2010 Volume 4 Issue 7 Pages 1027-1039
In the present paper, an influence of interlayer thickness on the singular stress field in 3D adhesive joints with three layers are investigated using eigen analysis formulated by finite element method (FEM) and boundary element method (BEM) using fundamental solutions for two-phase materials. A model for analysis is a three-layered block joint composed of Si, resin and FR-4.5 (Flame Retardant type 4.5, a kind of glass epoxy resin), which constitutes CSP (Chip Size Package) in the electric device. All stress components are expressed as spherical coordinate systems where their origins are located at the vertex of each interface. Firstly, the orders of stress singularity for vertex and lines characterizing singular stress fields are calculated from eigen analysis. Secondly, distributions of stress for the model subjected to an external load are calculated using BEM. Then, the intensity of singularity is derived from these results. Furthermore, 3D intensity of singularity is determined for evaluating a bonding strength in the 3D three-layered bonded joints. A relationship between the 3D intensity of singularity and the thickness of interlayer is finally examined. It was found that the 3D intensity of singularity becomes a small value when the interlayer thickness reduces, and the 3D intensity of singularity attains an upper limit when the interlayer thickness is larger than the width of the model.
