Removal Of Organics And Seperation Of Lead And Copper From Transistors On Waste Printed Circuit Boards

Waste printed circuit boards,as the core component of waste electrical and electronic equipment,are of high values as well as harmfulness with large quantities.Present technologies mainly focus on the treatment of waste printed wiring boards.The recycling of waste electronic components(ECs)has been paid little attention to.Therefore,the through resourcing of waste printed circuit boards has not been achieved.Transistors,as one of the crucial ECs,are widely used in various electrical and electronic devices.On one hand,transistors have high recycling values due to the presence of valuable materials(copper,silver,silicon and so on).On the other hand,there exists heavy metal(lead)in solder materials and brominated flame retardants in molding compounds of transistors,which require proper disposal to avoid pollution.Thus,the recycling of waste transistors is the mutual appeal for environmental protection and resource recovery.This thesis proposed a complete process to treat waste transistors based on pyrolysis and vacuum metallurgy.First,the structure and thermal characteristics of waste transistors were investigated to provide reference for subsequent treatment.Then,the transistors were pyrolyzed under argon atmosphere.The effects of temperature and holding time on removal of organics in epoxy molding compounds of transistors were investigated and the optimum parameters were 600? and 30 min.The composition and content of pyrolysis products were analyzed and the pyrolysis mechanism of epoxy molding compounds was proposed.After pyrolysis,the metals and nonmetals in pyrolysis residue were separated by crushing and sieving treatment with a crushing time of 5min and 0.6mm mesh size.The purity of copper reached 92.75% after sieving treatment.To achieve the removal of lead and further enrichment of copper,the derived metal concentrate was treated under high temperature in vacuum environment.Due to the differences of saturated vapor pressure,the lead was evaporated and separated from copper at the temperature lower than copper's melting point.The results showed that the optimal conditions for vacuum separation was 900?,60 min and 20 Pa.At this point,the separation efficiency of lead reached 99.86% and the copper purity reached 98.81%.The thesis proposed a complete efficient and effective process to dispose waste transistors on waste printed circuit boards,providing theoretical and practical basis for industrialization of waste transistor recovery.