Refining of precious metals

Primary processing of printed circuit boards

The dismantling process can be used as a preventive measure for the generation of printed circuit board waste by reusing it after changing the relevant functions. Also dismantling, carried out as the initial stage of modernization operations. These operations are performed manually. Electric or pneumatic tools such as pliers, screwdrivers, chisels, etc. are used for this purpose. 

Disassembly of different electronic components from printed circuit boards is one of the most important steps in the recycling process. This ensures the elimination of hazardous components (capacitors, batteries) from further recycling processes. Some components can be separated from the substrate with low force. Electronic components that are soldered to the substrate can be disassembled by melting the Sn / Pb solder. Air and certain liquids (silicone oils, ionic, water-soluble liquid) can be used as heat carriers to effectively remove solder joints. Nevertheless, care must be taken to avoid thermal decomposition of plastics and the release of toxic gases from resins and adhesives, which is quite common during the process. The disassembly process can be automatic or semi-automatic. The biggest advantage of automated disassembly is real-time product evaluation and a flexible disassembly algorithm that varies from product to product. Image processing and databases are acceptable to identify the different components. In most cases, automatic disassembly is identified as a more economical option, but manual disassembly is still commonly used. 

According to a study by Hanafi (2012), about 20% and 30% by weight of SP were eliminated when ten mobile phone and computer boards were dismantled using hot air, respectively. 

After removal of hazardous components, operations such as cutting, shredding and grinding are used, and these processes can be used to extract metals from resin, glass and plastic. The most commonly used are hammer, rotary, disc shredders, cutting, cutting equipment with bottom sieve, ball and disc mills. Because printed circuit boards are made of reinforced resin, conventional shredders for copper wires and fiberglass are not efficient.