, 100 % ICT.

Need a cost-effective epoxy board with better durability than phenolic?
Click for an instant FR-3 quotation from HighPCB and accelerate your next appliance or smart-home design to market!