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 two-kinds 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 effective method to enhance the selective grinding because the exfoliation of copper foil was increased, while the size of fragment was relatively large.