Laser Micro Machining for Continous 3-D Contouring of Airflow Blades for a MEMS Turbine

This paper describes an innovative KrF excimer laser fabrication approach for profiling opti- mally smooth airflow contours. The research merit of the process is its use in producing a new type of electrical transducer micro-turbine using a novel axial format. (1) The necessary micro- machining precision for this was achieved by computer-controlling a laser beam using an elevating stage to step a moving mask across a fixed mask, i.e. a variant of dynamic mask-dragging or mask- aperturing. The moving mask image was projected on to a series of flat 600 µm wide, 1000 µm deep preform surfaces, reducing each to 50 µm thickness with curvature. Precise control of each mask in- crement to ablation depth and focus allowed a range of 3-D curves to be realized. The ablation rate versus surface quality was optimized throughout by ablating just 300 nm per laser pulse and using 2000 pulses spread over 90 sites. The process represents a cost effective means of using basic masks to continuously shape flat surfaces in the axial direction with high aspect ratios, high speed and pre- cision, and is applicable to both micro streamlining and the manufacture of micro expansion nozzles.