Overview
FR4 is the world’s most widely used PCB substrate material, consisting of woven fiberglass cloth reinforced with flame-retardant epoxy resin. The designation “FR” stands for Flame Retardant, while “4” identifies the specific NEMA material classification.
FR4 offers an excellent combination of mechanical strength, electrical insulation, dimensional stability, moisture resistance, flame retardancy, and cost-effectiveness, making it the industry standard for printed circuit board manufacturing.
Today, FR4 is used in virtually every electronics sector, including:
- Printed Circuit Boards (PCBs)
- Consumer Electronics
- Industrial Equipment
- Automotive Electronics
- Telecommunications
- Medical Devices
- Aerospace Systems
- Power Electronics
Due to its balanced performance and affordability, FR4 remains the most commonly specified PCB material worldwide.
Material Specification
| Property | Value |
|---|---|
| Material Designation | FR4 |
| Full Name | Flame Retardant Glass Epoxy Laminate |
| Material Family | Glass Fiber Reinforced Epoxy Composite |
| Reinforcement Material | Woven Glass Fiber |
| Resin System | Flame Retardant Epoxy Resin |
| Density | 1.80–2.00 g/cm³ |
| Appearance | Green, Yellow, Natural |
| Standard Forms | Copper Clad Laminate, Sheet, Plate |
Material Composition
FR4 consists of fiberglass fabric impregnated with flame-retardant epoxy resin.
| Component | Function |
|---|---|
| Glass Fiber Cloth | Mechanical Reinforcement |
| Epoxy Resin | Structural Matrix |
| Flame Retardant Additives | Fire Resistance |
| Curing Agents | Crosslinking |
| Copper Foil (PCB Grade) | Electrical Conductors |
The combination provides excellent mechanical and electrical performance while meeting flame-retardancy requirements.
Common FR4 Grades
| Grade | Characteristics |
|---|---|
| Standard FR4 | General PCB Applications |
| High Tg FR4 | Enhanced Thermal Stability |
| Halogen-Free FR4 | Environmentally Friendly |
| Low Loss FR4 | High-Speed Electronics |
| High CTI FR4 | High Voltage Applications |
| Lead-Free Compatible FR4 | Modern Assembly Processes |
Mechanical Properties
Typical Values
| Property | Value |
|---|---|
| Tensile Strength | 280–400 MPa |
| Flexural Strength | 400–600 MPa |
| Compressive Strength | 450–650 MPa |
| Elastic Modulus | 18–25 GPa |
| Impact Resistance | Good |
Mechanical Performance
| Property | Performance |
|---|---|
| Strength | Excellent |
| Stiffness | Excellent |
| Wear Resistance | Good |
| Dimensional Stability | Outstanding |
FR4 provides excellent structural support for electronic assemblies.
Physical Properties
| Property | Value |
|---|---|
| Density | 1.80–2.00 g/cm³ |
| Water Absorption | <0.15% |
| Surface Hardness | High |
| Moisture Resistance | Excellent |
| Dimensional Stability | Outstanding |
Low moisture absorption helps maintain electrical and mechanical reliability.
Thermal Properties
| Property | Value |
|---|---|
| Continuous Service Temperature | 130–140°C |
| Short-Term Temperature Resistance | Up to 180°C |
| Glass Transition Temperature (Tg) | 130–180°C |
| Thermal Conductivity | 0.25–0.40 W/m·K |
| Thermal Expansion | Low |
FR4 performs reliably under typical electronic operating conditions.
Thermal Performance Comparison
| Material | Tg Range |
|---|---|
| Standard FR4 | 130–140°C |
| High Tg FR4 | 170–180°C |
| G10 | 120–140°C |
| G11 | 170–200°C |
Higher Tg grades are commonly selected for lead-free PCB assembly.
Strength-to-Weight Ratio
| Material | Density (g/cm³) | Tensile Strength |
|---|---|---|
| FR4 | 1.90 | 350 MPa |
| G10 | 1.90 | 300 MPa |
| Aluminum 6061 | 2.70 | 310 MPa |
| Stainless Steel 304 | 8.00 | 515 MPa |
FR4 offers excellent structural efficiency for electronic applications.
Electrical Properties
Typical Values
| Property | Value |
|---|---|
| Dielectric Constant (Dk) | 4.2–4.8 |
| Dissipation Factor (Df) | 0.015–0.025 |
| Dielectric Strength | 18–30 kV/mm |
| Volume Resistivity | >10¹⁴ Ω·cm |
| Surface Resistivity | >10¹³ Ω |
Electrical Performance
| Property | Performance |
|---|---|
| Electrical Insulation | Outstanding |
| Signal Transmission | Excellent |
| High Voltage Resistance | Excellent |
| PCB Applications | Outstanding |
FR4 has become the benchmark dielectric material for PCB manufacturing.
Flame Retardancy
| Property | Performance |
|---|---|
| UL94 Rating | V-0 |
| Self-Extinguishing | Yes |
| Fire Resistance | Excellent |
| Safety Compliance | Outstanding |
The flame-retardant properties distinguish FR4 from standard G10 laminates.
Moisture Resistance
| Property | Performance |
|---|---|
| Water Absorption | Very Low |
| Humidity Resistance | Excellent |
| Environmental Stability | Excellent |
| Long-Term Reliability | Excellent |
FR4 maintains performance in a wide range of environmental conditions.
Chemical Resistance
| Chemical Environment | Performance |
|---|---|
| Water | Excellent |
| Oils & Greases | Excellent |
| Fuels | Good |
| Mild Acids | Good |
| Mild Alkalis | Good |
FR4 performs well in most industrial and electronic environments.
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| PCB Fabrication | Outstanding |
| CNC Routing | Excellent |
| Drilling | Excellent |
| SMT Assembly | Outstanding |
| Lead-Free Assembly | Excellent |
FR4 is optimized for modern PCB manufacturing technologies.
Machinability
| Process | Rating |
|---|---|
| CNC Milling | Excellent |
| Drilling | Excellent |
| Routing | Excellent |
| Precision Fabrication | Excellent |
FR4 supports high-volume and precision PCB production.
International Standards
| Standard | Compliance |
|---|---|
| NEMA LI-1 | FR4 |
| IPC-4101 | Applicable |
| UL94 V-0 | Yes |
| RoHS | Compliant |
| REACH | Compliant |
Available Forms
| Product Type | Availability |
|---|---|
| Copper Clad Laminate | Yes |
| FR4 Sheet | Yes |
| FR4 Plate | Yes |
| Multilayer PCB Material | Yes |
| HDI PCB Material | Yes |
Typical Applications
PCB Manufacturing
- Single-Sided PCBs
- Double-Sided PCBs
- Multilayer PCBs
- HDI Boards
Consumer Electronics
- Smartphones
- Computers
- Home Appliances
- Gaming Devices
Automotive Electronics
- Engine Control Units
- ADAS Modules
- Battery Management Systems
- Lighting Controllers
Telecommunications
- Networking Equipment
- Routers
- Switches
- Base Stations
Industrial Equipment
- Automation Systems
- Power Supplies
- Motor Controllers
Medical Devices
- Diagnostic Equipment
- Monitoring Systems
- Imaging Electronics
Advantages
Excellent Cost-to-Performance Ratio
Offers balanced mechanical, electrical, and thermal properties at an economical cost.
Outstanding Electrical Insulation
Widely used in high-voltage and signal-processing applications.
Flame Retardant
Meets UL94 V-0 flame-retardancy requirements.
Excellent Mechanical Strength
Provides reliable support for electronic assemblies.
Moisture Resistant
Maintains performance in challenging environments.
Proven Industry Standard
Supported by virtually every PCB manufacturer worldwide.
Limitations
Limited High-Frequency Performance
Not ideal for very high-speed RF and microwave applications.
Moderate Thermal Conductivity
Requires thermal management solutions for high-power electronics.
Higher Signal Loss Than Advanced Materials
Less suitable for ultra-high-speed digital systems.
Temperature Limitations
Standard FR4 may not be suitable for extreme-temperature environments.
Comparison with PCB Materials
| Property | FR4 | High Tg FR4 | Rogers 4350B | Aluminum PCB |
|---|---|---|---|---|
| Cost | Low | Moderate | High | Moderate |
| Electrical Insulation | Excellent | Excellent | Excellent | Excellent |
| High Frequency Performance | Good | Good | Outstanding | Moderate |
| Thermal Conductivity | Low | Low | Moderate | Excellent |
| PCB Industry Usage | Outstanding | Excellent | Specialized | Specialized |
Comparison with G10
| Property | FR4 | G10 |
|---|---|---|
| Flame Retardancy | UL94 V-0 | |
| Electrical Properties | Similar | |
| Mechanical Strength | Similar | |
| Moisture Resistance | Similar | |
| PCB Applications | Preferred |
FR4 is essentially a flame-retardant version of G10 and is preferred for electronics applications.
Available Surface Finishes
Standard Finishes
- Copper Clad Surface
- Natural Laminate Surface
- Green Laminate Finish
Functional Finishes
- PCB Manufacturing Grade
- Electrical Insulation Grade
- High Reliability Surface
Specialty Configurations
- Standard FR4
- High Tg FR4
- Halogen-Free FR4
- Low Loss FR4
- HDI FR4
Frequently Asked Questions (FAQ)
What is FR4?
FR4 is a flame-retardant fiberglass-reinforced epoxy laminate widely used as the standard material for printed circuit boards.
What is FR4 used for?
Typical applications include:
- Printed Circuit Boards
- Consumer Electronics
- Industrial Controls
- Automotive Electronics
- Telecommunications Equipment
Is FR4 flame retardant?
Yes. FR4 is designed to meet UL94 V-0 flame-retardancy requirements.
Is FR4 electrically insulating?
Yes. FR4 provides excellent dielectric strength and insulation performance.
What is the Tg of FR4?
Standard FR4 typically has a Tg of 130–140°C, while High Tg FR4 can exceed 170°C.
Why choose FR4?
Because it combines:
- Excellent Electrical Insulation
- Flame Retardancy
- Mechanical Strength
- Moisture Resistance
- Cost Efficiency
What is the difference between FR4 and G10?
FR4 contains flame-retardant additives and meets UL94 V-0 requirements, while standard G10 does not.
Does GCNOV provide FR4 PCB manufacturing services?
Yes. GCNOV provides:
- FR4 PCB Manufacturing
- Multilayer PCB Fabrication
- HDI PCB Production
- PCB Assembly Services
- Prototype Development
- Low-Volume Production
- Mass Production