STUDY OF IMPACT STRESS OF CSP SOLDER JOINTS USING HOMOGENIZATION METHOD AND FEM DROP-SIMULATION

摘要

The relationship between the three-layered stacked vias in a build-up substrate and the impact stresses of chip size package (CSP) solder joints were examined using the homogenization method and the finite element method (FEM) drop-simulation by implicit method. The homogenization method which is known as a multiscale method and has been used in only medical areas until now. A model of the stacked vias was evaluated for the equivalent material property of the elastic modulus by the homogenization method. Instead of modeling many vias, the equivalent value was used for the area of the periodical vias in the build-up substrate model. Therefore, this drop-simulation did not require actual via models, and the model of the substrate could be reduced by the volume of the meshes. The results of the drop-simulation indicated that the equivalent material property of the vias had a large impact on the increase in the stresses of CSP solder joints.