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The properties of FR-4 PCB material make it versatile and affordable. This is why it is widely used in printed circuit manufacturing.
FR4 is the standard for glass fiber reinforced epoxy compounds defined by NEMA (National Electrical Manufacturers Association).
FR stands for "flame retardant" in English and indicates that the material meets UL94V-0 standards for flammability of plastic materials. The code 94V-0 is found on all FR-4 PCBs and ensures that when the material catches fire, it will not spread and will be extinguished quickly.
For high TG or HiTG, the glass transition temperature (TG) is 115°C to 200°C, depending on the manufacturing method and resin used. A standard FR-4 PCB will consist of one FR-4 layer sandwiched between two thin copper overlays.
FR-4 uses bromine, a chemical element called halogen, which is fire resistant. It replaces another compound, G-10, which has a lower resistance in most applications.
FR4 has the advantage of having a good strength-to-weight ratio. It does not absorb water and maintains a high mechanical load and good insulating ability in dry or humid environments.
Standard FR4: As the name implies, it is standard FR-4 with heat resistance of about 140°C to 150°C.
FR4 high TG: This type of FR-4 has a high glass transition temperature (TG) at 180°C.
FR4 high CTI: greater than 600 volts tracking index (or IRC in France for driving resistance index).
FR4 without copper laminate: ideal for insulation boards, stencils and clips
Component compatibility: Although FR-4 is used to manufacture many types of printed circuit boards, its thickness affects the type of components used. For example, THT components are different from other components and require a thin PCB.
Space saving: Space saving is critical for electronic card designs, especially for USB connectors and Bluetooth accessories. Thinner cards are used in configurations where space economy is critical.
Design and flexibility: Most manufacturers prefer thick cards over thin cards. With FR-4, a substrate that is too thin runs the risk of breaking if the card size increases. Thicker cards are flexible and can be used to make " V-slots", also known as recesses.
The environment in which the PCB is used should be considered. For electronic control units in the medical field, a thin PCB reduces stress. Cards that are too thin (and therefore too flexible) are more sensitive to heat. They may bend and form undesired angles during the soldering phase of the part.
Impedance control: The thickness of the board means the thickness of the dielectric, in this case FR-4, which makes impedance control much easier. When impedance is an important factor, the thickness of the card is therefore a determining criterion that must be taken into account.
Connection: The type of connector used for the printed circuit also determines the thickness of FR-4.
Due to its low price, FR4 PCB is the standard choice for small production of electronic boards or electronic prototypes.
