Metallization of Oxide/Hydroxide Film of Aluminum : the Palladium Activation Techniques

Palladium-activation-based techniques for area-selective microscale metallization on porous oxide film of aluminum and complete metallization of the oxide/ hydroxide surface of aluminum are demonstrated. For area-selective metallization, a porous anodic oxide film of aluminum was colored in an organic dye solution containing small amounts of palladium acetate. It was then hydrothermally sealed, thereby trapping the palladium acetate underneath the newly formed crystalline hydroxide layer. Removal of the surface hydroxide layer using a laser beam, exposes the palladium acetate, which also undergoes photothermal decomposition and reduction to metallic palladium and acts as a catalytic center for subsequent electroless plating. Similarly, complete metallization of the porous oxide and hydroxide of aluminum were performed by adsorbing palladium acetate onto the surface, followed by electroless nickel plating of the specimen. Here, palladium acetate (on the surface) was first reduced to metallic palladium by the hypophosphite that is present in electroless plating solution, providing a catalytic center subsequent electroless nickel deposition.