Micro-metalforming with silicon dies

Abstract

The introduction of forming technology into MEMS manufacturing demands forming dies being characterized by a high strength and hardness, a good micro-structurability, a low surface roughness, and a high precision of the microgeometry to be molded. Silicon structured by lithography and etching processes meeting these requirements especially concerning precision and surface roughness. For micro-metalforming silicon dies with different structural dimensions (>1 mum) have been used. The microstructures could be molded in different materials using cold and superplastic embossing. The precision and surface quality of the formed parts correspond to the high quality of the microstructured die. Both the low surface roughness and the accurate edges of the silicon structures are nearly represented in the molded structures. However, in particular during cold embossing die wear or even die failure could be observed limiting the implementation of silicon for micro-metalforming

Fabrication of self-encapsulated nickel microchannels and nickel nanowalls by reactive ion etching

“…With a growing demand in biotechnology, microfluidics, and nanofluidics, various fabrication technologies for microchannels and nanochannels have been extensively developed (Tamanaha et al, 2002;Najafi et al, 1998;Piotter et al, 1997;Quake and Scherer, 2000;Ko et al, 2003;Qin and Li, 2001;Pan et al, 2004;Lijima, 1991;Hosoda et al, 2003;Cheng et al, 2004;Zeng et al, 2005;Luchnikov et al, 2005;Routkevitch et al, 1996;Mikulskas et al, 2001;Yoo et al, 2002;Böhm et al, 2001;Engel and Eckstein, 2002;Sen and Shan, 2005;Joo et al, 2005). In the late 20th century, well established IC fabrication technology had a profound impact on the creation of silicon or glass-based microchannels.…”

Microembossing of ultrafine grained Al: microstructural analysis and finite element modelling

“…The minimum structure width was 10 μm. The cold embossed surface showed a better quality than that in their previous attempts [8] due to the finer grains, although the channel edges were still rounded [10]. In order to achieve complete moulding of the structure, a compressive stress much higher than the yield stress proved necessary.…”

“…A very high mould failure rate was observed, which was ascribed to misalignment of embossing [9]. Böhm et al [10] studied straight channels and complex structures fabricated by cold embossing and embossing at elevated temperatures. A silicon die in various relatively fine grained materials (grain size >3 μm) was used, including pure aluminium, stainless steel, pure copper and brass CuZn37.…”

Evaluation of roughness, hardness, and strength of AA 6061 molds for manufacturing polymeric microdevices

“…However, silicon molds are not feasible for mass production purpose as they can break easily due to their inherent brittleness when there is slight misalignment of mold and substrate. As an alternative, strong and tough metallic molds with longer lifespan can be fabricated by high precision micromachining (micromilling [5,6], micro electrical discharge machining (μEDM) [7,8], laser micromachining [9][10][11], and micro electro chemical micromachining (μECM) [12]); lithography, galvanoforming, and plastic molding (LIGA) [13]; or by cold and superplastic embossing [14]. The surface finish of molds manufactured by micromilling and μEDM methods is relatively higher than that by the lithography method (0.3 μm for micromilling and 0.4-0.5 μm for μEDM [15]).…”

“…LIGA method can provide high-aspectratio microstructures with smooth sidewalls and submicron features, but the process is costly and sophisticated [13]. Cold embossing and superplastic embossing are easy-to-apply methods, but they cannot create microchannels with sharp edges [14]. Polymer molds made by soft lithography [20] or two-stage hot embossing [21,22] can also be employed in the manufacturing of microfluidic devices; however, the intrinsic limitations of polymeric molds, such as their low melting temperature and strength as compared to the metallic molds, are the main drawbacks of these techniques.…”