According to UL standard (UL94, UL746E, etc.), the grade of plate burning can be divided into four types: UL94 V-0, UL94 V-1, UL94 V-2 and HB.
Generally speaking, the copper clad laminate that reaches the flame retardant HB level according to UL standard is called non flame retardant board (commonly known as HB board); Copper clad laminates (UL94 grade V-0 with the best flame retardant characteristics) that meet the flammability requirements of the vertical combustion method in UL standard are called flame retardant plates (commonly known as V0 plates)
"Flame retardant level" in PCB industry is a popular saying, and the scientific saying is "combustion performance level". As for the lowest level of material combustion performance classification, the horizontal combustion test method is adopted, and the corresponding standard in China is GB /T2408-1996 plastic combustion.
