Evaluation and Characterization of Reliable Packaging Method for Neuromotor Prosthetic Device

Neural probe array is used for neural recording and simulation applications. It will be implanted into the motor cortex of a paralytic human to control robotic arm and perform tasks such as grasping an object. The major components are silicon (Si) probes, Si platform, application-specific integrated circuit (ASIC), polyimide flexible cable and wireless IC. In-plane Si probes are inserted into the Si platform to form a three-dimensional (3D) probe array. Wirebonding technique is used to integrate the ASIC and the probe array. Pad finishes play an important role in wire bonding as it would affect the reliability of the electrical connections. As such, the focus of the paper will be on the evaluation and characterization of an electroless nickel immersion gold (ENIG) pad finishing and its bonding parameters for wirebonding application. ENIG pad having a 0.1-µm gold (Au) thickness combined with an additional Au stud and wirebonding temperature of 200 °C are found to have comparable wirebonding capabilities as a 0.3-µm thick Au finishing pad. The wire pull test result and SEM observation between the ENIG and Au finishing pad at different bonding parameters were presented and discussed.