Effect of synergistic nucleation on microstructural and mechanical characteristics of silver micro-devices with high aspect ratio

Silver (Ag) has widespread application potential in the field of non-silicon microelectromechanical systems (MEMS) due to its superior material properties. However, the current Ag-based prototyping technologies are mainly limited by harsh production conditions and poor compatibility with multiple processes. In this work, we present an Ag-based 3D electrodeposition manufacturing relies on synergistic nucleation mechanism, which combines UV-LIGA technology and bottom-up Ag electroplating. Based on the optimized Ag electroplating system, the synergistic nucleation mechanism of Ag is comprehensively investigated through the interplay between electrochemistry and microstructure. During the bottom-up filling process, the nucleation mode gradually transforms from instantaneous to progressive, which corresponds to the transition of Ag crystallization from large grains dominated by (220) crystal face to fine grains controlled by (111) orientation. And the Young's modulus and hardness are increased to 5.5% and 37.8%, respectively. Moreover, the forming capability and application potential of the proposed Ag electrodeposition technique are demonstrated, where the maximum aspect ratio is up to 10. The Ag-based heat sink is fabricated as a proof-of-concept by heterogeneously integrating Ag microchannels with an AlN heat source. It exhibits excellent mechanical stability (τ=71 MPa, σ0.2=257 MPa) and cooling performance approaching 1000 W/cm2. The proposed Ag-based 3D electrochemical deposition technology has controllable processes, multi-integration compatibility, and excellent performance, indicating a broad application prospect in MEMS devices.