Research on Fractal Mechanism of the Crushed Particle of Waste Printed Circuit Board

Waste printed circuit board (PCB) is the most important part of Waste electronic and electric equipment (WEEE), and also one of the most arduous job to deal with because of its heterogeneity and high complexity. Crushing is the crucial process for the technology of recycling waste PCB, for chemical and bio-metallurgy methods, the process of crushing could have enough chance to make the surface of particles contacting with medicaments, again for physical methods, the process of crushing could directly cause the efficiency of successive separation, the recovery rate and purity of metal. In order to study the rupture mechanism of waste printed circuit boards (PCB), an S-3000N scanning electron microscope (SEM) and electron spectroscopy (EDS) were adopted to analyzed boundary of PCB particles. The surface topography of PCB particles manifests self- similarity, which shows particle possesses fractal characteristics. Based on the fractal theory and computer images analysis technique, a MATLAB program which computes box fractal dimension of material fracture was designed. The linear degree of fit beeline of MATLAB program is high, which shows fractal behavior of the boundary of PCB particle is obvious. The different fractal dimension of 6 particles shows that complexity and roughness of fracture were different. The order of complexity and roughness of particle boundary from high to low is: d > c > a > f > e > b, and these accords with the visual observing, which further shows that the crushed PCB particle boundary possesses fractal characteristics.