FR4 is a printed circuit board based on glass-reinforced epoxy laminate material. It is one of the most used material because it is cheap in comparison with other materials and it can be used in many applications.
FR4 Types
You can find different FR4 boards:
Single layer boards, with only 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 thickness will depend upon the application it will be used. Common 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 thickness of the PCB. Greater thicknesses are utilized when high robustness of the PCB is needed because a big PCB is created.
With different copper layer thickness. Typical 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 on the final 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 producer jobs and also prevent 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 example, Rogers laminates have normal values of 0.002 and alumina PCBs have worths of around 0.0002. The dielectric loss tangent indicates the insertion losses of the material with the frequency. As can be seen, FR4 has greater values and this is the factor it can be used just for low-frequency applications. Due to the fact that at high frequencies, the insertion losses of the lines are higher, in contrast with other, more pricey, options.
Another essential specification is the dielectric constant. The normal value Browse this site is around 4.6. This value is a little dependent on the producer and likewise the density of the substrate, however it is a worth that generally offers great results when calculations are performed from it. From this parameter, the relation impedance/thickness of the line can be obtained. This is very beneficial when creating RF and digital circuits.
It is flame resistant.
It has hardly no water absorption
It has an extremely high dielectric breakdown, higher than 60KV. This implies a very high voltage is required to alter the homes of the material
It keeps its mechanical and electrical homes in various ecological conditions as dry or wet.
Typical temperatures in which FR4 can work is from -55 to +125 ºC.
There are improved 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 use them.
FR4 Uses
FR4 is utilized around the world for different applications, commercial, civil, automotive or even military applications.
It is utilized for DC, low-frequency and digital RF applications.
Almost the total of DC boards are done with FR4 because it is the most affordable material, with great performance and because it is the material all the makers have the possibility to utilize.
FR4 is a great alternative for digital applications, in which, FPGA, microcontrollers, ADCs, DCAs, buses, etc are utilized.
FR4 boards can be utilized for low-frequency applications. Up to 1-2 GHz the properties of this material can be compared with other more expensive options like Rogers laminates or alumina. From MHz approximately 1 GHz the outcomes will be somewhat even worse however the distinction in cost can help to decide for the FR4 alternative. From 2 GHz the distinctions are greater and generally 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 often forms the PCB core and prepreg layers. In a normal PCB, the core supplies the rigidness and the structure 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, additional layers of FR4 prepreg are sandwiched between the outer copper and the inner core layers. Common thinner thicknesses are used in multilayer boards in which the FR4 board is used to disperse signals to other boards, in order to not increase the density of the PCB. Higher thicknesses are utilized when high toughness of the PCB is required because a big PCB is developed.