Evaluation of a recycling process for printed circuit board by physical separation and heat treatment

•The parts mounted on printed circuit board (PCB) were liberated by underwater explosion and mechanical crushing.•The crushed PCB without surface-mounted parts was carbonized under inert atmosphere at 873K to recover copper.•The multi-layered ceramic capacitors including nickel was carbonized at 873K to recover nickel by the magnetic separation.•The tantalum powders were recovered from the molded resins by heat treatment at 723 and 823K in air atmosphere and screening.•Energy and treatment cost of new process increased, however, the environmental burden decreased comparing conventional one. Printed circuit boards (PCBs) from discarded personal computer (PC) and hard disk drive were crushed by explosion in water or mechanical comminution in order to disintegrate the attached parts. More parts were stripped from PCB of PC, composed of epoxy resin; than from PCB of household appliance, composed of phenol resin. In an attempt to raise the copper grade of PCB by removing other components, a carbonization treatment was investigated. The crushed PCB without surface-mounted parts was carbonized under a nitrogen atmosphere at 873–1073K. After screening, the char was classified by size into oversized pieces, undersized pieces and powder. The copper foil and glass fiber pieces were liberated and collected in undersized fraction. The copper foil was liberated easily from glass fiber by stamping treatment. As one of the mounted parts, the multi-layered ceramic capacitors (MLCCs), which contain nickel, were carbonized at 873K. The magnetic separation is carried out at a lower magnetic field strength of 0.1T and then at 0.8T. In the +0.5mm size fraction the nickel grade in magnetic product was increased from 0.16% to 6.7% and the nickel recovery is 74%. The other useful mounted parts are tantalum capacitors. The tantalum capacitors were collected from mounted parts. The tantalum-sintered bodies were separated from molded resins by heat treatment at 723–773K in air atmosphere and screening of 0.5mm. Silica was removed and 70% of tantalum grade was obtained after more than 823K heating and separation. Next, the evaluation of Cu recycling in PCB is estimated. Energy consumption of new process increased and the treatment cost becomes 3 times higher comparing the conventional process, while the environmental burden of new process decreased comparing conventional process. The nickel recovery process in fine ground particles increased energy and energy cost comparing those of t