Portable electronics devices such as mobile phone and portable music player become compact and improve their performance. High-density packaging technology such as CSP (Chip Size Package) 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 stress singularity, which lead to the failure of bonding part in structures.
In the present study, a strain singular field near inter-face edge in three-dimensional joints is investigated using digital image correlation method. A specimen which silicon chip was embedded in resin is used in experiment and tensile load is applied to the specimen. Photograph of specimen surface is taken before and after loadings by laser microscope. Displacement on the surface was evaluated by the digital image correlation method (DICM) using data of surface pattern on the specimen, which the cross correlation coefficients for surface pattern are maximized. Strain on surface of specimen is calculated by using the moving least square method. On the other hand, 3D element free Galerkin method is applied to compute the displacement and strain distribution in a three-dimensional model of the specimen. In the element free Galerkin method, the physical values, i.e., displacement, strain and stress, can be obtained by using the displacement data at node. In this research, strain distribution near the edge of interface is computed based on the element free Galerkin method. Finally, the strain distribution obtained by the digital image correlation method and the moving least square method is compared with that obtained by the element free Galerkin method. The intensity of strain singularity is determined numerically and experimentally.
The Evaluation of Formability of the 3rd Generation Advanced High Strength Steels QP980 based on Digital Image Correlation Method
