When it comes to one common material used for the fabrication of PCBs, Fr4 is usually mentioned. This material comes with very suitable characteristics and properties that make it affordable and versatile. Fr4 is widely used in the PCB industry because of its characteristics and properties. An Fr4 PCB prototype is a common practice in the industry.
When it comes to the most commonly available grade of dielectric material used for the production of circuit boards, Fr4 is the easiest option. Fr4 is a useful material that can be used to produce multi-layered, double-sided, and single-sided boards.
An overview of Fr4
Fr4 is a NEMA standard for epoxy resin laminate that has been reinforced with glass. FR means “flame retardant” which is used to indicate that the material complies with the specified standard that has to do with the inflammability of the plastic material.
All Fr4 printed circuit boards come with the 94V-0 code. It can be used to guarantee fire non-propagation as well as its quick extinguishing as the material burns off. The typical Fr4 PCB cones with an Fr4 layer that is enclosed between two slender laminated copper layers.
Fr4 works with Bromine, which is a chemical element of halogen that is resistant to fire. It is used to replace G-10 which is a different composite with less resistance in a majority of its applications.
One great advantage of Fr4 is the fact that it has an excellent resistance-weight ratio. The material does not take in water and is popular for its increased mechanical strength. It also has a great insulating capacity in humid or dry environments.
Fr4 as a PCB material will usually vary significantly based on the PCB manufacturer. But, the material is very popular due to its effective water resistance and mechanical strength. Fr4 is an important PCB insulator that can be used to isolate adjacent copper layers as well as being able to provide general mechanical strength.
Choosing PCB thickness: Important factors that should be considered
- Compatible components: Even though Fr4 works well when used to produce a lot of PCBs, its thickness affects the different components that have been used. For instance, THT components vary from all other components used, and it usually needs a thin PCB.
- Saves a lot of space: If you are planning and designing the layout of the PCB, saving space is very important. This is a very important component to consider, especially in the case of Bluetooth accessories and USB connectors. Boards with the thinnest profiles are used in layouts and configurations whereby is very crucial to save space.
- Flexibility and design: Many PCB manufacturers usually choose thick boards over thin options. If we use Fr4, if we apply a thin substrate, there is a risk that it will break if the dimensions of the board get increased. Alternatively, thicker boards have more flexibility and support the creation of V-grooves.
Also, you must consider the environment in which you will use the PCB. In the field of medicine, with electronic control equipment, thin PCBs are used to reduce stress. The boards are very thin, this increases their flexibility while also making them prone to heat.
Also, during the soldering stages, the boards tend to bend and form an unwanted angle.
- Control of impedance: The thickness of the board is used to indicate the thickness of the dielectric environment, which in this situation, is the Fr4 that is used to control impedance.
If the impedance is taken as a critical factor, then the thickness of the board should be considered.
- Connections: The specific connector type that is used in the production of printed circuits can be used to determine the thickness of the Fr4.
Why do we choose Fr4?
Because Fr4 come at affordable costs is the reason that they are used as standardised options for electronic prototyping or the production of small elements of PCBs.
Also, it is important to state that Fr4 isn’t suitable for producing printed circuits with high frequency. Similarly, if you are looking to create the PCBs into devices that do not permit adopting components and that have lesser suitability to the flexible PCBs, then you can choose polyamide/polyamide, which is another preferred material. Fr4 are popular because of a set of qualities that they possess. These qualities are:
- Its operating temperature ranges from 50°C to 115°C, which is a wide range.
- It possesses a very high Tg value which is about 180°C.
- It possesses suitable mechanical properties that can be used to maintain the integrity of the board structure.
- Fr4 is a very affordable material in comparison to other options.
Does Fr4 have any limitations?
For decades now, Fr4 is an important material that is useful for the production and fabrication of printed circuit boards. Fr4 is very affordable and is a great electrical insulating device. However, if you use Fr4s in applications that require high-speed performance, you may run into the following problems:
- Insulating stability: Fr4 is a very popular insulator in the PCB industry. However, it has a limited capacity when subjected to excess heat, voltage, or power. Also, if it exceeds certain limits, it means that the insulating characteristics of the materials will become compromised. This way, they instantly turn into conductors and pass on electricity. This is what causes some failures with circuit boards.
- Controlled impedance: Unlike high-speed PCB board materials, Fr4 lacks a uniform dielectric constant. This means that the DK varies each time the frequency increases. The variations in the DK values of the Fr4 create challenges as impedance values are being maintained.
- Signal losses: An important part of the design of PCBs is their signal loss. Especially in applications that work with high frequency. Fr4 is not the best material when it comes to these applications as it has an excellent dissipation factor, Df when compared to materials that have a high frequency.
- Temperature stability: It is not useful to use Fr4 materials for devices that work with high temperatures. Also, Fr4 materials do not work with no-lead soldering. This is due to the reflow temperatures used for lead-free PCB assembly that can get as high as 250°C.
PCB manufacturers can make single-sided FR4 PCBs, double-sided FR4 PCBs, multi-layer FR4 PCBs, rigid FR4 PCBs, and rigid-flex PCBs with FR4 base substrate. JHYPCB is an advanced PCB manufacturer that can provide you with various FR4 PCB manufacturing services; with us, you can enjoy high reliability and high-quality PCB customization and PCB assembly services.