Definition

Underwriters Laboratories (UL) is a safety certification organization that tests products for safety hazards. For PCBs, UL certification verifies the laminate meets flammability requirements (UL 94 V-0 means the material self-extinguishes within 10 seconds and doesn't drip flaming particles). UL maintains a database of certified materials and fabricators. UL recognition (UL marking on boards) is required for many end products sold in North America. The UL file number (E-number) identifies the certified construction.