What material is FR-4?

FR-4 is a common material in PCB production and stands as one of the most widely used substrates for manufacturing printed circuit boards in electronic devices that require a certain level of mechanical strength and electrical insulation performance.

Many people unfamiliar with PCBs might consider FR-4 to be a specific material, but that is not the case. In reality, the "FR" in FR-4 stands for "Flame Retardant," and the "4" indicates its flame retardant grade. Therefore, FR-4 is not a material name but rather a material grade. It can be understood as a glass fiber-reinforced composite with a flame retardant grade of 4.

FR-4 is composed of glass fiber cloth and epoxy resin. The glass fiber cloth provides FR-4 with excellent mechanical strength and rigidity, making it an ideal choice for manufacturing circuit boards. Simultaneously, the addition of epoxy resin imparts good electrical insulation properties to FR-4, ensuring accurate isolation between circuits. Furthermore, FR-4 exhibits outstanding flame retardancy, meaning it is less prone to combustion and can operate safely and stably at higher temperatures. It is these characteristics that have led to the rapid adoption and widespread application of FR-4 in the field of electronics.