Laser-patterning of thin films deposited on complex surfaces for the fabrication of micro-sensors

In the field of micro- and nano-technologies microstructures on flat substrates like silicon wafers are fabricated by using photo lithography and etching techniques. For the structuring of complex technical surfaces like e.g. the contact surface of ball bearings novel patterning techniques will be needed because contact printing can not be applied to such 3-dimensional surfaces. However, direct application of integrated thin film sensors on mechanical components will be an important issue for the future. That is the reason why we developed laser based patterning methods for the fabrication of electrical circuits on mechanical parts. For sensor preparation the complex surfaces at first will be coated by PVD- and CVD-techniques with an insulating layer (typical thickness 4µm and a sensor and circuit layer, with a thickness in the range of some nanometers to a few microns, preferably 200 nm to 300 nm. In case of thermal sensors, the films can be realised with chromium or titanium nitride for example. The layer system wil be completed after micro patterning by a wear resistant top coating. Since selectivity for direct laser structuring is a well known problem, we investigated different combinations of insulating base materials and electricallly conducting thin films. Moreover, an important item was also the variation of the film thickness to be structured. The results obtained at flat substrates were then used for the generation of micro structures on complex shaped mechanical parts. The characterisation of the laser structured micro sensors was done by light- and scanning electon microscopy and profilometry. Other important characterizations were performed by different electrical measurements. This paper will show results on laser structured microsensors for force and temperature measurements in combination with micro-sensors structured by photo lithography and eching for different bearings.