Manufacturing of metal-based microparts: Fabrication strategies and surface engineering applications

A wide range of industrial applications, current and anticipated, drive the process of miniaturization of thermal and chemical devices. In certain cases, metal-based microsystems enjoy advantages of performance, cost, or both, over silicon-based counterparts. The critical bottleneck restricting the use of metal-based microsystems in actual applications has often been the lack of effective and economical manufacturing methods for metal-based microparts. In this paper, our recent efforts in fabrication of metal-based high aspect ratio microscale structures through various replication strategies, such as compression molding and roll molding, are summarized. The need for engineering surfaces of microscale replication tools through conformal coating deposition is illustrated. Two attempts to experimentally measure shear strength of coating/substrate interfaces are described. An estimate of the limiting shear strength of coating/substrate interfaces is achieved through examination of transverse coating cracks induced by substrate tensile loading. Experimental data obtained from two series of TiN/Cr/steel and TiN/Ti/steel specimens are presented. Issues associated with this approach are discussed. Direct failure of coating/substrate interfaces has been induced through compression loading of micro pillars containing inclined coating/substrate interfaces. Preliminary experimental results obtained from TiN/Ti/Si micro pillars are presented.