Surface Of Al₂O₃ Ceramic Metallization With Copper

In this paper,thin Cu₂O films were first produced on Cu foil by electrodeposition at different pH values.Then the Cu₂O side of the Cu foil was closely attached to an Al₂O₃ ceramic substrate and heated to 1075? under N₂ atmosphere,then realized the copper metallization on Al₂O₃ ceramic.Investigated the influence of the the Cu₂O films microstructure and the bonding strength of the Cu/Al₂O₃.The main results are followed:? The microstructure of the Cu₂O films were changed when increased the pH value from 9 to 11 and 12.The pH values had a great impact on the Cu₂O preferred orientation and then the shape of the Cu₂O grains changed from a 4-sided pyramid?relatively small,dense,and uniform?to a triangular prism to a 3-faced pyramid?larger and irregular?when the pH value was further increased;The experiments revealed that the morphology of the Cu₂O films had an effect on the adhesion strength of the Cu₂O/Cu.The adhesion strength declined from 4950 mN to 4712 mN to 3935 mN for pH = 9,pH = 11 and pH = 12,respectively.? The current density also affected the preferred orientation of the Cu₂O grains,which was less influence compared with the pH value;The reaction rate of electrodeposition could be improved when increased the current density,but the Cu impurity was generated in the Cu₂O films;The main growth pattern of the Cu₂O film is island grown,the longer time of the electrodeposition,the thicker and uniformly continuous of the Cu₂O films.But it will affect the bonding strength of the Cu₂O/Cu,if the Cu₂O film is too thick.? The bonding strength of the Cu/Al₂O₃ decreased with increasing pH value after the eutectic reaction.The main reasons: 1)the pH value had a impact on the adhesion strength of the Cu₂O/Cu,which gradually decreased with increasing pH value.The adhesion strength of the Cu₂O/Cu indirectly affected the bonding strength of the Cu/Al₂O₃;2)the Cu₂O films became less uniform and dense,so the gap between Cu₂O film and Al₂O₃ substrate was bigger when the pH value increased,consequently N₂ or O₂ would be detained in the gap during the DBC process.The bigger of the gap,the number and the size of the holes would increase in the Cu/Al₂O₃ interface.i.e.,the actual contact areas between Cu₂O grains and Al₂O₃ substrates were decreased with increasing pH values,the smaller contact areas may reduce the bonding strength of the Cu/Al₂O₃.? The smaller pores with irregular shape may result from the Cu₂O particles remaining at the Cu/Al₂O₃ interface after the eutectic bonding;While the large spherical pores with regular shape are attributed to the presence of N₂ and O₂ during the eutectic reaction,also Cu₂O will decompose to generate O₂ in the condition of high temperature and low oxygen partial pressure;Besides,in this paper,we proposed a method to reduce the interface pores.? The CuO/Cu that produced by the thermal oxidation and the electrodeposition method eutectic reacted with Al₂O₃ substrate,the bonding strength of the latter was greater.? The growth rate of DBC eutectic reaction products is very slow.When the bonding time was short,the main reaction products were mixture of CuAlO₂ and CuAl₂O₄ in the Cu/Al₂O₃ interface,and there was no obvious interface layer;However,the bonding time was extended to 7 h,there was only CuAlO₂ phase,and CuAl₂O₄ phase almost disappeared in the interface,but about 1 ?m discontinuous interface reaction products layer could be observed in the Cu/Al₂O₃ interface.