Flexible circuit process saves energy and material

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With demand growing for flexible circuits and similar creations predicted to reach $16billion a year by 2014, the Fraunhofer Institute for Surface Engineering and Thin Films IST has developed a technology that allows conductive metal circuits to applied to plastic substrates in an energy and material friendly manner.

The technology is known as P3T, short for Plasma Printing and Packaging Technology. The approach requires fewer process steps and conserves raw materials. Rather than starting with a metallised polymer film and removing material, the process deposits copper on the substrate. However, for biosensors, palladium is used. Dr Michael Thomas, director of the IST research group, said: "During production of circuits for an RFID antenna, you often have to etch away up to 80% of the copper used. This results in considerable amounts of copper scrap." The first two steps in the process are plasma printing and metallisation. Plasma printing uses deeply engraved rollers similar to those used in rotogravure printing. During the process, microplasms are generated in the engraved recesses of the roller and these alter the surface of the plastic substrate. Dr Thomas noted: "The chemical changes we need begin to form on the surface of the film, ensuring the plastic can be wetted with water in precise areas and will be metallisable."