Product Code: ICAL07_1205

Influence of Incident Angle on Laser Drilling
Authors:
Schneider Matthieu, LALP; arcueil France
Laurent Berthe, LALP; ARCUEIL France
Maryse Muller, LALP; ARCUEIL France
Remy Fabbro, LALP; ARCUEIL France
Presented at ICALEO 2007

Laser drilling is able to use as an industrial process for several tens years. However, inherent factors due to laser source, material properties and dynamic of the process are still making physical understanding very difficult. Moreover mistake on measurements can be made with the established diagnostics, especially for deep holes. This paper deals with the study of holes properties drilled by laser with the HL201P from TRUMPF. It ensures top hat distribution in focal plane with constant diameter. The DODO (Direct Observation of Drilled hole) method is used as post-mortem metallographic analysis. This method solves most of the problems of traditional methods. It a very fast procedure and ensures an easy matching of the analysis plane with the drilling axe. So, this paper presents a physical comprehension based on parametrical study. The hole shape evolution is describe as a function of laser parameters and pulse number. It is classified in two categories, called U and V shape. We show with a physical description, hole can be drilled without any recast layer cracking for specific laser parameters. The repartition of peak power is adjusted in the sequence of pulses in order to eliminate the recast layer cracking. This problem results from the solidification of a melt layer located above a previous recast layer. To eliminate it, it is essential to remelt the previous recast layer with higher peak power pulse. We show the recast layer thickness is below 10 µm for a hole drilled with a single pulse and in the range of 50 µm for multi-pulse drilled hole. We show the relative influence of incident angle between normal incidence and a 30° angle. And finally, we show what our recommendations are for a good laser drilling hole quality.