Towards process control by detecting acoustic emissions during ultrashort pulsed laser ablation of multilayer materials

C. Lutz; R. Sommerhuber; M. Kettner; C. Esen; R. Hellmann

doi:10.1117/12.3000954

12 March 2024 Towards process control by detecting acoustic emissions during ultrashort pulsed laser ablation of multilayer materials

C. Lutz, R. Sommerhuber, M. Kettner, C. Esen, R. Hellmann

Author Affiliations +

Proceedings Volume 12873, Laser-based Micro- and Nanoprocessing XVIII; 128730U (2024) https://doi.org/10.1117/12.3000954
Event: SPIE LASE, 2024, San Francisco, California, United States

Abstract

We report on process sensing using a membrane-free optical microphone to monitor the acoustic emission during ultrashort pulsed laser ablation of multilayer materials. The acoustic emission during ablation is used to detect material transitions, with the specific signatures allowing to create a reliable process control for identifying individual layers. The outstanding properties of membrane-free optical microphones in terms of high bandwidth and high temporal resolution are ideally qualified for characterizing an ultrashort pulsed laser process, with its properties and capabilities being presented in this contribution. In particular, for layer- and material-selective ablation of multilayer printed circuit board components, copper and polyimide layers are ablated and the material transition is detected by analyzing the acoustic signal at different frequency levels, which is a novelty in the field of ultrashort pulsed laser process sensing. The investigations show that the optical microphone can be used to resolve both the scanning paths and ablated layers by means of interruptions in a time-resolved acoustic spectrogram. Furthermore, as a result of a higher ablation rate of polyimide compared to copper and thus the increase of the emitted acoustic energy, the material transition between copper and polyimide layers can clearly be detected. The detection of this process event can be used for process control.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

C. Lutz, R. Sommerhuber, M. Kettner, C. Esen, and R. Hellmann "Towards process control by detecting acoustic emissions during ultrashort pulsed laser ablation of multilayer materials", Proc. SPIE 12873, Laser-based Micro- and Nanoprocessing XVIII, 128730U (12 March 2024); https://doi.org/10.1117/12.3000954

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