Laser patterning of thin film strain gauges

Current trends of intelligent products and controlled processes show an increasing need for long-living sensors. Metal thin-film strain gauges are suitable for monitoring mechanical loads over the entire lifetime of a component. However, existing manufacturing methods can only pattern these gauges on flat components and in large quantities to ensure an economical process. To overcome these limitations, a patterning process based on ablation using picosecond laser pulses has been developed and is the subject of this paper. Starting with the analysis of the ablation behavior of the sensing and insulation film, a process window is derived. The sensing properties and the achievable reproducibility are characterized and a trimming process to improve the reproducibility of the patterning process is developed. The pattering process developed is an important prerequisite for the integration of thin-film strain sensors on 3-D surfaces for products such as bearings, or in products which are typically manufactured in small quantities, such as medical implants.