Gold alloys for resin bonding including small amount base metals--structural changes of alloy surface by the high-temperature oxidation.

To achieve durable bonding with adhesive resin, the surface roughness and the kinds of oxides, respectively to increase mechanical retention to enhance the chemical affinity of adhesive monomer with the gold alloy, were regulated by high-temperature oxidation together with the addition of small amounts of base metals. Alloys containing 2 mass% of Ni, In, or Cr with Cu were oxidized at 800 degrees C for 20 min in air, pickled in thioglycolic acid, and subsequently oxidized at 500 degrees C for 10 min in air. The morphology of the internal oxidation zone changed markedly according to the added base metals. Although the internal oxide particle composed of only Cu2O was removed by pickling, NiO, In2O3, and chromium oxides could not removed and remained on the alloy surface. The surface roughness was increased by addition of Ni, In, or Cr. Applying the present method can control the roughness and chemical states on a gold alloy surface to increase its adhesive ability with adhesive resins.