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Portable electric devices such as mobile phones and portable music players have become compact and improved their peiformance. High-density packaging technology such as chip size package (CSP) and stacked-CSP is used for improving the performance of devices. CSP has a bonded structure composed of materials with different properties. A mismatch of material properties may cause a stress singularity, which leads to the failure of the bonding part in structures. In the present paper, stress analysis using the boundary element method and an eigenvalue analysis using the finite element method are used for evaluating the intensity of a singularity at a vertex in three-dimensional joints. A threedimensional boundary element program based on the fundamental solution for two-phase isotropic materials is used for calculating the stress distribution in a three-dimensional joint. Angular function in the singular stress field at the vertex in the three-dimensional joint is calculated using an eigenvector determined from the eigenvalue analysis. The joining strength of interface in several kinds of sillicon-resin specimen with different triangular bonding areas is investigated analytically and experimentally. An experiment for debonding the inteJface in the joints is firstly carried out. Stress singularity analysis for the three-dimensional joints subjected to an external fo rce for debonding the joints is secondly conducted. Combining results of the experiment and the analysis yields a final stress distribution for evaluating the strength of interface. Finally, a relationship of force for delamination in joints with different bonding areas is derived, and a critical value of the 3D intensity of the singularity is determined. [ABSTRACT FROM AUTHOR]

Abstract: The stress singularity that occurs at a vertex in a joint with a slanted side surface is investigated. The orders of stress singularity at a vertex and at a point on stress singularity lines for various material properties are determined using eigenanalysis. The stress distribution on an interface and the intensity of stress singularity at the vertex are investigated using BEM. It is shown that the order of stress singularity at the vertex in the joints can be reduced by slanting a side surface so as to decrease the angle between the interface and the side surface. The results of BEM analysis reveal that the distribution of stress on the interface is influenced by the slanted side surface. Finally, the 3D intensities of the singularity for stress components which are continuous at the interface are newly defined and determined for various material combinations. [ABSTRACT FROM AUTHOR]

In the present paper, surface Green functions in an anisotropic elastic half-domain subjected to a concentrated force and a line force are derived using Stroh's formalism considering surface stress and surface elasticity. Formulation of the boundary condition based on Stroh's formalism is presented and is used to derive the surface Green functions. The displacement field far from the surface is affected only slightly by the surface stress and elasticity. However the stress field is influenced to a somewhat greater degree by the surface stress and elasticity. The influence of the mechanical properties of the surface on the distributions of displacement and stress near the surface is investigated for various values of surface elastic modulus and surface stress. The surface stress and surface elasticity affect the displacements and stresses, respectively, in different manners. Displacement fields in molecular dynamics are compared with those in the Green function, and it is shown that the results are in fair agreement. [ABSTRACT FROM AUTHOR]

Abstract: The characteristics of the stress fields around a singular point on the stress singularity line of dissimilar materials in three-dimensional joints are investigated using BEM. Contour for the order of stress singularity around the point is mapped on Dundurs’ parameters plane using eigen value analysis by FEM. The results in 3D joints are compared with those in 2D joints having the same cross section and material combination. The order of stress singularity around the singular point on the stress singularity line in 3D joints is almost identical with that in 2D joints in the singularity region. However, the zero boundary of singularity in 3D joints is slightly different from that in 2D joints. Furthermore, the multiple root of p=1 exists in the eigen value analysis by FEM. Therefore, logarithmic singularity possibly occurs around the singular point on the stress singularity line. Then, the stress distributions around this point are expressed by the combination of the rλ term and logarithmic singularity terms. Finally, the characteristics of the stress intensity factors of the rλ term and logarithmic singularity terms around the singular points are investigated. [Copyright &y& Elsevier]

Based on the three-dimensional anisotropic thermoelasticity theory, Green's function solutions are presented for a steady heat source in a two-phase transversely isotropic solid. The mirror reflection method is used and a general expression of the solutions in the Cartesian coordinate system is obtained. It is also shown that the solution includes the special cases of a homogeneous transversely isotropic elastic solid of infinite space and of semi-infinite space. In addition, numerical examples for the titanium-zinc composites are given. [ABSTRACT FROM AUTHOR]

A three-dimensional rest-to-rest attitude maneuver of flexible spacecraft equipped by on-off reaction jets is studied. Equations of motion of the spacecraft is developed by employing a hybrid system of coordinates and Lagrangian formulation. The finite element method is used to examine discrete elastic deformations of a particular model of satellite carrying flexible solar panels by modelling the panels as flat plate structures in bending. Results indicate that, under an unshaped input, the maneuvers induce undesirable attitude angle motions of the satellite as well as vibration of the solar panels. An input shaper is then applied to reduce the residual oscillation of its motion at several natural frequencies in order to get an expected pointing precision of the satellite. Once the shaped input is given to the satellite, the performance improves significantly. [ABSTRACT FROM AUTHOR]

A high-density packaging technology has been developed that uses new flip-chip bonding technology with a thin IC and a thin substrate. Numerical analysis with the finite element method as well experiments clearly showed that deflection of the IC and reliability were affected by the IC thickness. Consequently, reliability could be improved by reducing IC thickness. The dependency of the life in single-sided chip-size packages (CSPs) could be expressed using a normal stress value in thickness, which is computed by the IC thickness and substrate type and thickness. The dependency of the life in double-sided CSPs could be expressed using a shear stress value in the vertical cross section, which is computed in IC thickness and substrate type and thickness, respectively.Moreover, a double-sided flip-chip approach solved the problem of warpage. A high-capacity memory card of 512 MB was put to practical use by applying these results. This increased the Si density by four times over that of a conventional CSP. [Copyright &y& Elsevier]