Photo-electroforming: 3-D geometry and materials flexibility in a MEMS fabrication process

Photo-electroforming is a new manufacturing process for making microelectro mechanical systems (MEMS). Photo-electroforming builds parts by an additive process which defines geometry by depositing powder in layers and creating regions of selective conductivity by laser-enhanced electroless plating. T he conductive region is then joined by a second plating to form an integral part. The unmetallized portion is removed by selective etching in one step after all layers are defined and joined. Single-layer and two layer stand- atone parts made of nickel/silicon carbide composites of overall size 75-10 0 mu m and feature size 25 mu m mere treated. Writing speeds of up to 24 cm/s and in-plane resolution of 15 mu m were dem onstrated. The high laser-induced plating rates were found to be due to ele vated substrate temperatures under the laser spot and enhanced mass transfe r due to pumping by the hydrogen bubbles resulting from the plating reactio n. In the regimes studied, mass transfer defined the rate limit. The in-pla ne resolution was found to be limited by a combination of laser spat size, thermal conduction in the substrate, and laser divergence due to gas bubble s.