Ultra-short pulsed laser ablation enables a defined generation of micro-holes. A parameter study on the ablation characteristics of copper clearly reveals a benefit for green wavelength with lower threshold fluence, simultaneously increasing the Rayleigh length. The use of a circular drilling method allows a defined manufacturing of micro boreholes and micro through-holes with 35 μm diameter of up to 165 μm and 300 μm length. Introducing high-resolution micro-computed X-ray tomography studying the micro-hole evolution and adjacent geometrical transformations reveals micrometer resolution and high usability. The conical geometry evolving up to an aspect ratio of 5:1 fits well to established models known for percussion drilling. However, increasing the number of pulses leads to non-conical geometry evolution, and this resulting geometry is studied for the first time. Henceforth, the exact geometrical evolution from conical to cylindrical shape upon laser drilling can be resolved revealing the impact of multiple reflections at the generated steep flanks.

The original article contained a mistake. Section 1 Introduction& The unit of power density (W cm s −2 ) is incorrect.Correctly, it must be W cm −2 . Section 2.1 Material and machine & The dash in 515-nm is not correct. Correctly, it must be 515 nm.Section 2.2 Circular path laser drilling & The b in the formula symbol of hatching distance lb. is not subscripted. Correctly, it must be l b . & The path of the laser beam is termed by d hatch . Correctly, it must be d path as in Fig. 1. & The total diameter of the surface irradiated with the laser is termed by d hole . Correctly, it must be d as in Fig. 1. & The eq. (1) is incorrect. Correctly it must be d path = d − d foc Caption in Fig. 1.The FOV in the formula symbol of the length of the field of view lFOV is not subscripted. Correctly, it must be l FOV . Section 3.4 Through-hole of 300 μm depth. The dash in 300-μm is not correct. Correctly, it must be 300 μm.