FR4 is a printed circuit board based upon glass-reinforced epoxy laminate material. It is the a lot of utilized material due to the fact that it is low-cost in comparison with other materials and it can be used in many applications.
FR4 Types
You can discover various FR4 boards:
Single layer boards, with just copper in the top of the substrate or double layer, with 2 copper layers, one on each side.
With various substrate density. It can be discovered density from 0.1 mm approximately 3.2 mm. The needed density will depend on the application it will be used. Typical thinner thicknesses are used in multilayer boards in which the FR4 board is used to distribute signals to other boards, in order to not increase the thickness of the PCB. Since a large PCB is developed, higher thicknesses are used when high toughness of the PCB is needed.
With various copper layer density. Common copper densities are 17, 35 or 70 um.
Various panel sizes can be purchased, the usage of one or another will depend on the equipment the producer has and depending upon the last size of the requested PCBs. Typical panel sizes are 12x18 inches, 18x24 inches, and 21x29 inches. When you are designing a panel, you have to consider that not all the panel can be used to draw your PCBs. Around 2 inches length and 2 inches width will be utilized for other functions, like fiducial holes and other maker jobs and likewise prevent the panel can flex if work is carried out near the borders.
FR4 Properties
It has a dielectric loss tangent of around 0.017 to 0.025 while, for instance, Rogers laminates have normal worths of 0.002 and alumina PCBs have worths of around 0.0002. The dielectric loss tangent suggests the insertion losses of the material with the frequency. As can be seen, FR4 has greater values and this is the reason it can be used only for low-frequency applications. Because at high frequencies, the insertion losses of the lines are higher, in comparison with other, more expensive, options.
Another important criterion is the dielectric constant. The normal worth is around 4.6. Additional hints This worth is a little depending on the producer and likewise the thickness of the substrate, but it is a value that generally provides good results when estimations are carried out from it. From this criterion, the relation impedance/thickness of the line can be gotten. When developing RF and digital circuits, this is extremely useful.
It is flame resistant.
It has barely zero water absorption
It has a very high dielectric breakdown, greater than 60KV. This indicates a really high voltage is needed to alter the properties of the material
It preserves its mechanical and electrical residential or commercial properties in various ecological conditions as dry or damp.
Common temperatures in which FR4 can work is from -55 to +125 ºC.
There are improved FR4 versions that supply other attributes such as lower dielectric worths or greater temperature ranges. These boards are not standards and not all the vendors will offer them.
FR4 Uses
FR4 is used around the world for various applications, business, civil, automobile and even military applications.
It is used for DC, digital and low-frequency RF applications.
Practically the overall of DC boards are made with FR4 since it is the most affordable material, with excellent performance and since it is the material all the producers have the possibility to use.
FR4 is an extremely good option for digital applications, in which, FPGA, microcontrollers, ADCs, DCAs, buses, etc are utilized.
FR4 boards can be utilized for low-frequency applications. As much as 1-2 GHz the residential or commercial properties of this material can be compared with other more expensive alternatives like Rogers laminates or alumina. From MHz approximately 1 GHz the outcomes will be a little even worse however the distinction in cost can assist to choose for the FR4 choice. From 2 GHz the differences are higher and typically other materials are selected. With FR4 and the corresponding parts, a broad catalog of RF circuits can be correctly created and made as amplifiers, switches, attenuators, and so on.
The FR4 choice on the PCB order page is the grade designation for the epoxy fiberglass that typically forms the PCB core and prepreg layers. In a normal PCB, the core offers the rigidity and the foundation on which the PCB traces can be 'printed' onto. For double layer boards, an FR4 core separates the leading and bottom copper layers whereas, in multilayer PCBs, extra layers of FR4 prepreg are sandwiched in between the outer copper and the inner core layers. Normal thinner densities are utilized in multilayer boards in which the FR4 board is used to distribute signals to other boards, in order to not increase the density of the PCB. Greater densities are utilized when high toughness of the PCB is required because a big PCB is developed.