As next generation packages and package interconnects continue toextend the reliability performance envelope of current designs andmaterials it is necessary to predict the limitations of the currentpackage and assembly process. The flip-chip, multi-layer Organic LandGrid Array (OLGA) package was developed for the current and futuregenerations of microprocessors and chipsets to be used in applicationsranging from servers, desktops and laptops to embedded applications.During normal processing voids in the epoxy underfill between thepackage and die occur as a result of moisture evaporation and underfillreaction byproducts during dispense and cure. During temperature cyclingthe lead-tin bump material is extruded into adjacent voids resulting inelectrical shorts. As bump pitches are reduced, the risk of bumpextrusion failures post temperature cycle increases. A predictive modelto assess the potential reliability risk of bump extrusion over thecomponent lifetime was needed prior to process qualification and pitchreduction. Analysis of the experimental data showed that the variablesthat modulate bump extrusion are void count, bump pitch, bump layout,underfill properties and temperature cycle condition. Using the failurerate and extrusion rate, an empirical reliability model was derived topredict bump extrusion failure rates based on the key variables.Intrinsic and empirical reliability modeling techniques documented inthis manuscript can be used to assess the impact of bump pitchreduction, new process evaluations and manufacturing capability planningas related to flip-chip die-package bump extrusion
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