SHIZUOKA, JAPAN - NEC Corp. of Tokyo has improved its printed circuit board technology and can now recycle such boards from which components have not been removed. Previous NEC methods required that boards be stripped before recycling. With the improved method, 70 percent of total waste volume can be separated into reusable materials that include various metals, glass fiber and epoxy resin.
Printed circuit boards consist of glass fiber, layered epoxy resins and copper. Components consist of various nonmetallic and metallic elements, including gold as well as resins used for sealing and packaging. It has been difficult to recycle boards because waste epoxy resins harden when heated and cannot be fused back together.
The new recycling process begins with controlled infrared heating of the board to just above the melting point of solder and then removes components by applying impact and shearing forces. Any solder remaining on the board is removed by further heating and additional impact force. Once the components and solder have been removed, the board is pulverized into a powder.
Taking advantage of differ-ences in specific gravity and other physical properties in the materials that make up the powder, gravity and electrostatic separation methods are applied to separate the powder into a copper-rich component and a powder consisting of glass fiber and resin.
The method recovers more than 90 percent of the copper in the PC board. The recovered glass fiber and resin can be used as a filler that strengthens and improves thermal expansion properties of epoxy-based paints and adhesives and also can be used as a filler in other polymer products.
NEC presented the development at the Mining & Materials Processing Institute of Japan Conference, held Sept. 20 at Tokai University in Shizuoka.
