FR-4 Printed circuit boards (PCB) are fire-retardant circuit boards used for electronics. The boards can be made with four to eight layers of material, depending on their specific application. The National Electrical Manufacturers Association (NEMA) regulates the standards for FR-4 circuit boards, as well as other types of circuit boards. FR-4 PCB is a common type of board used in many applications.
Material
FR-4 circuit boards are made with woven fiberglass and covered with epoxy. It is a rigid board material that is not made to flex. It is also strong, and resists cracking due to bending and pressure. According to Plastics International, FR-4 circuit boards have a flexural strength of 70,000 pounds per square inch.
Fire retardance
Fire retardant type 4 (FR-4) boards can resist up to 120 degrees Centigrade (248 degrees Fahrenheit) before melting. Temperatures over this limit will cause the board to melt, but the damage from the heat will remain in the heated area; flames will not spread to the rest of the board. Even when exposed to very high temperatures, the boards may retain some functionality.
Fumes
FR-4 circuit boards contain halogens, and will give off poisonous fumes when burning. Therefore, if the boards suffer heat damage, you should make sure the room is well ventilated to dissipate the fumes. Some companies are researching ways to manufacture the FR-4 boards without the use of halogens.
