Fabrication of depth-controlled high-quality holes and lines on a metal surface by nanosecond laser pulses at 1064 nm

For laser micromachining of metal substrates, it is widely believed that an expensive femtosecond laser is necessary to fabricate high-quality holes with very little ablation rims, while the use of inexpensive nanosecond laser suffers from the formation of pronounced ablation rims. We demonstrate that the metal substrate with a metal film is a nice workpiece to realize high-quality nanosecond laser micromachining, and the kinds of metals for the film and substrate may be the same or different. This is because the ablation threshold of a metal film on a metal substrate is much lower than that of the bare metal substrate. Accordingly, under the certain laser fluence range, we can selectively ablate only the metal film while the metal substrate remains intact. The hole fabricated this way is of high quality since it exhibits a nearly flat bottom with well-defined depth and very little rims. Fabrication of high-quality lines is much more challenging, because the metal substrate, without or with a metal film, suffers from the accumulating heat during the repetitive irradiation of laser pulses with a short time interval and sufficient spatial overlap to form a line. In spite of such inherent difficulty, we demonstrate that the selective removal of a metal film from the metal substrate still works reasonably well to fabricate high-quality lines with little structures. The use of metal substrate with a metal film is a simple and effective strategy to significantly improve the performance of cost-effective nanosecond laser micromachining.

Automated summary

In laser micromachining of metal substrates, the use of a metal film on the substrate can result in high-quality nanosecond laser micromachining by selectively ablating the film while keeping the substrate intact. However, fabricating high-quality lines remains challenging.