Review of additive electrochemical micro-manufacturing technology

Additive electrochemical micro-manufacturing (micro-AECM) is a nontraditional fabrication method which fundamentally employs electrochemical deposition (ECD) mechanism in different forms to manufacture metal-based microstructures layer-upon-layer. Micro-AECM based on traditional mask-based ECD has long been widely adopted to manufacture large scale precision two-dimensional (2D) and quasi-three-dimensional (quasi-3D or 2.5D) metallic micro-sized geometries by inversely duplicating the photoresist though-masks patterned lithographically. Recently, micro-AECM has attracted increasing attention owing to its significant potential advantages in producing 3D complex void-free and crack-free microstructures with a favorable surface finish and now has emerged as a true additive micro-manufacturing (electrochemical additive manufacturing) technology based on ultrafine anode/electrolyte-jet-induced ECD (maskless micro-AECM). To date, several micro-AECM techniques have been developed to meet versatile applications, and some of them have already been used commercially. In this paper, the fundamental schematic of ECD closely related to micro-AECM is introduced, and several typical micro-AECM techniques are reviewed, including through-mask electroplating, instant masking (IM) plating, electrochemical fabrication (EFAB), localized electrodeposition (LECD), jet electrochemical deposition (Jet ECD), meniscus-confined electroplating (MCED), electrohydrodynamic redox printing (EHD-RP), tip-based nanofabrication (TBN), and fluidic force microscope electrodeposition (FluidFM electrodeposition). Furthermore, the challenges, development trends and perspectives of micro-AECM are discussed.