Ultra fine pitch flip chip interconnection for 3D integration

Abstract

■ C2 technology, which has solder capped Cu pillar structure, was developed for 50um pitch peripheral flip chip applications targeting mobile digital products. ■ Double side assembly with C2 technology was achieved and OSP material selection is important to keep wettability. ■ DTC result with both Cu/Sn and Cu/Ni/In IMC system was compared with and without an organic substrate to consider 3D integration structure. The mechanical stress during thermal cycling has a significant impact on the bonding interconnections and based on simulations, it is found that the stress in the Cu/Ni/In joint is about 30% lower that that in the Cu/Sn joint. ■ Stack Joining process was performed by using pre-applied Inter Chip Fill and high thermal conductivity and low cure shrinkage ICF characteristics is desired for 3D integration.