Halogenated fire retardants

07 April 2004

Printed circuit boards by their nature are a potential source of ignition. Because of this it has been standard practice to include fire retardants within the resin system used for the circuit board.

Halogens are the Group 7 elements in the periodic table and include fluorine, chlorine, bromine and iodine. TBBPA is the primary flame retardant used in polymers for printed circuit board production. TBBPA is an organic molecule that includes approximately 59% bromine and therefore falls under the category of "halogenated fire retardants".

Significantly, FR4 epoxy resin / glass cloth laminate, is amongst the circuit board laminate grades that use TBBPA as a fire retardant.

The driving forces behind the uptake of "halogen free" printed circuit boards are complex and include, legislation, general "greening" of the worldwide electronics industry, customer requirements and potential for market gain. Commercial OEMs are focusing on end of life disposal and how the materials used in electronics may adversely effect the environment. Incineration of bromine will provide a source of halogen for formation of dioxin.

Epoxy polymers will always contain a small amount of halogens as they are formed as a by-product of the chemical processes of manufacture.

Early drafts of the WEEE directive called for impending substitution of TBBPA, the current WEEE directive and RoHS do not contain any restriction on TBBPA. Other brominated flame retardants have been banned by the European Community.


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