FEM analysis of distribution of thermal stresses at sapphire/kovar alloy brazed joint

Using ANSYS finite element software, the stress field and temperature field of brazed joint which brazing filler metal is Ag-Cu-Ti8 was simulated between Sapphire and kovar alloy by the means of elasticplastic analysis. It is simulated that the different positions temperature has changed and filler metal thickness has effect on residual stress and its distribution. It is concluded that the best radial tensile stress of sapphire is 538 MPa in peripheral surface and extends to the border. The calculation results suggested that the real fracture pattern was consistent with the analysis of the finite element method. When the filler metal thickness is 150 μm, this would be lowest stress. Brazing parameters were optimized so that the reality brazing process can be operated .