The following conclusions can be drawn from the present
study. When printed circuit boards were milled in a stamp mill,
utilizing the up-and-down reciprocating motion of the hammer,
copper, tin, and lead were distributed in the finer fraction of the
milled printed circuit boards, while 85% of the nickel was concentrated
in the coarser fraction with particle size >5.0 mm. Copper,
the most abundant metallic element, which was present as thin
foils between the epoxy resin plates of printed circuit boards,
was fragmented through simultaneous tearing with the substrates
of printed circuit boards during fine milling by the up-and-down
reciprocating motion of the hammer.