09. Heat and Mass Transfer

Ultrashort pulse laser processing has a complicated physical picture compared to long pulse laser processing especially when the pulse width within the regime about 10 ps. The ablation evolution includes various mechanisms, such as the electron-lattice non-equilibrium and the nonlinear optical phenomena. This study presents a comprehensive numerical model on the ultrashort pulse laser processing to predict and optimize the micro hole drilling which is of paramount importance for electronics packaging applications. We integrated the two-temperature model (TTM) and fluid dynamics to study heat and mass transport in the electron-lattice non-equilibrium regime. The energy transfer and non-equilibrium state between electron and lattice are modeled by two-temperature model. The material deformation mechanisms, such as melting, vaporization and solidification are implemented by modeling fluid dynamics, in which we applied the volume of fluid (VOF) technique to capture the interface between different phases. This hybrid model allowed us to predict better the energy flow and associated material response compared with the single models. We also investigated the influence of laser parameters which affect the morphology of the ablation hole. Ablation hole depth is discussed through changing the laser pulse width, laser fluence and number of laser pulses. This research refines the modeling of the ultrashort pulse laser ablation and improves the study of laser processing quality for industrial demands.