Local brain connectivity is expected to lead to new models for neurological diseases, which may in turn result in advanced understanding and better treatment. This paper presents a neural sensing microsystem integrated with TSV-embedded dissolvable μ-needles array, ENIG bonding technology, biocompatible Au-TSV flexible interposer and neural recording circuits, for neural sensing implantation. An ultra-Thin film bonding approach is proposed for integration of interposer assembly. Removing bonding wire by proposed bonding technology, the dimension of neural sensing system can be minimized to reduce surgical area and promote implant success rate. The signal quality of neural recording can be significantly improved by eliminating complex signal paths with 2.5D TSV integration from neural sensing interface to neural recording circuits.