Electrodeposition in micromolds with a microscreen base

Electrodeposition in sacrificial micromolds with a microscreen base and thermoplastic sidewalls is one of the main techniques for rapid fabrication of high aspect ratio metallic microstructures. These micromolds with an integral microscreen base are fabricated through an injection molding process by forcing a softened thermoplastic through a metal microscreen into a master template with microfeatures corresponding to those desired in the micromold. During this injection molding process, the holes of the microscreen are filled by the thermoplastic and form insulating segments on the micromold base. Further, the micromold consists of microcavities with insulating sidewalls. During the electrodeposition process into the microcavities, the deposit originates from the conductive parts of the microscreen base and grows along the insulating walls conforming to the micromold geometry. In this work, computational models for the governing transport and electrochemical phenomena are used to simulate the shape evolution of the electrodeposition front and the spatial current density profile with time. The effects of the applied voltage and microscreen geometry (the size and number of the insulating parts on the micromold base) are systematically studied for their influence on the nonuniformity of the current density and deposit surface profile. Conditions that lead to desirable process and part quality are derived from the studies.