Inline quality control system for functional conductive 3D printing (PROPRIIS)

• Applicants: Professor Dr.-Ing. Welf-Guntram Drossel; Professor Dr.-Ing. Henning Heuer
• Subject Area: Production Automation and Assembly Technology ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525389037

The global trends of product customization and shorter life cycles present new challenges to the manufacturing industry. In order to guarantee the inquired customized functionality and to increase the autonomy of systems, the number of integrated sensors and actuators is constantly growing. This increases the demand for flexible production lines, while the problem of an adaptive integration of components and connectors remains unsolved. The automotive, aerospace, medical technology and household sectors are main examples of industries facing the challenges mentioned above. Digital drop-on-demand printing, such as ink-jet or jet-dispensing, is one of the possible solutions to these challenges. These technologies offer flexible integration and application of printed circuit boards, sensors, antennas, heating structures or actuators by printing functional inks or pastes directly onto the various complex-shaped components. This is a prerequisite for equipping parts with sensors and conductive functional structures without the need for assembly work. A conventional drop-on-demand production process consists of the printing process and the thermal post-treatment of the printed structures. During these technological stages inaccuracies of the printing and post-treatment processes occur, therefore drop-on-demand printing does not provide stable reproducibility and quality of the printed structures, which is one of the main reasons of limited application of such technologies. In order to automatically detect the rate of defects (with the concept of Industry 4.0), which occur during the printing and post-treatment process, the authors suggest to develop an inline measuring system, for quality control of tiny printed structures, based on the signals fusion of inductive impedance spectroscopy, laser geometry measurement system and pyrometry. The chosen non-destructive methods will provide geometrical and electrical data in each coordinate along the printed path. To achieve correct electrical data the influences of temperature variation and the lift-off of the eddy current sensor have to be compensated. The first challenge of the project is to develop and produce a high frequency eddy current sensor, sensitive to the tiny printed structures in a wet state. The laser system and pyrometer will be chosen from the available systems on the market. The second challenge is to create an empirical model for quality control of the conductive path, which fuses the geometrical and electrical signal data. The model determines the morphology and real conductivity (compensating lift-off and temperature influence) of the printed structure in each coordinate along the path in order to estimate if any morphological defect or deficiency of the post-treatment happened. The developed system is transferable and can be used for quality assurance of paths or patterns, applied by various printing techniques, which use of different conductive pastes.

• DFG Programme: Research Grants