What is FR4 PCB board ?

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There are many types of PCB substrate, such as fiberglass board, paper substrate, metal substrate, ceramic PCB, etc., different environments use different materials of the basic. Next, I will share with you the details of FR4 PCB board.

What is FR4 PCB board?

FR4 is a PCB substrate that is a glass fiber reinforced epoxy laminate in the form of raw material and substrate for circuit boards. Due to its robust nature and flame retardant properties, FR4 is a common laminate substrate used on printed circuit boards and it is vital to provide the required insulation to circuit boards.

FR4 boards have largely replaced G-10 boards.FR4 materials use bromine, a halogen chemical element that is fire-resistant and therefore valuable in providing flame-retardant properties.It is also unable to absorb water and maintains a high level of mechanical strength in addition to incredible insulation capabilities, especially in wet or dry environments.FR4 materials also have high glass transition temperatures ranging from 115 to 200 degrees Celsius, and its FR-4 flame-resistant material class code, which meets UL94V-0, ensures that it will not spread and extinguish the material as soon as it begins to burn.

Typical single, double-sided, and multilayer PCB circuit boards are made of FR-4, which is so strong and flame-resistant that most circuit boards choose FR-4 as a substrate. FR in FR-4 stands for flame retardant, and the number 4 distinguishes the material from others in this category.FR-4 is a fiberglass reinforced epoxy laminate, which looks like a thin, woven-cloth sheet. The term FR-4 also stands for the grade used to make these laminates. Fiberglass construction provides structural stability to the material. The fiberglass layer is covered with flame retardant epoxy resin. This brings durability and strong mechanical properties to the material.

What are the advantages of FR4 PCB boards?

1. High insulation: FR-4 material has high insulation performance, which can effectively prevent current leakage, thus ensuring the safety and stability of electronic products.

2. High heat resistance: FR-4 material has high heat resistance and can maintain good performance at high temperatures, thus showing good stability in some high temperature environments.

3. High moisture resistance: FR-4 material has good moisture resistance, can maintain good performance in humid environments, so it has a wide range of applications in some humid environments.

4. Good machinability: FR-4 material has good machinability and can be drilled, cut, ground and other machining operations, thus facilitating the production and processing of PCBs.

5. Low-cost materials

FR-4 printed circuit board materials are widely available and inexpensive. Nevertheless, they provide excellent functionality. However, high glass transition temperatures and high relative leakage trace index materials are somewhat expensive.


Applications of FR4 PCB boards

FR4 PCB boards are used in many electronic products, such as cell phones, TVs, and stereos. Due to its high strength, high rigidity and flame retardancy, FR4 PCB board can be adapted to a variety of circuit board design shapes and sizes, and has excellent dielectric constant and dielectric loss performance, so it is also widely used in the field of radio frequency circuits and high-speed signal transmission.

In addition, FR4 PCB boards are also used in the field of industrial control systems. Due to their excellent high frequency characteristics in electrical performance, they can be used for high frequency circuit design such as production line control and robot control.

In some specific areas, such as the military field, FR4 material flame retardant performance has also reached strict standards. Both high performance and safety can be used for surveillance systems, missile systems and other military equipment, high frequency routing and control circuit design.

How to choose FR4 thickness

The thickness of the circuit board is easily overlooked when designing, but it has important properties. The thickness of a circuit board affects the proper use of the entire circuit.

When ordering laminates for a PCB project, the designer or electrical engineer must specify the FR4 thickness. This is measured in inches, such as thousandths of an inch, thousandths of an inch, or millimeters, depending on which unit is most suitable for the setup. Depending on the needs of the project, the thickness of FR4 sheet varies widely, but is usually between 10,000 and 3 inches.

1. Space: The thinner the better

Some electronic devices have less space available, such as Bluetooth accessories, use linkers, etc. For these products, smaller FR4 PCBs are often preferred to save space inside the device.

2. Controlled Impedance

Some high-frequency/high-speed boards require controlled impedance. We know that a stable dielectric constant (Dk) and a low dielectric constant thermal coefficient help achieve controlled impedance. Maintaining the thickness balance of FR-4 material is critical. Thin PCBs face high heat and an increased thermal coefficient of dielectric constant (TCDK), which leads to fluctuations in dielectric constant (DK). Therefore, maintaining PCB thickness is critical to achieving a low dielectric constant (Dk).

3. Connections

Two PCBs need to be connected to each other by an edge connector or another matched socket. Connectors are only available in a limited number of sizes. Therefore they are only suitable for a specific PCB thickness. This can be a limiting factor for PCB thickness. If an existing PCB is being redesigned and is part of an older system, the PCB thickness must be checked twice. This is the fundamental reason why it is important to pay attention to the thickness of the board after the circuit design is completed and before ordering for manufacturing.

4. Impact matching should be good

Each multilayer board acts as a capacitor on an adjacent layer. This is why the thickness of the circuit board is so important. PCB FR4 material thickness determines the thickness of the dielectric, which in turn affects the capacitance value.

This is a particularly critical factor for some high-frequency PCBs, such as RF and microwave designs. High frequency designs focus on inductive quenching as an important component to maintain optimal board functionality, and getting the right capacitance for each layer is critical.

5. Flexibility Options

Flexibility is another important factor to consider when choosing the thickness of FR-4 PCB material. The thinner the board, the more flexible it is. Due to heat, highly flexible and thinner PCBs are often at high risk of soldering due to bending and angle changes during use. Heat management should be a priority in these designs.

Because thinner PCBs show effective performance against conventional stresses on flexible products. They have a wide range of applications in medical and automotive equipment.

6. Design and weight requirements

Thin PCBs are lightweight and small in size, thus facilitating consumer electronics. It is easy to carry out and also reduces the transportation cost of the material. But thin boards are not the answer to large boards. Increasing the size of thin boards can lead to PCB breakage and bending. However, extra thick boards take up a larger surface area and increase the total weight of the module/device, which has its own consequences.

What can an LST company do?

LST Technology has several years of experience in PCB manufacturing and can meet the needs of most customers. Compared to other manufacturers, we offer a wider range of options, such as various thicknesses and layers, multiple surface treatments, and different substrate materials. This makes it more advantageous for you to customize FR4 PCB to your specific requirements.

Regarding materials, we source our laminate and prepreg materials from top suppliers such as Isola, Taconic, Panasonic, and Shengyi Technology. This ensures that we provide high-quality materials that are consistent and reliable, resulting in superior circuit board.

We are a reliable company that can provide various industry certifications, including the conventional ISO9001 and 14001, as well as the “International Automotive Industry Technical Specifications” IATF16949 and “Medical Device Quality Management System for Regulatory Requirements” ISO13485. However, at LST Technology, qualification certification is only one aspect of demonstrating our capabilities to customers. We also formulate stricter operating specifications and testing services, which are essential in ensuring the smooth progress of your PCB project.