FR4 Material Guide

The specification standard of FR4 is set by NEMA (National Electrical Manufacturers Association). FR in NEMA classification standard stands for Flame-Retardant. FR-4 means the resin is epoxy resin, the reinforcement material is glass fiber cloth, and the flame retardant grade is UL94 V-0.

FR4 is a common composite material widely used in the manufacture of electronic circuit boards. It consists of a layer of glass fiber and a layer of epoxy resin. The glass fiber cloth, as a reinforcement material, provides good mechanical properties for FR4. Epoxy resin, as a matrix material, is bonded with the glass fiber cloth to form a strong composite material.

Specific values:

Conventional thickness: 0.5-50mm

Conventional size: 1020×1220/1220×2040（mm）

Insulation grade: Class F

Color: The main colors are white (primary color), aqua, black and yellow.

What are the characteristics of FR4?

1.High mechanical properties: FR4 has high mechanical strength and can withstand large mechanical stress and are not easy to break or deformation, which makes them ideal for the manufacture of precision instruments and high-end equipment.

2.Excellent electrical performance: FR4 has stable electrical insulation performance, which can effectively prevent current leakage and short circuit and provide reliable guarantee for the safe operation of electrical equipment. Its high insulation resistance and low dielectric loss make it excellent in high-voltage electrical appliances, electronic circuits and other fields.

3.Good heat and moisture resistance: FR4 can maintain stable performance in high temperature and humid environments and it is not easy to deform or age, which makes it work normally under harsh environmental conditions.

4.Good flame retardant performance: FR4 has flame retardant performance, which can prevent the spread of fire to a certain extent and provide protection for the safe use of electronic products.

Application areas of FR4 insulation sheets

Thanks to its excellent flame-retardant properties, FR-4 insulation sheets are widely used in many fields. The following are its main application areas:

1.Electronics industry: FR4 insulation sheet is one of the main materials for making PCB boards (printed circuit boards). In electronic equipment, PCB boards carry a variety of electronic components and circuit connections, so their flame retardant properties are critical to the safety and stability of the equipment.

2.Aerospace: In the aerospace field, FR-4 insulation sheets are used to make aircraft instrument panels, navigation systems, communication systems and other key components. These components need to withstand extreme environments such as high temperatures and high pressures, so the material is required to have excellent flame retardant properties and stability.

3.Automotive industry: In the automotive industry, FR-4 insulation sheets are used to make automotive circuit boards, engine control systems, in-car entertainment systems and other components. The flame retardant properties of these components are important for ensuring the safety and reliability of automobiles.

What is the density of FR4 sheets?

The density of FR4 sheet refers to the mass of FR4 material per unit volume, and it is usually expressed in g/cm³ or kg/m³. This parameter is an important physical property of FR4 sheet and is closely related to the composition, manufacturing process and use of the material.

In general, the density of FR4 sheets varies over a wide range, but common density values are usually between 1.7 and 2.2 g/cm ³. The density values in this range allow FR4 sheets to exhibit good combined properties in terms of electrical insulation, mechanical support, thermal stability and flame retardancy.

Density measurement is very important for the quality control and application of FR4 sheet metal. By measuring density, performance indicators such as uniformity, density and porosity can be assessed to ensure that the material meets the specific application requirements.

How is FR4 made?

1.Raw material preparation: The main raw materials of FR4  include glass fiber cloth and epoxy resin. First, select the appropriate glass fiber cloth and epoxy resin, and inspect and mix them.

2.Impregnation: Impregnate the glass fiber cloth in epoxy resin to ensure that the resin fully penetrates into the fiber cloth to form a uniform mixture.

3.Drying: Dry the impregnated material to remove excess water and solvent to ensure the stability and uniformity of the material.

4.Hot pressing: Put the dried material into the mold and perform hot pressing under high temperature and high pressure. This step is critical to ensure the density and strength of the material.

5.Curing: The hot pressing material is cured, which is usually under heating and pressure. The epoxy resin is completely cured to form a stable insulation board.

6.Inspection and cutting: Inspect the cured insulation board to ensure that its size, hardness, tensile strength, etc. meet the requirements. Then cut and process as needed to meet different application requirements.

How to choose a FR4 manufacturer?

1.‌Product quality and performance‌: Choosing a manufacturer with high-quality products and stable performance is the primary consideration. FR4 materials should have high mechanical and dielectric properties, good heat and moisture resistance, and good machinability‌. In addition, the dielectric constant (Dk) of FR4 materials is generally between 4.2 and 4.8, and the loss factor (Df) is usually 0.02~0.035, which is suitable for the transmission of medium frequency and high-speed signals‌.

2.‌Price and cost‌: Compared with high-performance materials such as PTFE and ceramics, FR4 materials have lower costs and are suitable for mass production‌. Therefore, choosing a manufacturer that provides cost-effective FR4 materials can reduce production costs.

3.‌Service and technical support‌: Choosing a manufacturer that provides one-stop processing services can ensure efficient connection from material selection to manufacturing, helping engineers create higher performance and more reliable electronic products‌. In addition, the manufacturer's technical support and after-sales service are also important considerations to ensure that problems encountered during use can be solved in a timely manner.

4.‌User reviews and reputation‌: Checking other users' reviews and reputation of the manufacturer can help understand the manufacturer's actual performance and service quality. You can learn about other users' feedback through online platforms or social media and choose manufacturers with better reviews‌.

What is the price of FR4 per kg?

The price of FR4 per kg is about 8 yuan. In addition, the price of FR4 sheet is about 320 yuan per sheet. The main material is imported semi-cured sheet, which has high mechanical strength and good electrical properties. It is suitable for insulating structural parts in the electrical and electronic industries.

Factors affecting the price of FR4 include material quality, purity and market supply and demand. High-quality FR4 usually has better performance, such as higher heat resistance, corrosion resistance and mechanical strength, so the price is relatively high. In addition, market supply and demand conditions and regional differences will also affect the price of FR4.