Why FR4 Material Dominates PCB Production

FR4 pcb

FR4, a widely utilized substrate in PCB manufacturing, serves as the cornerstone of rigid circuits. Despite its omnipresence, various stakeholders may lack nuanced understanding of this material, necessitating clarification regarding its selection as the preferred base for PCBs.

FR4, or Flame Retardant 4, refers to a type of material widely used as the substrate (base material) for printed circuit boards (PCBs). It is the most common and widely accepted material for PCBs due to its desirable properties. FR4 is not a specific material but rather a grade designation given to a type of glass-reinforced epoxy laminate.

Here are the key components of FR4 material in PCBs:

▶Epoxy Resin: FR4 PCBs are made using a type of epoxy resin as the matrix material. This resin provides the PCB with its rigidity and insulating properties. It is chosen for its ability to withstand high temperatures and provide electrical insulation.

▶Glass Fiber Reinforcement: The core of FR4 material is reinforced with a woven glass fiber cloth. The glass fibers provide strength and stability to the PCB. The most common type of glass used is E-glass (electrical glass), which is known for its electrical insulation properties.

▶Flame Retardant Additives: FR4 printed circuit board is treated with flame retardant additives to reduce the risk of the material catching fire. This is particularly important in electronic devices where safety is a primary concern.

The combination of epoxy resin and glass fiber reinforcement gives FR4 its excellent electrical insulating properties, mechanical strength, and dimensional stability. FR4 PCB board is known for its versatility, making it suitable for a wide range of applications in various industries.

When you see a PCB described as FR4, it means that the base material of the board conforms to certain standards for flame retardancy and electrical properties. FR4 printed circuit board is available in different grades and thicknesses, and it is commonly used in both single-layer and multilayer PCBs across a broad spectrum of electronic devices.


Why FR4 is the stand-alone PCB board manufacturer

The first widely used PCB boards are paper phenolic copper-clad substrates, such as XPC, XXXPC, because the price of the material is relatively cheap, but they are non-flame-retardant materials, in the 1970’s the emergence of fire accidents due to circuit failures, the major electrical equipment began to shift to the use of flame-retardant substrates, with flame-retardant characteristics of paper phenolic copper-clad substrate FR-1, FR-2 use The use of FR-1 and FR-2 copper-clad paper phenolic substrates with flame-retardant properties gradually surpassed that of non-flame-retardant XPC and XXXPC substrates.

In the 1980s, multimedia portable devices became popular, such as Walkman, BP machine, etc., PCB began to move towards miniaturization and high-density development, and the application of multilayer PCB became more and more common, which in turn led to the development of PCB substrates.

Paper substrates such as XPC, FR-1, although cheaper than epoxy fiberglass cloth substrate FR-4, but in moisture absorption, heat resistance and mechanical strength are not as good as FR-4. Early on, paper substrates were usually used for price-sensitive consumer products, and FR-4 was more commonly used for industrial products.

However, as consumer devices have moved towards smaller, lighter, and thinner devices, the use of FR-4 sheets has increased. As PCBs with a standard thickness of 1.6 mm to 0.8 mm became widely used, mechanical strength and moisture resistance of paper substrates became an issue. In addition, paper substrates are not suitable for the production of multilayer boards, and with the development of miniaturization of equipment, PCB wiring density is becoming higher and higher, and the market share of multilayer boards is also increasing. Therefore, despite the relatively high cost of FR-4 boards, consumer products are still gradually turning to FR-4 boards.

PCB prototype plants widely chose FR-4 and did not use the cheaper paper substrate . Another important reason is that the paper substrate is not suitable for drilling process, only suitable for punching process, while FR-4 is very easy to process.

With the capacity of epoxy resins and glass fiber cloth and other materials continuing to expand, the current standard FR-4 substrate has been a low-cost material, with excellent mechanical properties and excellent processability, so that it is welcomed by the world’s low-cost electronics manufacturers.

What are the Features of FR4 Sheets in Circuit Board?

FR4 sheets stand out as a favored choice among electrical engineers and designers for the foundation of printed circuit boards (PCBs). The material’s popularity can be attributed to its cost-effectiveness, versatility, and a multitude of advantageous physical properties. Notably, FR4 sheets serve as electrical insulators with robust dielectric strength.

Here are the notable features of FR4 sheets in the context of circuit boards:

Electrical Insulation:
FR4 sheets provide excellent electrical insulation, preventing unintended electrical contact between different circuit elements. This property is essential for maintaining the integrity of electronic circuits.

Flame Retardancy:
FR4 PCB board is inherently flame-retardant. This feature enhances the safety of electronic devices by reducing the risk of fire and limiting the spread of flames in the event of a fire.

Mechanical Strength:
The woven glass fiber reinforcement in FR4 sheets imparts mechanical strength to the material. This strength is crucial for the structural integrity of circuit boards, especially during manufacturing, assembly, and in the end-use environment.

Dimensional Stability:
FR4 exhibits good dimensional stability under varying environmental conditions, ensuring that the circuit board maintains its shape and size over time. This stability is important for reliable performance and compatibility with other components.

Thermal Resistance:
FR4 sheets have reasonable thermal resistance, allowing them to withstand elevated temperatures during soldering and other manufacturing processes. This property contributes to the durability of the circuit board.

Compatibility with Soldering Processes:
FR4 sheets provide a suitable surface for soldering. Copper traces on the FR4 surface adhere well to solder, facilitating the attachment of electronic components during the assembly process.

Versatility for Multilayer PCBs:
FR4 is well-suited for the construction of multilayer PCBs. The material allows for the stacking of multiple layers, accommodating complex circuit designs and enhancing the functionality of electronic devices.

FR4 is cost-effective compared to some alternative materials. Its widespread availability and ease of manufacturing contribute to its affordability, making it a preferred choice for a variety of electronic applications.

Standardization and Industry Acceptance:
FR4 has become a standard material widely accepted in the electronics industry. Its use is supported by established manufacturing processes and conformity to industry standards.

Environmental Considerations:
FR4 sheets can be manufactured with environmentally friendly considerations. Some versions are recyclable, contributing to sustainable practices in electronic manufacturing.


When to use FR4?

FR4 is a code name for a flame-resistant material grade, which represents a material specification that the resin material must be able to self-extinguish after a combustion state.FR4 sheet is a composite material, composed of fiberglass cloth and epoxy resin, which is widely used in the fields of electronics, electrics, communications, aerospace and so on, because of its excellent electrical properties, mechanical properties and chemical stability.

In electronic manufacturing, FR4 sheets are usually used in the manufacture of circuit boards, which can be used as the substrate material of circuit boards to ensure the stability and reliability of circuit boards. In addition, FR4 sheets can also be used as partition and insulation materials, with superb insulation properties and high temperature stability, to ensure the electrical safety of the equipment and avoid accidents caused by electrical failure. In the field of machinery, FR4 sheets can also be used as the material of mechanical parts, such as machine tool partitions, automobile engine hoods and so on.

Overall, the use of FR4 sheets depends on specific application scenarios and needs, as it has excellent performance and a wide range of application areas.

Share This Post