Table of Contents
What Is FR4 PCB?
FR4 PCB is a substrate for circuit boards (PCBs), mainly composed of glass fiber epoxy resin.
FR4 is a code for a fire-resistant material grade, representing a material specification where a resin material must be able to self extinguish after combustion. It is not a specific material name, but a material grade. FR4 board is mainly composed of glass fiber and epoxy resin, which give PCB hardness and thickness, making it a common circuit board substrate. FR4 board can be divided into general FR4 board and high TgFR4 board, where Tg represents the glass transition temperature, that is, the melting point. The circuit board must be flame resistant and cannot burn at a certain temperature, only soften, which is one of the basic requirements of FR4 board.
Characteristics of FR4 PCB
(1) Flame retardant performance: FR4 material has excellent flame retardant performance, which can slow down the spread of fire and protect electronic devices from damage in the event of a fire. Its flame retardant rating reaches UL94 V-0, which means that it produces almost no harmful gases during combustion.
(2) Mechanical and electrical characteristics: FR4 material has high tensile strength and compressive strength, reaching 65000 psi and 38000 psi respectively, making it perform well under mechanical pressure. At the same time, its electrical performance is stable, and it can maintain good insulation performance in both dry and humid environments.
(3) Thermal stability and durability: FR4 material will not easily deform under high temperature conditions and has good heat resistance. Its dimensional stability is extremely high, and it will not deform due to temperature or humidity changes. In addition, FR4 also has the characteristics of radiation resistance, chemical corrosion resistance, and thermal shock resistance, which can maintain performance in various harsh environments.
(4) Environmental characteristics: With the increasing awareness of environmental protection, the environmental characteristics of FR4 have also been valued. Its flame retardant rating reaches 94V-0, and it produces almost no harmful gases during combustion, making it more environmentally and human health friendly.
(5) Cost economy: Compared with other high-frequency materials, FR4 has a relatively low cost and is suitable for large-scale production. It has high insulation resistance and low dielectric constant, making it suitable for low-frequency and mid frequency circuit design.
Performance and Application of FR4 PCB:
- Flame retardant performance: FR-4 contains special chemicals that can slow down the spread of fire and protect electronic devices from damage in the event of a fire. This flame retardancy makes FR-4 the preferred material in electronic devices.
- Mechanical and electrical characteristics: FR-4 has high tensile and compressive strength, and can perform well under various mechanical pressures. At the same time, its electrical performance is stable, and it can maintain good insulation performance in both dry and humid environments.
- Stability and durability: FR-4 has extremely high dimensional stability and will not deform due to changes in temperature or humidity. In addition, it also has the characteristics of radiation resistance, chemical corrosion resistance, and thermal shock resistance, which can maintain performance in various harsh environments.
- Environmental characteristics: FR-4 has a flame retardant rating of UL94 V-0, and produces almost no harmful gases during combustion, making it more environmentally friendly and beneficial to human health.
- Widely used: FR-4 PCB has a wide range of applications in consumer electronics, communication equipment, automotive electronics, aerospace and other fields. Its high dielectric strength, bending strength, impact strength, and tensile strength enable it to meet various complex circuit design requirements.
FR4 PCBs of different grades and their applications
FR-4 PCB is classified into different levels based on its performance and quality, suitable for different application scenarios:
1) FR4 PCB A1 level
mainly used for high-end electronic products such as military, communication, computer, digital circuits, industrial instruments and automotive circuits.
2) FR-4 A2 level
suitable for ordinary computers, instruments, high-end home appliances, and general electronic products.
3) FR-4 A3 level
specifically developed for the home appliance industry, computer peripherals, and general electronic products, with performance that meets requirements and competitive pricing.
4) FR-4 A4 grade
suitable for low-end electronic products, with the most competitive price and performance that can still meet general needs.
5) FR-4 Grade B
Poor quality stability, suitable for small-sized circuit board products, with the lowest price.
Glass transition temperature (Tg) and thermal decomposition temperature (Td)
The indicators of FR-4 substrate include: glass transition temperature (Tg), thermal decomposition temperature (Td) of the substrate, loss factor (Df), dielectric constant (Dk), relative leakage tracking index (CTI), coefficient of thermal expansion (CTE), water absorption rate, adhesion characteristics of the material, etc.
Tg value refers to the temperature point at which a material transitions from a relatively rigid “glass” state to a deformable state. As long as the thermal decomposition temperature (Td) is not reached, this thermodynamic change is reversible, and when cooled below the Tg value, the material can return to a rigid state. When the thermal decomposition temperature is exceeded, FR-4 will undergo decomposition failure.
The industry usually divides FR-4 board into three levels based on Tg value: high, medium, and low
Low Tg FR4: Tg value around 135 ℃;
Medium Tg FR-4: Tg value is around 150 ℃;
High Tg FR-4: Tg value is around 170 ℃.
If there are multiple pressing cycles, multiple layers of PCB, high soldering temperature (≥ 230 ℃), high working temperature (over 100 ℃), and high soldering thermal stress (such as wave soldering) during PCB processing, high Tg boards should be selected.
Loss factor (Df) and dielectric constant (Dk)
The dielectric constant and dielectric loss angle are two fundamental properties of a medium, which vary with frequency. The larger the loss factor (Df), the greater the attenuation. The dielectric constant (Dk) has a greater impact on impedance.
FR-4 can be divided into:
Ordinary loss board: Df ≥ 0.02
Medium loss board: 0.01 ≤ Df<0.02
Low loss board: 0.005 ≤ Df<0.01
Ultra low loss board: Df ＜ 0.005
Relative Leakage Traceability Index (CTI)
The Comparative Tracking Index is used to measure the electrical breakdown performance of insulation materials. Leakage marks occur on the surface of insulating materials. Due to the presence of dielectric losses, the dielectric heats up, causing decomposition and carbonization of the dielectric, ultimately extending to the electrode and causing a short circuit.
The CTI value of the material is positively correlated with its insulation performance. A high CTI value means a lower required creepage distance, and the distance between two conductors will be closer.
SysPCB: Your Top Choice for FR4 PCB Solutions!
SysPCB, a China FR4 PCB board manufacturer, is able to assist you in your search for printed circuit boards made of FR4 or any other material.
Here are some reasons to select SysPCB as your FR4 PCB manufacturer：
Skilled Expertise
With over a decade of experience in producing high-quality FR4 printed circuit boards, SysPCB has earned a reputation for excellence. We are committed to delivering superior products and maintaining exceptional service standards.
Affordable Pricing
Our FR4 PCB manufacturing services are competitively priced, allowing you to optimize your project budget without compromising on quality or reliability.
No MOQ
SysPCB does not have a minimum order quantity (MOQ) requirement, so you can confidently partner with us. As an FR4 PCB manufacturer, we are committed to building long-term relationships based on mutual trust and benefit.
