Regarding Flex and TWINflex® circuit boards:
- UL-listed base materials are used
- UL certification is not possible!
Regarding flex-rigid and semiflex circuit boards
Depending on the materials used, UL certification according to the UL standard UL 94 V-0 is possible. The WE certification is WE-56.
Würth Elektronik UL Files:
The UL 94 flammability test:
The flammability of polymer materials is tested according to Underwriters Laboratories standard UL 94 (among others), whereby a classification of flammability is undertaken.
The best-known classifications are HB, V-2, V-1 and V-0.
UL 94 V 0 (Vertical Burning Test):
In this test, a standardised flame from a methane gas burner of 20mm length is held 10s long at the lower end of a vertically clamped specimen. After extinguishing the flame the procedure is repeated for a further 10s. This is carried out on 5 specimens. The times of burning and glowing are noted and summed together. It is also recorded whether drops fall from the specimen and whether the cotton mounted beneath the specimen ignites.
The UL 94 V classifications range from V-2 to best classification V-0. If a specimen fails to meet the requirements, 5 additional samples are tested. The V-0 classification requires that the cotton does not ignite through glowing or burning drops.
Marking of pcbs is available according to UL-94.