FR4 is a printed circuit board based on glass-reinforced epoxy laminate material. It is the a lot of used material due to the fact that it is cheap in contrast with other materials and it can be used in lots of applications.
FR4 Types
You can find various 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 thickness. It can be found density from 0.1 mm up to 3.2 mm. The needed thickness will depend on the application it will be used. Typical thinner densities are utilized in multilayer boards in which the FR4 board is utilized to disperse signals to other boards, in order to not increase the density of the PCB. Since a big PCB is developed, greater densities are utilized when high toughness of the PCB is needed.
With various copper layer density. Normal copper densities are 17, 35 or 70 um.
Different panel sizes can be purchased, making use of one or another will depend on the equipment the manufacturer has and depending on the final size of the requested PCBs. Normal panel sizes are 12x18 inches, 18x24 inches, and 21x29 inches. You have to consider that not all the panel can be used to draw your PCBs when you are developing a panel. Around 2 inches length and 2 inches width will be used for other purposes, like fiducial holes and other maker jobs and likewise avoid the panel can bend if work is performed close to the borders.
FR4 Properties
It has a dielectric loss tangent of around 0.017 to 0.025 while, for instance, Rogers laminates have common worths 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 reason it can be used just for low-frequency applications. Because at high frequencies, the insertion losses of the lines are greater, in contrast with other, more costly, alternatives.
Another important criterion is the dielectric constant. The common value is around 4.6. This worth is somewhat based on the producer and also the density of the substrate, but it is a value that normally provides excellent outcomes when computations are performed from it. From this criterion, the relation impedance/thickness of the line can be obtained. When developing RF and digital circuits, this is extremely beneficial.
It is flame resistant.
It has barely zero water absorption
It has an extremely high dielectric breakdown, greater than 60KV. This implies an extremely high voltage is required to change the properties of the material
It preserves its mechanical and electrical properties in various ecological conditions as dry or damp.
Common temperature levels in which FR4 can work is from -55 to +125 ºC.
There are better FR4 variations that offer other attributes such as lower dielectric values or higher temperature level varieties. These boards are not standards and not all the vendors will offer them.
FR4 Uses
FR4 is used around the world for different applications, business, civil, automotive or perhaps military applications.
It is used for DC, low-frequency and digital RF applications.
Almost the total of DC boards are done with FR4 given that it is the most inexpensive material, with really excellent efficiency and due to the fact that it is the material all the manufacturers have the possibility to use.
FR4 is a very excellent alternative for digital applications, in which, FPGA, microcontrollers, ADCs, DCAs, buses, etc are utilized.
FR4 boards can be used for low-frequency applications. Up to 1-2 GHz the properties of this material can be compared to other more pricey choices like Rogers laminates or alumina. From MHz as much as 1 GHz the outcomes will be a little even worse but the difference in price can assist to choose for the FR4 alternative. From 2 GHz the distinctions are higher and typically other materials are chosen. With FR4 and the matching parts, a large catalog of RF circuits can be correctly developed and produced as amplifiers, switches, attenuators, and so on.
The FR4 option on the PCB order page is the grade designation for the epoxy fiberglass that often forms the PCB core and prepreg layers. Article source In a common 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 top and bottom copper layers whereas, in multilayer PCBs, additional layers of FR4 prepreg are sandwiched between the inner core and the external copper layers. Common thinner densities are used in multilayer boards in which the FR4 board is utilized to disperse 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 large PCB is created.