New Halogen-Free Flame Retardants Based on Organic Phosphinate for Electronic Applications

摘要

An important issue for base materials used for PCB application is their flammability. The conventional flammability standard in this market is V-0 according to UL 94. An established technology is the modification of an epoxy resin matrix by incorporation of tetrabromobisphenol A (TBBPA) into the polymer backbone. Nowadays, the demand for environmentally friendly materials has become predominant in OEM (Original Equipment Manufacturer) innovation roadmaps, for both marketing (image) reasons as well as in response to recent regulatory issues. In Europe, this trend is mainly supported by two recent directives. The European Directive EC/2002/95 deals with the Restriction of Hazardous Substances (RoHS) and will ban a wide range certain chemicals like lead and other heavy metals. Except polybrominated biphenyls (PBB) and some polybrominated biphenylethers (PBDE), flame retardants are generally not affected by the RoHS Directive. On the other hand, another Directive EC/2002/96 (WEEE: Waste Electric and Electronic Equipment) deals with plastics at the end of life, and will make necessary the separation of plastic parts containing brominated flame retardant of any kind before further recycling or treatment of the E+E waste.rnHalogen-free alternatives have been already developed and some of them have been able to establish themselves in the market. Commercially available products are mainly based on reactive phosphorus compounds, which are reacted into the epoxy resin and sometimes combined with synergists like ATH (aluminium trihydrate). However, the use and/or the dosage of these flame retardants are limited to a certain extent, making them presumably not suitable in all applications fields, especially the strongly demanding high Tg FR4 (>170℃) or flexible printed circuits markets. For these reasons, new systems and new flame retardants have to be developed.