Product Code: ICAL05_1204

CO2 Laser Welding Fused Silica
Authors:
Danny MacCallum, Sandia National Laboratories; Albuquerque NM USA
Gerald Knorovsky, Sandia National Laboratories; Albuquerque NM USA
Presented at ICALEO 2005

The feasibility of laser welding of fused silica (aka quartz) has been demonstrated recently by others. An application requiring hermetic sealing of a thin, pressure-bearing quartz diaphragm to a thicker frame led us to explore this technique. We found that laser welding techniques normally used for metallic parts caused scorching and uneven melting. Contrary to ?standard? practices (near focus, high travel speed, high power density), successful welds in fused silica required a broad heat source applied over a large area under a slow rotation to gradually heat the glass through the annealing, softening and finally working temperatures. Furthermore, good mechanical contact between the parts to be joined played an even more important role in this process than in typical metallic joints.

A 50 W CO2 laser with 4? f.l. ZnSe2 lens and rotary head was used to weld 0.425? OD, 0.006?0.010? thick, disks to 0.500? OD tubing with 0.125? walls. Several joint geometries and beam orientations were investigated. Temperature profiles were measured and compared to an FEM thermal model. We will discuss the effects of laser power, travel speed, number of passes, joint geometry and part thicknesses on achieving hermeticity and cosmetically-acceptable joints.

* Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.