DPSS Lasers Overcome Glass Process Challenges 5
he cross-section cutaway of the holes shows near-vertical sidewalls of the cut and a fine, granular sidewall texture. The holes were processed in two stages, with the laser beam first incident upon one surface of the glass (stage 1) and next upon the opposite surface (stage 2). It can be demonstrated that such a processing strategy offers both quality and throughput advantages as compared with processing from just one side of the glass.
To improve throughput by reducing the volume of glass that must be removed, it is helpful to use two laser beams (either split from a single laser or from two lasers) to simultaneously or serially drill on opposite glass surfaces. Compared with the case of a single laser beam on a single side of glass, a significant reduction in the volume of material to ablate is achieved (Figure 5). Furthermore, as Figure 5 illustrates, two-side processing can reduce the overall taper of the hole as well because the difference between the outer and inner cutting diameters is halved.
For 5-mm-diameter holes similar to those in Figure 3, Figure 6 summarizes the drilling times for each of these three process approaches, clearly demonstrating that significant throughput improvement is gained with processing configurations 2 and 3.
Time, in Seconds, to Cut 5-mm-Diameter Hole in Various Glass Thicknesses
| Process Type |
| 1-mm Thick |
| 2-mm Thick |
| 3-mm Thick |
| One Laser, One Surface |
| 10.2 |
| 31.4 |
| 60.6 |
| One Laser, Two Surfaces |
| 6.2 |
| 18.5 |
| 36.4 |
| Two Lasers, Two Surfaces |
| 3.1 |
| 9.2 |
| 18.2 |
Figure 6. Drill times for 5-mm-diameter holes in 1-, 2- and 3-mm-thick glasses using various processing approaches. Using two lasers triples the throughput. Courtesy of Spectra-Physics.
The challenges of integrating two lasers for simultaneous processing of both surfaces of a glass plate are not trivial, and configuring a single laser to process from both sides is only slightly less complex. But considering the throughput improvements that can be realized, it may be a worthwhile challenge to undertake in many cases.