Nucleation of metals on aluminum by laser irradiation and the effect on Ni-P electroless deposition

The mechanism of direct Ni-P electroless deposition on aluminum by pulsed yttrium aluminum garnet (YAG) laser irradiation in Ni2+/H2PO2- solution was investigated by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) with energy-dispersive X-ray (EDX) analysis. Aluminum specimens covered with porous anodic oxide films were irradiated with a pulsed YAG laser in solutions containing Pd2+, Cu2+, Ni2+, or Ni2+/H2PO2- ions, and then localized Ni-P electroless plating was attempted at the laser irradiated area in Ni2+/H2PO2- solution. It was found that laser irradiation in solutions containing Pd2+, Cu2+, or Ni2+ ions causes the deposition of small metallic particles of Pd, Cu, or Ni at the laser-irradiated area on the aluminum surface which was exposed to the solution after removal of anodic oxide film. The deposition of the metals is due to a redox reaction between the aluminum substrate and the Pd2+, Cu2+, or Ni2+ ions. During laser irradiation in Ni2+/H2PO2- solution, Ni-P and Ni were deposited by redox reactions between Ni2+ and H2PO2- as well as between Ni2+ and Al. Palladium and nickel (Ni-P) particles deposited during the laser irradiation acted as catalytic centers for the subsequent Ni-P electroless plating, while Cu particles did not promote the electroless plating. (C) 1999 The Electrochemical Society. S0013-4651(98)11-019-4. All rights reserved.