The materials used in Printed Circuit Board (PCB) designs often include the FR4 materials. However, there are others that are not as popular as the former is. The FR2 PCB is one of such.
So, in this article, we discuss what this type of circuit board material is, as well as point out some of the differences from the FR1 and FR4 materials.
What is the FR2 PCB all About?
It is a type of material used for Printed Circuit Board (PCB) design, only that it shares some properties as the FR1 material. Like the FR1 material, it uses many layers.
Nevertheless, it has a couple of new features that set it apart from the FR1 PCB. These features include but are not limited to the composite material using a plasticized phenol formaldehyde resin. It also has a lower TG of 105˚C, which is lower when compared to the FR1 material’s 130˚C.
The “FR” in FR2 PCB
The “FR” stands for “Flame Retardant 2.” It signifies that the material is equipped with properties and is compliant with the UL94V-0 standard used for adjudging the inflammability of plastic materials.
It is to be noted also that the “flame retardant” design of circuit board materials also indicates the non-propagation of fire, as well as the ability to put out or rapidly extinguish the fire when the material is exposed to fire.
Features of the FR2 Material
Now that we are clear about some of the differences between the FR2 PCB and the FR1, as well as some of the capabilities – we will now look into some of the properties.
FR2 PCB is Less Abrasive
Perhaps, one of the biggest critics against this circuit board material is the use of laminated paper, which makes it less strong than the circuit boards made of glass.
However, it does have an advantage, which is the less abrasiveness. By this, we mean that the FR2 PCB provides a considerable reduction in production costs, while increasing the lifespan of the material.
Circuit Board Specifications
The FR2 material is to be used with the single-layer circuit board designs, for a couple of reasons. These are the reasons:
Through-Hole Technology Considerations
The use of the Through-Hole Technology (THT) has become popular, and has become one of the best processes for integrating components and materials into circuit boards.
It can, however, not be used to design multilayered boards relying on the FR2 materials. This is because these materials are not able to pass through the (drilled holes) on the circuit board.
Therefore, they cannot be used to connect multiple components on the board. This is why it is better to limit the usage to the single-sided Printed Circuit Boards (PCBs).
Water Resistance
Flame Retardant (FR) circuit board materials can also resist water. The FR2 material has a fair water resistance, but the usage should be limited to the applications, devices or electronics, likely to be exposed to or used in the standard humid areas.
Design Considerations for the FR2 Materials
You may be unable to maximize the benefits of a circuit board made with the FR2 materials due to some factors.
Here are some design considerations likely to impact the performances of those PCBs:
Ideal for Simple Applications
It is better to use the FR2 materials with the applications or electronics that don’t have much to power. For example, it is the choicest option for the low-end consumer electronic equipment, due to the lower rigidity.
Based on this rigidity level, it is impossible to use the materials for high-end electronics, especially automotive applications. The usage in this case would lead to vibrations capable of:
- Extending the hairline fractures in copper traces and;
- Propagating or extending cracks on the circuit board.
Phenolic Resin Composition
Wikipedia defines the FR2 material as a “composite material made of paper impregnated with a plasticized phenol formaldehyde resin.”
The phenolic resin composition is further divided into two – resoles and novalocs. Noteworthy is that this two works for a variety of applications, such as adhesives, coating and Printed Circuit Boards (PCBs).
Besides, the moisture-resistant and affordability of the phenolic resins facilitates the rapid cleaning of circuit board surfaces.
Design Difficulty
If you are looking for a circuit board material that offers less-complex design iterations, it definitely wouldn’t be the FR2 PCB material. This is because of the increase complexity level, attenuated by the complex and additional layers that extend the manufacturing process.
Other factors lending credence to the increased difficulty are:
- Etching the rectangular holes can sometimes be difficult.
- Cutting the tabs is tricky and could sometimes, lead to ruining the circuit board.
How the FR2 PCB Compares to the FR4 PCB
Both the FR2 and the FR4 materials are some of the most-used for Printed Circuit Board (PCB) designs.
Let us see how the two compares:
The Usage
The Flame Retardant 4 (FR4) material is a better option if you are looking to design multiple circuit boards. This is derived from the higher water absorption, the long-term cost-savings for multiple circuit designs and the combination of excellent stability and reliability.
Cost Considerations
It is easy to argue that the cost of manufacturing FR2 PCBs is lower than those of the FR4 PCBs. However, one of the significant cost metrics is the number of times the materials are used and the typical applications.
Considering the relegation of the FR2 materials for low-end electronic components and the use for single-layered board designs, we can say that the usage is limited. As such, circuit board manufacturers will likely charge more to get the job done.
This makes the cost higher when compared to the FR4 materials, which can be used to manufacture single-sided circuit boards, as well as multilayered PCBs, up to 32 layers.
Conclusion
Flame Retardant 2 (FR2) PCB materials can keep out the fire and resist water absorption in the humid areas. However, if you are looking for a circuit board material that supports multiple layer designs and reduced design costs, go for the FR4 materials.
