Roles of preoxidation, Cu2O particles, and interface pores on the strength of eutectically bonded Cu/α-Al2O3

The influences of CuO layer thickness, Cu2O particles, and pores on mechanical properties and microstructure of alumina–copper eutectic bond have been investigated. The furnace atmosphere in the first stage was argon gas with 2 × 10−6 atm oxygen partial pressure. In the second stage, the furnace atmosphere was same as the first stage except for the cooling interval between 900 and 1000 °C, the hydrogen gas was injected into furnace atmosphere. Finally, in the last stage a vacuum furnace with 5 × 10−8 atm pressure was chosen for bonding procedure. Peel strength of first stage specimens shows that CuO layer with 320 ± 25 nm thick generates the maximum peel strength (13.1 ± 0.3 kg/cm) in joint interface. In the second stage, by using the hydrogen gas, a bond interface free of any Cu2O oxide particle was formed. In this case, the joint strength has increased to 17.1 ± 0.2 kg/cm. Finally, the bonding process in vacuum furnace indicates that the furnace gas does not have considerable effect on joint interface pores. Furthermore, bonding process in vacuum furnace reduces the peel strength of joint due to formation of more pores. Thorough study of pores formation is presented.