PRECISION LASER-BASED DECONTAMINATION OF MICROCAVITIES

The removal of oil-based contaminants from microcavities with narrow a pertures and comparatively long axial dimensions presents a number of challenges in an industrial production line environment. Traditional s olvent-based approaches are costly to implement, inefficient in cleani ng such microcavity geometries, and increasingly unacceptable from an environmental standpoint. An attractive alternative is to employ high- energy laser pulses to selectively remove the contaminants without int roducing damage to the component undergoing the cleaning procedure. Th is paper will present results of initial oblation trials on example in dustrial oil-based organic contaminants whose residues within microcav ities in steel-based components are to be removed. At present, higher order lines from a frequency tripled/quadrupled Nd:YAG laser are used to study the optimum fluence for removal of the oil-based contaminant without inflicting damage to the steel. Absorption spectroscopy of the contaminant fluid indicates that photon wavelengths shorter than simi lar to 370 nm will interact with the material. Initial results show ch at the required intensity at 355 nm (> 25 J/cm(2)) also damages the ty pe of steel under investigation, but that exposure to even single puls es at 266 nm (similar to 100 mJ/cm(2)) shows adequate removal of the c ontaminant without significant damage to the steel. Monitoring of the removal process is achieved through exploitation of the blue fluoresce nce of the oil-based contaminant that occurs as a result of ultraviole t pumping. (C) 1998 Elsevier Science B.V.