Functional copper plating

A Cu skin film is formed of an aggregate of Cu crystals. Pyramid-shaped Cu crystals (Fig 4) and/or conical Cu crystals (Fig 5) exist in the surface of the Cu skin film. The area rate A of the pyramid-shaped Cu crystals, the area rate A of the conical Cu crystals or the sum A of the area rates of these Cu crystals in the skin film surface are set in a range of A * <------ solidus * 40 %. If such a film is formed, on a surface opposite from that surface of a backing of a slide bearing which is opposed to a rotary shaft, the film exhibits good oil retention and therefore seizure due to fretting can be avoided. Alternatively, the film can be used in heat- or light-absorbing applications. The film is made by an electrolytic plating process.