XPS investigation on Upilex-S polyimide ablated by pulse TEA CO2 laser

Laser ablation of Upilex-S polyimide films 80 mum thick was performed in ai r using a pulse TEA CO, laser with wavelength 9.3 mum. A halo surrounding t he hole was observed, which is covered with sub-micro particles. Pieces of ablation products protrude from the ablated surface, leading to considerabl e roughness of the ablated area. Chemical and structural changes of Upilex- S polyimide film surface irradiated by the pulse TEA CO, laser in air were analyzed by X-ray photoelectron spectroscopy (XPS). Relative C content in t he ablated area was found to be higher, whilst both O and N contents were l ower than in the untreated area. This means that TEA CO2 laser ablation rel eased both the O and N atoms. Also, the peak areas corresponding with carbo nyl group (C=O) in the imide system were reduced much more and a new compon ent at 287.0 eV assigned to the amide structure (N-C=O) was detected after laser ablation. These suggest that the pyrolysis of the Upilex-S polyimide was the decomposition of the imide ring between the nitrogenlaromatic carbo n atom and carbonyl carbon atom- In addition, another new component arising from >C=O groups was also detected for higher fluence (7.83 J/cm(2)), and its peak areas is very small. This result indicates that the slight oxidati on may take place with higher fluence, during laser ablation in air. Based on above-mentioned experimental results, a possible thermally-induced decom position path of Upilex-S polyimide ablated by TEA CO2 laser is presented. (C) 2001 Elsevier Science B.V. All rights reserved.