FR4 PCB – FR4 material properties and applications

Table of Contents

When one might have seen the term FR4 many times, it is quite natural to ask what it is.

Well, FR4 abbreviation means “Filled Epoxy Resin 4”, which is non-conductive material widely used for PCB manufacturing. FR4 materials are manufactured for high-quality industrial applications, such as consumer electronics and aerospace. What does FR4 stand for? What does it look like? Can someone make PCB from this material? Is it possible to order FR4 PCB with specific features from a custom PCB manufacturer? The article contains everything for a better understanding.

What is FR4 PCB?


FR4 is one of the most commonly used materials for PCBs. It is made from glass fabric, which is impregnated with resin. It has excellent strength, rigidity, and durability characteristics. FR4 has a high dielectric constant and can withstand high voltages and temperatures.

FR4 PCBs are mainly used in industrial applications where they need to withstand harsh environments such as extreme temperatures and chemicals. They are also used for automotive applications that must withstand vibrations and electrical noise.

What are the FR4 properties and materials in FR4 PCBs?

FR4 properties

Here are some main properties of FR4 PCB:

●Flame retardant: FR4 is flame retardant, which means it does not burn easily. It has a high ignition temperature and self-extinguishing properties. This makes it ideal for applications with a fire or explosion risk.

●Flexible: FR4 has good electrical properties and can be formed into different shapes. This makes it suitable for use in circuit boards and other electrical components.

●Low moisture absorption: FR4 has low moisture absorption, which means it can be used in environments prone to water damage. Such environments include bathrooms, kitchens, and garages.

FR4 material

FR4 material resembles the greenish substance seen on circuit boards. The excellent qualities of FR4 PCB make it popular across numerous sectors. Since it has an extremely low thermal expansion coefficient, temperature changes do not cause it to shrink or expand significantly. This makes it the ideal material for use in circuit boards. Additionally, unlike other materials, FR4 does not absorb moisture. This means that both dry and humid situations can make it remaining the same size or close.

Why is FR4 used in PCB? What are the benefits of FR4 PCBs?

Reasons why FR4 is used in PCBs

●High dielectric strength

●Low losses at microwave frequencies

●Good mechanical properties

●Easily processed by standard photolithography techniques

FR4 PCBs benefits

The Benefits of FR4 PCBs

FR4 has excellent mechanical and thermal properties, which makes it widely used in the manufacturing of PCBs. The following are some benefits of FR4 PCB:

High impact strength – FR4 PCB can withstand impacts better than other materials, such as glass-filled nylon or polyester. This makes it ideal for use in applications where devices like automobiles may be dropped or prone to impact damage.

Excellent thermal conductivity – FR4 PCB has excellent thermal conductivity. Heat dissipates quickly through the material, making it an ideal choice for electronic devices like computers, where there is constant heat generation from internal components such as CPUs, motherboards, and graphics cards.

High dielectric constant – FR4 PCB has a higher dielectric constant (K) than other insulators, such as glass-filled nylon or polyester, which results in lower EMI emissions from printed circuit boards made from this material. This makes it ideal for use in high-density interconnections.

What are the applications of FR4 PCBs?

Applications for FR4 PCB include:

●Commercial and industrial electronics

●Military electronics

●Medical devices

●Aerospace applications

●Automotive applications

How is FR4 used in PCBs?

How is FR4 used in PCBs

FR4 is the perfect default substrate material for high-quality PCB manufacturing operations because of these characteristics. These characteristics can also be the basis for high-quality and affordable PCBs when employed properly.

FR4 serves as the main insulating backbone of a PCB. This serves as the foundation upon which the manufacturer builds the circuit. The FR4 board is prepared and then heated and laminated with one or more layers of copper foil using adhesive. Depending on the board’s design, this copper may cover one or both sides and create the circuits in the finished result.

Complex PCBs may layer the circuit board or use more than one side to create more complex circuitry.

From here, the board is prepared for the final silkscreen layer and the subsequent soldering process by having the circuits designed and etched out before being covered with a solder mask layer.

How to select FR4 thickness in a PCB?

How to select FR4 thickness in a PCB The selection of FR4 PCB thickness depends on three factors:

Compatibility with components

The most important reason for choosing an appropriate FR4 thickness is to ensure that all components on the board will fit properly. If designers select a too-thin FR4 material, there may not be enough clearance between certain features, resulting in poor component quality or even damage to the component itself.

Design and flexibility

Another factor worth considering when selecting FR4 thickness is how much flexibility the board needs in design options. Generally speaking, thicker boards usually have more mechanical strength than thinner ones; however, they can also limit some design options due to their increased size and weight.

Impedance control

A printed circuit board (PCB) impedance measures how well it resists high-frequency signals such as radio waves or other electromagnetic radiation. The impedance of a PCB affects its electrical performance, which in turn impacts its ability to handle electromagnetic interference (EMI).

Tips for selecting the right FR4 material for FR4 printed circuit board

Tips for selecting the right FR4 material for FR4 printed circuit board

The following points will help to choose the right FR4 material for printed circuit board:

  • Cost: FR4 will be cheaper FR4 is cheaper than other materials such as glass epoxy and PTFE. Glass epoxy is a very good insulator but also very expensive. PTFE has properties similar to glass epoxy and will be more costly than FR4.
  • Signal loss: lower Df leads to lower signal loss The signal loss of FR4 is lower than that of other materials. The signal loss of FR4 is 0.1dB/cm at 1GHz, which is better than glass epoxy and PTFE, which have signal losses of 0.5dB/cm at 1GHz and 0.15dB/cm at 2GHz, respectively.
  • Impedance stability: Dk stability matters Another crucial consideration for many designs is stable impedance, which frequently translates into more predictable performance, particularly for bigger circuits or high-frequency designs. Again, FR4 and high-frequency laminates produce distinct outcomes in this area. A material must maintain a consistent Dk, or dielectric constant, throughout the material as its temperature varies to maintain stable impedance.


FR4 has been used in the PCB industry for a long time and is still a popular material choice. It’s easy to work with, has a reasonable price, and has a high strength-to-weight ratio and thermal stability. Other specialty substrates are available on the market, but FR-4 offers many desirable qualities that make it right for most PCBs.

Choose IBE to get top-notch and best-quality FR4 PCBs.

Sign up for newsletter

Get latest news and update

Newsletter BG