When products enter the United States, customs should also carry out UL safety certification inspection. So far, more than 2,000 PCB manufacturers have successfully obtained UL certification, most of which are rigid circuit boards. However, a large number of certified manufacturers does not mean that the industry has a deep understanding of UL standards. 1. Certification consultation 1, UL certification of single-layer board (single-layer single-sided and single-layer double-sided) 2, UL certification of prefabricated multilayer board 3, UL certification of multilayer board 4, UL certification of metal plate 5, application of flexible printed circuit board 6, addition of materials and processes 2, training of circuit board certification knowledge and factory audit 1, introduction of UL standard and product category of printed circuit board 2. 4.UL mark requirements 5. How to find file information on UL website? Matters needing attention in factory audit. How to avoid being fired from VN and VN's response?