Assembly process modeling for flip chip on flex interconnections with non-conductive adhesive

This paper presents a comprehensive methodology to model the assembly process of flip chip on flex interconnections with non-conductive adhesive (NCA). The methodology combines experimental techniques for material characterization, finite element modeling and model validation. The non-conductive adhesive material has been characterized using several techniques. A unique experimental technique has been developed to measure the cure force. A 2-D axisymmetric finite element model is used for analysis of flip chip on flex package with nonconductive adhesive, 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 contact pressure obtained from finite element simulation and the measured bump contact resistance has been established through the development of a dedicated experimental setup, which uses a microforce-tester combined with a digital multimeter and nano-voltmeter. The process modeling has been validated by comparing the predicted contact resistance value and the measured 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.