Abstract: A novel method for directly bonding a copper plate to an alumina substrate is disclosed. Also disclosed is a process by which bonded assembles of copper plate and alumina substrate can be produced in large volumes on an industrial scale in high yield and at low cost employing a simplified sequence of steps. According to this process, a copper plate is positioned in contact with an alumina substrate in an inert atmosphere, and the combination is heated to a temperature lower than the melting point of copper (1,083.degree. C.), preferably to a temperature lower than the eutectic point of copper-copper oxide eutectic, for example, to 1,063.degree. C..+-.0.5.degree. C.