Nikhil Lakhkara Sandeep Menonb and Michael Ostermanb
aCascade Engineering Services, Redmond, WA
bCenter for Advanced Life Cycle Engineering (CALCE), University of Maryland, MD, USA
Package on Package (PoP) technology has become a popular packaging solution because of its ability to save PWB real estate without compromising device functionality. In this paper, we have studied influence of the stacking process and three different solder materials on solder interconnect durability under harmonic vibration loading. The PoP assembly under study is a combination of stacked die package (memory package) stacked over a Flip Chip BGA package (logic package). Two stacking processes examined include assembly through a single re-flow process and a two re-flow process. Solders examined included SAC305, SAC105, and SAC125. In addition to testing PoP assemblies, the bottom package without the top package was tested independently on similar test vehicles under the same loading conditions. Tests were conducted to failure under the IPC 9701 standard. It was observed that single re-flow assemblies had better durability than assemblies created with two solder re-flows. Further, assemblies with lower silver content were found to have better durability compared with higher silver content solders.
Keywords : Package on Package (PoP), vibration, solder fatigue, assembly process
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