In-situ monitoring method of femtosecond laser welding between glass and copper with acoustic emission

Abstract

The use of femtosecond laser welding has created new possibilities for connecting glasses and metals, revolutionizing the fabrication and assembly of advanced electronic components. However, monitoring the connection process during femtosecond laser welding is challenging due to the small heat-affected zone and brief interaction time. This study utilizes acoustic emission to monitor femtosecond laser welding and introduces the “Sum of Relative RMS” feature to correlate connection formation with acoustic emission signals in glass-copper welding. The mechanism and signal occurrence trends during welding are explained through in-situ signal monitoring and offline scanning electron microscopy characterization. Additionally, a Convolutional Neural Network is enhanced by increasing the convolutional kernel size, integrating multi-dimensional features, and incorporating prior knowledge via a customized loss function, resulting in an increase in the accuracy of successful welding detection from 89% to 95%. This research provides new insights into the monitoring of femtosecond laser glass-metal heterogeneous welding.