Microdeformation analysis of packages and interconnects to improve finite element models for reliability assessments

The quality of mechanical modeling is of essential influence on the success of finite element analysis (FEA) and of subsequent studies of failure mechanisms. Missing knowledge about time and temperature dependent material behavior often leads to uncertainties in constitutive material description of rather complex structures like filled underfills or organic substrates. Micro deformation measurement methods help to overcome the problem by supplying displacement and strain fields comparable with FEA results. MicroDAC is an established versatile measurement tool for local and global deformation analyzes on thermally or mechanically stressed specimens. The paper presents the basics of the microDAC concept and different kinds of measurements on chip scale packages (CSP) and on flip chip assemblies to illustrate the application to integrated circuit (IC) packaging. A modified microDAC algorithm has been used to determine coefficients of thermal expansion (CTE) at small sized material samples and materials of anisotropic CTEs.