Ultrathin assemblies on flexible substrates

Miniaturization enforcement of electronic modules in complex as well as low cost applications is the driving force to integrate flip chip technology in common surface mount device processes. The use of flexible substrates enables a large variety of geometric possibilities including folding and bending. On the one hand there are numerous low cost applications for this technology such as smart cards and smart labels, on the other hand flexible substrates offer a wide potential for highly complex folded packages and 3D modules. Thinned silicon chips with subsequent very thin bumps mounted on flexible substrates open up new dimensions in packaging technologies. They can be integrated even in thin products, e.g. documents or stacked to low profile 3D modules. Beside the geometrical aspects the parasitic influences of silicon material can be eliminated by thinning of the wafers. This advantage is of great interest for applications in the GHz-area for example for GPS modules.