Effect of impact velocity control on selective grinding of waste printed circuit boards

To develop a low-cost recycling process for printed circuit boards (PCBs) in scrap electronics, a new grinding technique that can enhance the selective grinding effect between ductile and brittle materials was investigated with a personal computer-assisted impact grinding system which can automatically control various operating conditions in real time. The destruction behavior of twokinds of PCBs within the grinding chamber was captured on video with a high-speed camera, and then the effect of real-time control of the impact velocity of the mill on selective grinding between metallic and non-metallic components in the milled product of PCBs was examined. As a result, the destruction process of PCBs was found to be of a totally different form, according to the strength of base materials like paper-mixed phenol resin or glass-reinforced epoxy resin. The variable speed mode, i.e. accelerating the hammer rotation gradually from a very slow speed, was found to be an effectivemethod to enhance the selective grinding because the exfoliation of copper foil was increased, while the size of fragment was relatively large.