FR4 is a printed circuit board based on glass-reinforced epoxy laminate material. It is the most used material because it is low-cost in comparison with other materials and it can be utilized 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 found density from 0.1 mm up to 3.2 mm. The needed density will depend on the application it will be utilized. Normal thinner thicknesses are utilized in multilayer boards in which the FR4 board is utilized to distribute signals to other boards, in order to not increase the density of the PCB. Greater thicknesses are utilized when high robustness of the PCB is needed due to the fact that a large PCB is developed.
With different copper layer density. Normal copper thicknesses are 17, 35 or 70 um.
Different panel sizes can be bought, the use of one or another will depend on the equipment the manufacturer 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 creating 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 manufacturer tasks and likewise avoid the panel can bend if work is performed 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 values of 0.002 and alumina PCBs have worths of around 0.0002. The dielectric loss tangent shows the insertion losses of the material with the frequency. As can be seen, FR4 has higher worths and this is the factor it can be utilized only for low-frequency applications. Since at high frequencies, the insertion losses of the lines are greater, in comparison with other, more expensive, choices.
Another crucial parameter is the dielectric constant. The common value is around 4.6. This worth is slightly dependent Learn More on the producer and likewise the density of the substrate, but it is a value that generally provides good results when computations are carried out from it. From this parameter, the relation impedance/thickness of the line can be obtained. This is extremely beneficial when creating RF and digital circuits.
It is flame resistant.
It has hardly absolutely no water absorption
It has an extremely high dielectric breakdown, higher than 60KV. This indicates an extremely high voltage is required to change the homes of the material
It preserves its electrical and mechanical residential or commercial properties in different environmental conditions as dry or damp.
Normal temperatures in which FR4 can work is from -55 to +125 ºC.
There are better FR4 variations that supply other attributes such as lower dielectric worths or greater temperature ranges. These boards are not standards and not all the suppliers will offer them.
FR4 Uses
FR4 is used worldwide for different applications, commercial, civil, automotive or even military applications.
It is utilized for DC, low-frequency and digital RF applications.
Almost the overall of DC boards are finished with FR4 because it is the most affordable material, with excellent efficiency and due to the fact that it is the material all the manufacturers have the possibility to utilize.
FR4 is an excellent choice for digital applications, in which, FPGA, microcontrollers, ADCs, DCAs, buses, etc are used.
FR4 boards can be utilized for low-frequency applications. Approximately 1-2 GHz the homes of this material can be compared with other more expensive options like Rogers laminates or alumina. From MHz as much as 1 GHz the results will be somewhat even worse however the difference in price can help to choose for the FR4 choice. From 2 GHz the distinctions are higher and generally other materials are selected. With FR4 and the matching 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 classification for the epoxy fiberglass that typically forms the PCB core and prepreg layers. In a normal PCB, the core provides the rigidity and the foundation on which the PCB traces can be 'printed' onto. For double layer boards, an FR4 core separates the bottom and leading copper layers whereas, in multilayer PCBs, extra layers of FR4 prepreg are sandwiched in between the outer copper and the inner core layers. Typical thinner thicknesses are utilized in multilayer boards in which the FR4 board is utilized to disperse signals to other boards, in order to not increase the thickness of the PCB. Higher thicknesses are used when high effectiveness of the PCB is needed since a large PCB is designed.