Skip to content

Why FR4 PCB Assembly is Suitable for Some PCB Applications

The majority of electrical engineers, as well as those working with circuit boards, know much about FR4. The majority of rigid boards are constructed with FR4 as their base material. Many people don’t even know what FR4 is, let alone know why it’s the most often used PCB base.

After constructing the Circuit board, your task is far from finished. The board still needs to be put together by attaching electronic parts to it. When you’ve finished, your PCBA is complete. Continue reading to find out more regarding FR4 PCB assembly, including what exactly they are, why they have become so popular, as well as how their characteristics stack up against those of other options available in the market.

What Does FR4 Substrate Material Offer?

FR4 is a name as well as a standard rating, and it can also be written simply as FR-4. This name is used to describe the epoxy-laminated sheets with fiberglass reinforcement that are utilized in the production of printed circuit boards.

This name also serves as a specific grade for the sheets made of epoxy laminate, though. The grade, which is generally considered to indicate the basic quality of the laminate sheet, applies to a wide range of designs and sheet materials. Flame retardant is indicated by the “FR” present in its name, while the “4” distinguishes this material from the others in its class.

The substance widely termed FR4 is made of composite materials. Fiberglass that has been woven to a cloth-like, thin sheet forms the material’s base layer. FR4 receives the essential structural stability from the fiberglass.

A flame-resistant resin is then used to encircle and bind the inner fiberglass layer. Along with the other physical characteristics, the resin is whatever gives stiffness to the material.

Electrical designers and engineers adore FR4 sheets like a base material for PCBs. This popularity can be attributed to the material’s affordability, adaptability, and wide range of advantageous physical qualities. Electrical insulators having a strong dielectric strength are FR4 sheets. They are also low in weight, moisture resistant, and have a good strength to the weight ratio. FR4 material can function well in the majority of environmental situations when you combine this with their temperature resistance.

What are the Benefits of the FR4 PCB Material?


FR indicates flame retardant in the acronym FR4, and the 4 denotes a rating which sets the material apart from others. In the manufacture of PCBs, FR4 is a woven, thin epoxy fiberglass-reinforced laminated sheet. Its composite fiberglass layers structure, also known as FR4, gives the substance rigidity and stability.

The following advantages of FR4 makes it a well-liked material among the PCB manufacturers and OEMs. In light of that, let’s examine them.

Great electrical characteristics

Because they affect how quickly an electrical signal travels through a material, the electrical characteristics of the circuit board materials are crucial in signal impedance and integrity considerations.

FR4’s electrical insulating qualities are a result of its strong dielectric strength. The FR4 Dk fluctuates between 3.8 and 4.8 MHz which is dependent on the type of fiberglass weaving used, the resin used, and the thickness.

Retardant to flames

A flame retardant is incredibly adaptable for a variety of manufacturing processes and yield consistent results. FR4 is a popular choice for many electronics applications because of its excellent electrical, thermal, and mechanical characteristics.

Absorption of Moisture

One crucial characteristics of the FR4 material is this. The substance has a negligibly low rate of absorption of moisture at 0.10% when submerged in water. In addition to being mainly moisture resistant, the FR4 is also temperature resistant which can survive a wide variety of temperatures.

Cost Efficiency

Due to its low cost and consistent chemical and physical characteristics, FR4 is known as a frequently used foundation material for circuit boards. Many PCB makers and designers who are worried about costs gain from this.

Process of FR4 PCB Assembly

PCB Assembly Control Board
PCB Assembly Control Board

In this procedure, the bare substrate of the FR4 PCB is used to attach electronic components. The procedures for assembling a FR4 PCB are exactly the same as those for assembling any other PCB. An electronic component’s assembly is a challenging process that frequently calls for specialized equipment and tools.

One very typical type of electronic assembly is the assembly of circuits on the circuit boards. Based on the project’s complexity, design, and size requirements, circuit board assembly can differ greatly.

Printed Circuit Board

A PCB as well as the components which go onto it are the first steps in the FR4 PCB assembly process.  The circuit board is known as a little board

Apply solder paste

The screen-printer is used to apply paste on your circuit board after you have it. To ensure that the paste just coats the board precisely where required, a tiny stencil is utilized.


The parts are then positioned upon that circuit board. A device known as the Pick-and-Place performs this by picking up the components and placing them on your circuit board where they belong. Whatever the machine cannot do, then a technician completes manually.


The FR4 board goes through AOI procedure once the components have been attached onto it to make sure everything is in the right location, is orientated appropriately, and that there’s nothing missing.


The PCBA is placed in an oven as the final stage during the FR4 PCB assembly process. Metal microbeads in the paste are melted in the oven. This metal melts as well as solidifies as a single connection when this paste gets hotter. Through this, parts are linked to that same FR4 PCB.

FR4 PCB Assembly Mounting Technology Types

Smt Assembly Sim control PCB
Smt Assembly Sim control PCB

During FR4 PCB assembly, there are essentially two different mounting technologies. These consist of:

Through-hole technology

The thru-hole procedure, also known as through-hole assembly, is a very popular way to attach electrical components to the FR4 PCBs. This method, which predates SMT, was the norm for the PCB assembly for a considerable amount of time. During the 1980s, as SMT started to gain prominence, many people believed that thru-hole Circuit board assembly would become obsolete. Thought-hole technology is still the favored choice for various applications due to a number of its benefits.

As implied by the name, the process of thru-hole manufacturing entails poking holes through the FR4 PCB. According to the design of the client, this board house will drill these holes wherever the components would go. These leads are inserted through the holes after they have been bored or drilled. It is important that these leads are placed inside the holes in a proper and consistent manner.

Surface-mount technology

Modern electronics may now be produced with the smaller footprints because of the efficient and flexible SMT assembly method. All of the many components required for today’s gadgets are attached onto the circuit board’s surface using SMT. SMT is extremely configurable and could be largely automated, making it a perfect choice for clients that require circuit boards present in large quantities. SMT can be the best option if you require circuit boards built to satisfy certain standards.

As the name suggests, surface mount components are attached to the PCB’s surface rather than being inserted via the board’s holes as with the through-hole assembly. The process of SMT involves soldering the components onto the board’s pad locations.

Why FR4 PCB Assembly May be a Better Alternative in Some Applications


Because of its comparatively inexpensive cost, FR4 material exists as a highly popular PCB base. On the contrary hand, high-frequency laminates are significantly more expensive, which comes as a big disadvantage for manufacturers and designers who are worried about costs. This is known as the main criterion that businesses use to decide between FR4 as well as laminates of high-frequency.

Signal Loss

In so many cases, signal loss forms a crucial component of the PCB design, particularly in the high-frequency settings where the signal loss comes as a bigger issue. Since FR4 does indeed have a larger dissipation factor, than the high-frequency laminates, it isn’t the best material for all these designs. Accordingly, FR4 circuits would experience greater signal loss than a comparable circuit built on the high-frequency laminate.

Df for FR4 has a value of about 0.020. The dissipation factor of the majority of high-frequency laminates can be roughly 0.004, or one-fourth of dissipation factor of FR4. There is less total signal loss, then the lesser the dissipation factor.  The second problem is that as the frequency of the signal rises, greater loss of signal is experienced since the dissipation factor of FR4 rises. High-frequency laminates experience less loss over higher frequencies because they have higher consistent Df properties.

Impedance Stability

Another crucial consideration for so many designs has to do with stable impedance, which frequently translates into a performance that is more predictable, particularly for bigger circuits and high-frequency designs. Again, FR4 as well as high-frequency laminates produce distinct outcomes in this sector. A material must preserve a constant dielectric constant, throughout its entirety when the material’s temperature changes in order to maintain stable impedance.


The FR4 board is favored by several electronics applications. Electronics engineers should naturally default to using FR4 substrates due to its strength, dependability, and comparatively inexpensive cost. Unfortunately, FR4 isn’t the best option in every circumstance, particular




                Get Fast Quote Now