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FR-1 PCB | Difference Between FR-1, FR-2, FR-3 and FR-4 PCB

Posted:04:33 PM November 04, 2022 writer: NextPCB

What is FR-1?

FR-1 is a paper-based non-conductive printed circuit board (PCB) base material made of phenol-formaldehyde resin and paper. The FR-1 is used in PCB laminates. PCB laminates are comparatively thin panels coated with copper. In a PCB laminate, the FR-1 works as an insulator that separates the two conducting layers and provides the necessary mechanical support to the circuit board.

The FR in FR-1 material stands for fire retardant, which is a property of a material to extinguish fire itself. Throughout their lives, the PCBs went through a lot of heat and even sometimes, the components get a spark and catch fire. Hence, in such circumstances, the fire-extinguishing property of FR-1 helps the circuit to prevent a huge loss and spread of fire. Along with excellent fire-handling capabilities, FR-1 has great electrical specifications and mechanical strength. That is why PCB producers still prefer FR-1 for their circuits and especially for single-side circuit boards.

Fr-1 PCB Specification

The specifications e.g. properties of a product or material help define it uniquely and clearly. Here we are stating some basic properties of FR-1 material that are crucial to notice while selecting a substrate; 

High Glass Transition Temperature 130C
Decomposition Temperature Not available on the Internet 
Co-efficient of Thermal Expansion Not available on the Internet 
Dielectric Constant (@1 GHz) 4.0-5.0
Dissipation Factor (@1 GHz) Not available on the Internet 
Load Bearing Property of FR-1 Moderate

What are the Benefits of FR-1 PCB?

FR-1 PCB material is a widely used PCB base material with several advantages.

Flame Retardant

FR-1 PCB material meets the standard of UL94V-0. Hence, FR-1 is a flame-retardant material that does not catch fire easily and extinguishes the fire itself. The flame retardancy of FR-1 material makes it suitable for consumer electronics such as chargers, adapters and other home appliances.

Low-Cost Material

FR-1 is a low-cost material with good electrical specifications that meet industry standards while aiding the budget. Further, FR-1, due to its electrical properties and low price, is the first choice of PCB engineers for single-layer PCBs.

Good Glass Transition Temperature Tg of FR-1

FR-1 provides a glass transition value of 130C, which is not soo high and, of course, less than the glass transition value of FR-4 (150C to 170C). Firstly, the transition temperature of a PCB base material defines the temperature at which the PCB starts getting soft and losing its shape. But still, with a lower Tg than FR-4, FR-1 provides exceptional performance in his applications. The applications of FR-1 PCB material are not complex a lot. Hence, a glass transition temperature of 130C is enough to meet the criteria of its applications.

Mechanical Strength of FR- 1

FR-1 PCB material is a combination of paper and epoxy. Thus it provides high mechanical strength to the circuit board and makes the PCB withstand the load of components. The mechanical strength of FR-1 is somewhere near the mechanical strength of FR-4.

Environmentally Friendly PCB Material

FR-1 does not contain elements of the halogen group or any other harmful material. Hence, not only FR-1 but the whole family of Flame-Retardant materials are eco-friendly and do not produce toxic material or gas during operation.

What are the Drawbacks of FR-1 PCB?

Every matter present in the universe, along with its benefits, has some drawbacks; that may limit its use but never question its reliability and performance in the right places. The widely used PCB material FR-1 also has some disadvantages and limitations that restrict its use for some specific applications.

To understand the FR-1 PCB specifications and their behaviour deeply. It is significant to pay attention to its limitations. So, let's have a look at the drawbacks of FR-1 PCB material.

Lower Temperature Resistance

FR-1 is not a good base material for circuit boards that produce ample heat during operation and require high-temperature resistance. As stated above, the Glass transition temperature value of FR-1 PCB material is 130C. Hence, if the device generates a lot of heat, gradually, the PCB will start losing its shape and experience electrical and physical damage.

Lower Dissipation Factor (Signal Loss)

The higher dissipation factor of FR-1 material makes it unsuitable for high-frequency and high-speed applications. Due to the higher dissipation factor, the circuit board experience higher signal loss. That is why the manufacturers do not recommend FR-1 for complex electronic circuit boards that require specific undisturbed inputs to produce accurate outputs.

Poor Moisture Resistance

FR-1 PCB material has poor moisture resistance, at high-humidity areas, it absorbs a sufficient amount of water, enough to make it swell. Hence, FR-1 material is not a good option for devices that work in highly humid areas. FR-1 is also not a suitable material for marine applications.

Precise Calculation

FR-1 dielectric PCB material has some operating limitations. Hence, FR-1 requires a precise calculation of the maximum electrical properties the circuit board will operate. If the voltage, power or heat of the circuit board exceeds the limit of FR-1 PCB material, the material will face a dielectric breakdown. Due to the dielectric breakdown, FR-1 will initiate to lose its insulating properties. Hence, it will begin performing as a conductor instead of an insulator. To avoid such a disaster in a circuit, it is crucial to precisely calculate the values; the PCB will be operating.

Application of FR-1 PCB

FR-1 PCB material is a blend of two materials, paper and phenol-formaldehyde resin. The FR-1 is available in thin dielectric plates coated with copper, known as PCB laminates, used to insulate copper layers from each other and provide mechanical strength and shape to the circuit board.

When it comes to the applications of FR-1 PCB material, it has several uses in different domains. The mass producers of PCB emphasize FR-1 for single-layer circuit boards. Mainly FR-1 has applications in portable consumer electronics, such as adapters, chargers and some other, not soo complex devices. FR-1 may also use in industries like automobiles, medicine and telecommunication.

The Difference Between FR-1, FR-2, FR-3, FR-4

FR-1, FR-2, FR-3 and FR-4 all come under Flame-Retardent NEMA-graded materials. All four are significant PCB dielectric materials with good electrical specifications. The family members of Flame Retardent material have different specifications, which proves them better than each other for specific applications. Hence, we should know the differences between these materials to pick the best possible material for our project. To ease your learning about the family of flame-retardent material, NextPCB provides a chart that significantly covers basic to advance knowledge about all four materials.

A Comprehensive Chart to Describe the Difference between FR-1, FR-2, FR-3 and FR-4 PCB Material



FR-1 FR-2 FR-3 FR-4


Paper and phenol-formaldehyde resin. Paper impregnated with a plasticized phenol formaldehyde resin. Cotton linter/alpha cellulose paper impregnated with epoxy resin formulation. Woven / Unwoven fibre-glass cloth impregnated with epoxy resin.

Glass Transition Temperature

130C 130C 130C 140 to 170C

Co-efficient of Thermal Expansion

      2.5 to 3.8%

Decomposition Temperature 


Dielectric Strength

  740V   800 to 900V

Dielectric Constant or relative permittivity

4.0~5.0 4.5   4.25 to 4.55

Dissipation Factor

  0.024–0.26    0.016

Water Resistance

Low  -Not suitable for highly humid areas. Fair  - Appropriate for standard humid areas. Medium  -Appropriate for highly humid areas. High  -Surely suitable for marine applications and highly humid areas.

Chemical Resistance

Low Low Medium High

Suitability for Single-layer PCB

Recommended –due to its low price and good electrical properties. Recommended –due to its low price and good electrical properties. Yes Yes  -but quite expensive. Because if there are no specific requirements the FR-1 can perform the same function at much lower prices. 

Suitability For double-layer PCB

Fair Fair Yes Recommended –due to its low price compared to PTEF & Rogers and good electrical properties.

Suitability For Multi-layer PCB

No No Yes Recommended –due to its low price compared to PTEF & Rogers and good electrical properties.

Suitability for high-frequency PCBs

No Fair Fair Yes

Level of Complexity while Working with the Material

Low/Easy Hard/Complex   Low/Easy


A Comprehensive Understanding of the Difference Between FR-1, FR-2, FR-3 and FR-4

FR-1, FR-2, and FR-3 all provide good properties and have wide applications in different industries. However, FR-4 is the most commonly used PCB substrate. The exceptional properties of FR-4 support its hype in the market. The PCB producers certainly like to stick with FR-4 for multi-layer and complex circuit boards. But, when it comes to single-layer PCBs, they emphasize FR-1 due to its low cost and ease of handling.

The substrate selection for the PCB might be difficult. But it is crucial to identify an appropriate material for the circuit, as the properties of the PCB base material affect the performance of the circuit board. For example, if a circuit operates high-frequency or high-speed signals, it will need a substrate with a lower dissipation factor to minimize signal loss during signal transmission. So in such a case, if we use any other material rather than a substrate with a lower dissipation factor, we will lose on quality. Hence, it is mandatory to identify the requirements of the circuit and the properties of different substrates before selecting the base material for the PCB. 

NextPCB hopes that its provided information will certainly help you understand the difference between the different members of the family of Flame-Retardent material and will influence your selection of substrate for good.

Related: An Ultimate Guide to FR-4 PCB material

NextPCB: The Best FR-1 PCB Manufacturer around the Globe

NextPCB has been providing PCB manufacturing, testing and assembling services for more than 15 years. For so long, we have been serving the industry; we know how to work with different substrates and implement unique PCB design technologies.

FR-1 and FR-2 PCBs are complex and require skilful labour during manufacturing. We at NextPCB ensure that each PCB fabricate under the supervision of skilled labour and go through several automatic and manual tests because it is necessary to provide outstanding high-quality FR-1 and FR-2 PCBs.

Along with PCB manufacturing, NextPCB offers component sourcing services. To avail our PCB manufacturing services and experience maximum customer support, please contact us with your queries.


FR-1 PCB material is a member of the flame retardant family, with good electrical and mechanical properties. The sharp end of FR-1 is that it is cheaper than FR-4, and over time it has proven perfect for single-layer PCBs. That is why FR-1 is the first choice of PCB producers for simple and single-layer printed circuit boards.

However, FR-1 is a productive substrate, but the fact is that it is not appropriate for every type of circuit. High-frequency, high-speed or complex circuit designs require more critical and keen electrical values, which surely FR-1 fails to provide.

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