FR-4 material Guide for Printed Circuits Board

FR-4 material Guide for Printed Circuits Board


The properties and characteristics of FR-4 or FR4 make it inexpensive and versatile. This is why it is widely used in the production of printed circuits board. In this article, you will find more information on the following.

1. The actual meaning of FR-4

2. Characteristics and advantages of FR4

3.Different types of FR-4

4. Factors to consider when choosing the thickness

5. Why choose FR4?

6. FR4 type provided by Rocket PCB

7. Grades of FR4 materials

8. Make and model of FR4

9. High-frequency PCB material and metal-based materials

1. The actual meaning of FR-4

FR4 is the standard for glass-reinforced epoxy laminates as defined by NEMA (National Electrical Manufacturers Association).

FR stands for "flame retardant" and indicates that the material meets the UL94V-0 standard for the flammability of plastic materials. The 94V-0 code can be found on all FR-4 PCBs. FR-4 is a code for a flame-resistant material grade, which means that the resin material must be able to extinguish itself after a burning condition.

Therefore, there are many types of FR-4 grade materials used in general circuit boards, but most of them are based on the so-called Tera-Function epoxy resins with filler and glass fibers are used to make composites.

2. Performance characteristics of FR-4

FR-4 epoxy glass fiber substrate is a type of substrate that uses epoxy resin as the binder and electronic grade glass fiber cloth as the reinforcement material. Its bonding sheet and inner core thin copper-clad laminate are important substrates for making multilayer printed circuit boards.

Epoxy glass fiber substrate has higher mechanical properties, dimensional stability, impact resistance, and moisture resistance than paper substrate. Its electrical Excellent performance, higher working temperature, its own performance is less affected by the environment. In the processing process, to have a great superiority over other resin glass fiber cloth substrate. These products are mainly used for double-sided PCB, the amount is large. Epoxy glass fiber substrate, The most widely used product model is FR-4, and due to the development of electronic product mounting technology and PCB technology, there are high Tg FR-4 products.

For high TG, the glass transition temperature (TG) is around 170°C to 200°C, depending on the manufacturing method and resin used. A standard FR-4 PCB will have a layer of FR-4 sandwiched between two thin layers of laminated copper.

FR-4 uses bromine, a refractory so-called halogen chemical element. In most applications, it replaces G-10, which is another composite material with lower corrosion resistance.

FR4 has the advantage of a good resistance-to-weight ratio. It does not absorb water, maintains high mechanical strength, and has good insulating ability in dry or humid environments.

3. Different types of FR-4

Standard FR4: As the name suggests, this is standard FR-4, which has a heat resistance of approximately 140°C to 150°C. Although this may not be applicable to extreme temperature processes that are common in applications such as automotive, industrial or high-temperature electronics. In such cases, PCBs made of FR-4 material usually provide the best solution.

High TG FR4: This FR-4 has a higher glass transition (TG) of approximately 170°C.

High CTI FR4: Comparative tracking index above 600 volts.

FR4 without laminated copper: ideal for insulating panels and board supports.

PS: TG value of FR4 sheet: also called glass transition temperature, generally 130°C, 140°C, 150° C, 170°C.

The thickness of FR4 sheet is generally 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2.0mm, and the thickness error of the sheet depends on the production capacity of the sheet factory.

FR4 copper clad board commonly used copper thickness: 0.5 ounce, 1 ounce, 2 ounces, other copper thicknesses are also available, need to consult the PCB manufacturer to determine.

4. Factors to consider when selecting the thickness

Compatibility with components: Even though FR-4 is used to produce many types of printed circuits, its thickness can affect the type of components used. For example, THT components are different from other components and require thin PCBs.

Space-saving: Space-saving is essential when designing PCBs, especially for USB connectors and Bluetooth accessories. The thinnest boards are used in configurations where space-saving is critical.

Design and flexibility: Most manufacturers prefer thick boards to thin boards. If the substrate is too thin, there is a risk of breakage if the board size is increased when using FR-4. Thicker boards, on the other hand, are flexible and allow for the creation of V-grooves.

The environment in which the PCB is used must be considered. For electronic control units in the medical field, a thin PCB ensures less stress. Boards that are too thin (and therefore too flexible) are more susceptible to heat. They bend and form undesired angles during the component soldering step.

Impedance control: The thickness of the board indicates the thickness of the dielectric environment, in this case, FR-4, which contributes to impedance control. When impedance is an important factor, the thickness of the board is the deciding criterion to be considered.

Connection: The type of connector used for the printed circuit also determines the thickness of the FR-4.

5. Why choose FR4?

FR4 is reasonably priced, making it the standard choice for low-volume PCB production or electronic prototyping.

However, FR4 is not ideal for high frequency printed circuits. Similarly, if you want to make PCBs that do not easily adopt components and are hardly suitable for flexible PCBs, you should choose another material: polyimide/polyamide.

6. Rocket PCB offers different types of FR-4

Rocket PCB offers a wide range of high-temperature PCB product manufacturing services using FR-4 or other high-quality heat and temperature-resistant Tg materials. We are able to perform high temperature PCB manufacturing for automotive, industrial and high-temperature electronics applications. We can manufacture high Tg PCBs with Tg values up to 180°C.

No matter how complex the scope of your PCB application, we have the technical expertise to develop custom PCBs that can meet your specific needs. Check out our features here.

7. How many grades of FR4 material are there?

Generally, there are 5 levels:

<1> FR-4 A1 grade copper laminate is mainly used in military, communication, computer, digital circuit, industrial instrumentation, automotive circuit, and other electronic products. The quality of this series of products has completely reached the world's first-class level and has the best performance.

<2> FR-4 A2 grade copper laminate This grade is mainly used for general computers, instruments, advanced home appliances, and general electronic products. This series of copper laminates are widely used, and all performance indicators can meet the needs of general industrial electronic products. There is a very good price-performance ratio. Can enable customers to effectively improve price competitiveness.

<3> FR-4 A3 grade copper laminates are FR-4 products developed and produced by some companies specifically for the home appliance industry, computer peripherals, and general electronic products (such as toys, calculators, game consoles, etc.). Its characteristic is that the price is very competitive while the performance meets the requirements.

<4> FR-4 AB grade copper laminate is a low-grade product exclusive to some companies. However, the performance index can still meet the needs of common home appliances, computers, and general electronic products, and its price is the most competitive and the performance-price ratio is quite excellent.

<5> FR-4 B grade copper laminate is a subgrade of some companies, with poor quality stability, and is not suitable for large area circuit board products, but generally for 100mmX200mm. Its price is the cheapest, but customers should pay attention to the choice of use.

8. FR4 Brand and Model






General FR-4


Sheng Yi, King Board, ITEQ


General FR-4


Sheng Yi, King Board, ITEQ

Medical Devices

Premium FR-4


Sheng Yi, ITEQ

Aviation, Oil

Advanced FR-4


Sheng Yi

8.1 Major brands commonly used models


IT180A/ IT170GRA1/ IT958G/ IT968/ IT968SE/ IT988GSE


Tu862HF/ Tu872L K/Tu872SLK/Tu872SLK-SP/Tu883/ Tu933+



Park Meteorwave Series:

MW1000/2000/3000/4000/ 8000

ShengYi: S1000-2(M)/ S7439/S6, etc.

8.2 Recommended material type

FR-4 for general TG  S1141/Sheng Yi Technology  TG value 140℃ can meet the needs of general civil and industrial PCBs

FR-4 with high TG  IT-180A/ITEQ Electronics  TG value 175℃ can meet the general civil, industrial, military, and other industries' PCB needs

General TG Halogen Free FR-4  S1155/Sheng Yi Technology  TG value 140℃, halogen-free, choose according to the environmental requirements of the product

High TG Halogen Free FR-4  S1165/Sheng Yi Technology  TG value 170℃, halogen-free, choose according to the application of the product and environmental requirements

The PCB cost order of the above materials is S1141<IT180A<S1155<S1165.

Of course, there are many types of FR-4 on the market, among the above-recommended sheets, S1141 can be said to be the best performance among the ordinary TG FR-4; IT180A has excellent performance in the comparison of ordinary high TG FR-4, and can replace S1170, S1000-2, FR406, PCL- 370HR, N4000-6, etc. Shengyi-Tech and ITEQ Electronics are strategic partners in our supply chain, giving priority to guarantee the demand for Rocket PCBs with no supply risk and short delivery time.

9. High frequency material and metal substrate materials

In addition to FR4 material, high-frequency sheet can be used according to the special requirements of dielectric constant, dielectric constant stability, and dielectric loss of the material. The world's top three suppliers of high frequency materials are ROGERS, TACONIC, and ARLON, in addition to Neclo, Panasonic and other companies also produce high-frequency plates, and domestic manufacturers include Taizhou Wangling, Xianyang 704 factory, etc.

Models such as Rogers series R04003/R03003/R04350B (RF material), etc.

Metal substrates are mainly used in special heat dissipation fields, such as automotive electronics, power supplies, amplifiers, LEDs, etc. Metal substrates are generally single layer, Its structure is circuit, thermal insulation layer, heat dissipation metal base, metal base mainly has a copper base, aluminum base two categories. The main manufacturers of aluminum base plates include Bergquist in the United States and Laird in the United Kingdom. There are also many domestic manufacturers of metal substrates, such as Quan Bao, Danyang, Chaoshun, and Betsy, but their reputation in the industry is not as good as that of foreign metal substrate materials, which are characterized by lower prices. According to the demand of heat dissipation, you can choose the appropriate thermal conductivity of the aluminum base plate in the design, the thermal conductivity of 0.4-3.0W/M.K can be selected. Copper substrates are mainly used in amplifier modules in the communication field, and TACONIC of the United States holds most of the global market.

You can use our PCB inquiry form to get prices for FR4 PCB and HF material manufacturing. Simply upload your Gerber file and the corresponding PCB price will be reviewed and sent to your email in a timely manner.

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