An alternative environmentally benign process for printed circuit board recycling
In recent years there has been increasing concern about the growing volume of end-of-life electronic products. As the primary elements in most electronic products, Printed Circuit Board (PCB) is widely used and its recycling becomes a challenge not only to the industry, but also to the society. As an alternative environmentally benign method for PCB recycling, this dissertation adopts a novel processing method to separate the PCB scraps, which would increase the recycling rate and reduce the negative environment impact. Various solvent systems, i.e., carbon dioxide and water, are explored for delaminating PCB scraps at certain high temperature and pressure. For the purpose of finding an optimal condition for PCB delaminating, the experiment facilities were set up at the Advanced Manufacturing Lab (AML) in the Department of Industrial Engineering. Through series designed experiments, input parameters such as temperature, pressure and process time were recorded, and the output parameters, i.e., weight reduction, thickness expansion, impact energy variation were measured to evaluate the PCB delaminating results. Response Surface Method (RSM) was applied for selecting the input parameters. Multiple Objective Optimization method (MOO) was adopted to evaluate the overall delaminating effects. The utility theory was utilized to set up the utility function and figure out the optimal solution. Furthermore, the fundamental mechanism which caused the epoxy resin decomposing was interpreted. The explanation was helpful for selecting various solvents to speed up the reaction and improve the efficiency. In this research, the effectiveness of the alternative method to delaminate waste PCB scraps, that is, utilization of the chemical process was examined. Based on this method, series experiments were designed and implemented to search for an optimal condition. Through the output data analysis, optimization process conditions were determined. Consequently the reaction mechanism was interpreted. Some other solvent systems were tested to hasten the reaction speed, i.e., ternary solvent system of carbon dioxide, water, and ethanol. This alternative printed circuit board recycling process is promising for industrialization in the future.