Latest Results with New Halogen‐free Flame‐retardant Base Materials

In order to meet international standards, PCB base materials have to be flame‐retardant according to the UL 94V specification. Up to now this has been achieved with FR‐4 materials by using brominated aromatic components. Unfortunately, in the case of fire or smouldering, these materials evolve highly corrosive and, under unfavourable conditions, even highly toxic decomposition products. In the search for flame retardancy without the use of bromine, the effect of different structural elements on the burning behaviour of cured resins has been investigated. As a result of these investigations an epoxy resin was developed which contains tailor‐made N‐ and P‐ containing constituents that form flame‐retardant structures during processing and curing of the material. The new material meets all requirements for printed circuit boards and can be processed without any need to modify established technologies. Analytical and ecotoxicological investigations of the combustion products of the new material show that they are comparable with those of wood from the beech tree. The project has already produced first samples of a PCB assembly that successfully passed all functional tests.