Copper distribution during pyrolysis of FR-4 laminates

Abstract

Electric and electronic wastes (e-wastes) are generally composed of various metals (including precious metals), glass, and plastics (PP, PE, PS, ABS) containing brominated flame retardants (BFRs). In recent years, exploration in developing of an innovative technology for the recovery some of the metals (e.g. Cu, Au, Ag) from e-wastes become of the highest importance. Nowadays, printed circuit boards - PCBs (the highest metal-rich type of e-wastes) are mainly thermally treated in incinerators (e.g. rotary kilns) to decompose plastics, and to concentrate the metals in the bottom. The concentrated metals can be supplied as a secondary raw material to metal smelters. The above procedure is commonly practiced for extraction of Cu from PCBs. However, during thermal treatment of the e-waste containing BFRs huge amount of HBr gas, product of their thermal decomposition, is generated. Our previous study carried on mixtures of pure chemicals showed that the HBr can brominate Cu which in form of bromide vaporize from the residue, being thus lost for the recovery process. In the present studies, we are focusing on fate of Cu during thermal treatment of two types of PCBs containing epoxy woven fiberglass copper clad laminates.