Process Date: June 2003

When drilling hole diameters significantly larger than the focused spot size, a method known as trepanning is used. Trepanning involves moving the laser beam in a circular path to effectively cut out the hole. Depending upon the size of the hole required, beam movement can be achieved using rotating optics, or more commonly, by simply moving the material or the laser beam while cutting.

The hole shown in the photo to the left was made at a speed of 10 inches per minute (IPM) using 25W of power, due to the limitations of the particular X-Y stage used for applications testing. While trepanning, the laser was pulsed at 60 Hz with a pulse length of 4.9 milliseconds (ms). Straight-line cuts on the same material were achieved using 50W of power at a speed of 40 IPM, as the laser was pulsed at 240 Hz with a pulse length of 1.24 ms. Cut edges exhibited only a small amount of dross.

The beam was delivered by an X-Y stage using a 2.5" positive meniscus lens that provided a 0.004" diameter spot with a 0.07" depth of focus. 40 PSI nitrogen was used as the assist gas. It should be noted that identical parameters (speed, power, etc.) were set when performing cuts on a 0.010"- thick sheet of ceramic.

This 0.014" diameter hole was trepanned through a sheet of 0.005"-thick ceramic.