The US Environmental Protection Agency has published an update of the Printed Circuit Boards Partnership report (DfE: Design for the Environment) on alternatives to the brominated flame retardant TBBPA used in printed circuit boards. Public comment is open until 15th February 2015. Most printed circuit boards (PCBs) for consumer electronics are so-called FR-4 boards, which means that they are based on glass-reinforced epoxy laminate sheets and fulfil certain performance requirements including the UL94-V0 fire safety standard.
The report, updated from the first publication in 2008, assesses ten flame retardants: TBBPA, 2 reactive and 5 additive PIN FRs and two polymeric FRs (one brominated, one P-based). High persistence is indicated for all flame retardants and is linked to the required chemical stability for their function. Two of the mineral PIN FRs (aluminium and magnesium hydroxide ATH, MDH) achieve “low” or “very low” for all relevant toxicity and environmental end-points (persistence/biodegradability not applicable to inorganics/metals) and two other PIN FRs ( dihydro-oxy-phosphaphenanthrene-oxide DOPO and aluminium diethylphosphinate DEPAL / Alpi) show only low to moderate concerns for all other criteria. For some PIN FRs questions regarding long-term health impacts or bioaccumulation suggesting that further optimisation is possible or that data is inadequate.
The updated study looked at smoke and toxicity emissions in different combustion conditions, reflecting both end-of-life incineration and accidental fires. Smoke release was around twice as high for brominated FR boards than for phosphorus FR boards in both combustion scenarios. Emissions of particles were also 25 – 50 higher with brominated FR boards. Brominated FR boards emitted 2-3 times more PAH (poly aromatic carbons) than phosphorus FR boards in both incineration and open fire conditions. Brominated dioxins/furans (PBDD/F) were detected in all scenarios with brominated FR boards.
The report underlines that material performance characteristics are essential for selecting alternative halogen-free flame retardants for circuit boards, including electrical and mechanical parameters, cost and reliability and refers to the iNEMI and HDPUG studies of halogen-free materials, including halogen-free flame retardants. The EPA press release accompanying concludes that “industry trade groups tested alternative non-halogenated flame retardants and found that they function equally as well or better than TBBPA-based circuit boards for certain products”.
FRs considered in the report: 1 reactive brominated FR (TBBPA); 2 reactive P-based PIN FRs (DOPO, Fyrol PMP); 5 additive PIN FRs (aluminium diethyophospinate, ATH, MDH, melamine polyphosphate, amorphous silicon dioxide); 2 reactive polymeric FRs (DER 500 series – brominated, Dow XZ-92547 – P-based)
“Flame Retardants in Printed Circuit Boards Partnership”, US EPA (Environmental Protection Agency) Design for the Environment (DfE) http://epa.gov/dfe/pubs/projects/pcb/
“Flame Retardants in Printed Circuit Boards – Updated draft report”, December 2014 http://epa.gov/dfe/pubs/projects/pcb/141215_pcb_flame_retardants_report_updated_draft_full_report_and_appendices.pdf
Public comment on this draft report is open until 15th February 2015: http://www.epa.gov/dfe/pubs/projects/pcb/index.htm