FR4 is a printed circuit board based on glass-reinforced epoxy laminate material. It is the many utilized material since it is low-cost in contrast with other materials and it can be used in lots of 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 two 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 upon the application it will be utilized. 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 thickness of the PCB. Higher thicknesses are used when high effectiveness of the PCB is needed because a big PCB is developed.
With different copper layer thickness. Typical copper thicknesses are 17, 35 or 70 um.
Different panel sizes can be bought, the usage 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 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 used for other purposes, like fiducial holes and other manufacturer tasks and also avoid 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 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 higher values and this is the reason it can be used only for low-frequency applications. Due to the fact that at high frequencies, the insertion losses of the lines are greater, in contrast with other, more expensive, alternatives.
Another important specification is the dielectric constant. The normal worth is around 4.6. This worth is a little depending on the maker and likewise the density of the substrate, however it is a value that generally offers great results when calculations are performed from it. From this parameter, the relation impedance/thickness of the line can be obtained. When creating RF and digital circuits, this is really helpful.
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 properties of the material
It keeps its mechanical and electrical homes 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 provide other attributes such as lower dielectric worths or greater temperature level 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, industrial, 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 considering that it is the least expensive material, with excellent performance and because it is the material all the makers have the possibility to utilize.
FR4 is a really great choice for digital applications, in which, FPGA, microcontrollers, ADCs, DCAs, buses, etc are used.
FR4 boards can be used for low-frequency applications. Approximately 1-2 GHz the homes of this material can be compared to other more costly options like Rogers laminates or alumina. From MHz up to 1 GHz the outcomes will be a little worse but the difference in rate can assist to What is FR4 choose for the FR4 option. From 2 GHz the differences are greater and usually other materials are chosen. With FR4 and the corresponding components, a large brochure of RF circuits can be properly designed and fabricated as amplifiers, switches, attenuators, and so on.
The FR4 alternative on the PCB order page is the grade designation for the epoxy fiberglass that often forms the PCB core and prepreg layers. In a typical 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 bottom and top 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 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 effectiveness of the PCB is required because a big PCB is created.