Recycling of printed wiring boards with mounted electronic parts

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Abstract
A practical technology has been developed for the recycling of printed wiring boards (PWBs) with electronic parts mounted on them. The recycling ratio of useful materials recovered from a test PWB with our method was 65%, as compared to 23% with a previous method of refining useful metals from the PWB as a whole. The electronic parts on the PWBs were effectively removed by combination of heating to above the melting point of solder and applying such external forces as impact, shear and vibration. We have developed an automatic part removal apparatus (practical model) on the basis of tests for the removal of electronic parts and of our measurements of the forces needed for part removal. The apparatus successfully removes through-hole devices (THDs) as well as surface mounted devices (SMDs) from PWBs with almost no damage. Most of the solder is also removed in this process, while that remaining on the resin board surface can effectively be removed later by surface abrading followed by heating/impacting. Tests shows final solder removal to total 96 wt%. After electronic part and solder removal, the resin-boards are pulverized, and the resulting materials are separated into a copper-rich powder and a powder consisting of glass fiber and resin (GR powder). The recovered electronic parts (including gold) are valuable metal resources for refining, while some have the potential to be reused for their original purpose after being checked for reliability. The copper-rich powder (copper content: 82 wt%) is also a valuable metal resource for refining.

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