Thermomechanical stress analysis of Flip-chip-on-flex (FCOF) has been investigated. The effect of bonding pressure on the reliability is analyzed. Key findings are: shear forces are the dominant forces acting across the interconnect and govern the reliability of the package, FCOFs bonded at higher pressures develop lower shear stress and packages with higher bump heights exhibit better performance. This study encompasses testing of packages under thermal shock treatment and results being verified by a 2D linear elastic model. Parametric studies that might provide useful design guidelines are also included.

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