New Technologies for Ultra Thin Chips

Christine Kallmayer, Rolf Aschenbrenner
Fraunhofer IZM, Berlin, Germany

Julian Haberland, Herbert Reichl
Technical University Berlin, Berlin, Germany

This paper shows different approaches to use the availability of ultrathin chips for the realization of new packages with high density and improved performance. For several years technologies have been developed for the embedding of chips in circuit boards in order to achieve 3-D-packages using conventional processes from PCB manufacturing. Ultrathin chips are suited to be integrated in rigid circuit boards as well as on and in multilayer flexible substrates. The use of interposers prior to embedding can facilitate the embedding of components with ultra fine pitches. An example for a complex RFID-based product will be shown which is enabled by the integration of ultrathin dies

In general the supply of ultra thin chips or components is the bottleneck for the new enabling embedding technologies of active components. The assembly of thin chips can be realized with good results by various flip-chip technologies. Contact thicknesses < 10 µm can be achieved.

Embedding of thin chips in flexible multilayer flexes can be used to obtain thin modules with several layers of active components. As a demonstrator 4 layers with -ICs have been realized with 450 m thickness.

For the integration of chips with pitches < 100 µm the iBoard technology has shown very promising results. Using either FR4 or thinfilm PI interposers, a wide range of chip types with different bump metallurgies can be integrated with chip thicknesses of 50 m or even higher. As an example for the potential of this technology a display RFID module with 6 integrated ICs has been described.

Although there are many potential applications for such technologies the manufacturers are reluctant to use modules with embedded components processed in printed circuit board technology. Only the growing necessity to use this technology in order to overcome the gap between chip pitches and line geometries on FR4 has lead to the big interest in recent years. One prerequisite to achieve a higher degree of acceptance would be the availability of the corresponding design tools for this 3D integration to facilitate the design flow.