Precise laser-assisted 3-D microstructuring of metals and alloys

In the following three different laser-assisted processes are described and herewith produced components in the fields of micromechanics are presented. First, excimer laser projection technology is modified in order to produce large-area micro structures. It enables the transfer of structures having dimensions much larger than the laser beam section by synchronized scanning of the mask and the substrate. This technology is used to manufacture master structures in polymers for injection molding inserts. The insert tool itself is produced by electroforming of the master leading to a metallic copy of the master. In this way a metallic insert tool is performed for the production of microfluidic components. Its structured area is 2 cm(2) at a resolution better than 3 mum. Second, laser-induced wet chemical etching using a cw-Nd:YAG laser is described. The principle of this micromachining method is based on a local thermal activation of chemical etching reactions on the surface of the material. The direct processing of the workpiece resulted in high accuracy microstructuring with smooth surfaces and without any debris or thermal influence on the material properties. Among others one example in the field of application in micromechanics is the fabrication of superelastic micro-grippers prepared by cutting of temperature sensitive shape memory alloys. The achieved sidewall angle is about 3 degrees and the surface roughness less than 0.4 mum for machined 200 mum thick foils. Third, a combination of the two afore mentioned processes leads to complex shaped microstructures in metallic parts. Thereby, additional microstructures of specific shape, e.g. v-shaped grooves, are machined by laser-induced wet chemical etching into metallic inserts produced by electroforming of excimer laser machined masters. They are used for hot embossing tools enabling the production of special housings which can be hermetically sealed by ultrasonic welding.