Renta-Rosa, Lorraine M.

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On the selection of commercially available Sn-Ag-Cu Pb-free balls components over re-balling the components with Sn37Pb balls to comply with the restriction of hazardous substances directive in the aerospace industry
(2009) Renta-Rosa, Lorraine M.; Valentín, Ricky; College of Engineering; Cáceres, Pablo; Quintero, Pedro; Department of Mechanical Engineering; González, David
A modeling approach based on physics of failure is presented that quantifies the interactions between different thermal cycles applied to Ball Grid Arrays (BGA). The approach is formulated at the microscale, incorporating physical mechanisms of intermetallics, and at the macroscale, capturing the creep phenomenon as dominant failure driver. The prediction trends agree with experimental results, confirming that the dominant damage switches have been captured in the Finite Element Models. Both macroscale and microscale damage models are applied to predict the durability of two BGA structures: backward compatible SAC balls soldered to eutectic SnPb paste, and reballed eutectic SnPb balls soldered to eutectic SnPb paste. Results show that re-balled cases have higher inelastic energy density per cycle averaged over damage volume. Results also show that the inelastic energy density is higher across the bulk of the improperly mixed backward compatible solder balls when compared to properly mixed backward compatible solder balls.