This paper presents lifetime predictions, based on Finite Element Analysis (FEA), for the copper via connectors present in High Density Interconnectors (HDI) used for mounting of CSP's. The life-saving impact of various fillings of these connectors is investigated using different FEsub-models for capturing the intricate HDI substructure. A ranking of the impact on lifetime of the various fillings is presented. Moreover, the structural integrity of the solder bumps of a flip chip structure with and without underfill is examined using FE. It is demonstrated analytically that the underfill may lead to an improvement in lifetime of 300% and more.

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