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Topography of features machined into bisphenol A polycarbonate using closed thick film flowing filtered water immersed KrF excimer laser ablation
journal contribution
posted on 2010-08-27, 13:16 authored by Colin F. Dowding, Jonathan LawrenceLaser micromachining with the use of liquid immersion allows debris control. Use of
an immersion technique potentially modifies the ablation mechanism when compared
to laser material interactions in a medium of ambient air. Equipment has been
developed to allow feature machining under a controllable liquid film and thereby
elucidate and quantify and changes in feature topography caused. The findings of this
study revealed that immersion of bisphenol A polycarbonate samples in closed thick
film flowing filtered water during KrF excimer laser ablation markedly altered feature
geometry, waviness and roughness laser machining in ambient air. Feature geometry
definition improved with flow velocity. Waviness was found to be less regular and
less predictable and roughness became fluence dependant. Variation of flow velocity
during immersion resulted in modification of the surface waviness: an optimum flow
velocity exists, producing maximum waviness. Surface roughness displayed a power
law relationship with flow velocity. These observed effects are explained through
examination of the flow – plume interaction: closed thick film flowing filtered water
immersion caused a combination of photomechanical etching promoted by plume
confinement, laser etching and plume distortion by rapid flow velocity. Furthermore,
the influence each of these interactions varied depending on the flow velocity. This is
not an eventuality possible when using an open thin film immersed laser ablation
technique: film rupture and splashing limited the plume etching contribution to the
confined laser ablation process. It is apparent that the changes to feature geometry,
waviness and roughness observed when KrF excimer laser machining under closed
thick film flowing filtered water were brought about directly by the immersion, rather
than by variations in fluence level
History
School
- Mechanical, Electrical and Manufacturing Engineering
Citation
DOWDING, C.F. and LAWRENCE, J., 2010. Topography of features machined into bisphenol A polycarbonate using closed thick film flowing filtered water immersed KrF excimer laser ablation. Lasers in Engineering, 20 (3-4), pp.241-262.Publisher
© Old City Publishing Inc.Version
- AM (Accepted Manuscript)
Publication date
2010Notes
This article was published in the journal, Lasers in Engineering [© Old City Publishing Inc.] and the definitive version is available at: http://www.oldcitypublishing.com/LIE/LIEissuecontents.htmlISSN
0898-1507;1029-029XPublisher version
Language
- en