Introduce

FR4 stands for “Flame Retardant 4” and is the grade designation for glass-reinforced epoxy laminate, a composite material composed of fiberglass woven cloth and an epoxy resin adhesive that is flame retardant. This material is known for its high strength-to-weight ratio, excellent electrical insulation, and stability under different environmental conditions.

Material and function of FR4

FR4 material composition

• Fiberglass: The backbone of FR4 is woven fiberglass, which provides structural strength, rigidity and dimensional stability.
• Epoxy Resin: Glass fibers are impregnated with epoxy resin, which bonds the fibers together and provides the material with electrical insulating properties and flame retardancy.
• Fillers: Some FR4 materials may also contain fillers to enhance certain properties (such as thermal conductivity) or reduce cost.
• Curing agents and accelerators: These are used in epoxy resin mixtures to control the curing process and the final mechanical and thermal properties of the material.

FR4 features

• Mechanical Strength: High tensile and bending strength make it durable and resistant to bending.
• Electrical insulation: excellent dielectric properties and high dielectric breakdown voltage.
• Heat Resistance: It maintains its structural integrity and electrical insulation properties at high temperatures.
• Flame retardant: It is flame retardant in nature, which is essential for the safety of electrical and electronic applications.
• Chemical Resistance: Resistant to many solvents and cleaners used in industrial processes.
• Moisture resistance: low water absorption, maintains performance in humid conditions.
• Thermal Expansion: The coefficient of thermal expansion is relatively low, which is critical to maintaining alignment of the copper traces on the PCB.

What is the difference between FR4 and aluminum substrate?

Material ingredient

• FR4 PCB: Made of fiberglass reinforced epoxy laminate with good strength, heat resistance and electrical insulation.
• Aluminum PCBs: These have a metal core (usually aluminum) and can also include a thermally conductive dielectric layer to transfer heat away from the components.

Thermal Conductivity

• FR4: It has relatively low thermal conductivity, which can be a limiting factor in high heat applications.
• Aluminum: High thermal conductivity is one of the defining characteristics of aluminum PCBs, making it ideal for high power and heat dissipation applications.

Heat dissipation

• FR4: Poor heat dissipation, which can cause hot spots and potentially shorten the life of the board and its components.
• Aluminum: Excellent heat dissipation capabilities, helping to effectively cool components and increase device performance and lifespan.

Application:

• FR4: Used in a wide range of standard electronic equipment, from consumer electronics to industrial control systems, where extreme conditions are not a concern.
• Aluminum: Commonly used in LED lighting, power supplies, and automotive systems where heat dissipation is critical.

Durability

• FR4: Sensitive to high temperature fluctuations and may not be as durable in harsh environmental conditions.
• Aluminum: More durable in extreme conditions and provides additional physical stability to the board.

Cost:

• FR4: Typically less expensive than aluminum PCBs, making it a cost-effective choice for a variety of applications.
• Aluminum: Due to the price and manufacturing process of aluminum, the cost may be higher, but this can be offset by its performance in specific applications.

Conclusion

In the intricate world of electronic design, FR4 stands out for its superior electrical insulation, flame retardancy and cost-effectiveness, making it ubiquitous in standard electronic equipment. Its versatility and reliability continue to support its widespread adoption in everything from consumer electronics to complex industrial systems. The future is being built on circuit boards today, and FR4 remains a key material in that construction. For those ready to realize the potential of FR4 in their products, the opportunities are endless.