Laser spot welding is a non-contact process which uses a laser to create a single weld spot to weld metals together. Lasers are capable of delivering a pulse of light with accurate, repeatable energy and duration. When the pulse is focused into one place - a small spot - (adjustable anywhere from approximately 0.1 to 2.0 mm in diameter) on the part, the energy density becomes quite large. The light is absorbed by the material causing a "keyhole effect" as the focused beam drills into, vaporizes, and melts some of the metal. As the pulse ends, the liquefied metal around the keyhole flows back in, solidifying and creating a small spot weld. This entire process just a few milliseconds.
Lasers can fire many pulses per second, and, by moving either the work piece or optics, allow either separate "spot" welds or a series of overlapping spot welds to create a laser seam weld that can be structurally sound and/or hermetic.