Electroless copper plating obtained by Selective Metallisation using a Magnetic Field (SMMF)

Lithography is the most commonly used method for the selective metallisation of non-conductive surfaces in the manufacture of electronic devices such as printed circuit boards and antennae. However, when used in subtractive mode, lithography results in the generation of large amounts of organic solvent and metal containing waste and requires high initial capital investment. For these reasons, additive methods of selective metallisation are being widely investigated. In this work, a novel additive approach of Selective Metallisation using a Magnetic Field (SMMF) was studied. This method uses a magnetic catalyst to initiate the electroless plating process. Magnetic catalyst particles composed of magnetite-silicon dioxide-silver were synthesised by a wet-chemical procedure. Their composition was analysed by scanning electron microscopy and energy dispersive X-ray spectroscopy and the phase formation was confirmed by X-ray diffractometry. Catalytic activity towards formaldehyde oxidation and the magnetic properties of particles were confirmed by cyclic voltammetry and vibrating sample magnetometry, respectively. The results showed that the particles can be used as a catalyst for electroless copper plating and are attracted by the magnetic field. The pattern of deposition of the magnetic catalyst is defined by the magnetic field. Two different configurations of magnet and substrate were used to deposit the catalyst dispersion onto the substrate surface. In both cases, the particles were attracted by the magnetic field and deposited exclusively where the magnetic field was applied. Subsequent electroless copper plating also only occurred at these areas. Parallel lines of electroless copper were obtained. The effect of the magnetic field on magnetic catalyst deposition and subsequent electroless plating was studied and key process-specific defects were identified.