Melt dynamics and hole formation during drilling with ultrashort pulses

Abstract

Drilling with ultrashort laser pulses is a suitable technique for the production of micro-holes with high aspect ratios. For best quality an appropriate drilling strategy, e. g. helical drilling, has to be applied. The reasons for improved hole quality compared to percussion drilling are investigated. Melt transport is studied using special sandwich samples consisting of iron and nickel layers. Spa-tially resolved EDX analysis of the deposited melt helps to estimate the mechanism of melt trans-port. It seems that the melt expulsion at the beginning of the process which is responsible for the burr formation is more efficient in the case of percussion drilling than for helical drilling. The qual-ity advantages of helical drilling are assumed to result from a different hole geometry during proc-essing.