Finite element simulation of thermal stress during diffusion bonding of Al₂O₃ ceramic to aluminium

The development of thermal stress during the diffusion bonding of Al₂O₃ ceramic to aluminium is analysed via the finite element analysis method using a commercial software package, namely, MARC/MENTAL. Before diffusion bonding, a 0.2 mm copper layer is sintered onto the ceramic. The results show that shear stress concentration exists in the ceramic near the corner of the Al₂O₃/Cu interface, and tensile stress concentration occurs near the corners of the Al₂O₃ outer surface when the sample cools from bonding temperature to room temperature. When the concentrated tensile stress on the Al₂O₃ undersurface increases to a certain value, the ceramic will deform gradually, which results in stress relaxation. The stress relaxation originates in the stress concentration region of the Al₂O₃ outer surface.