Alumina-Copper Eutectic Bond Strength: Contribution of Preoxidation, Cuprous Oxides Particles and Pores.

The influences of cupric oxide layer thickness, cuprous oxide particles and pores on the mechanical properties and microstructure of an 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 the same as the first stage except that the cooling interval was between 900-1000°C and the hydrogen gas was injected into the furnace atmosphere. Finally, in the last stage, a vacuum furnace with 5 * 10^-8 atm pressure was chosen for the bonding procedure. The peel strength of first stage specimens shows that a cupric oxide layer with 320 (plus-minus) 25 nm thickness generates maximum peel strength (13:1 (plus-minus) 0:3 kg/cm) in the joint interface. In the second stage, by using hydrogen gas, a joint interface free from any cuprous oxide particles was formed. In this case, the joint strength has increased to 17:1 (plus-minus) 0:2 kg/cm. Finally, the bonding process in the vacuum furnace indicates that the furnace gas does not have a considerable effect on joint interface pores. Furthermore, the bonding process in the vacuum furnace reduces the peel strength of the joint due to the formation of more pores. A thorough study of pore formation is presented.