Characterizing Non-Conductive Adhesives using Finite Element Analysis: Residual Stress Determination

ABSTRACT This study aims to establish a methodology for determining the residual contact stress developed during fabrication of nonconductive adhesive (NCA) bonded flip-chip-on-flex (FCOF) microelectronics systems. The method is demonstrated for a selected non-conductive adhesive. Fabrication of an NCA bonded FCOF system requires a compressive force large enough to compensate for the inherent coplanarity differences in chip bump heights. This paper investigates a method for determining the residual contact stress in the flip-chip bump and flexible substrate pad interconnects. This is done via a global-local methodology using finite element simulation, with results to be compared with forthcoming experimental data. The magnitude of the residual compressive contact forces is key to the performance and durability of the interconnects under life cycle loads, as it serves as an “initial condition” for the degradation of interconnect stress.