Top 8 brand of Fr4 Material

Fr4 Material

Most electrical engineers and individuals involved in the electrical industry know that when your company wants to make sure you’re wearing a flame-resistant suit. At the same time you work, they’ll ask if you have an Fr4 material. However, most of us have no clue what it means or where to find one.

What Is Fr4 Substrate Material

We call the material used to make Fr4 uniforms the Fr4 Substrate. It is a fire-resistant synthetic fabric that resists radiant heat transfer and has more excellent flame retardancy than conventional fabrics.

The material composition includes:

Polyester fibers have the following thermal properties:

Polyester fiber has an excellent performance in high temperature, high oxidation environmental conditions. We use it in the clothing industry and other applications, including protective garments (safety helmets, drill head protection, etc.). Polyester fiber also acts as a flame retardant in many garments because of its ability to resist thermal damage. Fire does not penetrate it; it does not burst into flame and does not ignite anything in the presence of smoke. Fire does not make any critical changes on the fiber from the oxidation process; therefore, there is no smoke in the air.

Polyester is a flexible and kind-to-skin fabric. We use it in many garments, including:

Fire-resistant coat

In addition to making flame retardant products, certain companies have started manufacturing completely fire-resistant apparel throughout the United States. One company that MANUFACTURES uniforms and helmets, gloves, and other apparel compatible with official protective gear is Marmot Incorporated. A company specializing in making the components is Rayming PCB & Assembly.


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Nylon fibers have the following thermal properties:

Nylon fiber has an excellent performance in high temperature, high oxidation environmental conditions. As a result, we use it in the clothing industry and other applications, including protective garments (safety helmets, drill head protection, etc.). Nylon fiber also acts as a flame retardant in many garments because of its ability to resist thermal damage. Fire does not penetrate it; it does not burst into flame and does not ignite anything in the presence of smoke.

Polyester fibers hybridized with Nylon have high resistance against fire and we call it the FR4 substrate. We use them in fire-retardant and FR4 textiles. The combination of fibers produces a so-called “ultra-high molecular weight” (UHMW) fabric. The extrusion process causes the fibers to melt together and form a single polymer fiber mass called the UHMF (Ultra-high molecular weight fiber). The UHMF fabric has significantly greater flame resistance than single Nylon or polyester fibers.

FR4 Substrate is a textile substrate where we lubricate the fibers with a flame retardant (FR) coating. Then, we apply a chemical coating to the substrate to provide flame resistance to the FR4 product. As a result, FR4 products have excellent thermal stability, dry quickly, and have 3-6 times greater resistance than conventional fabrics of the same weight. These properties are essential for low-maintenance products, especially for critical environments where there is a risk of contact with fire or heat.

How We Use Fr-4 In Pcbs

FR4 is an acronym for ‘flame-resistant fiber-reinforced epoxy FR4 laminate.’ We use it to fabricate PCBs (printed circuit boards), an essential electronic component.

The schematic diagram of the PCB shows that it contains at least one regular copper layer and one or more layers from FR-4.

There are two main methods of manufacturing FR4 PCBs: wet and dry processes. We apply FR-4 to copper foil in the wet process by a solvent. This method does not require any toxic materials, but the time to complete fabrication is comparatively longer. On the other hand, the dry process is more common. It requires only molten resin and a binder as the main raw material.

These qualities make FR4 suitable for use in fire and impact-resistant applications.

We laminate the FR-4 film onto the copper foil. Then, one uses a smooth roller, wherein we transfer the finished component through a heat transfer mold. We can do the heat transfer on a large scale, such as the fabrication of large PVC pipes. In the case of PCBs, we can laminate one or more layers with FR-4 onto a regular printed circuit board by using a heated roller. In this way, there is also no need to use toxic materials to manufacture PCBs since the manufacturing method does not require cutting or drilling into any printed circuit board dielectric.


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What to consider when selecting FR4 thickness

We use FR4 substrate in electronics, cables, and other applications. Therefore, we need to consider several factors when selecting the thickness of FR4 suitable for the use case.

When the application calls for a high heat requirement, we can use thicker FR4. However, that certainly means that you will have to purchase and process a higher amount of FR4.

The same goes for using higher amounts of FR4 in layup materials, as it will reduce the weight and flexibility of the final product. That also changes some other parameters, like flex-crack resistance and stiffness.


The final product’s weight depends on the thickness, width, and length of FR4 used. While weight is less of a concern in some applications, it is always important to consider the final product’s weight when designing. Lighter products are more economical but also require more advanced processes and procedures.

Component Compatibility

We should select the thickness of FR4 with component compatibility in mind. For example, a too-thick component will not fit on the board if they require a similar thickness. The thickness of a board can also affect the amount of FR4 tg170used. It can also prevent the use of the board for the intended use case.

Design Requirements

The thickness of FR4 can affect the design of a PCB. The thickness affects the number and width of layers of copper on the board. If we need more copper, it can indicate that a different material may be a better option for the project. Thick boards can accomplish more specific tasks, but we can do the same with thinner boards with FR4.


When selecting the thickness, it is essential to consider the flexibility of the final product and how flexible it will be. FR4 tg130 can be flexible to some degree, but that depends on the specific thickness of the final component. Regarding flexibility, we consider a material with less than 0.5% elongation flexible in most cases. Of course, there are instances where this percentage will vary due to size or weight requirements for a given board.

An extra filler is essential in forming an alloy with sufficient mechanical properties. We should add the moisture-absorbent filler in an adequate quantity. It should eliminate any entrapped moisture from getting into intimate contact with the base metal substrate or coating layers and thus causing corrosion problems.

Impedance Matching

The impedance of the FR4 substrate is very low. However, the difference in impedance between a conductor (i.e., copper) and an insulator (i.e., FR-4 tg180) can cause signal reflection, transmission loss, and impedance mismatch problems in high-speed digital circuit applications where the signal travels at high-frequency 10GHz and above.

Surface Imperfection

FR-4 substrate has a fine surface imperfection on its surface which may affect the wettability of the solder mask during the soldering process. So, paying attention to the surface treatment of FR-4 material is vital for PCB production having tackiness requirements in solder mask application processes like chemical etching, immersion gold plating, or immersion silver plating method.


Solder joints will be fragile when board thickness is below 1.6mm, so FR-4 thickness should be thicker than 1.6mm for assembling flex circuits. A two-sided PCB design requires an FR-4 thickness of at least 2.0mm. This can be a significant limiting factor in FR-4/copper foil thickness selection.

Space Assignments

We must consider material and processing thicknesses when designing a board. The FR-4 thickness should be adequate to accommodate components, as too thin of a board can cause issues with components not fitting due to improper spacing.

The following are the eight best brands of Fr4 material out there and what they mean for those who need to protect themselves from fire:


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Blue Frog Insulation

Fiberglass is durable, lightweight, and waterproof, so it’s perfect for use on construction sites. In addition, it’s inexpensive, which is why we find it in everything from suitcases to coffins. It’s also incredibly fire-resistant, making it the perfect material for flame-resistant clothing. Blue Frog Insulation makes clothing that meets USA Standard NFPA 701-2003 and UK Standard EN 406 for flame resistance.


While the name might sound like a Detroit-born company, Carhartt is in Nebraska and has made leather products since 1908. Carl A. Barney Co-founded the company. Carhartt makes a wide range of products but specializes in work clothing. Their Fr4 material is a 100% cotton duck, which is good for working on the railroad or repairing old cars.

GH Fire Resistant Clothing

GH Fire Resistant Clothing has been making clothing that meets international standards since 1999, making them one of the oldest companies on this list. They are in New Hampshire and have over 400 employees. GH is one of the best-known Fr4 companies and has made clothing for NASA astronauts.

Hustler Garment Co

Hustler Garment Co started operations in Australia in 1980 and has since expanded to become a large company with over 300 employees. While they still make most of their products in Australia, they’ve branched out into other products and several other countries. For example, their clothing is an Fr4 material because of its flame resistance, and numerous celebrities have used it over the years, including Prince Charles.

Marmot Equipment Company

This American company started operations in 1910 by Irving Marmot and had offices located in Maryland and New York. They make many different products ranging from camping gear to clothing to saddles. Their clothing is an Fr4 material because it consists of several different materials, including cotton, polyester, wool, hemp, and Nylon.


Miwox has been a company making textiles for the textile industry for over 100 years. While it’s primarily known for its textile production, the company has branched out into other areas as well, including clothing. Their Fr4 material consist of several different materials, including polyester and Nylon, and includes flame-resistant fiberglass, making it fire-resistant.

North Face Co

This American company started operations in 1963 in California and has made clothing since 1970. They’re known for their quality merchandise, including clothing and outdoor gear. The North Face makes clothing made out of different types of material but primarily uses Nylon and polyester, and some other synthetic fibers. The company has been successful due to its use at specialty stores in North America, Asia, and Europe.

Schneiders Salzburg

Schneiders Salzburg is an Austrian company that specializes in making work clothing. They’ve been in the industry for more than 100 years and have many different products. Their Fr4 material consists of several fabrics, including wool, polyester, cotton, and synthetic materials.

These are the eight biggest brands of Fr4 clothing that companies around the world use. We also consider their top brands in their own right because they make quality clothing made out of high-end materials.


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Common defects and solutions of FR-4

It generates the surface defects in the FR-4 substrate during manufacturing, identified as waviness. Waviness on the surface results from several issues, including poor resin transporting ability, uneven work platform, and poor workmanship.

We measure the surface roughness by the average upward deviation from a perfectly flat surface. We express it in two values: root means square (RMS) and peak to valley (PTV). You can express RMS with an average value that describes how many square inches of manufacturing area contain an imperfection equal to or greater than a given size.

Thickness tolerance

The thickness tolerance of FR-4 material is ±3% by weight. The tolerance is a range, not an absolute value, so if the actual thickness of FR-4 is greater or less than the nominal thickness, it can meet the specific requirement. When ordering FR-4 material, it should specify its size in millimeters and note that the EIA standard (JEDEC) has a pitch of 0.1”.

 a) Substrate tolerance damage:

The substrate has a certain tolerance for the intended use (such as 1% in the production of printed circuit boards). Therefore, it is essential to maintain its original shape when folding the FR-4 material. There may be damage on the surface of the substrate, so you can only note it when you handle it. The damage will affect its use, so you must strictly control its size.

  1. b) Edge Damage:

When cutting FR-4 material into pieces, do not let the saw blade cut through completely. If there is a deep cut on the surface of FR-4 materials, there will be some problems, such as placing components on it or connecting wires to electronic components.

 c) Stretching damage:

When stretching FR-4 materials, you should be careful not to stretch them too much, and the stretched area is not liable to produce defects. If you are trying to bend or fold the material, you can use a pair of flipping pliers to avoid over-bending and breaking the material.

d) Solder Mask adhesive damage:

Placing FR-4 substrate into the solder masking machine while applying solder mask is easy. But when removing these products from the machine, some of them may be stuck together and you cannot separate them, or some masked surface may have scratches on it. This will affect its luster or functionality.

How to prevent the thickness of the tolerance

When purchasing FR-4, you should carefully and thoroughly check the specifications of the material. If these specifications are unavailable, there will be a thin line indicating the thickness tolerance. There are a lot of ways to overcome this problem. The first is to use resin with a low residual void content with less acidity and alkalinity. The second is to choose the proper positioning method for resin pressing and undercoat application or use special accessories for FR-4 to ensure good contact between the substrate after coating with the resin.

The following methods can control the thickness of FR-4:

– Add more solvent to increase the thickness of the film. The higher the solubility, the larger the permeability and more resin can improve adhesion and flexibility.

– Increase mixing ratio: The mixing ratio directly affects the film thickness by controlling how much resin you apply. More resin results in thinner film. Adding an appropriate amount of catalyst will increase its viscosity and increase adhesive capacity, increasing film thickness. But if you add too much catalyst, it may cause a swelling problem in FR-4.

– Add more catalyst: The more you add the catalyst proportion, the thicker the film will be. This is because, by mixing both resin and catalyst, you can improve the curing mechanism. Also, you can achieve thermoregulation of cross-linking while maintaining a sufficient level of flexibility.

Add more solvent: Adding additional solvent to increase resin solubility will increase permeability while decreasing film thickness. Although this effect is generally small, it can significantly improve thin film properties in special applications such as high-temperature process PCBs.

– Increase evaporation distance: When deploying, extended evaporation distance will solve problems such as poor adhesion to substrates or continuity between layers in some cases.


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Substrate from the flower hazards

Because the shallow cuts made when cutting FR-4 material may cause scratches on the surface of FR-4, it is necessary to check the surface after cutting and cleaning.

You can randomly check the flower hazard by visual inspection of the material. However, different defects result from different reasons. Therefore, we use different methods to identify and eliminate these defects.

If the cut edge of a piece of FR-4 does not look good or has a hole on one side, you can use an awl or a knife to twist it from one side to the other side until you ultimately turn it off. Then clean up the remaining adhesive residue with acetone.

If there are scratches on the surface of the FR-4 piece, you can use a knife or an awl to rub it with a small amount of pressure several times. After that, it can reduce the scratch.

Substrate delamination

Delamination is one of the most common problems with FR-4 substrate. It is a form of reaction in which the epoxy curing agent on its surface separates from the bulk resin, leaving a thin layer at its edges. In addition, the environmental humidity and temperature rise after curing can cause this separation. Both cases will result in a thin layer of resin on the surface and some cracks spreading inward through the base layer to cause delamination.

You may not notice delamination during production, but when it arrives at the customer’s site, they will find it challenging to install PCB board components or connect wires to electronic components. As a result, the final product will be affected by this problem.


The causes of this problem are mainly related to the following:

– Adhesion of amines: When we add an amine to a resin, it will significantly reduce the tension in the amine molecule. That is why most epoxy resins require that after they have undergone curing. You should wash them with at least 1% amine to recover their original performance. However, with FR-4, due to its high solvent resistance and good weatherability under low humidity and cool temperature conditions, many manufacturers do not insist on washing this substrate after curing. Not washing it may lead to delamination problems.


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Substrate white spot

The oxidation of the resin molecules causes white spots. It is the most common form of delamination, also known as “paint film delamination.” This phenomenon occurs at the surface of FR-4 to cause cracks and microcracks.

Different reasons can cause it, and different methods we use to eliminate these defects:

– Remove excess heat: After completing the curing process, it is essential to remove excess heat so that this phenomenon will not occur. In addition, it is necessary to keep the temperature of the substrate in an appropriate range during rest periods such as overnight or during one week after curing.

– Fix the material: Some defects may be caused by fixing procedures. Examples include using a heat press to fix a piece of the FR-4 to another. When the fixing is too heavy, it will cause delamination. Therefore, controlling the weight of a piece of FR-4 and fixing items separately is necessary.

Substrate white line

The difference between the thermal expansion coefficient and the shape of FR-4 causes the white line. A substrate whose thickness is greater than 0.2 mm and width is smaller than 10 mm may cause this phenomenon. Different reasons can cause it, and we use different methods to eliminate these defects:

As a result of the friction when pulling an FR-4 board from a CNC machine, its surface layer may be scratched or broken, or slight delamination may occur because of this tension. You need first to use an awl to determine the depth of each scratch before repairing it by hand if this happens.

If scrapes damage an FR-4 board, the repair method depends on the severity of the damage. However, if the damage is light, we can repair it by polishing it. If severe, we should use a new piece of FR-4 to replace it. Additionally, if a board needs fixing with an area larger than about 20 square millimeters, you should inspect whether there is another similar damage on it before performing repairs. If so, complete the repair on these areas as well.

As with other boards, dry cloth or membrane will not effectively clean stains and residues from FR-4 surfaces.

Substrate exposed cloth pattern

The pattern exposed in the FR-4 substrate results from dry cleaning and some chemical substances. Although they are not harmful to the material, they may cause scratch damage to its surface layer when cleaning the substrate. There are different ways to deal with this problem:

– Use a clean, soft cloth or sponge instead of sandpaper during cleaning.

– Eliminate the use of abrasive cleaners (including steel wool) and harsh detergents as much as possible.

– After cleaning, we should use a soft cotton cloth to remove any residues on the surface of FR-4. Then, it should be thoroughly washed with water and dried in high-temperature air for about half a day before being stored away from heat sources.

After repair, do not forget to scrutinize the surface of FR-4. If there is any damaged area, it should be replaced with a new piece of FR-4 because small scratches and cracks caused during this process will cause problems to the product.

One of the biggest problems with FR-4 substrates is that they have a high coefficient of thermal expansion. The coefficient, in this case, can be up to 3 times higher than that of copper foil (Cu foil: 0.069 nm/A; FR-4: 0.175 nm/A).


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Substrate impurities, black spots

The impurities in the FR-4 substrate results from many factors, including the impurities caused by soldering materials, post-processing chemicals, and debris.

FR-4 ball grid array (BGA) substrates have some special requirements. They have to have a thickness of 0.2 mm and a surface width of 6 mm or less. This requires that the boards’ production with high accuracy and consistency. Otherwise, they will cause problems when they arrive at customers’ sites.

Copper foil wrinkled surface

The oxidation of copper causes the wrinkled surface of copper foil. When the surface layer is scratched or broken, it will cause the characteristic black spots on FR-4. There are different methods to eliminate this defect:

– Before repairing a board, make sure that there are no other similar damages on it. If so, repair should also be performed on these areas as well.

– We should make adhesive or solder joints with pure copper to avoid the occurrence of this defect.

– Copper foil should not be used for repairs when it has become fragile after performing chemical processes such as etching and plating; instead, we can use pure copper for repair.

Plastic dot on FR-4

Different reasons cause plastic dots to vary in size, shape, and position. Therefore, the occurrence of this defect depends on different causes and causes and determines whether it is easy or hard to remove. Some of the problems that can cause these defects are:

– After overheating the substrate during cleaning or repair, the plastic dot will melt and become a molten mass. We can avoid this problem by ensuring that the substrate is under control for quality inspection before being shipped out.

– When negative resistance materials are helpful for plating (such as chromium), something similar to a plastic dot will appear in a very short time after plating and then disappear over time.

We find polarity marks in two places on an FR-4 board. The first is at the bottom edge of the board. The marks are on both sides of the edge, and we should mark them as embossing. The other location is near the die pad; we mark them with a “crow’s foot” symbol. A crow’s foot symbol looks like this.

The purpose of polarity marks is to indicate which side of the board is “ground” or “common.” Two solid lines near each corner indicate power/ground connections within a package and between components on opposite sides of a board. The thicker line indicates positive, while the thinner line indicates negative.


In conclusion, FR4 brands highly qualified performance, reliable, and quality products. Super-high-quality FR4 boards provide excellent performance for users because FR4 products are both reliable and effective.



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