Cortical visual prosthesis are nowadays investigated as a promising solution for visually impaired people. Precise electrical stimulation of the visual cortex by penetrating microelectrodes demonstrated phosphene activation at specific points on the visual field, facilitating a nuanced perception of the surroundings in a grid-like manner. The Smart Micro Neural Dot project aims at a wireless, miniaturised and large-scale cortical visual prosthesis relying on thousands of free-standing CMOS microstimulators. Penetrating microelectrodes directly stimulate the visual cortex in a one-to-one correlation with the perceived pixel in the blind visual field. The integration of such penetrating microelectrodes with CMOS implants represents a challenge in terms of assembly, reliability, repeatability, and scalability.