An FR4 PCB is a printed circuit board made with FR4. FR4 is the most important material in the PCB assembly. Electric engineers and technicians popularly use PCB boards with the FR4 material.
In the PCB assembly, there is a lot of demand for FR4. FR4 PCB is compact and easy to design.
The FR4 printed circuit boards are popular as they are affordable and can be used in a lot of electric devices.

What is FR4?

FR4 stands for two things:

  • Material:

As a manufacturing material, it means fiberglass-reinforced epoxy-laminated sheets. it is used in FR4 PCB manufacturing.

  • Grading:

It is also a rating unit. The epoxy laminate was graded. This grading indicates the base quality of an epoxy sheet.

This rating helps in determining the quality of various types of sheet materials and designs.

In this,

FR means flame retardant.

4 refers to the factors that distinguish it from other materials refers to 4most

What is FR4 PCB Board?

A print circuit board with FR4 is called the FR4 PCB board. It is a printed circuit board that essentially uses the FR4 sheets.
At first, the FR4 is used in the insulating layer of the circuit board. Then, we add a copper layer on either side of the FR4 sheet.
As a result of this, it becomes CCL (Copper Clad Laminate). Due to FR4, CCL acts as an insulating material.
It is then used in manufacturing FDR PCB boards
The FR4 gives PCB boards a strength. Moreover, they are great at absorbing moisture and resisting fire.
Therefore, these boards are very popular in the market.

Features of FR4 to Consider When Choosing FR4 PCB

When choosing or ordering FR4 printed circuit board, an electrical engineer or technician must look at the following features:

  • Thickness:

The thickness of an FR4 sheet varies depending on your project. Ideally, you will require an FR4 with a thickness of 1.3 thou to 3 inches.

  • Impedance Matching:

The impedance matching is very important in high-frequency PCBs. It helps to maintain the function of the board of directors. It also determines the capacitance of the layers in multi-layered boards.

  • Space & Flexibility:

Depending on your project, you can choose an FR4 material for your PCB boards. Mostly, people prefer thinner sheets as they take less space and are more flexible.

  • Weight of the FR4:

Since, the thickness of the board determines its weight. For lighter products, choose FR4 boards with lighter

  • Thermal Conductivity:

To determine the temperature management of the FR4, look at the value of the thermal coefficient of dielectric constant. However, FR4 is heat resistant and it is one of the main reasons for its popular use.

Types of FR4 Materials and Parameters
  • Materials of FR4:In FR4 PCB fabrication, FR4 doesn’t use any specific types of material. However, to determine the material of manufacturing, the grade of material is more important than the type of material.

    NEMA LI 1-1998 specification defines the grading system for FR4 materials.

    Types of FR4 Printed Circuit Boards:

    The types of FR4 boards depends on the method of classification.

    According to the number of layers, they are divided into the following types:

    • Single-sided FR4 PCB
    • Double-Sided PCB
    • Multi-layer PCB

    However, another classification of FR4 circuit boards is according to the core material used in their fabrication. Usually, there are two types of boards as per these criteria:

    • Rigid FR4 boards

    In the rigid FR4 printed circuit boards, the core material is FR4 only. Therefore, it is rigid for the whole board.

    • Rigid-flex FR4 boards

    These types of PCB boards have core materials that are rigid FR4 and flexible circuits.

    Parameters of FR4:

    In order to determine the parameters of FR4, you will need to understand some keys:

    • LW= lengthwise, warp yarn direction
    • CW= crosswise, fill yarn direction

    They refer to the probable upright alignments of the fiberglass.

    • LW is along the x-axis.
    • CW is along the y-axis.

    The values of the parameter vary depending on the FR4 PCB manufacturing process. For high-frequency designs, feel free to ask for our datasheets.

    The following is an example of what the parameters for FR4 printed circuit boards look like:

Parameter Standard Values (may vary)
Specific Gravity/ Density 1.850 g/cm3
Temperature Index 284 °F
Water Absorption value <0.10%
Thermal Conductivity 0.29 W/(M·K) through-plane
0.81 W/(M·K) in plane
Bond strength >1,000 kg
Flexural strength– LW > 415 MPa
Flexural strength– CW > 345 MPa
Dielectric strength 20 MV/m
Relative permittivity 4.4
Dissipation factor 0.017
Dielectric constant permittivity 4.70 max.
Glass transition temperature >120 degrees (Celsius)
Young's modulus 24 GPa 21 GPa
Coefficient of thermal expansion X (10−5 K−1)
x-axis 1.4
y-axis 1.2
z-axis 7.0

Poisson's ratio

0.13 0.12



Sound speed

3602 m/s 3369 m/s
LW acoustic impedance 6.64
Uses and Applications of FR4 PCB

FR4 is much cheaper than the laminated boards. It is, therefore, used in many complex devices.

For instance:

  • Relays of electric systems
  • Electric switches
  • Washers
  • Standoffs
  • Busbars
  • Arc shields
  • Screw terminal strips
  • Transformers
FR4 PCB Specification of MOKO Technology

At MOKO Technology, we offer a variety of PCB manufacturing. Our FR4 printed circuit boards have the following specifications:

Layers 1-50
Material FR4
FR4 Thickness 1.34 thou to 3 in.
FR4 Thermal Conductivity 0.29 W/(M·K) through-plane
0.81 W/(M·K) in plane
Coefficient of thermal expansion X (10−5 K−1)
x-axis 1.4
y-axis 1.2
z-axis 7.0
Why Choose MOKO Technology as Your FR4 PCB Manufacturer?

FR4 board is a very widely used printed circuit board. As you know, it is cheaper than other laminated PCBs and is fire-resistant. Therefore, these fiberglass epoxy laminated sheets are in great demand in PCB assembly.

At MOKO Technology, we use high-quality materials with optimum skilled manufacturing. Therefore, we can make sure to present the best FR4 Printed Circuit Boards for you.

We manufacture and deliver thousands of PCBs. Take a look at our comprehensive list of products and services here.

MOKO Technology promises to bring the best quality FR4 PCB in China.

Contact us for premium-quality, great service, affordable rates, and fast turn out.

Scroll to Top