Home / Blog / What is FR4? Flame Retardant 4 Explained in 2022

What is FR4? Flame Retardant 4 Explained in 2022


Fr4 stands for flame retardant 4. FR4 is a composite material that consists of two layers of fiberglass mat laminated to a tough, corrosion-resistant phenolic resin surface. It is standardized as EIA-481 by the Electronic Industries Alliance.

Mechanical property data is available for FR4. There are several different grades. These grades are based on the phenolic and fibrous materials used, varying cost and performance.

FR4 is a best fire retardant material for PCB. It is flame, heat, and smoke resistant. It won’t melt, burn or char when exposed to flames because it’s made of a glass woven fabric with aluminum foil on both sides of the glass fabric. But it has the highest flame resistance rating possible: FR4 has a Class 1 rating.

FR-4 or FR4’s properties and characteristics make it very versatile at an affordable cost. It’s so widely used in printed circuit production that the technology is known simply as FR-4 (the 4th generation of Fiberglass Resin). In addition to this, its flame resistance, also chemically stable..


FR-4 Material Explained 

Fr4 also knowns as Fr-4 or Flame retardant 4 is a glass-reinforced epoxy laminated composite material used for printed circuit boards. This material is the most widely used for printed circuit boards (PCBs) used in the electronics industry. It features superior thermal, chemical and mechanical properties to FR-1 and FR-2 materials.

One of the most common types of material for PCBs (printed circuit boards) is FR4. Its material, also known as flame-retardant 4, is an epoxy laminate board material. Moreover, it contains woven fibreglass that reinforces it while still keeping it light and flexible.

This Flame Resistant 4 material is used in various applications that require heat or flame resistance. Thanks to its high heat tolerance and electrical insulating properties.

Above all, there are many different variations of Flame Resistant 4, but they all have the same core benefits. FR4 is a strong material that can be used in various ways — from PCBs to flexible boards. Its properties don’t just make it versatile. Moreover, it is always the most cost-effective option for printed circuit production.

Properties Of FR4 – Flame Retardant 4

Flame Retardant 4 is a glass epoxy laminate, and the National Electrical Manufacturers Association has specified it as a standard (NEMA). The material is flame-resistant plastic and meets the requirements of the UL94V-0 standard. Insulators and structural components that are produced from FR4 and bear the UL standard marking are guaranteed to stop the spread of fire and put it out promptly. Choosing fr4 is a wise choice for a high level printed circuit board.

Depending on the production method and the type of resin used, Flame Retardant 4 has a glass transition (Tg) temperature that ranges anywhere from 115 to 200 degrees Celsius. As a result of the presence of the halogen chemical element bromine, the material possesses characteristics that make it resistant to fire. FR4 also has a high strength-to-weight ratio in addition to a high hardness, which guarantees that the material will not break easily either under load or when it is being machined.

FR4 PCB Material

The FR4 PCB material is an excellent insulator that does not contract or expand. Flame Resistant 4 can be used to manufacture a huge variety of products. It ranges from electronic circuits for computers and smartphones to automotive electronic parts.

FR4 PCB material is a perfect insulator, keeping your devices safe in humid and dry environments. So, FR-4 PCB material is a glass fibre laminate specifically designed for Printed circuit board use especially. In PCB design or PCB prototype fr4 is widely used substrate for printed circuit board designs with excellent heat, flame, and electrical insulation properties.

FR4 PCB material has great properties and is widely used in various PCB industries. It has a very low coefficient of thermal expansion and does not expand or contract a lot with temperature change. Making it perfect for use in circuit boards.

Limitation of FR4 for your board:

As was stated before, FR4 is often a decent choice to make as the default standard or default option for the material of your board. However, there are scenarios, some of which are noted below, in which FR4 might not be the optimum material for your board.

  • If lead-free soldering is required

If your boards will be distributed in Europe and must adhere to The Restriction of Hazardous Substances Directive (RoHS), or if your client necessitates that lead-free soldering be used, then you may want to investigate other material options. RoHS stands for The Restriction of Hazardous Substances Directive.

This is as a result of the fact that reflow temperatures for lead-free PCB assemblies (no-lead PCBA) can become as high as 250 degrees Celsius, which is a significant amount higher than the glass transition temperature of many different types of FR4.

  • If high-frequency signals are used

FR4 circuit boards are unable to maintain a constant impedance at high frequencies; as a result, reflections may arise, which have the potential to compromise the integrity of the signal. This is an effect that arises as a direct result of dk’s – dielectric constant relatively high value.

  • If the board will be exposed to extremely high temperatures during operation

while it is being operated It is also not a good idea to utilize FR4 if the printed circuit board (PCB) is going to be used in an environment that has extremely high temperatures. An illustration of this would be the region close to the engine compartment of an airplane vehicle.

Contact us for Fr4 consultancy.

FR4 Best Uses:

Although Flame Retardant 4 is well recognized for its use in the production of printed circuit boards (PCBs) and PCB manufacturing, it is also a good material for the following:

  • Industrial Wear Applications
  • Electrical Insulation
  • Screw Terminal Strips
  • Busbars
  • Standoffs
  • Switches
  • Relays
  • Transformers
  • Arc Shields
  • Washers
  • Printed Circuit Boards

Cost Effective: FR-4 Is Cheaper.

PCB bases are typically made of FR4 material because of its widespread availability and the reasonable cost it maintains. On the other hand, high-frequency laminates come at a price that is noticeably higher than average, which is a big disadvantage for manufacturers and designers who are worried about costs. When it comes to deciding between FR4 and high-frequency laminates, this is the key limiting element that organizations must consider.

It has an amazing material. It has mechanical, chemical, and fire resistance properties that make it ideal for use in printed circuit boards. Moreover, businesses of all kinds commonly use it because it’s so cost-effective.

email chevron up