Soldering-based easy packaging of thin polyimide multichannel electrodes for neuro-signal recording

We propose a novel packaging method for preparing thin polyimide (PI) multichannel microelectrodes. The electrodes were connected simply by making a via-hole at the interconnection pad of a thin PI electrode, and a nickel (Ni) ring was constructed by electroplating through the via-hole to permit stable soldering with strong adhesion to the electrode and the printed circuit board. The electroplating conditions were optimized for the construction of a well-organized Ni ring. The electrical properties of the packaged electrode were evaluated by fabricating and packaging a 40-channel thin PI electrode. Animal experiments were performed using the packaged electrode for high-resolution recording of somatosensory evoked potential from the skull of a rat. The in vivo and in vitro tests demonstrated that the packaged PI electrode may be used broadly for the continuous measurement of bio-signals or for neural prosthetics.