Surface Patterning of Aluminum Using Pulsed-YAG Laser

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Aluminum specimen covered with porous anodic oxide films was irradiated with a pulsed Nd-YAG laser in solutions containing metal ions, and then electro- or electroless- plating was carried out. Fine pattern was produced on an insulating organic board by the successive processes of anodizing, laser irradiation, metal deposition, insulator gluing, and metal substrate dissolution.The main results obtained in this investigation are in the following.1) Reaction during laser irradiationIt was found that laser irradiation causes the anodic oxide film to be removed effectively from the substrate at the laser-irradiated area, and that the film removal can be explained in terms of the laser ablation of the metal substrate. Spot size, D, and line width, W, of laser irradiated area was examined as the functions of laser power, distance between lens and specimen, and focal length of lens, and the D and W was found to be controlled in the range 15- 500 mm.During laser irradiation in solutions contai … More ning Pd2+, Cu2+, and Ni2+ ions, fine particles of metals, Pd, Cu, and Ni, deposited on the surface at the laser-irradiated area, and this was verified by XPS and rest potential measurements. This is due to the redox reaction between metal ions and the aluminum substrate.2) Metal deposition after laser irradiationDuring cathodic polarization of the specimen in the solution containing Cu2+ or Ni2+ ions after laser irradiation lead to the deposition of a dense layer of Cu or Ni only at the film-removed area. The current efficiency for Cu or Ni deposition was about 100 %.Localized electroless plating of Ni-P was also accomplished at the laser-irradiated area by changing the Pb2+ ion concentration in the electroless plating solution. At the initial stage of the Ni-P electroless plating, the fine particles depositing during laser irradiation were observed to act as nuclei of Ni-P deposition. The Pd particles enhanced Ni-P deposition very much, while Cu particles did not show any effect.3) Fine patterning on organic insulating boardBy computer control, fine patterns could be drawn, using Ni and Cu deposition after laser irradiation on aluminum. The patterned specimen was glued on a glass fiber-reinforced epoxy resin board, and the metal substrate was removed by dissolution in NaOH solution. The successive processes showed a possibility of the development of a new technology in the printed wiring board manufacturing industry. Less