Process Date: March 2001

250 & 100 micron hole sizes drilled with a Synrad 48-2 CO2 laser with 20 watts of power.

The term "tip processing" has been discussed in previous newsletters, and this concept is expanded here. By using a burst or train of pulses, a precise amount of energy is delivered to the material. The final hole diameter depends on where that matches the threshold of the material on the beam's gaussian profile. Additionally, the number of pulses, duration of the pulse, and pulse frequency all enter into the equation. Small diameter increases can be made by altering the pulse numbers, larger ones by changing pulse duration and/or frequency. Changing the power is optional, and in many cases can be held at a constant value.

In this instance, the focused spot size was around 200 microns, but holes with larger diameters can be produced. The use of excessive pulse power can be used to enlarge the hole by conduction effects. It is worth noting that no assist gas was used in this case, as it can disrupt the drilling process, causing ragged outer edges.
The laser excels at drilling small holes (small defined as less than 0.01" in diameter) - in fact, in most cases, the smaller the diameter, the better, down to a minimum size of about 50 microns. These holes can be directly drilled without the need for trepanning, resulting in reduced drilling times and highlighting one of the unique characteristics of the laser - one laser and one focused spot diameter can produce a range of hole sizes (in a range of different materials). In this instance, the hole diameters ranged from 75 to over 300 microns. This is possible due to two features of the laser - the gaussian mode of the beam, and fine energy input control.