SURFACE PROCESSING & ABLATION

 LASERS FOR SURFACE PROCESSING & ABLATION

Pulsed Nd:YAG lasers are used in a wide variety of materials processing applications. As well as obvious industrial applications such as cutting and welding, surface treatment is increasingly being done with lasers.

Litron pulsed Nd:YAG lasers are in use at semiconductor plants for deflashing. This involves the selective removal by ablation of surplus resin encapsulation material from the lead frames of packaged chips. 532nm is used as it is strongly absorbed by the resin but reflected by the metal lead frames. Using the differential absorption between a substrate and contaminant, the technique is extended to cleaning of a variety of materials, such as stone, paper and even works of art without the use of chemicals or abrasives.

Laser shock peening is analogous to shot peening to harden metal surfaces. An intense Q-switched pulse is sufficiently absorbed to create a shock wave, which propagates through the material causing work hardening.

Lasers are also used for annealing materials during manufacture. A metal absorbs heat from a laser beam and this heat treatment can be used to reduce the brittleness of cast components.

Pulsed laser deposition (PLD) is a technique where a surface coating can be created using the interaction between a laser and a gas containing the material to be deposited. Examples include photodissociation of silane to create a silicon film or of methane, which under special temperature and pressure conditions can yield a diamond film.