Photolithography is commonly used in various manufacturing sectors to achieve metal patterning of non-conductive materials. However, the high cost and toxicity of reagents used in this process have prompted the investigation of alternative approaches to selective metallisation. The present work shows a novel approach that utilizes a gradient magnetic field to achieve selective metallization on the millimeter scale. The magnetic field is applied during the seeding (catalysation) stage, which is required to initiate electroless copper deposition. Subsequent copper deposition occurs selectively according to the pre-defined pattern of the magnetic field.

The modified approach uses a new type of magnetic catalyst i.e. a Fe_­3O₄-Ag composite material, which was obtained by a wet chemical synthesis method. The Fe component of these particles enables them to be arranged on the substrate in a way that directly corresponds to the pattern of the magnetic field and therefore subsequent electroless copper plating will follow this pattern. The magnetic and catalytic properties of particles for the initiation of electroless copper deposition were characterised by vibrating sample magnetometry and cyclic voltammetry measurements. The Fe₃O₄-Ag composite colloid solution was optimized by varying the pH, mixing approach and particle concentration.

This paper will demonstrate the potential for selective catalysation in a magnetic field to compete with the commonly used photolithography and ink-jet printing approaches for macroscale selective metallisation of non-conductive materials.

Figure 1. The schematic representation of standard electroless copper plating process and modified process of selective metalization in a gradient magnetic field.