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Title: Laser ablation of Upilex-S polyimide : influence of laser wavelength on chemical structure and composition in both ablated area and halo
Authors: Yung, KC 
Zeng, DW
Keywords: Laser ablation
Upilex-S polyimide
X-ray photoelectron spectroscopy (XPS)
Issue Date: 2001
Publisher: Elsevier
Source: Surface and coatings technology, 2001, v. 145, no. 1-3, p. 186-193 How to cite?
Journal: Surface and coatings technology 
Abstract: Blind craters (diameter 200 μm) on Upilex-S polyimide films (80-μm thick) were drilled by irradiation with three different laser systems [KrF excimer: wavelength λ = 248 nm (UV); acoustic optical Q-switch Nd:YAG: λ = 355 nm (UV); and TEA CO 2: λ ≈ 9.3 μm (IR)] in air. Modifications of chemical structure and surface morphology in both the ablated area and halo were examined using X-ray photoelectron spectroscopy (XPS) and a scanning electron microscope (SEM). In the halo, nano-particles were observed with UV lasers, but submicro-particles were observed with the IR laser. The results of XPS analysis show that the C content increased, while the O content and N content decreased in the ablated area at all wavelengths, due to photo-thermal or photochemical decomposition of polyimide. These are substantiated by decreases of the carbonyl groups (C=O) at 288.2 eV and an increase of C-C groups at 284.8 eV. However, the N content in the ablated area with TEA CO 2 laser is higher than that with UV lasers. Also, amide groups were detected in the ablated area with TEA CO 2 laser and 355-nm Nd:YAG laser, but few with 248-nm excimer laser. Furthermore, in the halo, the O content with the 355-nm laser is higher than that of the 248-nm laser. Also, the shoulder of C 1s peak was observed at 288.5 eV in the halo due to oxidation of fragments erupted from the plume in air, but did not occur at the 248-nm wavelength. These findings indicate that the chemical structure and composition are highly dependent on laser wavelength.
ISSN: 0257-8972
EISSN: 1879-3347
DOI: 10.1016/S0257-8972(01)01295-6
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