What is an FR4 PCB?
Flame Retardant 4, or FR4, is a material grade used in PCB manufacturing. It is made of fibreglass and "4" represents the UL94 V-0 flammability standard (it must self-extinguish after being ignited). Fibreglass reinforced woven glass fibre and epoxy resin with makes it excellent for electrically insulated applications. FR4 is a widely used material due to its low cost and high reliability.
FR4 Material Overview
FR4 represents flame-retardant grade 4 glass-reinforced epoxy laminate. The material's dielectric constant and dissipation factor (loss tangent) are moderate. FR4 can be used in low-speed and high-power applications, making it the first choice for many hobbyists. This makes it suitable for general-purpose electronic designs.
Dielectric constant: around 4.5 at 1MHz (moderate). Loss tangent: around 0.02 at 1MHz (moderate). The glass transition temperature (Tg) determines how the material behaves under heat. It is one of the most important thermal properties in the classification of FR4 materials.
- Low Tg (130–140°C)
- Standard Tg (150–160°C)
- High Tg (>170°C)
Structure and Properties of FR4
Benefits of FR4 PCB Material
How FR4 Thickness Affects PCB Performance
Signal Integrity and Impedance Control
- Thicker FR-4 increases the dielectric spacing, which raises impedance by introducing parasitic components. FR-4 thickness can be adjusted to control impedance for different circuit applications.
- Thinner FR-4 has a smaller dielectric spacing between copper layers, which lowers the impedance of traces. However, the higher dielectric loss of FR-4 limits performance above a few GHz regardless of thickness.
Thermal Management
Mechanical Stability
Common Applications of FR4 PCBs
Consumer Electronics
- FR4 PCBs balance cost and strength for everyday electronic devices. From smartphones to wearables, FR-4 provides durable and reliable PCB solutions.
Industrial Control Systems
Automotive Electronics
JLCPCB FR4 PCB Manufacturing Capabilities
Features | Capabilities |
|---|
Layer count | 1, 2, 4, 6, ...32 layers |
Controlled Impedance | 4/6/8/10/12/14/16/18/20/.../32 layers |
Impedance Tolerance | ±10% (±5Ω if value ≤ 50Ω) |
UL Number | E479892 |
Maximum Dimensions | 670 × 600mm (Thickness ≥ 0.8mm); 500 × 600mm (Thickness < 0.8mm); 2-layer reaches 1020 × 600mm. |
Minimum Dimensions | 3 × 3mm; 70 × 70 for V-cut panel |
Outer Copper Thickness | 1oz, 2oz (2.5oz, 3.5oz, 4.5oz for 2-layer) |
Inner Copper Thickness | 0.5 oz, 1 oz, 2 oz |
Surface finish | HASL (leaded / lead-free), ENIG(1u" / 2u") |
Minimum Via Hole/Diameter | 0.15mm / 0.25mm |
Hole Size Tolerance | ① Plated: Through-holes: +0.13 / -0.08mm ; Press-fit holes：±0.05mm ② Non-plated: ±0.2mm |
Minimum Plated Slots | 0.5mm |
Minimum Non-Plated Slots | 1.0mm |
Plated Edges | Available with PCB size 10 × 10mm, thickness: 0.6mm. ENIG is required. |
Blind Slot | Available in 2-32 layer boards with a thickness of ≥ 0.8mm. |
Countersink Hole | Available in 2-32 layer boards with a thickness of ≥ 0.6mm. Supported countersink angle: 90°/135° |
Backdrill | Available in 4-32 layer boards with a thickness of ≥ 0.8mm. Holes will be epoxy resin filled after backdrilling. |
Castellated Holes | Available with PCB size 10 × 10mm. |
Minimum Track Width and Spacing | ① 1oz: 0.10 / 0.10mm (4 / 4mil) for 1/2-layer ; 0.09 / 0.09mm (3.5 / 3.5mil) for muliti-layer ② 2oz: 0.16 / 0.16mm (6.5 / 6.5mil) for 1/2-layer; 0.16 / 0.20mm (6.5 / 8mil) for multi-layer |
Minimum BGA Pad Diameter | 0.25mm |
Gold Fingers Bevelling | 30° or 45° |
Why Choose JLCPCB FR4 PCBs?
How to Order JLCPCB FR4 PCBs in 3 Easy Steps
