FR-4 is a glass epoxy laminate, most commonly used in PCBs (printed circuit boards). It is used in various flexible printed circuit boards and other semi-rigid variants. It shows excellent high strength and flame retardancy. The easy integration of applications and the allowable component mounting make it the material of choice for most PCBs.

FR-4 Production Process

The fiberglass board is impregnated with epoxy resin. These sheets are used to construct FR-4. Eight of these reinforcing sheets are covered with a layer of copper foil. The entire structure is then placed in a press and then glued into a sheet of FR-4 sheet.

Materials Used to Make FR-4

The glass in the FR-4 sheet makes it very strong. Unless otherwise stated, the epoxy resin used is usually a flame retardant. Bromine is used to impart flame retardancy to epoxy resins. This makes the entire PCB flame retardant. In most applications related to high temperatures, this is critical.

The copper used helps designers and manufacturers to etch patterns onto the PCB. These etched patterns form the basic circuits that connect various components. It also connects the interconnector to the basic circuit. Interconnectors are used to connect the various layers of the PCB.

Dicyandiamide, also called "die", is the material most commonly used to harden epoxy resin. The maximum allowable temperature is 300?C. If a phenolic substance is used to cure the epoxy resin, it is called "non-succinic acid." Its maximum temperature tolerance is 350?C.

FR-4 is used for single-layer or multi-layer PCBs with surface mount components. From a manufacturing point of view, FR-4 is easy to use. Therefore, it provides the designer with great flexibility, enabling him to take advantage of the inherent characteristics of the material to bring benefits to the application and process.