Development of process modeling methodology for flip chip on flex interconnections with non-conductive adhesives

This paper presents a comprehensive methodology to model the assembly process of flip chip on flex interconnections with non-conductive adhesives (NCAs). The methodology combines experimental techniques for material characterization, finite element modeling, and model validation. A non-conductive adhesive has been characterized using several techniques. A unique experimental technique has been developed to measure the cure shrinkage. A 2D axisymmetric finite element model is used for analysis of flip chip on flex package with the non-conductive adhesive (NCA), which takes into account assembly force, cure shrinkage, adhesive modulus buildup, removal of assembly force, and cooling down to room temperature. The relationship between the bump contact resistance and the bump pressure has been established through the development of a dedicated experimental setup, which uses a micro-force tester combined with a digital multimeter and a nano-voltmeter. The process modeling has been validated by comparing the predicted bump contact resistance value and the measured bump contact resistance value after assembly process. The approach developed in this paper can be used to provide guidelines with respect to adhesive material properties, assembly process parameters, and good reliability performances.