Molecular dynamics-guided quality improvement in the femtosecond laser percussion drilling of microholes using a two-stage pulse energy process

During percussion laser drilling, the taper of microholes is commonly considered to be difficult to control due to cluster re-solidification at the bottom of the hole. Due to the lack of detailed analysis and understanding of ablation clusters, accurate control of the cluster behaviour in the ablation plume has not been realized, resulting in limited taper control in femtosecond laser percussion drilling. To address this issue, molecular dynamics (MD) simulation is used to analyse the cluster behaviour during femtosecond laser ablation in detail. More importantly, the results provide guidance for the optimization of the femtosecond laser percussion drilling technology. The evolution of clusters of various sizes is described in detail at the atomic scale, and the effect of the energy on the cluster size and ablation ratio is discussed. Furthermore, based on the guidance of MD, a two-stage pulse energy percussion drilling process is proposed. The pulse sequence of femtosecond laser percussion drilling is divided into two stages, where the second stage energy is higher than the initial stage energy. For blind holes, an increase in the pulse energy reduces the average size of the clusters in the ablation plume and promotes the upward removal of clusters. A second increase in the pulse energy when the hole breaks through to the exit side of the sample promotes the downward removal of clusters. The two-stage pulse energy percussion drilling process provides a new method for controlling the behaviour of clusters during femtosecond laser percussion drilling, reducing the re-solidification of clusters and ultimately reducing the taper of microholes.

Automated summary

By using molecular dynamics simulation to analyze cluster behavior during femtosecond laser ablation, a two-stage pulse energy percussion drilling process has been proposed to effectively control cluster behavior and reduce the taper of microholes.