Technology

Lightmotif uses two different drilling techniques. The drilling technique used for the smallest holes is percussion drilling, where the laser spot is kept stationary on the substrate surface and a defined number of pulses is released. The hole diameter directly depends on the laser spot size, resulting in typical diameters ranging from several micrometers to some tens of micrometers. The diameter at the laser exit side is a bit smaller than the spot size as the holes are tapered. A tapered shape is intrinsic to laser drilling of small holes; it can be reduced by a careful selection of the process settings but not fully avoided. The smallest holes that have been demonstrated have a sub-micrometer diameter at the laser exit side. The example of such a hole shown here was fabricated in a thin titanium foil (for gas leakage tests).

Example of a hole with a sub-micrometer diameter in titanium, made with percussion drilling.

Holes can be drilled in almost any material, with an accuracy in the micrometer range on the position of the hole as well as on the diameter. General advantages are small diameters, high aspect ratios, very smooth side walls, and avoiding burrs or cracks in brittle materials. Typical substrate thicknesses range from a couple of micrometers up to a millimeter.

For making holes that are larger than the spot size a second technique is used, where the laser spot is scanned in a circular or spiral pattern. Below, the exit and entrance of such a hole are shown, with a diameter that is roughly an order of magnitude larger than that of the focused laser spot. These images illustrate the perfectly smooth walls that can be achieved and the absence of burrs.

Entrance of a hole drilled in stainless steel.

The accompanying exit hole.

Examples

Moving the laser spot can also be used to tailor the cross-section of a hole, for example, to machine funnel shapes as shown in the first examples.

The examples of holes drilled in glass show that very sharp edges can be created without cracks or chipping. Compared to powder blasting this method is much milder and results in significantly less tapering.

The hole drilled in a porous polymer sheet shows that because of the low heat input the porosity of the hole walls could be retained.