Abstract:

This study aims to establish a methodology for determining the residual contact stress developed during fabrication of non-conductive adhesive (NCA) bonded flip-chip-on-flex (FCOF) systems. The method is demonstrated for a selected non-conductive adhesive, and uses previous work on the determintation of the bonding forces required due to variability of the bump height. The magnitude of the residual compressive contact forces is key to the performance and durability of the interconnects under life cycle loads. Key findings include: the accuracy of the simulation is very sensitive to the accuracy of the gold and flex constitutive models used; the inclusion of viscoelastic properties for the epoxy has a dramatic effect on simulations; and better stress development comes from a higher concentration of short bumps than tall bumps.

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