Laser micromachining of metallic mold inserts for replication techniques
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Laser micromachining of metallic mold inserts for replication techniques W. Pfleging, A. Meier, T. Hanemann, H. Gruhn and K.-H. Zum Gahr Forschungszentrum Karlsruhe GmbH, Institute for Materials Research, P.O. Box 3640, 76021 Karlsruhe, Germany ABSTRACT The laser microcaving (LMC) of steel is performed with cw Nd:YAG laser radiation. LMC enables a "clean" patterning process with only a small amount of debris and melt. During LMC the formation of a Ni-enriched interface layer and an oxide surface layer may be observed. The formation of these reaction layers as well as the etch rate and the surface quality strongly depend on the chemical composition of the steel and the process parameters. Surface qualities with an roughness of about R,(center line average)=300 nm can be realised. The ablation rates are in the range of 106 P.m 3/s. With excimer laser radiation a further improvement of surface topographies can be achieved via laser planarisation. Mold inserts are manufactured by LMC, and microstructures composed of PMMA are successfully demolded by using the Ultraviolet light induced Reaction Injection Molding (UV-RIM) or Photomolding technique. CE(Capillary Electrophoresis)-Chips made of PMMA are successfully demolded, and the functionality of the CEChips is demonstrated. INTRODUCTION Microsystem technology has been the subject of research and development since the 1980s and will be a key technology for the new century. Different technologies have been developed, such as modified "classical" semiconductor technology using silicon [1], the LIGA technique [2], micromechanical abrasion or precise laser material processing [3,4]. The lateral dimensions of the generated microcomponents and systems are ranging from the nm to the mm scale depending on the method of manufacturing and on the type of application. For a necessary resolution of about several ptm in lateral direction laser processing may be a suitable method for the manufacturing of microsystem components. But often laser beam processing is a slow serial step by step material removal by means of movement of laser beam and/or substrate. In order to realise a fast and reasonable large scale fabrication of microcomponents a laser material processing with respect to the manufacturing of mold inserts for micro injection molding techniques such as the Ultraviolet light induced Reactive Injection Molding (UV-RIM) designed for rapid prototype fabrication was developed [5-7]. Micro injection molding is an established and economic technology for the large scale fabrication of microcomponents made of polymers [8]. Main advantages of the laser material processing compared to the commonly used LIGA technique, spark erosion and micromechanical or chemical fabrication processes are a large choice of materials and a shorter processing time. The time consumption for manufacturing a mold insert via LIGA technique is generally in the range of several weeks up to several months depending on the structure height and structure complexity. The plating time of the nickel body alone is in
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