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In order to meet international standards, printed circuit board (PCB) base materials have to be flame‐retardant according to the UL 94V specification. Up to now this has been achieved with FR4 materials by using brominated aromatic components. FR4 materials are glass epoxy based and are by far most prevalent in PCB production. Unfortunately, in the case of fire or smoldering, these materials evolve highly corrosive, and, under unfavorable 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 behavior of cured resins has been investigated. As a result of these investigations an epoxy resin was developed that 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. PCBs and electronic assemblies manufactured therefrom successfully passed all functional tests. The base materials recently became commercially available.

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L Due to legal specifications and standards flame retardant polymers are used as insulating materials for electrical cable and wire, as casing and constructive materials in electrical engineering, as encapsulation materials for electronic components and in laminates for printed circuit boards. The most effective way to achieve flame retardancy is by using halogenated organic materials. Because of ecological reasons a major trend is the development of halogenfree non-corrosive flame retardant polymer materials. On the laminate side Siemens R&D developed a way to halogenfree laminates meeting the UL 94V-0 specification.Polymers are finding widespread use in electrical engineering and electronics as insulating materials, as construction and housing materials and as encapsulating and protecting materials as well. In the fiscal year 89/90 the total consumption of polymeric materials within Siemens was well beyond 100.000 t, of which more than 20.000 t wgre flame retardant. The electrical and electronic industries are major consumers of flame retardant polymers. Flame retardancy is specified in those areas of electrical engineering and electronics where safety considerations are of prime importance, such as for instance manprotection and fail-safe applications, and whenever high value electronic components need to be protected, such as in printed circuit boards. In the case of fai'lure or fire due to thermal overload, short circuit or remote action of fire, the flame retardant polymeric materials should be difficult to ignite not propagate a fire be self-extinguishing after removal of the igniting source. 0 1993 Huthig & Wepf Verlag, Base1CCC 0258-0322/93/$04.00

Die Trithione 1 reagieren rnit Trichlormethyl-isocyaniddichlorid (3) oder Thiophosgen (4) zu den 3-Chlor-1.2-dithioliumchloriden 6, welche zu den 1.2-Dithia-cyclopentenonen 2 hydrolysiert werden. 1,2-DithiacycIopentenes, X X l ) . --3-Chloro-I,2-dithiolium Chlorides from TrithionesThe trithiones 1 react with trichloromethyl isocyanide dichloride (3) or thiophosgene (4) to give the 3-chloro-I ,2-dithiolium chlorides 6 , which are hydrolyzed to the 1,2-dithiacyclopentenones 2. Die Chlorierung (CIz, auch Oxalylchlorid) von Trithionen 1 rnit R4 = Alkyl, Aryl und R5 = H, Alkyl fiihrt zu 3-Chlor-1.2 dithioliumchloriden 6 rnit R5 = H, Alkyl, C12,6,12,14.17). 3-Chlor-1.2-dithioliumchloride 6 rnit R4 = H, Alkyl, Aryl, C1, Br und R5 = H, Aryl, Amino, Alkylmercapto oder R4R5 = Benzo sind aus entsprechenden 1.2-Dithiacyclopentenonen 2 rnit Oxalylchlorid 1.3-6,31), Phosgens), PC156), POC138) zuganglich. 3-Brom-1.2-dithioliumbromide rnit R4 = H, Br und R5 = Aryl oder R4R5 = Benzo sind aus entsprechenden 1.2-Dithidcyclopentenonen mit Oxalylbromid dargestellt worden.