Various replication techniques for manufacturing three-dimensional metal microstructures

Abstract

In microsystem technology a large range of different materials will be available only after the necessary micromanufacturing techniques have been developed or adapted. Existing manufacturing techniques are structuring or shaping techniques producing three-dimensional microstructures out of silicon (silicon etching, silicon surface micromechanics), mostly unfilled plastics (lithographic techniques, injection molding, hot embossing, reaction molding) or a few pure metals or binary alloys (electroforming).The choice of materials for microcomponents is determined by the function and conditions of use of microsystems. Especially the range of metals is still restricted considerably because the only processes available are electroforming and thin-layer techniques.It is for these reasons that we are developing various processes for manufacturing three-dimensional metal microstructures. In addition to direct electroforming of injection molding lost plastic micromolds, these are a new microcasting process and Micro Metal Injection Molding (Micro MIM). Microstructures have already been molded from mold inserts made by micromechanical cutting or by the LIGA technique. The results achieved, and future prospects, are outlined below.

Formability and accuracy of micropolymer compound with added nanomaterials in microinjection molding

“…To exploit the potential of microsystem technology, economical mass production of microcomponents is necessary. 1,2 Most of the components for miniaturized systems have been fabricated using silicon, glass, or quartz. However, for many applications, these materials and the associated fabrication methods are too expensive and complicated.…”

Micro-Replication: Precision Metal parts from Electronformed Master Molds

“…[4][5] This process was followed by conventional Ni electrodeposition into the features after making electrical contact to the Ag clusters (no details as to how this was done are given). 4 Attempts at micro precision casting (using molten metal to fill ceramic molds) and micro metal injection molding (using fine metal powders with binder to fill molds) are summarized by Ruprecht et al 6 These latter two methods, while potentially viable at some point in the future, are in need of further development before they are used on a routine basis for fabrication of metallic microstructures. 7 Another interesting approach to the problem has been the use of conductive plastic material that may be formed and simultaneously patterned by injection molding.…”

“…The conducting plastic, bearing the desired features, is then used as a substrate for electrodeposition. 6 The plastic mold with the metal microstructures is then planarized, after which the plastic is dissolved in an organic solvent such as acetone. The process is summarized in Figure 1.…”

A net shape process for metallic microcomponent fabrication using Al and Cu micro/nano powders

“…The master mould is relatively rigid, of high precision and usually fabricated using MEMS technology, such as deep reactive ion etching (DRIE) and X-ray exposure on SU-8 photoresist. The moulds used in [3] are an example of the process of Xray lithography on SU-8, also referred as LIGA process. In an X-ray lithography, very high exposure energy is applied to ensure deep light penetration and result in a vertical sidewall.…”

“…µMIM provides an alternative way to semiconductor fabrication process based MEMS technology [2]. Its distinguishing feature from MEMS technology is the capability of producing metallic micro components [3]. When compared micro EDM and micro laser fabrication, µMIM has the advantage of volume production at low costs.…”