Yuji Ikuta

Recycling system for printed wiring boards with mounted parts

A practical recycling system has been developed for printed wiring boards (PWBs) with electronic parts mounted on them. This system consists of part-removing, solder-removing and resin-board pulverizing/separating processes, and is effective in the recovery of useful materials. The authors have developed a part-removal apparatus which successfully removes through-hole devices as well as surface mounted devices from PWBs with almost no damage to the devices themselves. Most of the solder is removed by the part-removal, and later by surface abrasion followed by heat/impact. After the removal of parts and solder, the resin-boards are pulverized and the resulting powder is then separated into two types: a copper-rich powder and a powder which consists of glass fiber and resin (GR powder). The copper-rich powder is a good copper resource for refining; the GR powder is usable as a filler for polymer products. Recovered parts which contains valuable metal resources (including gold), can be refined out, as is most commonly the case in other recycling systems, but a more economic and ecologically sound approach would be to exploit the potential of parts removed in this system to be reused for their original purposes after being checked for reliability.

A pyrolysis-based technology for recovering useful materials from IC package molding resin waste

This paper describes a pyrolysis-based technology for recovering useful materials from molding resin waste, which is the main type of thermosetting plastic waste generated in the fabrication of IC packages. In our pyrolysis of molding resin waste, the main impurities in the recovered silica were carbon (C), antimony (Sb) and phosphoric acid ion (PO/sub 4//sup 3/). The amount of carbon and phosphoric acid ion decreased with increased heating temperature and oxygen concentration. However, the antimony remained constantly between 400 and 1000/spl deg/C because diantimony tetraoxide (Sb/sub 2/O/sub 4/), which is hard to volatilize, was formed by oxidation. Our experimental results suggest that the most effective way to reduce the impurities is to heat at between 1000-1100/spl deg/C and to keep oxygen concentration at about 8 vol%. On the basis of these results, we used a roller kiln type furnace as a prototype practical pyrolysis system for recovering high purity silica. The purity achieved was as follows: C<100 ppm, Sb<1000 ppm, and PO/sub 4//sup 3/<20 ppm, pure enough to be used as inorganic filler for cast insulating materials. The combustion exhaust gas generated by pyrolysis of the molding resin waste was decomposed by a secondary combustion method which was found to decrease organic brominated substances to a sufficiently safe level, and also, to convert the antimony tribromide to diantimony trioxide, which can be collected by a dry recovery process at a high recovery rate and at a useful purity.

Pyrolysis-based Technology for Recovering Useful Materials from Epoxy Resin Compounds for Molding for Electronic Components.

A pyrolysis-based technology was applied to recover high purity silica filler from epoxy resin compounds (molding resins) for electronic components, and to reuse it as a filler in the present paper. Molding resins mainly contain epoxy resin, harder, silica filler (70-85 wt %) and flame retardant consisting of brominated epoxy resin and antimony trioxide. Most effective conditions to reduce impurities in the recovered silica were found as heat around 1,000-1,100 °C and to keep oxygen concentration 5-10 vol. %. On the basis of these results, we have developed a practical process for recovering silica filler from molding resins using a roller kiln-type furnace. The recovered silica achieved a purity of C < 0.01 wt %, Sb < 0.4 wt %, and PO43- < 0.002 wt %. A jet-mil treatment was effective to grind the aggregates of recovered silica powder and to increase the reactivity of its surfaces. The recovered silica treated with the jet-mill showed good properties as a filler for a cast insulating epoxy resin compound. A secondary combustion method was successfully applied to the decomposition of the combustion gas. The treatment of the gas by heating at 1,100 °C decreased the toxic organic bromine compounds to a safe level and converted the antimony tribromide to diantimony trioxide, which could be collected by a dry recovery process at high recovery rate.